(U-Th)/He chronometry of zircon has a wide range of potential applications including thermochronometry, provided the temperature sensitivity (e.g., closure temperature) of the system be accurately constrained. We have examined the characteristics of He loss from zircon in a series of step-heating diffusion experiments, and compared zircon (U-Th)/He ages with other thermochronometric constraints from plutonic rocks. Diffusion experiments on zircons with varying ages and U-Th contents yield Arrhenius relationships which, after about 5% He release, indicate E a = 163-173 kJ/mol (39-41 kcal/mol), and D 0 = 0.09–1.5 cm 2 /s, with an average E a of 169 ± 3.8 kJ/mol (40.4 ± 0.9 kcal/mol) and average D 0 of 0.46 +0.87 -0.30 cm 2 /s. The experiments also suggest a correspondence between diffusion domain size and grain size. For effective grain radius of 60 µ m and cooling rate of 10 °C/myr, the diffusion data yield closure temperatures, T c , of 171-196 °C, with an average of 183 °C. The early stages of step heating experiments show complications in the form of decreasing apparent diffusivity with successive heating steps, but these are essentially absent in later stages, after about 5-10% He release. These effects are independent of radiation dosage and are also unlikely to be due to intracrystalline He zonation. Regardless of the physical origin, this non-Arrhenius behaviour is similar to predictions based on degassing of multiple diffusion domains, with only a small proportion (<2-4%) of gas residing in domains with a lower diffusivity than the bulk zircon crystal. Thus the features of zircon responsible for these non-Arrhenius trends in the early stages of diffusion experiments would have a negligible effect on the bulk thermal sensitivity and closure temperature of a zircon crystal.

The ß - transition of 187 Re to 187 Os has a half-life approximately 10 times the age of the Earth, which makes it ideally suited to geologic investigations. The key interest in this geochronometer stems from the contrasting geochemical behaviour of the parent and daughter: Re and Os are severely decoupled during igneous processes. Rocks that crystallise from magmas have very high Re/Os whereas the residuum (the unmelted refractory source material) has very low Re/Os. The crystallised magmas can be dated using the well-established isochron approach and the age of the residuum can be estimated by the intersection of the measured Os isotopic composition with the "Earth's upper mantle reservoir".

The Dabie Shan of eastern China is a ~200-km wide mountain range with nearly 2 km of relief and is an archetype of deep ultrahigh-pressure metamorphic rock exhumation. Despite its regional and petrologic importance, little is known about the lowtemperature and post-orogenic evolution of the Dabie Shan. Here we present apatite and zircon (U-Th)/He (AHe and ZHe, respectively) and apatite fission-track (AFT) cooling ages from the Dabie Shan that constrain the patterns and history of exhumation over the last ~115 myr. On the scale of the whole orogen, ZHe and AHe ages are inversely correlated with mean elevation and are systematically younger in the core of the range. These cooling ages were converted to exhumation rates assuming steady-state erosion and accounting for topographic effects. These results indicate that, since the Eocene, flanks of the range have eroded at rates as low as 0.02 km/myr, while the range core has eroded at about 0.06 km/myr. Even in the core of the range, these recent exhumation rates are at least 10-20 times slower than those estimated for the initial stages of exhumation in the Triassic-Jurassic. In a 1.4-km vertical transect in the core of the range, all ages are positively correlated with elevation, with ZHe ages increasing from 76 to 112 Ma, AFT from 44 to 70 Ma, and AHe from 24 to 43 Ma. We present a simple model for topographic correction of thermochronometric ages in vertical transects, using the admittance ratio (ratio of isotherm relief to topographic relief). Applied to the AHe age-elevation relationship, this yields Tertiary exhumation rates of 0.05-0.07 km/myr in the core of the Dabie Shan, in good agreement with regional exhumation rate patterns. Finally, age-elevation relationships for all three chronometers in the vertical transect are consistent with a constant exhumation rate of 0.06 ± 0.01 km/myr since the Cretaceous, with a possible modest increase in exhumation rates (as high as 0.2 km/myr) between 80-40 Ma. These data show no evidence for significant variations in exhumation rates over the last ~115 myr, as might be expected for decay of old topography or tectonic reactivation of old structures.

The ELAN® DRC™ II (PerkinElmer SCIEX, Concord , Ontario , Canada) is designed and constructed for rapid, routine trace and ultratrace element analysis of a wide variety of materials and to handle around-the-clock operation in a high throughput semiconductor laboratory. The ELAN DRC II utilizes chemical resolution which is achieved by the use of a Dynamic Reaction Cell™ (DRC). The reaction cell is pressurized with a reactive gas that chemically removes the interferences from the ion beam before they enter the analyzer quadrupole. Dynamic reaction cell technology removes interferences by up to nine orders of magnitude and enables part-per-trillion detection limits for all common semiconductor elements while using one high-temperature plasma setting.

Eclogites from Trescolmen , Switzerland , derive from basaltic protoliths that experienced variable degrees of low-T seafloor alteration prior to high pressure metamorphism. δ7Li of the eclogites (-11 to +5.) range to dramatically lower values than observed in fresh MORB, or altered MORB (+4.5 to +14. for low T and .2 to +8. for high T altered MORB). These low values cannot be explained by fluid interaction with surrounding garnet mica schist, which is generally isotopically heavier (δ7Li of +2.4 to +3.8.). The low δ7Li values were likely produced by isotope fractionation through Rayleigh distillation during dehydration of clays and/or chlorite at early stages of metamorphism. These data are consistent with isotopically heavy Li being released into the forearc mantle wedge in subduction zones, while an isotopically light component is subducted deeply, and may form a distinct mantle reservoir that could be sampled by plume-related magmas.

Low closure temperatures of the apatite and zircon (U-Th)/He thermochronometers allow valuable constraints on timing and rates of bedrock exhumation through shallow crustal depths, but raise the possibility that shallow-level processes other than exhumation-related cooling may also influence He ages. A simple He diffusion model predicts that wildfires can completely or partially reset apatite He ages as much as 3 cm below rock surfaces and partially reset zircon He ages in the outermost 1 cm. Measured He ages in bedrock and sediments from the Washington Cascades that were exposed to extensive wildfires in 2001 show strong agreement with these model predictions. Apatite He ages decrease from a regionally consistent age of 19.5 ± 1.2 Ma at a distance >3 cm from the rock surface to as low as 1.9 Ma in the outermost 1 cm, whereas zircon He ages decrease from 65 to 55 Ma over the same distance. Thin (<3 cm) flakes shed from a nearby boulder during or after the most recent fire have apatite He ages ranging from 9.7 ± 0.6 to 17.2 ± 1.0 Ma. The partial-resetting profiles are best explained by model thermal histories involving at least one short-duration (~5–10 min), high- T (575–650 ° C) event and at least one longer (30–40 min), lower- T (350–450 ° C) event. Age-depth profile data may be useful in determining wildfire intensities or locations and also suggest that He ages of detrital apatites from some environments may be subject to bias from the thermal effects of wildfires.

A combined sample preparation and analytical technique to detect contamination offers accurate results, low detection limits, and the confirmation of interfering peaks.

This paper presents data to support the presence of (1) intra-annual signals in the chemical composition (d 18O and Sr/Ca) of the skeletons of sclerosponges from the Bahamas and (2) variable rates of skeletal accretion. These conclusions are based on data obtained by using a microsampling method for the stable oxygen and carbon isotopes in which material was extracted at a resolution of one sample every 34 mm and a laser microprobe which obtained trace element data every 20 mm (Sr, Mg, and Pb). An age model was established using a combination of changes in the concentration of Pb, the change in the d 13C of the skeleton of the sclerosponges, and U/Th isotopic measurements. These methods yield a mean growth rate of 220 mm/yr but suggest that the growth rate in this particular sclerosponge was not constant. The calculated growth rate is within error identical to that determined by U/Th methods. The variable growth rate was confirmed through spectral analysis of the d 18O and Sr/Ca data that showed peaks corresponding to the annual cycle in these parameters as well as peaks corresponding to growth rates of approximately 128, 212, 270, and 400 mm/yr. The presence of these additional frequencies suggests a growth rate between approximately 100 and 300 mm/yr. These conclusions were supported by modeling of oxygen isotopic data measured on a scleractinian coral as well as model isotope data generated on synthetic time series. These findings have important implications for the use of sclerosponges as proxies of paleoclimate because they emphasize the need for a precise yearly chronology in order that proxy data can be compared with climatic variables.

The rapid and reliable determination of natural 234U and anthropogenic 236U in environmental samples is challenging as these isotopes have very low abundances of only several ppm relative to the major uranium isotope 238U. These low abundances make analyses difficult, requiring the most sensitive and stable instrumentation.

Inductively coupled plasma mass spectrometry is a powerful tool for the investigation of many materials. The Agilent 7500c with Octopole Reaction System was used to analyze major, minor and trace elements in two standard reference plant materials. The data obtained using the 7500c is compared to the certificate reference values and to results that were generated using inductively coupled plasma optical emission spectroscopy. Results for all elements obtained using the 7500c agree with the certified values.

