Determination of pesticide residues in leafy vegetables at parts per billion levels by a chemometric study using GC-ECD in Cameron Highlands, Malaysia

•A simple and sensitive method for screening 15 pesticide residues in leafy vegetables.•Vegetable samples found to be contaminated with a number of pesticides.•Pesticides extraction was optimized by chemometric study.•Developed GC-ECD method applied to vegetable samples.

A simple and sensitive analytical method has been developed employing gas chromatography coupled with electron capture detector (GC-ECD), and validated for screening and quantification of 15 pesticide residues at trace levels in cabbage, broccoli, cauliflower, lettuce, celery, spinach, and mustard. The method consists of two steps, first, to determine the significance of each factor by Pareto chart followed by optimization of these significant factors using central composite design (CCD). Minitab statistical software was used for these multivariate experiments for the generation of 24-1 design and CCD matrices. The method evaluation was done by external standard calibration with linearity range between 0.5 and 3 mg/kg, with correlation coefficient 0.99, limit of detection (LOD) ranges between 0.02 and 4.5 ng/g, and limit of quantification (LOQ) ranges between 0.2 and 45 ng/g. The average recovery was between 60% and 128%, with RSD 0.2-19.8%. The method was applied on real vegetable samples from Cameron Highlands.