Rapid Determination of Aldicarb and Its Metabolites in Water Environment by Real-Time Direct Analysis-Tandem Mass Spectrometry

Aldicarb, aldicarb sulfoxide (aldicarb) and aldicarb sulfoxide (aldicarb) are carbamate insecticide and acaricide, which are widely used in the growth of crops. Aldicarb and its metabolites will create pollution for aquatic environment during the spraying process, and enter the human body directly or indirectly. At present, the detection standard of aldicarb and its metabolites in water environment has the problems of complicated sample pretreatment process and long time consuming in instrument detection, it is difficult to meet the demand of increasing sample size. Therefore, it is of great significance to establish a rapid detection method for alidcarb and its metabolites in different water environment. In this study, the parameters of ionization gas temperature, sampling speed, vacuum degree of external vacuum pump, point sample quantity, point sample mode, point sample position were optimized. There were two problems in the determination of alidcarb and its metabolites in water environment by real-time direct analysis ion source. Firstly, the real-time direct analysis ion source is an open ion source, after the analyte was ionized in the open environment, the parallelism between the samples was poor because of the difference in the amount of analyte entering the mass spectrometry. The difference of ionization efficiency between the parallel samples due to the different positions of the target compound in TIP leads to the poor parallelism. Secondly, if the solvent of the water sample cannot completely volatilize after sampling, the water solvent will consume too much energy in the process of ionization, the target material cannot be sufficiently ionized because it cannot distribute enough energy, which affects the detection sensitivity. A rapid method for the determination of aldicarb and its metabolites in water environment was established. The results showed that the best detection condition was when the temperature of ionized gas was 300 ℃, the sampling speed was 0.6 mm/s, the vacuum degree of external vacuum pump was -70 kPa, the sample amount was 10 L and the sample position was 1.5 mm. Under the optimized conditions, 0.5-10 g/L for aldicarb and 0.1-10 g/L for its metabolites had good linear relationship with the correlation coefficient of 0.995 6-0.998 9. The detection limit was 0.1-0.5 g/L and the recovery was 94%-109%. This method is simple and rapid, which can be used to detect aldicarb and its metabolites in water environment in real-time and high-throughput.