Part II of Robert Thomas’ series on inductivelycoupled plasma mass spectrometrylooks at one of the most critical areas of theinstrument — the sample introduction system.He discusses the fundamental principlesof converting a liquid into a fine droplet aerosol suitable for ionization inthe plasma, and provides an overview ofthe different types of commercially available nebulizers and spray chambers.

This application note demonstrates the determination of metallic impurities in semiconductor grade sulfuric acid. The Agilent 7500s ICP-MS instrument with its ShieldTorch technology was used to analyze sulfuric acid for all the metals required by the semiconductor industry.

Sclerosponges are slow growing, long-lived calcareous organisms that secrete aragonite skeletons, and are therefore well suited for providing continuous proxy records of ocean variability over the last millennium. However, the slow growth rate of these skeletons (~200m yr-1), at least compared to coral skeletons, places a premium on maximum spatial resolution in any analyses of trace elements or stable isotopes. We therefore developed a method for rapid and precise determinations of element/calcium ratios (Mg/Ca, Mn/Ca, Sr/Ca, Ba/Ca, Pb/Ca and U/Ca), and Pb isotopes, in Sclerosponge skeletons using Laser Ablation ICP-MS. The technique we have developed for these analyses uses He to transport ablated material from the laser cell to the Element2. The carrier gas is then mixed with Ar sample gas and a wet aerosol (introduced via a Microflow PFA nebulizer) in the endcap of a Scott double pass spray chamber. The nebulizer is, in turn, connected to an autosampler, and liquid standards are introduced throughout the sample run (every 5-10 samples) to monitor variations in mass bias. Spatial resolution of approximately 20m was achieved with a Merchantek EO 266 LUV laser system. The precision, accuracy and reproducibility of this multi-ratio method is evaluated and compared to previously reported ICP-MS methods. Results to date suggest that it will be possible to generate high resolution temperature records from Mg/Ca and Sr/Ca ratios in Sclerosponge skeletons once adequate temperature calibrations can be attained. Other environmental phenomena, including the introduction and subsequent phasing out of leaded gasoline, may also be reconstructed from Sclerosponge skeletons. Together, these data suggest that Sclerosponges represent a unique, and as yet underutilized, tool for reconstructing paleoceanographic and climate variability.

High-speed photographs and video footage of an ICP are used to examine the validity of a solution calibration method for laser ablation ICP-MS. Desolvated particles from a microconcentric nebulizer and particles ablated from a yttrium oxide pellet are mixed and introduced simultaneously to an ICP. High-resolution digital photographs and video sequences are captured using shutter speeds of approximately 65 us in order to study the emission behavior of particles traversing the plasma under a variety of conditions. A quadrupled Nd:YAG laser (266 nm, CETAC LSX-100) and an ArF laser (193 nm, MPB PSX-100) are used to ablate the solid sample, and either argon or helium is used as the transport gas through the ablation cell. No red emission clouds from YO+ are visible in the plasma when a 20-uL/min PFA nebulizer (PFA-20, Elemental Scientific) is used to spray a 2000 ppm Y solution, suggesting that the wet droplets from this nebulizer desolvate almost completely before entering the ICP. These desolvated particles atomize and ionize like the small dry particulates from laser ablation. However, some large ablated particulates are observed to fly through the plasma intact. Nevertheless, accurate calibration results using solution standards can be obtained for elements not affected by fractionation. Using a Finnigan Element 1, the accuracy of the quantitative analysis of NIST SRM 612 glass is within 3% for analyte concentrations ranging from 15-51 ppm.

We quantified Mg/Ca, Mn/Ca, Sr/Ca and Ba/Ca molar ratios from an area representing the summer 2000 growth season on otoliths and scales from 1-year-old westslope cutthroat trout, Oncorhyncus clarki lewisi, collected from three streams of the Coeur d'Alene River , Idaho USA . We also quantified Mg/Ca, Sr/Ca, and Ba/Ca molar ratios in the water during summer 2000 and regressions were used to model the assimilation of element/Ca into the otoliths and scales. Otolith and scale chemistries were linearly related to Sr/Ca and Ba/Ca in the water. The partition coefficients for Sr/Ca into otoliths and scales are higher in this freshwater system than experimental results from a saline environment. We attribute differences in partition coefficients to differences in biology of saltwater and freshwater fish. In contrast, Ba/Ca partition coefficients are similar between the two environments suggesting that our estimates represent those for a wide range of concentrations, temperatures, salinities, and at least two families of fish. Magnesium/Ca, Sr/Ca, and Ba/Ca varied significantly in otoliths from the three streams and could be used to reclassify individual fish to the stream from which they were collected with 100% accuracy. Manganese/Ca, Sr/Ca, and Ba/Ca varied significantly in scales from the three streams and could be used to classify individuals with 82% accuracy. Given the heterogeneity of basin geology, the stability of water chemistry, and the degree of discrimination noted for the three streams we sampled, we believe that examination of the elemental composition of fish otoliths and scales could be used to describe the movements of fish in this and similar freshwater systems. Further, the high correlation of element/Ca in scales to that in otoliths suggests scales may offer a non-lethal sampling alternative to otoliths.

Trace metals were determined in pentane using the Agilent 7500c. Direct analysis precludes the use of more labor intensive and contamination prone techniques such as dry ashing, digestion and dilution.

This application note describes the 4500 ICP-MS analysis of concentrated nitric and hydrofluoric acids used in semiconductor production. PPT level determinations are required for these reagents. Sample preparation was just simple dilution. Low dilution factors were used to analyze the acids thereby minimizing sample contamination and allowing for the best possible detection limits. Ten elements were analyzed. The ShieldTorch and cool plasma conditions made the analysis of K, Ca and Fe possible. All elements were analyzed under the same conditions. Detection limits were in the range of 1 to 30 ppt. MSA calibration curves in this concentration range were linear.

This report describes an analytical procedure for the determination of trace metal impurities at low pg/ml levels in high purity isopropyl alcohol (IPA). IPA was introduced undiluted into the ICP using a Microflow PFA nebulizer (20 µl/min uptake rate) in combination with a water-cooled, Scott type spray chamber. Oxygen was added to the argon nebulizer/carrier gas stream to prevent clogging effects at the interface and to stabilize the plasma. Because of the formation of polyatomic interfering species originating from the solvent (as shown in Fig. 1 for Zn), most elements had to be determined in medium (R = 4000) or high resolution (R = 10000) modes (Table 2). A standard addition analysis procedure was used for quantification purposes. Low fg/ml detection limits were achieved for most elements.

Shielding materials for nuclear applications are made of boron alloyed stainless steel. Storage bins and transfer containers are the main products, they have to be corrosion resistant under heavy duty conditions. An essential requirement for these materials is the uniformity of the absorption cross section over the whole sheet of metal to fulfill safety standards. The neutron absorption properties of boron alloyed steel depends on the content of the 10-B-Isotope. This isotope has an absorption cross section for thermal neutrons of more than 3800 barns. Absorption capabilities of 10-B are exceeded only by cadmium, gadolinium and samarium, with 10-B the ony isotope suitable for steel making. Steel can be alloyed with boron in concentrations of up to 2% without restricting the processability in subsequent working processes. In naturally occurring boron the isotope 10-B is limited to about 20% abundance. The content of 10-B in isotopically enriched Boron can theoretically reach 100% abundance but only with dramatically increasing costs. Enriched boron is added as ferroboron to the stainless steel, a very demanding process due to the high costs for raw materials and the high standards of the product. This requires optimized process control and high standards in the chemical analysis of this materials throughout the whole production process. Especially the isotopic composition of boron needs to be determined with high precision and accuracy. As analysis time is limited and high quality standard have to be maintained, the analytical method of choice is inductively coupled plasma mass spectrometry (ICPMS).

Boron isotopes fractionate at temperatures of a few hundred degrees centigrade and can therefore be used, for example, in hydrothermal studies. The 10 B isotope also behaves as a neutron moderator in nuclear reactors. Traditionally, boron isotopes have been measured by thermal ionisation mass spectrometers (TIMS). Because of the high ionisation potential of B the usual method is to analyse B as a molecular species such as Na 2 BO 2 or Cs 2 BO 2 by positive ionisation, or as BO 2 by negative thermal ionisation. Typically, precisions obtained using TIMS are 0.1% to 0.03% 1SD on sample sizes of a few hundred nanograms Multi-collector ICP-MS allows much smaller samples to be analysed to higher precision than by Thermal Ionisation Mass Spectrometry. The data in this application brief was obtained using the Micromass IsoProbe. In contrast to TIMS, the ICP ion source is extremely efficient, such that the atomic species 10 B and 11 B are measured directly. ICP-MS techniques do generally have a higher mass bias than TIMS techniques due to space charge effects in the interface region. The mass bias of the IsoProbe has been found to be extremely stable and therefore corrections for mass bias are simple. The IsoProbe multi-collector ICP-MS is able to simultaneously measure 10 B and 11 B using Faraday collectors, since the M17 multicollector is able to accommodate isotopes with up to 17% mass dispersion. The separation required for B is 10%.

