Coupled Plasma Mass Spectrometric Method Research Articles

Comparison between hydride generation and nebulization for sample introduction in the determination of lead in plants and water samples by inductively coupled plasma mass spectrometry, using external calibration and isotope dilution

Four inductively coupled plasma mass spectrometric methods: nebulization sample introduction with external calibration; hydride generation with external calibration; isotope dilution with nebulization; and isotope dilution with hydride generation, have been tested and compared. Multimode Sample Introduction System (MSIS™) was employed in either nebulization or hydride generation mode. Best limits of detection (below 0.1 μg L − 1 ) and accuracy were obtained for isotope dilution techniques in hydride generation and sample nebulization mode. A mixture of HNO 3 and H 2O 2 served both for microwave-assisted digestion as well as a medium for subsequent plumbane generation. Optimal reagent concentrations for hydride generation stage were 0.1 mol L − 1 HNO 3, 0.28 mol L − 1 H 2O 2 and 1.5% m/v NaBH 4. Critical effects of acidity, blanks and concomitants have been discussed. Analytical methods were validated by use of plant and water certified reference materials and spiked high-salt solutions (seawater and 20% m/v NaCl) at lead levels in nanograms per gram to micrograms per gram range.

Determination of Si in Standard Reference Material SRM 295x Silica-on-Filter

Respirable crystalline silica is an occupational hazard whose presence in the workplace is strictly regulated. A new series of Standard Reference Materials (SRMs) is being developed to assure the quality of silica measurements and to provide for accurate instrument calibration. SRMs 295x (the value x will designate a specific level of silica loading), Silica-on-Filter, have been prepared by gravimetric delivery of SRM 1878a Respirable Alpha Quartz onto individual filters. The silica on the filter has been verified indirectly by the measurement of the elemental silicon, taking advantage of the knowledge in the filter preparation. An HF acid digestion method has been developed for sample digestion, and a high-resolution inductively coupled plasma mass spectrometric method for the determination of silicon has been developed and validated.

A simple co-precipitation inductively coupled plasma mass spectrometric method for the determination of uranium in seawater.

Inductively coupled plasma mass spectrometry (ICP-MS) was used in the determination of 238uranium in seawater after concentration by a simplified co-precipitation with iron hydroxide. Ocean water and reference seawater were used in the study. The co-precipitation method required a smaller sample volume (10 fold less), and less column separation to recover the uranium from the seawater matrix, compared to the original iron hydroxide method. The direct seawater dilution technique requires only a small seawater volume (0.5 mL) and offers a rapid, reliable method for uranium analysis in seawater compared to traditional methods. Comparison of the results for simple co-precipitation, direct dilution of seawater, and theoretical uranium values based on salinity concentrations, yielded negligible differences. Data from this work show that the certified value for NASS-4 is low.

The determination of selenium in serum and urine by inductively coupled plasma mass spectrometry: comparison with Zeeman graphite furnace atomic absorption spectrometry

An inductively Coupled Plasma Mass Spectrometric (ICPMS) method for the determination of selenium in both serum and urine is described. 78Se is used analytically in spite of 38Ar40Ar isobaric interference at mass 78. Initially 82Se was monitored but, limited isotope abundance and therefore limited detection capability for urine selenium precluded continued use. An ethanol–Triton X-100-nitric acid diluent was used to dilute serum and urine and enhance selenium ionization so that both serum and urine can be analyzed with the same calibration curve. Results derived by the ICPMS method were compared with Zeeman Graphite Furnace Atomic Absorption Spectrometry (ZGFAAS) using nickel as the matrix modifier. Detection limits for ZGFAAS and ICPMS using mass 78 are 2.9 and 0.25 μg/l, respectively. ICPMS and ZGFAAS instrument responses were recorded for additions of inorganic selenium, trimethylselenonium iodide, seleno-dl-methionine, and seleno-dl-cystine to urine and serum. ICPMS slopes for all compounds added to urine and serum were found to be nearly identical. ZGFAAS response for each compound was more variable than ICPMS. ZGFAAS response for trimethylselenonium iodide was approximately 3-fold lower than for the other compounds. ZGFAAS regression slopes and correlation coefficients were 0.72 and 0.8139 for reference urine samples. ICPMS regression slope and correlation coefficient vs. the reference target values were 0.95 and 0.9700 for the same urines. Regressions slopes and correlation coefficients for reference sera were 1.01 and 0.9912 for ICPMS and 1.12 and 0.9648 for ZGFAAS. We conclude that ICPMS produced more accurate results than ZGFAAS for selenium in serum and urine.

Development of a ‘collect and punch’ cold vapour inductively coupled plasma mass spectrometric method for the direct determination of mercury at nanograms per litre levels

A highly sensitive ‘collect and punch’ CV–ICP-MS method for the direct determination of mercury at ng l–1 levels is described. Mercury, after reduction to elemental form with SnCl2, was collected in a glass chamber prior to injection into the plasma and the time resolved acquisition mode was used for signal measurement. This arrangement provided a 10–15-fold enhancement of sensitivity compared with continuous vapour injection. The detection limit (3s) of the method was close to 6 ng l–1. Linear calibration was obtained over three orders of magnitude of concentration. The method was validated through the analysis of NIST SRM 1566a Oyster Tissue. Mercury at the 50 ng l–1 level in aqueous solutions can be determined with a precision of approximately 2%. This method is much simpler than the amalgamation approaches for the determination of mercury at these levels.

