Daniel R. Wiederin

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).

Measurements of Aerosol Particle Sizes from a Direct Injection Nebulizer

Photographs and laser-scattering measurements showed that a direct injection nebulizer (DIN) produced a finer aerosol with a narrower drop size distribution than that for a conventional glass concentric nebulizer when both were operated at the same liquid and nebulizer gas flow rates. The droplets from the DIN were slightly larger, however, than those leaving a Scott-type spray chamber with a glass concentric nebulizer. The droplets from the DIN had a Sauter mean diameter of ∼7 μm and a 90% mass diameter of 11–16 μm. The droplet size distribution became narrower and shifted to lower diameters as the aerosol gas flow rate increased.

Frontiers in elemental analysis by mass spectrometry

Abstract New developments in inductively coupled plasma mass spectrometry (ICP-MS) and laser desorption-time-of-flight mass spectrometry (LD-TOF-MS) for inorganic analysis are described. These include fundamental studies of the ion extraction, process in ICP-MS, development of a highly efficient nebulizer, isotope tracer studies, measurement of elemental speciation by liquid chromatography with ICP-MS detection and characterization of the structures of solids by ion association. The possibilities of determining inorganic species in solutions by electrospray MS are also described.

Removal of organic solvents by cryogenic desolvation in inductively coupled plasma mass spectrometry. Invited lecture

Methanol, ethanol, acetone or acetonitrile were nebulized continuously with an ultrasonic nebulizer. The solvent was removed from the aerosol stream by repetitive heating at approximately 100 °C and cooling in a set of cryogenic loops at –80 °C. The resulting aerosol was then introduced into an inductively coupled plasma mass spectrometer. Ethanol was the only solvent that required a continuous dose of additional O2(1–5%) in the aerosol gas to prevent deposition of carbon on the sampler. Oxide ratios for LaO+:La+ and UO+:U+ were 0.03–0.1%. Cryogenic desolvation attenuated but did not eliminate the usual carbon-containing polyatomic ions (e.g., CO+, CO2+, ArC+ and ArCO+). Analyte sensitivities from metal nitrate salts in methanol were comparable to the sensitivities from aqueous metal solutions. Substantial memory effects were observed from several metal complexes.

An externally air-cooled low-flow torch for inductively coupled plasma mass spectrometry

Abstract A low-flow torch specifically designed for inductively coupled plasma mass spectrometry (ICP-MS) was developed and evaluated. The outside of the torch is cooled externally by pressurized air flowing at ∼70 l min−1 through a fourth tube sealed onto the usual ‘outer’ tube of a standard minitorch. This external air flow merely cools the outer tube of the torch and does not enter the plasma. Although plasmas can be sustained at operating power as low as 400 W with a 2 l min−1 outer Ar flow, somewhat higher power and flows are advisable. A stable and analytically useful plasma can be obtained at 850 W with an outer Ar flow rate of only 4 l min−1. Under optimum operating conditions, the externally air-cooled plasma produces comparable sensitivities, M2+/M+ signal ratios, matrix effects and other analytical figures of merit as those produced by a conventional torch while using much less argon. MO+/M+ signal ratios are slightly higher with the externally cooled torch.

Molecular hydrogen emission in the vacuum ultraviolet from an inductively coupled plasma

Abstract Vacuum ultraviolet radiation is observed through a sampling orifice in a metal cone inserted directly into an Ar inductively coupled plasma (ICP). The many-lined spectrum of the H 2 Lyman bands is observed from an argon ICP with either H 2 gas or nebulized water added. The most prominent bands are from the ν = 3, 4, 5 or 6 vibrational levels of the B 1 Σ + u electronic state of H 2 . The energies of the ν = 3, 4 and 5 levels are close to those of the Ar metastable levels and of photons from the Ar resonance lines (11.5 to 11.8 eV). These H 2 levels are probably populated at least in part by selective energy transfer reactions between Ar metastable atoms and H 2 and/or by absorption of Ar resonance photons by H 2 . The H 2 emission emanates only from the upstream reaches of the axial channel, i.e. the part of the axial channel that is inside the load coil and induction region.