Solid-Phase Microextraction Combined with GC–MS for Determination of Diquat and Paraquat Residues in Water

Abstract

We have developed a method for the determination of diquat (DQ) and paraquat (PQ) in aqueous samples and applied it to environmental water samples. The method involves sodium borohydride–nickel chloride (NaBH₄–NiCl₂) reduction and headspace solid-phase microextraction of the perhydrogenated products. GC–MS in SIM mode was used to identify and quantify the analytes. The conditions affecting the reduction and extraction were investigated. The optimum conditions for reduction were: 100 mg NaBH₄, 200 μL 10 % (w/v) NiCl₂, and 90 °C for 30 min. For extraction, the SPME fiber was exposed for 20 min at 60 °C; 1 mL 10 % NaCl (w/v) solution was added to the sample vial. Under these conditions, intra-day and inter-day precision for the target analytes were 1.21–6.21 % and 1.14–6.26 %, respectively. The detection limits for DQ and PQ in water were 0.1 ng mL⁻¹. Recovery of DQ and PQ were between 91.28 and 100.34 %. The method is easy, sensitive, and environmentally friendly.