The authors names should read as above, not as given previously: i.e., for Egwel H. Evans read E. Hywel Evans.

An He -Ar mixed gas inductively coupled plasma (ICP) was investigated for use as an ion source for plasma mass spectrometry (MS). The addition of He to Ar produces a plasma capable of ionising high ionisation potential elements more efficiently than the pure Ar plasma. The best signal to noise ratios for metallic elements were obtained with a 20% He plasma, and for halides with a 30% He plasma. The He -Ar mixed gas plasma shows an improvement of one order of magnitude in the detection limits of several metallic elements studied and an improvement of two orders of magnitude for non-metals in comparison with Ar ICP-MS. Figures of merit, including detection limits, linear dynamic ranges, metal oxide ratios and doubly to singly charged ion ratios, are reported and compared with those for Ar ICP-MS.

Ion chromatography has been combined with inductively coupled plasma mass spectrometry for the speciation of arsenic compounds commonly found in urine. Ion chromatography was used to eliminate or reduce the mass spectral interference formed from chloride, namely argon chloride, by resolving chloride chromatographically from the arsenic compounds. A 20-fold dilution of the urine samples was necessary in order t o avoid column overloading from chloride and subsequent argon chloride interference. Detection limits in urine of 3.4 p.p.b. As"', 4.2 p.p.b. As" and 7 p.p.b. dimethylarsinic acid were obtained. Three commercially available freeze-dried urine standards were analysed using the standard additions method. Good agreement was obtained for total arsenic content, which was calculated from the sum of the species with accepted arsenic concentration. The relative standard deviation of peak height for each of the species was approximately 5% in urine.

The moderate-power nitrogen plasma is evaluated as an alternative ion source for plasma mass spectrometry. The nitrogen MIP-MS exhibits linear dynamic ranges of about 3–4 orders of magnitude and low ppb to sub-ppb detection limits for most elements under multielement scanning conditions. Nitrogen MIP-MS is capable of determining K, Ca, Cr, As, and Se at their major isotopes. In addition, nitrogen MIP-MS provides lower detection limits than argon ICP-MS for K (0.48 ppb) and Ca (0.24 ppb). The nitrogen MIP-MS system allows the determination of isotope ratios for 10 ppm of Ca (40/44) and 100 ppb of K (39/41), Cr (52/53), and Se (80/78) with less than 5% error.

An on-line flow system for anodic stripping voltammetry has been investigated for the pre-concentration of cadmium and copper and the separation of copper from a sodium matrix for detection by inductively coupled plasma atomic emission spectrometry and inductively coupled plasma mass spectrometry (ICP-MS). Good signal enhancement was obtained with pre-concentration of moderate sample volumes. Matrix elimination of more than 99% was possible for reasonably high concentrations of undesired matrix elements, namely Na and U. Isotope ratio data for ICP-MS indicated that the interference of ArNa+ on Cuf at m/z 63 could be mini mised.