Fred G. Smith

Metal speciation by means of microbore columns with direct-injection nebulization by inductively coupled plasma atomic emission spectroscopy

Abstract Ion chromatography can be used to perform speciation of several elements. This paper examines the use of ion chromatography with inductively coupled plasma atomic emission spectroscopy detection. A new type of nebulizer, the direct-injection nebulizer, was used to introduce the sample into the plasma. Columns were developed to interface with the direct-injection nebulizer at a flow-rate of 80–100 μl/min. The speciation of arsenic, selenium and chromium is discussed.

Measurement of boron concentration and isotope ratios in biological samples by inductivey coupled plasma mass spectrometry with direct injection nebulization

A method for the determination of boron in a variety of biological samples is described. Sample material is fused with sodium carbonate and boron is separated from matrix components by using Amberlite IRA-743 boron selective ion-exchange resin. Boron is eluted with 1% HNO3 and samples are introduced to an inductively coupled plasma mass spectrometer with a direct injection nebulizer. This nebulizer provides a fast sample cleanout of ca. 15 s. The 10B/11B ratio is determined with a relative standard deviation (RSD) of 0.4–1.5%, and the detection limit for boron is approximately 1 ng g−1 in these samples. Stable isotope dilution methodology for quantitation of boron shows that: (1) fusion of sample with sodium carbonate avoids volatilization of boron from samples; (2) approximately 80% of submicrogram amounts of boron from samples can be recovered from the resin with insignificant isotopic fractionation; (3) results for biological reference materials are in agreement with certified values; and (4) the boron concentration of pooled human blood plasma is 24 ± 4 μg l−1 (95% confidence interval).

Matrix interferences in inductively coupled plasma-mass spectrometry: some effects of skimmer orifice diameter and ion lens voltages

Abstract A new, home-made instrument for inductively coupled plasma-mass spectrometry (ICP-MS) was used to study the influence of Na, K and U salts on ion signals for Y, Co and As. In general, the analyte signals were suppressed in the presence of excess matrix element. When the skimmer orifice was larger than the sampler orifice, the extent of suppression was greatest for the analyte of highest ionization energy (As) and least for the analyte of lowest ionization energy (Y). In this case, the extent of signal suppression induced by the three matrix elements did not differ much despite their substantial difference in mass, in contrast to some other reports. When the skimmer orifice was smaller than the sampler orifice, the analyte signal was suppressed more extensively. The three analytes were suppressed by about the same extent by a given matrix element, and the heavier matrix element (U) induced much more suppression than the lighter ones (e.g. Na). Thus, simply reducing the diameter of the skimmer orifice altered the trends in the interference effects to conform to those generally reported. With the skimmer orifice larger than the sampler orifice, the trends in interference effects could also be changed if the first element of the ion lens was biased at a positive voltage. Addition of U to the solution induced an increase in the kinetic energies of analyte ions (e.g. Co + ) by approximately 1 eV.

Mass spectrometric measurement of ionization temperature in an inductively coupled plasma

Abstract Degrees of ionization for As and Sb in an inductively coupled plasma (ICP) were measured using mass spectrometry (MS). Electron density ne in the plasma just upstream from the sampling orifice of the mass spectrometer was measured optically from Stark broadening of the H I 486.13 nm emission line. Ionization temperature (Tion) for Sb and As was calculated over a range of plasma conditions. The electron density upstream of the sampler varied with plasma conditions in a manner consistent with that described for ICP optical emission sources, and ne at that point was the same as that in the ICP alone under identical plasma conditions. Variations in Tion of Sb with plasma conditions were consistent with that expected of the ICP itself, however, such was not always the case for Tion of As. Tion for Sb was generally higher than that of As. These results indicate that the kinetics of the ionization process can differ substantially for these elements. Temperature measurements made on a commercial ICP-mass spectrometer yielded trends similar to those observed for Sb, although Tion for As and Sb was generally the same on this instrument.

Charge transfer reactions between xenon ions and iron atoms in an argon-xenon inductively coupled plasma

Abstract Xenon is added to the axial channel of an argon inductively coupled plasma (ICP) at doses up to 1.5% of the aerosol gas flow. Emission is collected from the gas flowing into the sampling orifice of a mass spectrometer (MS). These Xe doses have little effect on the electron density n e or on the intensities of Fe (I) emission lines. Certain Fe (II) lines are enhanced when Xe is added, particularly those from Fe + states that can be populated by near-resonant charge transfer between Xe − and neutral Fe. Calculations based on measured values of n e indicate that Xe + should be present at densities of up to 7 × 10 14 cm −1 , which should be sufficient Xe + to drive the proposed charge transfer reactions.

Alleviation of polyatomic ion interferences for determination of chlorine isotope ratios by inductively coupled plasma mass spectrometry

A simple variation in sample preparation and introduction allows the measurement of chlorine isotope ratios by inductively coupled plasma mass spectrometry (ICP/MS). Dissolution of the sample in D2O rather than H2O attenuates the major polyatomic ion 36ArH+ and frees m/z 37 for determination of 37Cl+. The isotope ratio 35Cl/37Cl in a 50 mg/L solution of Cl as LiCl is determined with a relative standard deviation of 0.21%. Sample memory is low, as the 35Cl signal decays to less than 1% of its original value after ∼2 min of cleanout with D2O . The detection limit for Cl using this procedure is approximately 20 μg/L.