Determination of thiamethoxam residues in banana stem and fruit through LC-MS/MS

An analytical method based on liquid chromatography coupled with mass spectroscopy/mass spectroscopy was developed and validated for the determination of thiamethoxam residues in banana fruit and stem tissue samples. In this study, Waters Alliance LC and Acquity TQD were used with an electrospray ionization interface in the positive ion mode. An isocratic flow of 0.5% HCOOH in water and 0.05% HCOOH in CH₃CN was used for separation. Thiamethoxam residue was extracted from the samples using CH₃CN and a dispersive solid-phase extraction method was used for subsequent cleanup. Linearity studies were conducted between 0.001 and 0.1 μg mL^-1 of standard solution with three replicates for each concentration. Satisfactory recoveries (107.21 to 115.16% and 90.94 to 109.22%) and high precision (relative standard deviations of 3.71 to 12.83% and 3.24 to 10.78%) were obtained for the banana stem and banana fruit matrix, respectively. The lower limits of detection and quantification achieved were 0.002 and 0.008 μg g^-1 for banana stem and 0.001and 0.005 μg g^-1for banana fruit, respectively. The developed method was used to analyze the banana stem and fruit samples collected from thiamethoxam-treated fields and stems from the local market.