Magnetic Sector Inductively Coupled Plasma Mass Spectrometry Research Articles

Analysis of Mn, Fe, Co, Ni, Cu, Zn, Cd, and Pb in seawater using the Nobias-chelate PA1 resin and magnetic sector inductively coupled plasma mass spectrometry (ICP-MS)

A method was developed using the chelating resin Nobias-chelate PA1 in an off-line pre-concentration manifold with magnetic sector inductively coupled plasma mass spectrometry (ICP-MS) detection for analysis of Mn, Fe, Co, Ni, Cu, Zn, Cd, and Pb. This multi-element method allows for the simultaneous extraction of eight samples in a closed column manifold. Standard additions to seawater demonstrated quantitative recovery and eliminated the need to use isotope dilution to account for non-quantitative recoveries of the metals on the resin. UV-oxidation of seawater samples before extraction was necessary to provide accurate total dissolved concentrations of Co and Cu. Samples (40mL) were loaded onto the chelating resin column at a pH of 6.2±0.3 after pH adjustment with a basic ammonium acetate (NH4Ac) solution. The columns were rinsed after sample loading with a weak (0.05M) NH4Ac solution to remove the bulk of the major ions in seawater. The trace metals were eluted with 3 to 4mL of 1N Q-HNO3 and analyzed on a magnetic sector ICP-MS. This multi-element method is ideal for high sample throughput and quantification over a broad range of element concentrations with low blanks and detection limits. We report results here from the SAFe and GEOTRACES reference samples as well as the U.S. GEOTRACES Atlantic and Pacific Baseline profiles.

The evolution and applications of multicollector ICPMS (MC-ICPMS)

Inductively coupled plasma mass spectrometry (ICPMS) instrumentation has evolved rapidly in the 25 years since the introduction of the first commercial ICPMS instruments. All possible analyzers have been explored (and many commercialized), including magnetic sector (single and double focusing), time of flight, ion trap, triple quadrupole, Fourier transform ion cyclotron resonance (FT-ICR), and Orbitrap, as well as various hybrid analyzers. ICPMS instruments predominantly use quadrupole mass filters, but magnetic-sector ICPMS, in the form of single collector (HR-ICPMS) and multicollector (MC-ICPMS), has garnered a significant portion of the market. Since the introduction of the first MC-ICPMS in 1992 (the Plasma 54 from VG Elemental), 190 MC-ICPMS have been installed in 170 different labs worldwide. The initial hope for MC-ICPMS was that it would simplify measurements normally made with thermal ionization mass spectrometry (TIMS) (e.g., Pb, Sr, Nd, U, Th, Pu, Os) by marrying the favorable characteristics of an ICP source with the precision that can be attained with a multicollector array. While this goal has been largely met, if not exceeded, exploration of the periodic table with MCICPMS has led to the discovery of small but meaningful isotopic variations in nature in a number of elements that were hitherto not accessible or were difficult to analyze. This field is sometimes referred to as “non-traditional stable isotope geochemistry” [1], in contrast to “traditional” stable isotope geochemistry which encompasses the isotopic variations of HCNOS [2], and it includes elements from Li to U. MC-ICPMS, increasingly an essential analytical technique in isotope geoand cosmochemistry, is also expected to find widespread acceptance in other disciplines, such as environmental biology, biochemistry, ecology, and archaeology, to name but a few.

Application of transition metal isotope tracers in global change research

High-precision isotope composition determinations using multicollector, magnetic-sector inductively coupled plasma mass spectrometry (MC-ICPMS) have recently revealed that some transition metal isotopes such as those of Mo, Fe, Cu, Zn etc. can be used as biogeochemical tracers in global change research. The Mo isotope system may be useful in paleoredox investigations indicating that δ97/95Mo in seawater may co-vary with changes in the relative proportions of anoxic and oxic sedimentation in the ocean, and that this variation may be recorded in δ97/95Mo of anoxic sediments. The Mo continental flux into the oceans and the global Mo isotope budget can be estimated from δ97/95Mo values. The Fe isotope composition in seawater is an important issue because Fe plays a controlling role in biological productivity in the oceans and its abundance in seawater may have substantial effect on climate changes. Iron isotope fractionations could result from bio- and abio-processes and have about 0.1% variation (δ56/54Fe), so Fe isotopes considered alone cannot be used to distinguish the products of abiotic and biotic Fe processing in geological records. Cu and Zn isotopes are also used as biogeochemical tracers, but the researches are relatively less. This review mainly focuses on the methods for preparation, purification and determination, of new isotope tracer samples, and on isotope applications in marine environmental changes.

Comparison of methods for the determination of total selenium in plasma by magnetic sector inductively coupled plasma mass spectrometry

