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

Abstract

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.