Development of thin film microextraction method for the multi-residue analysis of selected pesticides

Pesticides are a class of compounds that are used to protect agricultural products. However, the uncontrolled use of these chemicals increases the risks associated with their overdosing and rises a significant concern about their effect on human health and the ecosystem. Albeit many concerns about their effects, the use of pesticides is inevitable due to the incline in population growth and the presence of limited food resources. As a result, regulatory control of the use of chemicals is critical and the development of methods that provide a reliable determination of pesticide residues in fruits and vegetables is of great importance.

In the present study, a new method based on thin film microextraction was developed for the extraction of pesticides from fruit matrices prior to their gas chromatography-mass spectrometric (GC–MS) determination. As a first step, the thin film extractive devices were prepared by immobilization of hydrophilic-lipophilic balanced (HLB) particles on the surface of carbon mesh. The samplers were optimized in terms of extraction and desorption conditions first in PBS and then in apple juice. The final method was also validated in apple juice samples. Analytical figures of merits of the final method showed acceptable precision for intra- and inter-day reproducibility with ≤20% relative standard deviation (RSD%) and accuracy of ≤15% relative error (RE%), except for trifluralin at 300.0 ng mL⁻¹ level. The limits of quantitation (LOQ) for the selected pesticides were found between 1.0 and 5.0 ng mL⁻¹ . The samplers developed in this study were also successfully tested in preliminary investigations for the extraction of the pesticides from the surface of fruits and vegetables using agarose gel as a model matrix with the primary aim of showing the step towards the sampling directly on the field.