Dynamic behaviour and residual pattern of thiamethoxam and its metabolite clothianidin in Swiss chard using liquid chromatography–tandem mass spectrometry

•Thiamethoxam and its metabolite, clothianidin were determined in Swiss chard.•The parent and the metabolite were extracted and analysed using the same method.•The total residues fell below the MRL, zero day post-application.•The difference in dynamic behaviour was attributed to humidity.•The developed method is effective and reliable. A simultaneous method was developed to analyse thiamethoxam and its metabolite clothianidin in Swiss chard using tandem mass spectrometry (in the positive electrospray ionisation mode using multiple reaction monitoring mode) to estimate the dissipation pattern and the pre-harvest residue limit (PHRL). Thiamethoxam (10%, WG) was sprayed on Swiss chard grown in two different areas under greenhouse conditions at the recommended dose rate of 10g/20L water. Samples were collected randomly up to 14days post-application, extracted using quick, easy, cheap, effective, rugged, safe (QuEChERS) acetate-buffered method and purified via a dispersive solid phase extraction (d-SPE) procedure. Matrix matched calibration showed good linearity with determination coefficients (R2)⩾0.998. The limits of detection (LOD) and quantification (LOQ) were 0.007 and 0.02mg/kg. The method was validated in triplicate at two different spiked concentration levels. Good recoveries (n=3) of 87.48–105.61% with relative standard deviations (RSDs)