Analysis of Pesticide Residues in Fresh Peppermint, Mentha piperita L., Using the Quick Easy Cheap Effective Rugged and Safe Method (QuEChERS) Followed by Gas Chromatography with Electron Capture and Nitrogen Phosphorus Detection

A new analytical method for the determination of 14 pesticide residues in fresh peppermint was developed based on the QuEChERS sample preparation technique followed by gas chromatography coupled to electron capture and nitrogen phosphorus detectors (GC/ECD/NPD). The validation study clearly demonstrated suitability of the method for its intended application. The overall recoveries of the pesticides from peppermint, at the three spiking levels of 0.01, 0.1 and 1.0 mg kg−1, were 100 % ± 10 % with relative standard deviations of 6 % ± 5 % on average. The limit of quantification was 0.01 mg kg−1 for all the pesticides. The expanded uncertainties were in the range between 7 % and 30 % (14 % on average), which was distinctively less than a maximum default value of ±50 %. Compared with our previous method, that entailed dichloromethane/acetone extraction and florisil column cleanup with collection of four fractions, the new method was more straightforward, less time and labour intensive as well as more sensitive, selective and accurate, simultaneously.