Gas chromatographic determination of pesticides in vegetable samples by sequential positive and negative chemical ionization and tandem mass spectrometric fragmentation using an ion trap analyser
Md. Hernando et al., Gas chromatographic determination of pesticides in vegetable samples by sequential positive and negative chemical ionization and tandem mass spectrometric fragmentation using an ion trap analyser, ANALYST, 126(1), 2001, pp. 46-51
A selective and sensitive chromatographic method is described for the deter
mination of nine organochlorine and organophosphorus pesticides in vegetabl
e samples by gas chromatography-mass spectrometry. The proposed method comb
ines the use of positive and negative chemical ionisation and tandem mass s
pectrometric fragmentation, resulting in a significant increase in selectiv
ity and allowing the simultaneous confirmation and quantification of trace
levels of pesticides in complex vegetable matrices. Parameters relative to
ionisation and fragmentation processes were optimised to obtain maximum sen
sitivity. Repeatability and reproducibility studies yielded relative standa
rd deviations lower than 25% in all cases. Identification criteria, such as
retention time and relative abundance of characteristic product ions, were
also evaluated in order to guarantee the correct identification of the tar
get compounds. The method was applied to real vegetable samples to demonstr
ate its use in routine analysis.