A Simple and Improved HPLC Method for the Analysis of Dithianon in Red Pepper with Tandem Mass Spectrometry Confirmation

A simple and rapid method was developed for the analysis of dithianon in red pepper using HPLC-UV. Sample extraction was carried out using acidic acetonitrile as a solvent and sodium chloride as a salting out agent. The extract was then purified through solid phase extraction procedure. The method was validated using standard calibration. A linear range of standards were determined with excellent correlation coefficients (r (2)) > 0.999. Limits of detection and quantification were 0.01 and 0.03 mg/kg, respectively. Recovery was assessed by spiking blank red pepper samples at two different concentrations (0.3 and 1.5 mg/kg) with three replicates. A consistent recovery was determined (72.2 and 79.1 %) according to SANCO guidelines for repeatability, and based on the relative standard deviation which was < 4 within 3 days (intra- and inter-days) of experiment. The method was applied to field samples to determine the dissipation and pre-harvest residue interval (PHRL). From the PHRL curve, it can be predicted that if the residual amount of dithianon is below 8.5 mg/kg at 10 days or below 5.51 mg/kg at 7 days before harvest, then the residue of dithianon will be below the MRL during the harvest time. The levels of residues in field samples were confirmed using LC-MS/MS in negative electron spray ionization mode.