A newly developed, high sensitivity reaction cell ICP-MS was used for the determination of inorganic impurities in semiconductor-grade tetramethyl ammonium hydroxide (TMAH). The Agilent 7500cs ICP-MS, which features a high sensitivity version of the Octopole Reaction System (ORS), was used to analyze TMAH for all the metals according to SEMI Tier A specifications. The ORS eliminates all plasma and matrix based polyatomics that interfere with the measurement of elements such as K, Mg, Ca, Al, Cr, Fe, Co, Ni, and Cu and provides excellent ion transmission and sensitivity. All analytes can be measured at high plasma power to promote complete decomposition of the TMAH in the plasma. Sample preparation is a simple 5× dilution of the 25% TMAH solution in deionized water, followed by direct analysis by the ICP-MS.

The quantitative determination of mercury in foodstuffs is presented using a 7500I ICP-MS. Microwave digests were prepared and then analyzed by the ICP-MS. To avoid memory effects often experienced with mercury, gold was added offline to all standards/samples and wash solutions to act as a cleansing agent. The instrumental setup used a second vacuum pump, the integrated sample introduction system in the high sample throughput mode, and a Microflow concentric PFA nebulizer. This allowed the robust and rapid determination of mercury in the digests at the ppt range. Excellent agreement with the certified value was obtained for two certified reference materials and stability of the system was demonstrated over a 36-hour analytical run.

The drive for more compact integrated circuits and smaller electronic devices has put challenging demands on the manufacturers of analytical instrumentation used by the semiconductor industry. Nowhere is this more obvious than in the analysis of high purity chemicals, which are used in various stages of the manufacturing process of the semiconductor devices. In order to reduce costs and increase yield, chip manufacturers are using ever larger diameter wafers and ever narrower line widths in order to produce more semiconductor devices per wafer. This trend has resulted in a demand for lower and lower trace element contamination levels in the process chemicals. Whereas 10 years ago, the SEMI (Semiconductor Equipment and Materials International) organization deemed that 10 ppb purity levels were adequate for many of the process chemicals, today 100 ppt is typical; and for some of the more critical materials like hydrogen peroxide (H2O2), 10 ppt purity levels are currently being proposed. Traditionally, ICP-MS has been the technique of choice for ultratrace element determinations in high purity hydrogen peroxide. It has been successfully used to determine trace impurities at the 100-ppt level (Grade 4) using SEMI methodology. Unfortunately, it didn’t have the detection capability for all 21 trace metals to reach the next purity level of 10 ppt (Grade 5) - even with the use of traditional background reduction techniques. However, a novel approach to improve ICP-MS detection limits using Dynamic Reaction Cell™ (DRC™) technology has recently been developed. This technique utilizes ion-molecule chemistry to eliminate many argon and solventbased interferences in order to improve detection limits and background equivalent concentration (BEC**) for the problematic ICP-MS elements.
This paper will describe the principal uses of hydrogen peroxide in the semiconductor industry and focus on Solvay Interox, a leading manufacturer, who uses DRC technology to help meet the next generation of purity levels. It will go on to describe the dynamic reaction cell in greater detail and explain how the detection limit and background equivalent concentration improvements are achieved. Data will be presented showing method detection limits and spike recoveries at the Grade 5 level (10 ppt) in 31% hydrogen peroxide using methodology described in the Book of SEMI Standards (BOSS).

The Department of Earth Sciences at the Open University was rated grade 5 in the last and previous Research Assessment Exercises and has an international reputation for isotope geochemistry. In order to develop trace element studies to a level similar to isotope research, we applied for and were awarded funding under the NERC JREI scheme to buy a new ICP-MS system to replace an outdated neutron activation laboratory. Further funding was secured from the University and two years ago we took delivery of a new Agilent 7500s instrument and one of the first New Wave UP213 UV laser ablation systems to be delivered in the UK . Overnight we found that instead of analysing 20 elements in 40 samples with detection limits of at best 10ppb each month, we could analyse over 40 elements in hundreds of samples with ppt detection limits in days! The transformation was exciting and has encouraged the development of unforeseen projects on samples as varied as the title of this short article suggests.

A consistent method for stable lead isotope analysis of marine carbonates and seawater is presented, utilizing multiple collector ICP-MS (MC-ICP-MS). This study presents new observations of the large (0.7% amu_ 1), time-dependent mass bias determined by thallium normalization, including preferential light ion transmission induced by the acceleration potential and plasma interface (b =_1.3 to 0.9). These experiments show equivalent results for three empirical correction laws, and the previously proposed bPb/bTl correction does not improve isotope ratio accuracy under these conditions. External normalization to SRM-981 following the thallium correction provides one simple alternative, and a rationale is provided based on secondary bias effects. With current intensities less than 1.5_10_ 12 A, external isotope ratio precision better than 250 ppm for SRM-981 207Pb/206Pb and 208Pb/206Pb ratios is observed (2r). From reconstructed lead isotopic variability in the North Atlantic , this instrumental precision results in a signal-to-noise ratio greater than 100. Matrix effects are significant with concomitant calcium in SRM-981 (_280 ppm at 257 AM [Ca]). With the appropriate corrections and minimal concomitants, MC-ICP-MS can reliably determine 207Pb/206Pb and 208Pb/206Pb ratios of marine carbonates (30 mg) and seawater (160–200 g).

An inductively coupled plasma mass spectrometer (ICP-MS) was used as a detector for gas chromatography (GC) and high performance liquid chromatography (HPLC) analysis of organotin compounds. ICP-MS is a highly sensitive detector with detection limits in the pg-ng range, as well as enabling calibration by isotope dilution mass spectrometry (IDMS). Calibrating using isotopically labeled organotin species reduces measurement uncertainties and leads to greater precision compared to external calibration methods. This application note details the relative merits of the two techniques for the analysis of organotin compounds.

Quadrupole Inductively Coupled Plasma Mass Spectrometry (ICP-MS) was used to determine lead (Pb) isotope ratios in Dan-shen, a type of herb used in Traditional Chinese Medicines (TCM), and in water and soil samples all taken from the same geographical location. The precision obtained for the 208Pb/206Pb ratio, the 207Pb/206Pb ratio and the 204Pb/206Pb ratio values was considerably lower than 0.5% demonstrating the applicability of the technique for Pb isotope ratio studies. The results show that it is possible to distinguish Dan-shen samples originating from different geographical areas using Pb isotope ratio measurements. As the medicinal effectiveness of a TCM is highly dependant on the source of origin of its herb components, it is useful to have a reliable, routine means of “fingerprinting” the components grown in different habitats.

In order to measure isotope ratio of uranium in safeguards environmental samples with ICP-MS precisely, production of polyatomic ions of IrAr, PtAr and AuAr was measured and mass bias of ICP-MS is investigated by using isotopic standards of uranium and lead. The intensities of IrAr, PtAr, and AuAr relative to the atomic ions were found to be 1.8x10 -6, 1.6x10 -5 and 4.1x10 -5, respectively. The production of 193Ir40Ar is too small to interfere with the measurement of 233U, if the concentration of Ir is the same level as that of 233U. However, there is possibility that the presence of Pt and Au interferes with the measurement of minor isotopes of uranium and 237Np. On the other hand, the mass biases of 235U/238U and 208Pb/206Pb were measured with the parameter of 238U16O/238U. Since unexpected change of the mass bias during measurements causes frequently erroneous results, the monitoring of 238U16O/238U is effective for the precise isotope ratio measurement.

The molecular structure and microstructure of a suite of fine particulate matter (PM) samples produced by the combustion of coal, residual fuel oil, diesel fuel, and model compounds has been investigated by an array of analytical techniques. Analyses were conducted of PM <2.5 µm (PM2.5) and >2.5 µm (PM2.5+) in mean diameter. The analytical techniques included XAFS spectroscopy, XRF, INAA, ICP-MS, GC/MS, 13C NMR, computer-controlled SEM, high-resolution TEM, scanning transmission x-ray microspectroscopy (STXM), and Mössbauer spectroscopy. Some of the results are briefly summarized below. Coal PM: Sulfate was the dominant form of S. Some thiophene, associated with unburned carbon, was observed. Cr6+, the more toxic form of Cr, was observed only in PM from CFA from several western coals, but not in PM from CFA from several eastern coals. Ca-Cr6+-O complexes in western flyash are a possibility. Only As5+ was detected in all of the PM samples investigated; the more toxic As3+ oxidation state was not observed. The dominant form of Zn in PM from the eastern CFA is ZnFe2O4. The Zn chemistry of the western CFA PM is complex. The microstructure is dominated by spherical and rounded aluminosilicate glass particles that contain significant amounts of Ca in western CFA PM and Fe and K in eastern CFA PM. ROFA PM: Unburned carbon in the form of graphitic soot was the dominant species. Molecular forms of sulfur, in order of abundance, include sulfate, thiophene, inorganic sulfide and elemental sulfur. The latter three are higher in PM2.5+ than in PM2.5, indicating association with unburned carbon. Metals were predominantly present as sulfates, including VOSO4·xH2O, NiSO4, PbSO4, Fe2(SO4)3 and ZnSO4·xH2O. Small amounts of metal sulfides were observed in the PM2.5+ samples, including Ni3S2, which is known to be carcinogenic. Water leaching removed essentially all sulfates. NiFe2O4 was observed as a secondary phase in the PM2.5 samples. The exception to sulfate dominance was Cu, present primarily as CuNO3. Arsenic was present only as arsenate (As+5). The most interesting microstructure consisted of small metal sulfate particles on high surface area carbon. For both ROFA and CFA PM, particle size distributions (PSD) based on number are dominated by large numbers of small particles, while PSD based on volume are dominated by small numbers of large particles. Diesel PM (DPM): A small diesel engine test facility with extensive on-line analytical monitoring was established. 13C NMR established a .graphite factor. for quick determination of graphite in DPM. Both GC/MS and NMR indicated significant amounts of unburned diesel fuel and lubricating oil in DPM, particularly under idle running conditions. S, Ca, and Zn were all much higher in DPM under idle than under load conditions. HRTEM detected small (~4nm X 1 nm) graphitic islands in spherical DPM globules. Exploratory STXM clearly showed variable C molecular structure in 50-100 nm DPM.

