Showing papers in "Analytical Chemistry in 1980"

Inductively coupled argon plasma as an ion source for mass spectrometric determination of trace elements

Abstract: Solution aerosols are injected into an inductively coupled argon plasma (ICP) to generate a relativly high number density of positive ions derived from elemental constituents. A small fraction of these ions is extracted through a sampling orifice into a differentially pumped vacuum system housing an ion lens and quadrupole mass spectrometer. The positive ion mass spectrum obtained during nebulization of a typical solvent (1% HNO/sub 3/ in H/sub 2/O) consists mainly of ArH/sup +/, Ar/sup +/, H/sub 3/O/sup +/, H/sub 2/O/sup +/, NO/sup +/, O/sub 2//sup +/, HO/sup +/, Ar/sub 2//sup +/, Ar/sub 2/H/sup +/, and Ar/sup 2 +/. The mass spectra of the trace elements studied consist principally of singly charged monatomic (M/sup +/) or oxide (MO/sup +/) ions in the correct relative isotopic abundances. Analytical calibration curves obtained in an integration mode show a working range covering nearly 4 orders of magnitude with detection limits of 0.002 to 0.06 ..mu..g/mL for those elements studied. This approach offers a direct means of performing trace elemental and isotopic determinations on solutions by mass spectrometry.

Determination of atmospheric sulfur dioxide without tetrachloromercurate(II) and the mechanism of the Schiff reaction

Abstract: Formaldehyde (7 mM) buffered at pH approx. 4 is used to stabilize atmospheric SO/sub 2/ as hydroxymethanesulfonic acid. Equilbrium data for the above reaction are presented. Sulfite, liberated from the compound by base, is added to acidic pararosaniline for color development by the Schiff reaction, and absorbance is measured at 580 nm. The procedure has been optimized with regard to acidity and reagent concentrations. The method is comparable to the West-Gaeke method in absorption and recovery efficiency, sensitivity, and precision. No unusual interferences are observed due to O/sub 3/, NO/sub 2/, and transition-metal ions, except Mn(II). A novel ion chromatographic procedure to determine hydroxymethanesulfonate and sulfate in the same sample is also described. Enhancement of sensitivity in the colorimetric method by solvent extraction has been studied. Investigations into the mechanism of the Schiff reaction and structure of the products have established the validity of the alkylsulfonic acid theory. Mechanistically an aminocarbinol seems to be the first intermediate, which undergoes subsequent nucleophillic substitution by bisulfite ion. To account for the high absorptivity of the product, we suggest that the sulfonic acid group is significantly ionized.