COMPARISON OF CRYOGENIC AND MEMBRANE DESOLVATION FOR ATTENUATION OF OXIDE, HYDRIDE AND HYDROXIDE IONS AND IONS CONTAINING CHLORINE IN INDUCTIVELY-COUPLED PLASMA-MASS SPECTROMETRY

Conventional, cryogenic and membrane desolvation methods were compared with respect to sensitivity, MO+/M+ signal ratios and the aerosol gas flow rate required to maximize M+ and MO+ signals, Thorium was used t o represent the actinides, which form relatively strong hydrides and h ydroxides, The LaO+/La+ ratio is reduced from 0.24% with conventional desolvation to 0.08% with membrane desolvation and 0.01% with cryogeni c desolvation, Membrane desolvation reduces ThH+ and ThOH+ 2-fold comp ared with conventional desolvation, Cryogenic desolvation attenuates T hH+ 7-fold and ThOH+ 20-fold compared with conventional desolvation, T he three desolvation methods were also evaluated for the removal of CI O+ and ArCl+ for the determination of vanadium and arsenic at trace le vels in the presence of chloride, The density of oxygen atoms is reduc ed as water vapor is removed, and chloride is also removed, presumably as hydrogen chloride, The concentration of vanadium in a urine standa rd reference material was determined by standard additions to be 7 ppb with cryogenic desolvation and 5 ppb with membrane desolvation, Analy sis of several nasal wash samples using cryogenic and membrane desolva tion yielded results that agreed within 5% for the two methods in all cases except for the sample with the highest V+ concentration.