Quantification of particulate (w0.45 mm) and dissolved (v0.45 mm) trace elements in seawater is imperative for understanding geochemical cycling in the marine environment. Suspended particulate trace element concentrations are typically v10% of total element concentrations in seawater. To overcome analytical difficulties associated with low analyte concentrations, it is common to filter large volumes (tens to thousands of litres) of seawater. We report a novel method for the rapid quantification of Al (324 ppb), P (159 ppb), V (2.02 ppb), Cr (2.85 ppb), Mn (22.3 ppb), Fe (304 ppb), Co (0.129 ppb), Ni (0.817 ppb), Cu (1.68 ppb), Zn (3.25 ppb), Mo (0.264 ppb), Ag (0.079 ppb), Cd (0.029 ppb), Ba (3.54 ppb), Pb (1.13 ppb) and U (0.053 ppb) in digest solutions of suspended matter, filtered from 0.2 to 5.0 L of seawater. Filter digest solutions, consisting of a complex matrix of filter residue, sea salt, dissolved solids and strong acids, are analyzed on the ELEMENT, a high resolution, inductively coupled plasma mass spectrometer (Finnigan-MAT, Bremen, Germany). High sensitivity (w16106 counts s21 ppb21 In; with shielded torch) combined with low flow rates (MicroFlow PFA nebulizer, Elemental Scientific) provide excellent absolute detection limits (0.4 to 720 pg depending on the element). A resolution of 300 (low resolution) is appropriate for interference-free high mass analytes of interest (Ag, Cd, Pb, Ba and U), whereas 4300 (medium resolution) is sufficient to resolve all plasma-, water- and matrix-based polyatomic interferences on low mass analytes (Al, P and first row transition metals). The precision of the method is better than ¡4% for most analytes. Accuracy could not be determined conventionally using a certified reference material (not available), but was estimated from spiked samples to be v¡4% when calculated using a standard additions curve and v¡10% for most elements if using an external standard curve.

At the ICP-MS measurement, organic solvent such as isopropyl alcohol (IPA) is known to generate polyatomic interference such as 12C2 on 24Mg, 40Ar12C on 52Cr and 12C14N1H on 27Al. The ICP-DRC (Dynamic Reaction Cell)-MS is possible to remove polyatomic ions that were generated by argon, sample matrix etc. The conventional cool plasma needs to run 2 methods to a single sample, because the hot plasma is essential for W, Zn, U and others. On the other hand, ICP-DRC-MS is possible to determine all elements under only one method and plasma condition. In this study, under the conditions such as optimum cell gas flow rate, ICP-DRC-MS performed successfully the analysis of typical organic solvent of IPA. The detection limits for Mg, Cr and Al were 6, 4 and 6 ng/L (ppt), respectively.

Ammonium sulfates and nitrates form as a result of the reaction of ammonia with SO2 and NOx released by several sources, including coal and fuel oil combustion, vehicular exhaust, and other combustion sources. We are currently investigating whether it may be possible to determine the fraction of ammonium sulfate in PM2.5 derived from various combustion sources by measuring the isotopic ratios of sulfur. The isotope ratio measurements are being performed on a VG Axiom high-resolution inductively coupled plasma mass spectrometer. Thus far, we have been able to obtain a precision of 0.2 % RSD for 34S/32S ratio measurements using a single collector. Results will be presented for sulfur isotope ratio measurements on PM2.5 derived from large-scale combustion experiments of various fuel oils and coals.

The precise and accurate determination of Ca isotope ratios in biological samples is imperative in limiting the expense of enriched isotopes used in human metabolic tracer studies. Here we evaluate the use of the ELEMENT (Finnigan MAT, Bremen , Germany ); a High-Resolution, inductively coupled plasma mass spectrometer (HR-ICP-MS) for rapid determination of Ca isotope ratios in 20 fold dilutions of raw urine and oxylate preconcentrates. Free aspiration of samples using the micro-flow 100 PFA nebulizer (Elemental Scientific, Omaha, NE) avoids pump noise and provides a stable aspiration of high TDS solutions at low flow rates. This combined with jumping the magnet to 42Ca and electrostatically scanning the 42 to 48 mass range, provides rapid scanning requirements for determination of precise isotope ratios. Precise < 0.5% (1-sigma) and accurate isotope ratios are obtained at resolutions sufficient to resolve all polyatomic interferences. Reducing water based interferences on 42Ca (ArHH and MgO) and 44Ca (CO2 and SiO) by desolvation (MCN-6000, CETAC, Omaha , NE ) provides typical sub permil (<0.06% 1-sigma) precision and accuracy for 42Ca/44Ca and 43Ca/44Ca in low resolution (R=300). Furthermore removal of matrix by Ca oxylate preconcentration yields similar precision for 42Ca/44Ca and 43Ca/44Ca while reducing interferences which prohibit the determination of 46Ca/44Ca and 48Ca/44Ca ratios.

The analysis of wastewater for mercury by ICP-MS can present a number of challenges. First, mercury has a relatively low response factor since it is only about 40 percent ionized in a typical argon plasma. It is also subject to ionization suppression in the presence of easily ionized matrix elements that can reduce the response even further. Secondly, because of its high vapor pressure, it can be subject to severe memory effects. Finally, the most abundant Hg isotope available for quantitation is 202Hg, which is only 29.9% abundant.
In order to analyze mercury efficiently in high matrix samples like wastewater, the ICP-MS must be able to maximize the transfer of energy to the analyte atoms. This is achieved in the Agilent 7500i ICPMS by minimizing the matrix load on the plasma, so ensuring a high and stable plasma temperature. The high plasma temperature also ensures good matrix decomposition, which reduces the impact of the matrix on the interface, ion lenses, vacuum pumps and mass analyser. The use of constant-flow nebulization with the Agilent PFA-100 MicroFlow PFA nebulizer significantly reduces memory effects for Hg, by reducing the total sample flow to the nebulizer and spray chamber. A low sample flow rate, removal of water vapour and use of a widebore injector in the plasma torch all contribute to a reduced total matrix load on the plasma, increasing the available energy for analyte ionization. The Agilent 7500’s good stability and low random background also allow accurate and precise measurements to be made at very low concentrations.

When performing trace analysis, two parameters are vital in order to attain the best possible quantification limits: the experimental environment and the reagents used, including the ultrapure water used to perform blanks, dilute standards, and wash glassware. Weakly charged elements or elements that are not well dissociated in water are not removed efficiently by conventional water purification technologies. In the production of high-purity water, silica and boron are generally the first elements to break through into purified water when the ion-exchange resin approaches complete depletion. Much work has been done in the past decade to remove and measure silica. Recently, boron breakthrough was correlated with dissolved silica and an associated drop in resistivity. The study of the behavior of these two elements through various steps in a water purification chain is described. Boric acid is a very weak acid with an equilibrium constant (pKa) value of 9.2; it is only slightly stronger than silicic acid, which has a pKa of 9.5. At a pH lower than 7, boron is present in its nondissociated form; at a pH greater than 11.5, it is present in the dissociated borate form. Much attention has been given to the interaction of these ions with various chemicals such as carbohydrates. Negatively charged borate can be retained by anion exchange resin. Various chemistries were tried for chromatographic studies of boron. A synthetic polymer containing a hydrophobic styrene backbone as well as a tertiary amine and polyhydric alcohol group is more suitable for boron removal resin. This type of boron-specific resin (whose use has been described 8,9 ), in combination with advanced water purification system materials and configuration, enable the production of boron-free ultrapure water suitable for ultratrace analyses.

