Organic and inorganic arsenic speciation through ion exchange chromatography with particle beam-glow discharge mass spectrometry detection

Abstract

A mixture of organic and inorganic arsenic compounds has been separated using ion exchange liquid chromatography and detected using a particle beam glow discharge mass spectrometer (PB-GDMS). The particle beam interface makes use of nebulization and momentum separation to deliver a stream of dry analyte particles to the glow discharge source from the LC output. In the glow discharge, the analyte particles are vaporized and ionized at or near the cathode surface. The ions are analyzed by a quadrupole mass spectrometer collecting data in either single ion monitoring (SIM) or total ion counting (TIC) modes. The separation of arsenobetaine (2-(trimethylarsonio)acetate), arsenic(III) chloride and dimethylarsenic acid was performed on a universal cation-exchange column using an isocratic mobile phase, with a total elution time of less than four minutes. The mass spectrum for each of these compounds contains a strong elemental arsenic signal as well as the molecular fragments that allow for the identification of the specific species responsible for the chromatographic peak. The limits of detection (LOD) for organic arsenic (dimethylarsenic acid) were found to be 2 ppm (90 ng DMA molecular ion) in the TIC mode and 15 ppb (0.8 ng As from DMA) in the SIM mode. Inorganic arsenic(III) chloride has an LOD of 11 ppb or 0.55 ng As absolute. This work suggests that the PB-GDMS has high potential as a comprehensive (inorganic/organic) detector for both biological and environmental speciation work.