REMOVAL OF ORGANIC-SOLVENTS BY CRYOGENIC DESOLVATION IN INDUCTIVELY-COUPLED PLASMA-MASS SPECTROMETRY

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-degrees-C and cooling in a set of cryogenic loops at -80-degrees-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.