A quadrupole inductively coupled plasma mass spectrometer (Q-ICP-MS) equipped with a dynamic reaction cell (DRC) and coupled with a desolvating nebulization system (APEX-IR) was employed to determine 17 elements (Al, As, Ba, Cd, Co, Cr, Li, Mn, Mo, Ni, Pb, Sb, Se, Sn, Sr, V, and Zr) in blood samples. Ammonia (for Al, Cr, Mn, and V) and O2 (for As and Se) were used as reacting gases. Selection of the best flow rate of the gases and optimization of the quadrupole dynamic bandpass tuning parameter (RPq) were carried out, using digested blood diluted 1 + 9 with deionized water and spiked with 1 μg L−1 of Al, Cr, Mn, V and 5 μg L−1 of As and Se. Detection limits were determined in digested blood using the 3σ criterion. The desolvating system allowed a sufficient sensitivity to be achieved to determine elements at levels of ng L−1 without detriment of signal stability. The accuracy of the method was tested with the whole blood certified reference material (CRM), certified for Al, As, Cd, Co, Cr, Mn, Mo, Ni, Pb, Sb, Se, and V, and with indicative values for Ba, Li, Sn, Sr, and Zr. The addition calibration approach was chosen for analysis. In order to confirm the DRC data, samples were also analyzed by means of sector field inductively coupled plasma mass spectrometry (SF-ICP-MS), operating in medium (m/Δm = 4000) and high (m/Δm = 10,000) resolution mode and achieving a good agreement between the two techniques.

Determination of trace elements in serum by dynamic reaction cell inductively coupled plasma mass spectrometry Developing of a method with a desolvating system nebulizer
S. D’Ilio, et. al. Analytica Chimica Acta, 28 July 2006, Vol. 573-574, 432-438 Instrumental Methods of Analysis -IMA 2005 [link]

An inductively coupled plasma mass spectrometer (ICP-MS), equipped with a dynamic reaction cell (DRC) and coupled with a desolvating nebulizing system (Apex-ACM) to reduce the oxide formation, was used in the determination of Al, Co, Cr, Mn, Ni and Se in serum samples. The effect of the operating conditions of the DRC system was studied to get the best signal-to-background (S/B) ratio. The potentially interfering molecular ions at the masses m/z 27Al, 59Co, 52Cr, 55Mn, 60Ni and 78Se, were significantly reduced in intensity by using NH3 and H2, as the reaction cell gases in the DRC, while a proper Dynamic Bandpass Tuning parameter q (RPq) value was optimized. The detection limits for 27Al, 59Co, 52Cr, 55Mn, 60Ni and 78Se, estimated with 3-σ method, resulted to be 0.14, 0.003, 0.002, 0.01, 0.01 and 1.8 μg L−1, respectively. This analytical method was developed on both a human serum certified reference material and a lyophilized animal serum produced and proposed in an intercomparison study. The results obtained for the reference samples agreed satisfactorily with the certified values. Precision (expressed as CV%) between sample replicates was better than 10% for elements determination, with the only exception of aluminium (14%).

Determination of extremely low 236U/238U isotope ratios in environmental samples by sector-field inductively coupled plasma mass spectrometry using high-efficiency sample introduction
Sergei F. Boulyga, and Klaus G. Heumann, Journal of Environmental Radioactivity2006, 88 (1), Pages 1-10 [link]

A method by inductively coupled plasma mass spectrometry (ICP-MS) was developed which allows the measurement of 236U at concentration ranges down to 3 × 10−14 g g−1 and extremely low 236U/238U isotope ratios in soil samples of 10−7. By using the high-efficiency solution introduction system APEX in connection with a sector-field ICP-MS a sensitivity of more than 5000 counts fg−1 uranium was achieved. The use of an aerosol desolvating unit reduced the formation rate of uranium hydride ions UH+/U+ down to a level of 10−6. An abundance sensitivity of 3 × 10−7 was observed for 236U/238U isotope ratio measurements at mass resolution 4000. The detection limit for 236U and the lowest detectable 236U/238U isotope ratio were improved by more than two orders of magnitude compared with corresponding values by alpha spectrometry. Determination of uranium in soil samples collected in the vicinity of Chernobyl nuclear power plant (NPP) resulted in that the 236U/238U isotope ratio is a much more sensitive and accurate marker for environmental contamination by spent uranium in comparison to the 235U/238U isotope ratio. The ICP-MS technique allowed for the first time detection of irradiated uranium in soil samples even at distances more than 200 km to the north of Chernobyl NPP ( Mogilev region). The concentration of 236U in the upper 0–10 cm soil layers varied from 2 × 10−9 g g−1 within radioactive spots close to the Chernobyl NPP to 3 × 10−13 g g−1 on a sampling site located by >200 km from Chernobyl.

Determination of ²³⁴U/²³⁸U isotope ratios in environmental waters by quadrupole ICP-MS after U stripping from alpha-spectrometry counting sources
J. L. Mas, et al., nalytical and Bioanalytical Chemistry, 2006, 386(1): 152-160 [link]

High A rapid technique for the determination of Pu in urine samples using flow injection (FI) on-line preconcentration, desolvation nebulization using highly sensitive APEX device and inductively coupled plasma mass spectrometry with a dynamic sell (ICP-DRC-MS) was developed. Using the DRC avoided the necessity to separate Pu from U, and thos made the technique more rapid. Effective preconcentration and matrix separation for urine samples was achieved using TRU resin as the ion exchanger. A detection limit for ²⁴²Pu of 1.9 pg L^-1 was achieved for raw, undigested urine samples using a 10 ml sample volume. The reproductibility of the method was demonstrated by recovery measurements performed on urine that had been collected from several non-exposed volunteers and spiked with Pu. ²⁰⁵Ti and¹⁷⁵Lu were used as an internal standard and yeild tracer, respectively. The method provides a rapid (~11 min) means of measuring Pu in urine with no off-line sample pre-treatment, at levels below the regulatory requirements for drinking water.

High resolution ICP-MS is used to evaluate the APEX-ACM membrane desolvator for the determination of 42Ca/ 44Ca and 43Ca/ 44Ca isotope ratios using low resolution. The APEX-ACM has a rapid uptake and wash and lower Ca blanks than a conventional spray chamber. The APEX-ACM also reduces the ArH 2 + interference on 42Ca by more than 100x, lowers total polyatomic interferences and blanks to <0.5% of the Ca signal, and provides excellent short term and run to run precision on Ca isotope ratios.

Here we present sensitivity data of the ThermoFinnigan NEPTUNE using various sample inlet systems in combination with different skimmer cones. In particular we will investigate the performance of a cyclonic spray chamber, a Scott type spray chamber and a combination of both: the stable introduction system (SIS). The spray chambers will be operated at room temperature and at low temperatures down to about 2°C.

MC-ICP-MS based stable isotope procedures are suitable to detect small variations in metal isotope composition of natural samples, but they are prone to substantial bias introduced by inadequate sample preparation. Such a “cryptic” bias is not necessarily identifiable from the measured isotope ratios. An analytical protocol for Fe isotope analyses of organic and inorganic materials is described that allows to identify and avoid such pitfalls. Using a ThermoFinnigan Neptune MC-ICP-MS sensitivity of 56Fe in medium-mass resolution mode (allowing resolution of molecular interferences) for a 1 ppm Fe solution with an uptake rate of 50-70 µL min-1 is 3 Volts for the Finnigan "SIS" glass spray chamber and 12-18 Volts for the ESI Apex-Q uptake system. Sensitivity was increased again 3-5 fold when using Finnigan X-cones instead of the standard H-cones. The combination of the ESI Apex-Q apparatus and X-cones allowed determination of the isotope composition on as little as 50 ng of Fe. Isotope ratios were acquired with the standard sample bracketing method. External reproducibilities at the 95 % confidence interval for δ56Fe, δ57Fe, and δ58Fe, assessed from 318 measurements of natural samples, were 0.049 ‰, 0.071 ‰, and 0.28 ‰, respectively. Strong error correlations of the data are observed in three isotope diagrams. Therefore, it is suggested that the quality assessment in such diagrams should be performed with error ellipses rather than error bars. Reproducibility of 2 δ56Fe, δ57Fe, and δ58Fe values of natural samples alone is not a sufficient criterion for accuracy. A set of tests is lined out in this study that bear the capability to reveal the presence of cryptic artefacts. The most powerful test involves exchanging the Fe from a sample’s matrix with that of a standard of well-known isotope composition.

Analysis of Wastewater and Mine Tailing Samples Using Octopole Reaction System Agilent 7500cs for Sub Parts Per Billion Reporting Levels [pdf]
Marshall Pattee, North Creek Analytical, Inc.

Environmental laboratories continue to seek high performance instruments to meet ever-changing EPA regulations and data quality objectives. Accurate analysis of wastewater without matrix bias is vital in today’s environmental laboratory. Today’s economics prohibits laboratories from financially investing in highly selectively methods and extraction techniques, such as atomic fluorescence and hydride generation-ICP-MS, for achieving required reporting levels for multiple metals. Today’s environmental laboratory needs one instrument flexible enough to handle ever changing matrices and capable of sub parts per billion analysis.

Analysis of Hexavalent Chromium From Alkaline Digestion EPA 3060A, Using Octopole Reaction System Agilent 7500cs [pdf]
Marshall Pattee & Mustahsan Farooqui, North Creek Analytical, Inc.

