Evaluation of selected analyte protectant to improve performance of gas chromatographic analysis of pesticide residues (Penilaian pelindung anilit terpilih untuk meningkatkan prestasi analisis kromatografi gas residu pestisid)

The effectiveness of three analyte protectants, namely, D-sorbitol, 3-ethoxy-1,2propanediol (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. *Strategic Resources Research Centre, MARDI Headquarters, P.O. Box 12301, 50774 Kuala Lumpur, Malaysia Authors’ full names: Mohammad Shahid Shahrun, Ngan Chai Keong and Khairatul Azmah Mohamed E-mail: [email protected] ©Malaysian Agricultural Research and Development Institute 2012 Introduction One of the major problems in pesticide residue analysis using gas chromatography (GC) is analyte loses (Mastovska et al. 2004; Dömötörováa and Matisova 2008; Przybyliski and Hommet 2008). This problem arises due to interaction of analytes with active sites in the GC inlet and column during elution process resulting in poor peak shape which is difficult to identify and quantify because of susceptibility to interference (Hajslova and Zrostlikova 2003; Hoh and Mastovska 2008). Recent studies by Anastassiades et al. (2003) showed that by applying analyte protectant, peak distortion in fruits and vegetables matrices was significantly enhanced. These analyte protectants help to improve peak shape by filling in the active site thus reducing analyte interactions (Rodriguez et al. 2008). This study explored the possibility of three analyte protectants: Gulonolactone, D-sorbitol and 3-ethoxy-1,2-propanediol in improving peak shape of various pesticide residues by gas chromatographic analysis. Three groups of pesticide were evaluated which consist of organochlorine group (γ-HCH and α-endosulphan), organophosphorous group (chlorpyriphos, fenitrothion and prothiophos) and synthetic