Evaluation of selected analyte protectant to improve performance of gas chromatographic analysis of pesticide residues

S. Mohammad Shahid, C.K. Ngan and A.M. Khairatul

Abstract
The effectiveness of three analyte protectants, namely, D-sorbitol, 3-ethoxy-1,2 propanediol (ethoxypropanediol) and L-gulonic acid γ-lactone (gulonolactone) in improving peak shape of analytes for better peak sensitivity and quantitation during GC-MS analysis of pesticide residues were evaluated. The use of these analyte protectants were investigated with three pesticide groups i.e. organochlorine (γ-HCH and α-endosulphan), organophosphate (chlorpyriphosmethyl, fenitrothion and prothiophos) and synthetic pyrethroid (bifenthrin,fenpropathrin, cypermethrin and deltamethrin). The analyte protectants were fortified in mixed pesticide standard at a rate of 1 mg/ml prior to GC-MS analysis. Improvement of analytes was seen as peak was enhanced as much as 41% and better separation obtained with application of analyte protectants. These compounds fill in the active sites in the inlet and column of the GC-MS, thus reducing analyte interactions. The ethoxypropanediol seems adequate to provide protection for pesticide during early to mid-eluting process while sorbitol and gulonolactone can be used for mid to late-eluting process. However, a combination of all three analyte protectants will provide better protection.

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