MULTIELEMENT DETECTION USING 2ND SURFACE TRAPPING WITH ELECTROTHERMAL VAPORIZATION MASS-SPECTROMETRY

A new technique for electrothermal vaporization mass spectrometry using second surface trapping is presented. The method involves atmospheric pressure vaporization of the analyte from a graphite cup and condensation of the vapour onto a cooled tantalum surface. The tantalum surface is introduced into a vacuum chamber through a series of differentially pumped seals and is positioned under a quadrupole mass analyser and radiatively heated using a 250 W filament. An electron impact ionizer (70 eV, 3 mA) is employed for ionization. The system allows thermal pre-treatment of the sample in the cup prior to vaporization and trapping, thereby enabling the analytes studied (Ag, Cd and Pb) to be trapped and simultaneously detected in their elemental forms. Detection limits for the current system for the elements studied are in the low nanogram range.