Three sample preparation methods (dilution, microwave digestion and ethanol addition) were evaluated for the determination of Se in human plasma using magnetic sector inductively coupled plasma mass spectrometry (ICP-MS). A number of instrumental parameters were also considered, namely the choice of internal standard (Sc, Rh, In) and pre-defined spectral resolution ( m/Δ m ∼300 (low resolution, LR) and ∼7500 (high resolution, HR)). The isotopes 77 Se and 82 Se were selected for analysis avoiding the major and unresolvable Ar dimer interferences associated with other Se isotopes. Ethanol addition was found to be the most suitable and reliable sample preparation method. The optimum ethanol concentration for a 1+9 dilution of the plasma sample was 0.5% (v/v). Indium or Sc were selected over Rh as internal standards as Seronorm™ Level 1 target values were achieved at lower concentrations of ethanol modifier. Representative ICP-MS detection limits for this method using 77 Se (HR) and 82 Se (HR), were 0.1 and 0.2 μg l −1. Accurate analysis of Se in Seronorm™ Level 1 (MI0181) was found using either 77 Se or 82 Se and HR (86±5 and 83±5 μg l −1 respectively, n=5, In internal standard, target value=83±6 μg l −1). Although offering improved precision (e.g. 82 Se LR: 0–3% versus HR: 1–6%), accurate results were only obtained with LR for the Seronorm™ Level 1 sample when using 82 Se (86±1 μg l −1). The major 40 Ar 37 Cl interference precluded accurate Se analysis using 77 Se and LR for all samples considered. Reliable Se concentrations were only found for a “real” pooled sample when using 82 Se (HR), in part a result of non-negligible and unresolved 81 Br 1 H interference when using LR. Consistently elevated Se concentrations were found under all conditions when Seronorm™ Level 2 (NO0371) was analysed. These results were confirmed by independent GF-AAS analysis. Magnetic sector ICP-MS with 82 Se (HR), in combination with the ethanol addition sample preparation method, was used for the analysis of Se in human plasma samples as part of a small pilot study. Average measured selenium concentrations were 102±18 μg l −1 ( n=18).

Further investigations on optimized tail correction and high-precision measurement of uranium isotopic ratios using multi-collector ICP-MS

In the present paper, we further examine the optimum conditions for rapid, precise and accurate determination of 234U/ 238U ratios in geological materials by multiple collector (magnetic-sector) inductively coupled plasma mass spectrometry (MC-ICP-MS). In our experiments, isotopic measurements were performed on a Micromass IsoProbe™ instrument, using Faraday collectors in static mode only. Unlike the ion counting system coupled with an energy filter, this technique eliminates the difficulty of proper calibration of the Daly/Faraday gain ratio. On the other hand, since our Micromass instrument has a poor abundance sensitivity (the proportion of the 238U ion beam measured at mass 237 is ∼25 ppm), the major issue to be addressed is the tail correction. For this purpose, we have developed a tail correction method slightly modified from Thirlwall [J. Anal. At. Spectrom. 16 (2001) 1121]. This method is based on correction of the actual tail contribution under each peak, as assessed by the tail shape measurements on mono-isotopic ion beams, instead of the usual half-mass zeroes baseline estimation. Our approach enabled us to correct for the large offset that can be observed on isotopic data when tail correction is done by means of linear interpolation between half-mass zeroes, and showed that this latter tail correction method results in nearly 3% underestimation of 234U/ 238U ratios on the GEOTOP IsoProbe™ for material at secular equilibrium. A 236U– 233U double spike was employed to correct for mass discrimination bias. Using an Aridus™ micro-concentric, desolvating nebulizer sample introducing system, a minimum of 200 ng of sample-U was consumed to carry out a precise 234U/ 238U analysis, thereby allowing a 234U signal of ∼4–5 mV to be monitored for 50 measurement cycles of 5 s each. This time-consuming, 10-min procedure allowed us to obtain an external reproducibility of 0.8‰ (2 σ) for isotopic measurements of the NBL-112a standard solution. Replicate measurements of this reference material yielded a mean δ 234U value of −36.42±0.80‰ (2 σ, n=19), which is highly consistent with values reported by other laboratories. The total reproducibility, including both chemical separation and spectrometric measurement, was assessed using geological samples (a coral and a carbonate rock); the long-term reproducibility obtained was about 1.3‰ (2 σ).

Automation of a flow injection system for the determination of dissolved silver at picomolar concentrations in seawater with inductively coupled plasma mass spectrometry

An automated flow injection system for the determination of dissolved silver at ultratrace concentrations in seawater, and controlled under LabVIEW™, is described. The flow injection system allows online processing of seawater samples before their analysis using a magnetic sector inductively coupled plasma mass spectrometry (MS-ICP-MS) instrument. Samples were analysed with a minimum amount of manipulation, thereby reducing the risk of contamination. In addition, the flow injection approach with incorporation of an anion exchange minicolumn allowed ready removal of analytical interferences caused by the saline matrix. The software allowed full control of all flow injection components (valves and pumps) and removed manual time control and, therefore, operator errors. The optimized system was capable of five sample injections per h, including preconcentration and wash steps. The limit of detection was 0.5 pM for a 240-s sample load time, which allowed the determination of dissolved silver in open ocean waters, where picomolar concentration levels are typically encountered.

Trace Element Microanalysis in Iron Meteorites by Laser Ablation ICPMS

A laser ablation microanalysis system has been developed that can analyze trace elements with a sensitivity in the ppb range, using a CETAC LSX-200 laser ablation system with a Finnigan Element. This capability has been applied to a set of iron meteorites to demonstrate the laser microprobe's analytical capability for the determination of platinum group elements (PGEs) with a spatial resolution of ∼20 μm, comparable to that of dynamic secondary ion mass spectrometry (SIMS). The laser is shown to provide an accurate means of solid sampling for magnetic sector inductively coupled plasma mass spectrometry (ICPMS), allowing the determination of bulk metal composition, chemical zoning within the sample, and depth profiling. Recovery of the chemical zoning in taenite lamellae was achieved for Ru, Rh, and Pd, which was not previously possible using SIMS. The methods presented here show that magnetic sector ICPMS can be successfully coupled to a laser ablation system, providing the advantages of higher sensitivity of the sector instrument, low background count rates (<0.1 counts/s), and flat-topped spectral peaks, while minimizing tradeoff against the speed of data acquisition required to handle the transient signals from the laser ablation system.