Determination of technetium-99 in aqueous samples by isotope dilution inductively coupled plasma-mass spectrometry

An isotope dilution/inductively coupled plasma mass spectrometric method (ID/ICP-MS) for measuring the concentration of technetium-99 in aqueous samples was developed at the Savannah River Technology Center (SRTC). The procedure is faster than radiometric tecniques, is less subject to interferences, and has equal or better detection limits. It is currently being used to measure the concentration of99Tc in samples of Savannah River water collected in the vicinity of the Savannah River Site. In this method one liter samples of water are spiked with97Tc. After equilibration, the technetium is extracted from the sample with a chromatographic resin. Interfering elements, molybdenum and ruthenium, are either not retained by the resin or are washed off with, dilute nitric acid. The technetium is then eluted with more concentrated nitric acid, and the99Tc/97Tc ratio in the eluant is measured with an ICP-MS. The99Tc concentration in the original sample is calculated from the99Tc/97Tc ratio. The chemical recovery of the extraction procedure is greater than 90%. The detection limit of the instrument, taken as three times the background counts atm/z=99, is 0.6 part per trillion (ppt). The detection limit of the procedure, taken as three times the standard deviation of several reagent blank analyses, is 0.33 pCi/l.

Performance of inductively coupled plasma mass spectrometric methods used in the determination of trace elements in surface waters in hydrogeochemical surveys

The capability of ICP-MS in determining trace and ultra-trace elements at their natural concentrations in stream and lake waters is evaluated. The need to preconcentrate trace elements such as the first-row transition elements and REEs is demonstrated and figures of merit given for the chelation method employing the iminodiacetate resin, MetPac CC-1. For example, chelaton results in method detection limits of 0.1–1 ng l–1 for Cd, U and REEs, and improves precision of their measurement 2–5 fold at low ng ml–1 levels. Long-term quality control data for in-house and international standard water samples (SLRS-2, SLEW-1, CASS-2, NASS-3 and 1643C) are presented for both direct and chelation ICP-MS. Detection limits of 2–3 ng l–1 are achieved for Bi, Sb, Se and Te by HG-ICP-MS and field duplicate data show precision generally of the order of 10–20% RSD at levels below 100 ng l–1. Considerations with respect to filtration and preservation protocols for hydrogeochemical surveys are discussed. Field and laboratory (i.e., analytical) duplicate data indicate good precision for trace and ultra-trace elements, averaging 13% RSD across all the elements determined.

Tutorial review. Advanced electroanalytical techniques versus atomic absorption spectrometry, inductively coupled plasma atomic emission spectrometry and inductively coupled plasma mass spectrometry in environmental analysis

The challenge for the chemical industry in the 1990s and beyond is: (i) innovation and profitability, and (ii) environmental protection and safety. This is also true for analyses in which the needs are for simple, reliable and viable techniques. Analyses are costly, running costs especially can be very high. There are still too many poor quality analyses. The task of the analytical chemist is to choose the most appropriate procedure in order that the desired information about the particular material of interest can be provided. The pros and cons of advanced electroanalytical techniques versus modern atomic absorption spectrometric, inductively coupled plasma atomic emission spectrometric and inductively coupled plasma mass spectrometric methods commonly in use in industrial and technical laboratories are discussed. The features that make electroanalytical methods competitive techniques are: the very large useful concentration range (from 1 to 10–10 mol l–1 and less for inorganic, organometallic and organic species), the larger linear ranges than many commonly used instrumental techniques, the ability to assay dissolved and solid samples, the ability to speciate on the basis of complex lability and to distinguish between different states of valency, and the immunity of the matrix to samples with high ionic content, etc. These are illustrated by practical examples in this work. However, the still limited commercial availability of highly automated electroanalytical instrumentation is a serious limitation for the large-scale routine use of these methods in the industrial and control laboratory.

Dry-chlorination inductively coupled plasma mass spectrometric method for the determination of platinum group elements in rocks

A dry-chlorination procedure has been developed for use in the determination of low concentrations of platinum group elements (PGE) and Au in rock pulps. The PGE and Au, present as native metals, natural alloys and as PGE-(or Au-) bearing sulfide group minerals, are converted by dry-chlorination into PGE (or Au) sodium salts. These salts are dissolved in weak HCl. The solutions are analysed for PGE and Au content by inductively coupled plasma mass spectrometry (ICP-MS). Tests on three reference rock pulps [diluted South African Bureau of Standards Reference Material (SARM)-7 Platinum Ore; diluted INCO S-1800; Nevada Bureau of Mines (NBM) 6a Stillwater] and one gabbro rock showed that the dry-chlorination–ICP-MS method produced results that were usually comparable to, and often better than, fire assay techniques. Reagent contamination was extremely low (Pt⩽1 ng g–1; other PGE and Au⩽0.2 ng g–1). The recoveries of PGE obtained by dry-chlorination–ICP-MS were often >90%.

Voltammetric determination of platinum in inorganic complexes and in water, geological and biological matrices using laboratory- and field-based instrumentation

The extremely sensitive catalytic hydrogen ion reduction wave observed after the formation of a platinum-formazone complex at a mercury electrode in a hydrazine-formaldehyde-H2SO4 medium has been utilised to determine platinum voltammetrically in well characterised platinum inorganic complexes (oxidation states O, II and IV) and in biological, geological and water samples. Experimental conditions have been optimised and sample-treatment procedures for various matrices have been critically evaluated for the quantification of platinum by the standard additions method. The determination of platinum in geological samples by this method has been compared with an inductively coupled plasma mass spectrometric method. Both conventional and portable field-based instrumentation have been used in the studies, and the possibility of developing a field-based method for the determination of platinum has been investigated. Despite the inherent sensitivity of the method, which enables concentrations down to 0.01 p.p.b. to be detected in simple matrices, natural levels in water and biological materials, where matrix effects suppress the voltammetric response, are often below the detection limit.