Preparation and application of polystyrene-divinylbenzene sorbent with weak cation-exchange character for the selective extraction of illicit drugs in environmental water

A novel mixed-mode weak cation-exchange sorbent (PS-DVB-WCX-II) was prepared by the modification of polystyrene-divinylbenzene with mercaptosuccinic acid for the selective extraction of illicit drugs in environmental water. The PS-DVB-WCX-II was synthesized through the Friedel-Crafts acylation reaction on the surface of polystyrene-divinylbenzene, followed by nucleophilic substitution reaction and thiol-ene click reaction. The sorbent can selectively absorb illicit drugs through the reverse-phase interactions provided by benzene ring on the polymer backbone and the ion-exchange interactions provided by functional group (-COOH). As compared with the extraction performance of three commercial SPE cartridges, it was found that the prepared sorbent had better adsorption performance with the recovery values between 84.1% and 106.0% for the selected 11 illicit drugs under the optimized SPE conditions. Illicit drugs in environmental water were extracted by the sorbent, prior to the detection of UHPLC-MS/MS. Two quantitative methods were established respectively for the detection of 11 illicit drugs in different matrices of river water and wastewater. Both methods had good determination coefficient (r2>0.992) in the range of 0.5-50 ng/L, 2.5-250 ng/L, 5-500 ng/L, and low limits of detection (S/N = 3) of 0.17-1.67 ng/L. In the real wastewater samples, the concentration of morphine was 18.3-126.3 ng/L, and the methamphetamine was 12.7-27.4 ng/L. Meanwhile, PS-DVB-WCX-II was compared with Oasis MCX and Oasis HLB in the detection of real wastewater samples. The results revealed that PS-DVB-WCX-II and Oasis MCX had better performance in absorbing methamphetamine than Oasis HLB, and PS-DVB-WCX-II had better ability to remove the matrix. The results suggested that the prepared weak cation-exchange sorbent had the potential in the application of illicit drug detection in environmental water.