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 CHCN was used for separation. Thiamethoxam residue was extracted from the samples using CHCN and a dispersive solid-phase extraction method was used for subsequent cleanup. Linearity studies were conducted between 0.001 and 0.1 μg mL 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 for banana stem and 0.001and 0.005 μg gfor 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.

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A simple, sensitive and inexpensive analytical method was developed using solid-phase extraction for the simultaneous determination of five neonicotinoid insecticides in soil matrix using LC-MS/ MS and validated. The samples were extracted with acetonitrile and subsequent cleanup was done by dispersive solid-phase extraction (QuEChERS method). The quantification was carried out by liquid chromatography-tandem mass spectrometry with electrospray ionization source (LC-ESI-MS/MS). After the optimization of the extraction parameters, the method was validated by evaluating, linearity, limits of detection and quantification, precision (repeatability) and accuracy (recovery). Validation was based on analysis at three fortification levels and showed satisfactory recoveries (77.03 to 115.08 %) and high precision (RSDs between 2.01 to 13.83%). Low limits of detection and quantification could be achieved for all the five analytes ranging from 0.0007 to 0.002 and 0.002 to 0.008 μg/g, respectively. The developed method was applied to the analyses of neonicotinoid residues in soil from sugarcane field and pot soil.