SPECIATION OF ARSENIC OXIDES USING LASER DESORPTION IONIZATION TIME-OF-FLIGHT MASS-SPECTROMETRY/

Positive and negative ion mass spectra of arsenic trioxide (As2O3) and arsenic pentaoxide (As2O5) have been obtained by single-step laser de sorption/ionization time-of-flight mass spectrometry. Pulsed UV radiat ion at 266 nm was used for tile simultaneous desorption and ionization of the solid sample, High-mass cluster ions that are unique to the ox idation state of each oxide sample appear in the negative ion mass spe ctra, The As2O3 produces As3O5-, while the As2O5 yields As3O8-. The fo rmation of unique negative cluster ions presents the capability for ar senic oxidation state speciation by laser desorption/ionization mass s pectrometry. The ability of time-of-flight mass spectrometry to examin e the relative amounts of each arsenic oxide present in a series of mi xtures is discussed. Application of our speciation technique to a mode l incinerator sample is demonstrated.