Environmental laboratories have needed the development of a high production procedure for parts per billions analysis of hexavalent chromium in soil, sediment and sludge matrices. Applying EPA 3060A, alkaline digestion for hexavalent chromium as a guideline, North Creek Analytical has developed a routine procedure for the environmental laboratory. Traditionally, ICP-OES has been used to analyze the difficult alkaline digestions. Now the Octopole Reaction ICP-MS analysis allows for the elimination of common isobaric molecular-ion interferences such as ArC+, ClO+, ClOH+, allowing the concise determination of Cr52 & Cr53 in an alkaline digestion solution at 2.5% total dissolved solids which contains 0.28 M Na2CO3/0.5M NaOH.

Agilent Technologies has the 7500cs ICP-MS for the determination of inorganic impurities in high purity matrices. The new instrument features a high sensitivity version of the Octopole Reaction System (ORS) to eliminate plasma and matrix based polyatomics that interfere with the measurement of elements such as Ca, K, Fe, Ti, Cr, Co, Ni, Cu, and Zn. The 7500cs reaction cell uses simple gases to remove interferences, so avoiding the formation of new interfering cluster ions that are observed with highly reactive gases. The ORS cell combined with an innovative ion optic provides high sensitivity and low ppt Background Equivalent Concentrations (BECs) for all of these key analytes and easily ionized elements (EIEs) such as Li, Na, and Cr while operating the ICP source at high RF power. The 7500cs also features an analyzer with hyperbolic rods, a detection system that operates simultaneously in analog and pulse-counting modes and operating software that includes Multi-tune functions for easy set-up and analysis.

Agilent 7500cs Inductively Coupled Plasma Mass Spectrometer (ICP-MS) Data Sheet
Agilent Technologies, Inc., Application Note 5988-8991EN, 3/2003 [link]

The 7500cs is the successor to the Agilent 7500s – the most widely used ICPMS in the semiconductor industry. The sample introduction system comprises a quartz torch and quartz double-pass spray chamber fitted with a MicroFlow PFA nebulizer. A PFA inert kit is also included for use with HF containing matrices.

The control of impurity levels in silicon-based semiconductor devices is critical because even ultratrace amounts of impurities, including alkali and alkali-earth elements and transition metals, can cause defects such as voltage breakdown or high dark current. For quality control purposes, there are two types of silicon that are routinely analyzed, bulk silicon and the surface of silicon wafers. Bulk silicon analysis can be performed by totally digesting the silicon using a very aggressive acid. Vapor phase decomposition is the most common method used for the analysis of silicon wafers. For bulk silicon analysis, sample volume is not an issue; however, small sample volumes are desirable in order to minimize time-consuming sample preparation. For the analysis of silicon wafers, impurities on the wafer surface are collected using a very small amount of acid deposited on the surface as a droplet. This results in a typical sample volume of around 200 µL. Both types of silicon analysis require the ability to handle small sample volumes and high silicon matrices, as well as a hydrofluoric (HF) acid-resistant sample introduction system. Since a typical analysis may take 2–3 minutes per sample, low-flow nebulizers with sample uptake rates from 40–100 µL/min are routinely used.
Adding to the complexity of the analysis for silicon impurities is the fact that many of the critical analytes are difficult to analyze by inductively coupled plasma mass spectrometry (ICP-MS) because they suffer from plasma-based molecular and isobaric interferences such as ArO, ArH, and Ar. Cool plasma has previously been used to reduce these nterferences. However, the amount and type of sample introduced into the plasma plays an important role in the performance achievable using cool plasma conditions. When low-flow nebulizers are used with cool plasma, the low sample flow rate does not cool the plasma enough to eliminate the Ar and ArH interferences, resulting in higher backgrounds for Ca and K, respectively. In addition, cool plasma suffers from severe matrix suppression with high matrix samples because the plasma is insufficient to break up the sample matrix. As a result, the method of standard additions (MSA) calibration is often used. MSA has many disadvantages, such as being a time-consuming procedure, requiring multiple sample aliquots, and acid blank contamination levels cannot be subtracted. This combination of factors makes the analysis of high silicon samples with cool plasma difficult due to matrix effects and the inability of cool plasma to reach the necessary detection limits.

Metallic impurities in semiconductor grade phosphoric acid were determined by a newly developed high sensitivity reaction cell ICP-MS. The Agilent 7500cs ICP-MS features an Octopole Reaction System (ORS) for interference removal. 85% (w/w) phosphoric acid (H3PO4) was diluted 100 fold then analyzed for SEMI specified elements. Detection limits were in the 0.06-28ppt range, even for elements that suffer P-based interferences like Ti, Cu and Zn. Excellent spike recovery data at the 50 ppt level is also presented.

The drive for more compact integrated circuits and smaller electronic devices has put very stringent demands on suppliers of high purity chemicals used in the semiconductor manufacturing process. In order to reduce defects and increase yield, lower trace element contamination levels are being required in all process chemicals, especially as initiatives like the International Technology Roadmap for Semiconductors (ITRS) (1) are setting the course for the next generation of semiconductor devices. Of particular significance are contamination issues associated with high purity acids, because their aggressive dissolution properties make them prone to "pick up" metal from other sources. In addition, they are often used in large quantities with other chemicals to dissolve metals from the surface of silicon wafers, to build a layer of silicon dioxide on top of the silicon substrate, or as an etchant. For these reasons, trace element purity levels in concentrated mineral acids must be monitored very closely.
Two of the most important acids used in the manufacture of semiconductor devices are phosphoric (H3PO4) and sulfuric (H2SO4) acids. Even though trace element purity levels are not as strict for acids such as hydrofluoric (HF) and hydrochloric (HCl), they are still low enough to present problems for the analytical techniques being used. The major difficulties are related to their extremely high acid concentration (phosphoric acid is ~85% w/v and sulfuric acid is ~98% w/v), which produces corrosion problems and very high specific gravity (phosphoric acid is 1.70 g/mL and sulfuric acid is 1.83 g/mL), which in turn produces sample viscosity effects. In addition, when inductively coupled plasma mass spectrometry (ICPMS) is required to analyze the highest purity acids, the phosphate (PO4) and sulfate (SO4) matrices generate a significant number of plasma-based ionic species, which interfere with many of the analyte elements.

Manufacturing processes of semiconductor devices require a variety of chemicals and materials, which must be ultra pure because the presence of impurities degrades the performance of the resultant devices. Cationic impurity levels in these chemicals have been commonly determined by ICP-MS because of its ability to perform ultra trace level analyses. Unfortunately, some important common contaminants, such as potassium, calcium, and iron, suffer from plasma-generated polyatomic interferences. A possible solution to this problem is the use of cool plasma. With this technique, the energy of the plasma is lowered, thus minimizing the formation of species with higher ionization potentials, such as Ar, ArH, and ArO, while elements with lower ionization potentials (i.e., K, Ca, and Fe) are effectively ionized. In this way, the plasma-based interferences on K, Ca, and Fe are reduced, and these analytes can be determined at lower parts-per-trillion (ppt) levels.
However, there are drawbacks to the cool plasma technique, mainly due to the lower plasma energy. The problems associated with cool plasma analysis can be circumvented with Dynamic Reaction Cell‘ (DRC‘) ICP-MS. This technique uses a hot, high-energy plasma for all analytes. The DRC eliminates interferences by simultaneously employing two techniques: chemical resolution and dynamic bandpass tuning (DBT). Chemical resolution involves the use of a gas within the DRC, which reacts with the interference to completely eliminate it. At the same time, DBT is applied. DBT acts as a mass filter, thus preventing the formation of species that may interfere with the analytes.
In this paper, DRC-ICP-MS was used for the determination of various chemicals used in the semiconductor industry. Several benefits of hot plasma with DRC are also discussed.

The manufacturing processes of semiconductor devices require a variety of chemicals which must be ultrapure because the presence of impurities degrades the performance of the resultant devices. Impurity levels in these chemicals are usually determined by ICP-MS because of its ability to perform low-level analyses. Unfortunately, some important analytes, such as potassium, calcium, and iron are present at parts-per-trillion levels and suffer from plasma-generated polyatomic interferences. As a result, determination of these elements is difficult.
For the past several years, cool plasma has been used to reduce these interferences. With this technique, the energy of the plasma is lowered, thereby minimizing the formation of species with higher ionization potentials, such as Ar, ArH, and ArO. Yet elements with lower ionization potentials (e.g., K, Ca, and Fe) are effectively ionized. In this way, the plasma-based interferences on K, Ca, and Fe are reduced, and these analytes can be determined at low levels. However, drawbacks to the cool plasma technique exist, mainly because of the lower plasma energy. Due to the fact that some important analytes have high ionization potentials (e.g., boron and zinc) or strong bond energies with oxygen (e.g., titanium and tungsten), the lower plasma energy of cool plasma prohibits their ionization or decomposition and, therefore, analysis. As a result, these analytes must be analyzed separately with a hotter, more energetic plasma.
Another problem with coolplasma is that analyte sensitivity is greatly affected by sample matrix and acid concentration. To overcome this limitation, the method of standard additions, matrix-matched calibration standards, or sample pre-treatment must be used for quantitation. Although acid content and matrix effects can be minimized through dilution, the very low analyte levels prohibit extensive dilutions.

