Detection limits and surface interactions in quantitative negative chemical-ionization mass spectrometry Ultratrace determination of metals and organic compounds by means of their complexes.

Details are given of a selective negative-ion mass-spectrometric method appropriate for the ultratrace determination of metals and organic compounds by means of their complexes. Direct introduction of the sample into the ion-source, attachment of low-energy electrons, and selected-ion monitoring are described, and comparative data are given relating to surface effects at the tips of insertion-probes on detection limits. Detection limits for chromium and cobalt, determined as their tris(2,2,6,6-tetramethylheptane-3,5-dione) chelates, were respectively 1.0 and 0.16 pg, and that for nickel [as its bis(N,N-diethyldithiocarbamate) complex] was 1.0 pg. Detection limits of 2.0 and 1.0 ng are attainable for malathion and ethion by measurement of the nickel(II) complexes of their O,O'-dialkyldithiophosphate hydrolysis products.