Fast gas chromatography for pesticide residues
analysis using analyte protectants
Abstract
Fast GC–MS with narrow-bore columns combined with effective sample preparation technique (QuEChERS method) was used for evaluation of
various calibration approaches in pesticide residues analysis. In order to compare the performance of analyte protectants (APs) with matrix-matched
standards calibration curves of selected pesticides were searched in terms of linearity of responses, repeatability of measurements and reached
limit of quantifications utilizing the following calibration standards in the concentration range 1–500 ngmL−1(the equivalent sample concentration
1–500 g kg−1): in neat solvent (acetonitrile) with/without addition of APs, matrix-matched standards with/without addition of APs. For APs results
are in a good agreement with matrix-matched standards. To evaluate errors of determination of concentration synthetic samples at concentration
level of pesticides 50 ngmL−1 (50 g kg−1) were analyzed and quantified using the above given standards. For less troublesome pesticides very
good estimation of concentration was obtained utilizing APs, while for more troublesome pesticides such as methidathion, malathion, phosalone
and deltamethrin significant overestimation reaching up to 80% occurred. According to presented results APs can be advantegously used for “easy”
pesticides determination. For “difficult” pesticides an alternative calibration approach is required for samples potentially violating MRLs. An
example of real sample measurement is shown. In this paper also the use of internal standards (triphenylphosphate (TPP) and heptachlor (HEPT))
for peak areas normalization is discussed in terms of repeatability of measurements and quantitative data obtained. TPP normalization provided
slightly better results than the use of absolute peak areas measurements on the contrary to HEPT.
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