High sensitivity (>1´106 cps ppb-1 In), high mass resolution (10, 000) and stable mass response curve are attributes of sector field ICP-MS (ELEMENT) that make it the instrument of choice for most trace metal marine geochemists. Quantification of particulate (>0.45mm) and dissolved (<0.45mm) trace elements in natural waters is imperative for understanding their geochemical cycling in the environment. Over the past 6 years we have developed several methods for the determination of dissolved and particulate trace metals in marine, estuarine and fresh water samples. Key to all of these methods is the sample introduction system's and instrument's compatibility high TDS samples and ability to obtain low blanks. A stable mass response curve allows for simple, yet precise and accurate standardization. Using a method of pseudo-standard additions, combined with a single element drift monitor yields excellent precision and accuracy (<± 5%) for all sample matrices. Furthermore, with appropriate sample introduction systems (guard electrode, MCN-6000, Cetac, PFA nebulizer and spray chamber, Elemental Scientific) high sensitivity (>2´106 cps ppb-1 In) and low blanks (eg. Fe = 3.8 ppt and Pb = 0.09 ppt) can provide unprecedented detection limits (eg. Fe = 0.81 ppt and Pb = 0.014 ppt). A brief overview of the methods will be presented and their applicability to natural system will be demonstrated using examples from the Hudson River estuary, New Jersey coast, open ocean surface waters, hydrothermal vents and Lake Superior.

This application note describes the determination of metallic impurities in semiconductor-grade hydrogen peroxide (H2O2) at the proposed Semiconductor Equipment and Materials International (SEMI) Tier D level by inductively coupled plasma mass spectrometry (ICP-MS). The Agilent 7500s ICP-MS system featuring Agilent's exclusive ShieldTorch System was used to determine all 21 elements currently proposed by SEMI for monitoring at the 10-ppt level directly in 35% (w/w) H2O2. The combination of the Agilent 7500s, robust 27-MHz RF plasma generator, Omega II off-axis ion lens assembly, high-sensitivity ShieldTorch System, and inert sample introduction system (Elemental Scientific, Omaha , NE ) provided excellent signal/background resulting in exceptional detection limits for all elements. Quantitative spike recoveries at the 5-ppt level, 50% of the proposed maximum level of 10-ppt as per SEMI methodology, indicated excellent measurement accuracy. This further highlights the suitability of the Agilent 7500s for the determination of all SEMI required elements in H2O2 at both current and future required purity levels.

This application note describes the analysis of metallic impurities in semiconductor grade hydrofluoric acid by inductively coupled plasma mass spectrometry (ICP-MS). The Agilent 7500s ICP-MS instrument with its ShieldTorch Technology was used to analyze 38% (w/w) hydrofluoric acid (HF) directly for all of the elements commonly required by the semiconductor industry. Combined with the high sensitivity characteristic of the ShieldTorch System, the off-axis ion lens assembly utilized in the Agilent 7500s provided excellent signal/background resulting in exceptional detection limits for all elements (0.02 – 5 ppt range). Excellent spike recovery data at the 5 ppt level further highlights the suitability and accuracy of the Agilent 7500s for the determination of all SEMI required elements in HF at ultra-trace levels.

The elemental and isotopic analysis of uranium in urine has been previously used to monitor contamination in workers from nuclear power plants and, more recently, in military personnel exposed to depleted uranium used in modern munitions.
The quantification of uranium in urine is complicated by:
- the low concentrations found in urine
- variable amounts of salts in urine.
The second point makes the matrix matching of standards to samples for direct analysis impossible and, in order to normalize all samples to a similar matrix, the analysis of a diluted (or digested) solution is preferable. High instrumental sensitivity is then required to reliably measure the resulting single digit pg g-1 uranium concentrations.
While the quantification of uranium is therefore demanding in the diluted sample, uranium isotope ratio determination requires the ultimate in instrumental performance as good precisions for large isotope ratios are required at low concentrations. The abundances of the three naturally occurring U isotopes are shown in Table 1, together with the 234U/238U and 235U/238U ratios. The nuclear industry removes the majority of 235U and 234U for use in nuclear fuel rods, leaving behind “depleted uranium” (DU). This material typically has a 235U/238U ratio of 0.0025, and therefore an increased 238U abundance of approximately 99.75%. In the diluted urine sample matrix however, this analysis is further complicated as minute contaminations of isotopically enriched or depleted uranium must be identified in a much larger quantity of isotopically normal uranium - all this at the pg g-1 level.
This report summarizes examples of both concentration and isotopic uranium analyses in urine. All analyses were performed on the Thermo Finnigan ELEMENT2, a single collector double focusing ICP-MS that provides high sensitivity, low background, an extended dynamic range (pre-requisites for quantification over a wide range of uranium concentrations) and flat top peaks (required for precise and accurate isotope ratio measurements). The detection range and isotope capabilities of such instrumentation allow the monitoring of uranium related environmental pollution from natural uranium, DU (munitions, armor) or enriched uranium (nuclear processing plants) by analyzing total uranium content or/and its isotopic composition.

Ruthenium isotopic data for a pure Aldrich ruthenium nitrate solution obtained using a Nu Plasma multi collector inductively coupled plasma-mass spectrometer (MC-ICP-MS) shows excellent agreement (better than 1 e unit = 1 part in 104) with data obtained by other techniques for the mass range between 96 and 101 amu. External precisions are at the 0.5–1.7 e level (2s). Higher sensitivity for MC ICP-MS compared to negative thermal ionization mass spectrometry (N-TIMS) is offset by the uncertainties introduced by relatively large mass discrimination and instabilities in the plasma source-ion extraction region that affect the long-term reproducibility. Large mass bias correction in ICP mass spectrometry demands particular attention to be paid to the choice of normalizing isotopes. Because of its position in the mass spectrum and the large mass bias correction, obtaining precise and accurate abundance data for 104Ru by MC-ICP-MS remains difficult. Internal and external mass bias correction schemes in this mass range may show similar shortcomings if the isotope of interest does not lie within the mass range covered by the masses used for normalization. Analyses of meteorite samples show that if isobaric interferences from Mo are sufficiently large (Ru/Mo < 104), uncertainties on the Mo interference correction propagate through the mass bias correction and yield inaccurate results for Ru isotopic compositions. Second-order linear corrections may be used to correct for these inaccuracies, but such results are generally less precise than N-TIMS data.

Precise isotopic analysis of Li is required in a number of different applications, including geochemistry and nuclear sciences. Thermal ionization mass spectrometry (TIMS) is the preferred technique used for precise measurements of the 7Li/6Li. Recently, Tomascak et al. (1999) presented a new method for Li isotope analysis using Multi Collector Magnetic Sector Inductively Coupled Plasma Mass Spectrometry (MC-ICPMS). Here, we report on the short-term reproducibility of Li isotope analyses of NIST L-SVEC lithium carbonate standard and two international rock standards, BHVO-1 (USGS) and JG-2 (GSJ) with the Thermo Finnigan Neptune MC-ICPMS.

The Sm-Nd and Lu-Hf isotope systems are widely used as dating tools and geochemical tracers to provide important information in geo- and cosmochemistry. Because of recent technological development, multicollector-inductively coupled plasma mass spectrometry (MC-ICPMS) has now gained acceptance in the geoanalytical community. In particular, interest in Hf analysis with MC-ICPMS has increased as the inductively coupled plasma (ICP) ion source offers improved ionization over traditional thermal ionization (TI). This allows precise Hf isotopic determinations on small sample amounts. Additionally, sample throughput is significantly increased and preparation simplified, compared to what was previously required for TI mass spectrometry (TIMS). The Thermo Finnigan NEPTUNE is a new double focusing high resolution MC-ICPMS, based on the high precision multicollector technology from the TRITON, (the latest Thermo Finnigan TIMS) and the advanced and proven ICP source and transfer optics from the ELEMENT2 (the latest Thermo Finnigan HR-ICPMS).
This report describes the short- and long-term performance of the NEPTUNE . The short-term reproducibility is demonstrated by the measurement of a Nd standard solution over three and a half hours. The long-term reproducibility of Hf isotope composition measurements is demonstrated for a Hf standard solutionthat was repeatedly measured over a nine-month period.

High-resolution sector-field ICP-MS is used to quantify seventeen elements at trace levels in blood, serum and urine samples. High mass resolution was used to unequivocally identify matrix induced polyatomic interferences. The range and complexity of the interferences observed required the use of medium resolution (R = 4000) to ensure the accurate analysis of Al, Cd, Co, Cr, Cu, Fe, Mn, Mo, Ni, Sb, Tl, V, and Zn, and high resolution (R = 10000) for As and Se. Low resolution analysis was possible for the non-interfered Bi and Pb. The analysis of all isotopes was made within a single sampling with no change in instrument operating conditions, besides the choice of resolution mode.
The sample preparation method used was a simple 50-fold dilution with a TMAH/HCl mixture and addition of internal standard. Because of the high instrumental sensitivity of the ELEMENT2 (> 20 kcps/ppb In at R = 10000) a relatively large dilution factor of 50 can be used. As a result of this dilution of the sample matrix, all samples could be quantified by external calibration using aqueous solutions, and clogging of the sample introduction system was minimized. Precision for all elements was 2 - 10 % RSD, and the results fell within the certified range for the reference controls studied (Biorad urine and Seronorm whole blood).

