New thin-layer chromatography (TLC) based sample preparation method for pesticide analysis with liquid chromatography-mass spectrometry (LC-MS)

Abstract

In this research, a new thin layer chromatography (TLC) technique was developed as a simple and selective sample preparation approach to improve pesticide analysis with liquid chromatography hyphenated with tandem mass spectrometry (LCMS/ MS). The sample preparation was performed by sample loading and separation on a TLC plate using 3:2 v/v hexene:acetone mobile phase system followed by selective cut of the target regions and the analyte recover into acetonitrile prior to the LCMS/ MS analysis. The approach was initially investigated for removal of majority of matrices in vegetable and supplementary bee pollen samples. Further analysis was performed for the target pesticide analytes (carbaryl, chlorpyrifos and atrazine) spiked into the bee pollen sample. With 4 times loading of the sample, the method detection limits are 1.383, 0.012, and 0.001 ppm for carbaryl, chlorpyrifos, and atrazine, respectively. The method limits of quantifications are 4.611, 0.039, and 0.003 ppm, respectively. The sensitivity could also be improved by increasing sample loading amounts as illustrated for atrazine (0.01 ppm), where 10 times loading (400 µL) resulted in 9 times improved peak areas compared with the 4 times loading. The obtained results were also compared with that prepared by the conventional Quick, Easy, Cheap, Effective, Rugged, and Safe (QuEChERS) method. For the intraday repeatability, the percentages of relative standard deviations (%RSD) obtained with the TLC based approach were 10.90, 10.58, and 13.47 for carbaryl, chlorpyrifos, and atrazine, respectively, which were better than that offered by the QuEChERS method with the %RSD of 29.71, 21.67, and 18.23, respectively. The TLC approach more effectively removed the sample matrix and required lower amounts of solvent and sample. However, QuEChERS provided the higher analyte peak areas and recoveries for the investigated sample. The developed TLC method can be an alternative choice for selective sample preparation of target pesticides in food and environmental samples in the future.