LC-MS/MS determination and quantitation of some pesticides residues in thyme and guava leaves extracts: Application of QuEChERS protocol

This study aimed to develop new, green and sensitive analytical method for quantitation of two pesticide residues namely imidacloprid (IMD) and deltamethrin (DLM) in thyme and guava leaves. QuEChERS protocol was used for the extraction of both pesticide residues from aforementioned leaves followed by their analysis using liquid chromatography triple quadrupole mass spectrometry (LC-MS/MS). Separation was done by using X-bridge waters column C18, 3.50 mu m 15 cm x 4.50 mm with temperature 30 degrees C. Injection volume was adjusted to be 10 mu L with autosampler Temperature 14-16 degrees C. The mass spectrometry system was a triple quadrupole which was equipped with Agilent Jet Stream (AJS) source. Chromatographic separation was carried out in gradient mode. The performance of the method was validated according ICH guidelines. A linear response of was obtained and was found to cover a wide concentration range of 0.40-2.40 ng mL-1 for IMD and 0.30-1.80 ng mL-1 for DLM with good correlation coefficient 0.996 and 0.999 for IMD and DLM respectively. The limits of detection of IMD and DLM were 0.12 and 0.03 ng mL-1, respectively. The newly developed method was used to monitor the decline of the residues of both pesticides and estimate the pre-harvest interval for both pesticides in thyme and guava leaves. Analytical eco-scaling depending on penalty point which was calculated to be 86 for the suggested method and for the reported methods were 79 and 82, for IMD and DLM, respectively, showing that the suggested method was more eco-friendly than the reported methods for both pesticides.

Automated summary

This study developed a new, green, and sensitive analytical method for quantifying pesticide residues in thyme and guava leaves. The method involved using the QuEChERS protocol for extraction and analysis using liquid chromatography triple quadrupole mass spectrometry. The newly developed method showed good performance in terms of linear response, wide concentration range, and low limits of detection for both pesticides. It was also found to be more eco-friendly compared to reported methods.