The ELEMENT2, a high-resolution sectorfield ICP-MS, is used to determine sub-ppb levels of metal contaminants in liquid crystal. The liquid crystal sample is dissolved ( 1:20 m/m) in an organic solvent (propylene glycol methyl ether, PGME) for analysis. Instrumental sensitivity in the organic diluent is identical to that in dilute nitric acid (>1000 cps per pg/g (ppt) In). High mass resolution is used for the analysis of ten of the fifteen elements determined due to the presence of matrixinduced polyatomic interferences. Detection limits in the PGME solvent are between 0.7 to 50 pg/g for the elements determined.

High-resolution sector-field ICP-MS in both hot and cold plasma operating conditions is used to determine sub-ppb levels of metals in semiconductor grade 0.3N TMAH developer. Instrumental sensitivity in the TMAH matrix is identical to that in dilute nitric acid with >1000cps per ppt (ng/g) In. High resolution was used to determine the existence of matrix induced polyatomic interferences. The interferences found were of sufficient severity that high resolution had to be used for the analysis of ten of the fifteen trace metals elements investigated. By means of computer controlled switching between low and high resolution and hot and cold plasma conditions, interference-free analysis was possible during a single analysis. Detection limits in TMAH ranged from 0.1ppt for Li to 9ppt for Cu.

The ELEMENT2, a single collector double focusing sector field ICP-MS, was used for the determination of Sr/Ca and Mg/Ca elemental ratios in microgram samples taken from seasonal growth bands in a coral skeleton (Diploria strigosa). Variations in d18O values were found to be in good agreement with the results for Sr/Ca and Mg/Ca elemental ratio determinations. As shown in a previous Finnigan Flash Report (Finnigan MAT Flash Report No. E4), the ELEMENT2 provides a higher sample throughput compared to TIMS while providing precision of better than 0.1 % RSD for both Sr/Ca and Mg/Ca elemental ratios. Compared with ICP-AES, major and trace elements can be analyzed simultaneously.

A simple and rapid procedure for routine high precision measurement of Sr/Ca and Mg/Ca elemental ratios is presented. The ELEMENT2, a single collector double focusing ICP-MS, was used to measure Sr/Ca and Mg/Ca elemental ratios in microgram samples of corals. The concentrations of Sr, Mg and Ca were determined using external calibration with 103Rh as internal standard. The calibration curves had correlation coefficients > 0.99996 (Fig. 1). The external precision of Sr/Ca and Mg/Ca was 0.07 % RSD. The analysis time for the determination of both ratios in a single sample (5 replicate analyses) was 12 minutes.

Sector Field ICP-MS enables routine clinical laboratories to accurately determine trace element concentrations in human body fluids and tissues1-3. The ELEMENT2 offers the mass resolution necessary to eliminate interferences from the matrices normally unfavorable for ICP-MS, and has the sensitivity required for ultra-trace element analysis. The method described here for a set of evaluation samples, is currently in use at ERASMUS hospital, Bruxelles , Belgium , for a suite of elements commonly regarded complicated for ICP-MS analysis. The results presented in this paper were obtained from a set of evaluation samples. The requirements for introducing the ELEMENT2 at ERASMUS hospital were:
- Rapid analysis from ultra-trace to matrix concentration levels
- Reliable separation of the matrix-induced interferences from smallest amounts of analytes
- Easy sample preparation method suitable for introducing all clinical sample types (blood, serum, urine) for ICP-MS analysis
- Routine capability and automation suitable for a sample throughput of >100 samples per day

We report a method for the rapid ultra-trace (v1 ppb to v 1 ppt) quantification of P, V, Cr, Mn, Fe, Co, Ni, Cu, Zn, Y, Mo, Cd, Re, Tl and Pb in fresh water. High sensitivity (w2 6 106 cps ppb21 In) combined with a careful blank control provide unprecedented detection limits (e.g., Fe ~ 0.81 ppt and Pb ~ 0.014 ppt) that are approximately 10 fold better than previously published methods. Such low detection limits are required for the investigation of biogeochemical cycling of elements in some natural systems. One example is Lake Superior, where dissolved trace element and phosphorus concentrations in offshore waters are all less than 1 ppb, with some metals (such as Co, Re, Tl and Pb) reaching levels lower than 1 ppt. Depth profiles from Lake Superior exhibit the lowest concentrations of certain metals (Fe, Mn, Co, Zn, Re, Tl and Pb) ever measured in natural fresh waters. The precision of the method is better than ¡20% (2s) for all analytes of interest except Co (30%; 2s) and accuracy determined from the analysis of certified reference material SLRS-4 indicates excellent (within certified 2s) agreement for all elements.

Precise and accurate determination of calcium isotope ratios in urine is imperative in limiting the expense of enriched isotopes used in human metabolic tracer studies. The calcium isotope spectrum obtained from an ICPMS (using conventional spray chamber), operated in low resolution mode (LR ~ 300), is subject to numerous polyatomic, isobaric and doubly charged interferences. The most severe polyatomic interfences can be resolved at resolutions greater than 3500, whereas, isobaric and doubly charged interferences are easily corrected. Precise (v0.1% 1s) isotope ratios, however, are not routinely obtained in medium resolution (MR ~ 4300). Here we use a HR-ICP-MS in MR to identify and determine methods to reduce polyatomic interferences. Using oxalate precipitation of urinary calcium and desolvation sample introduction, interferences can be reduced sufficiently to allow determination of the 42, 43, 44, 46 and 48 isotopes of calcium with the precision of LR. Isotope ratio precision and accuracy is v ¡0.1% (1s) for analysis of three isotopes (42, 43, and 44), as required for clinical studies. Propagating this level of uncertainty indicates that w4% enrichments provide v ¡10% (2s) uncertainty in the calculated fractional calcium absorption values. Minimizing unnecessary enrichments can increase the number of subjects in studies without increasing the substantial cost of enriched isotopes. This new analytical method is applied to our on-going clinical trials where 0.017 mg kg21 of 42Ca (90.8%; intravenous, IV) and 0.012 mg kg21 43Ca (52.1%;oral) administered to postmenopausal women show average 24 h (pooled) urinary enrichments of 5.0% and 5.1% from the intravenous and oral doses, respectively.

Understanding the trace metal marine geochemistry of temporally variable coastal systems requires intensive sampling programs with attendant analytical burdens. Most established techniques for multi-element trace metal determinations are slow, require a skilled chemist, and are not easily automated. Advances in sample introduction systems and ICP-MS instrumentation now provide marine chemists with the sensitivity and mass resolution necessary to determine many trace metals at natural concentrations in coastal seawater. A new method has been developed for the rapid (10 samples h−1) determination of V, Cr, Mn, Fe, Co, Ni, Cu, Zn, Cd and Pb in diluted seawater, requiring just 50 mL of seawater and no reagents other than pure nitric acid. A sensitivity of 800 000–1 200 000 cps ppb−1 86Sr in a 10% sea water matrix is obtained when microconcentric desolvating nebulization is combined with a shielded torch and hot plasma high resolution ICP-MS. Analyses are standardized by a matrix-matched external calibration curve with variations in sensitivity corrected by normalizing to the natural internal standard Sr, a conservative ion in seawater. The method thus depends on mass bias stability for each analyte relative to Sr, which was examined as a function of forward power and matrix and found to be optimized at 1100–1350 W. Precision and accuracy are limited by appropriate correction for blanks, which derive mainly from the ICP-MS introduction system, and are equivalent to about 10% of typical coastal seawater concentrations for these metals. Preliminary evaluation of a new low-flow nebulizer (MicroFlow PFA nebulizer, Elemental Scientific, Omaha , NE , USA ) suggested lower blanks and compatibility with solutions high in total dissolved solids compared with standard microconcentric designs. Determination of dissolved concentrations in reference seawater (CASS-3) demonstrate very good agreement with certified values (within 95% confidence limit) and a precision of 3–12% (1s) for all elements except Cr (15%). The utility of the method is demonstrated by the determination of spatial trends for these metals in a transect of seawater samples from shelf waters off southern New Jersey , USA . The new technique is sufficiently sensitive to determine some of these metals in open ocean seawater and, with minor modifications, should be applicable to a larger suite of analytes in a wide variety of natural waters.

On-line measurement of chemical baths located within a manufacturing site has several advantages over the traditional method of sample gathering. Imagine a situation where a chemical contamination is suspected in a chemical bath located within a semiconductor manufacturing site. To check for this contamination using ICP-MS technology located in a laboratory would require several time consuming steps. First, a laboratory person must be called by a person working at the chemical bath. The laboratory person would need to gown up, approach the chemical bath to collect the sample, remove the gown to exit the manufacturing site, then carry the sample to the laboratory for analysis. This could easily result in an hour or more elapsing before the sample results could be sent back to the person at the chemical bath. The time elapsed could be very costly in either down time or in poor product quality. A system that would continuously monitor the chemical in the bath and keep the operator informed of any contaminations that may be present could significantly improve productivity.