Resolution and quantitative determination of coeluted pesticide mixtures in liquid chromatography-thermospray mass spectrometry by multivariate curve resolution

Abstract

Resolution and quantitative determination of a mixture of coeluted pesticides (carbofuran, propoxur and pirimicarb) in liquid chromatography- thermospray mass spectrometry by multivariate curve resolution is shown. Carbofuran and pirimicarb both exhibit an ion with m/z 239 in their thermospray mass spectrum. For the first compound this ion is attributed to the ammonium adduct [M+NH4]+ ion, whereas the corresponding ion of pirimicarb is the protonated molecule, [M+H]+. A third carbamate, propoxur, was added because this compound partly coelutes with carbofuran under normal experimental conditions during multiresidue analysis of carbamates with C18 packed analytical columns. With this additional compound, the so-called suppression effects on the ion formation of these compounds in thermospray mass spectrometry and their quantitative resolution using chemometric methods were studied.