Abstract:

A simple and rapid pretreatment procedure was developed for the simultaneous determination of aldicarb and its metabolites, aldicarb sulfone and aldicarb sulfoxide, in ginger. The samples were extracted with acetonitrile, and then cleaned up with multiplug filtration using multiwalled carbon nanotubes (MWCNTS). The eluate was dried with nitrogen gas at room temperature, and redissolved in an acetonitrile-water (5:95, v/v) mixture, then quantified by ultra performance liquid chromatography coupled with electrospray ionization tandem mass spectrometry (UPLC-ESI-MS/MS) operated in positive multiple reaction monitoring (MRM) mode. A linear relationship was achieved in the range of 0.5-200 μg/L for the peak areas to the mass concentrations of the target compounds with the linear correlation coefficients (r²) higher than 0.99. The recoveries at three spiked levels of 2, 20 and 200 μg/kg were in the range from 71.4% to 89.8% with the relative standard deviations (RSDs, n=6) from 0.7% to 13.2% under the selected conditions. The limits of quantification (LOQ, S/N=10) of aldicarb, aldicarb sulfone, and aldicarb sulfoxide in ginger were 1.0, 2.0 and 1.0 μg/kg, respectively. The results demonstrate that the developed method is rapid, cost-effective, and can meet the requirements of the multiple pesticide residue analysis. The method is applicable to determine aldicarb and its metabolites in ginger.

Key words: aldicarb, ginger, metabolites, multiplug filtration clean-up (m-PFC), multiwalled carbon nanotubes (MWCNTS), ultra performance liquid chromatography-tandem mass spectrometry (UPLC-MS/MS)