Ultrasound-Assisted Switchable Solvent in Determination of Quaternary Ammonium Herbicide Paraquat in Biological, Environmental Water, and Apple Juice Samples Using Chemical Reduction Process Coupled to GC–MS Detection

Abstract

An ultrasound-assisted switchable-hydrophilicity solvent (SHS)-based homogeneous liquid–liquid microextraction (UA-SHS-HLLME) coupled to gas chromatography–mass spectrometry (GC–MS) detection was applied to determine paraquat (PQ) in biological and environmental samples. A chemical reduction of the analyte was performed to produce a volatile derivative of PQ by adding sodium borohydride (NaBH₄) to the sample solution. The reduced PQ derivative was extracted into triethylamine (TEA). Two ionic and non-ionic forms (TEA and protonated triethylamine carbonate, P-TEA-C) were reversed by adding or removing CO₂. The two phases were separated by addition of sodium hydroxide. Ultrasound was used to form fine droplets of the extractant in the sample solution. The effects of some important parameters on the extraction recovery of the reduced PQ derivative were assessed. Under optimum conditions, the limits of detection and the limits of quantification were found in the range of 0.06–0.13 and 0.20–0.30 µg L⁻¹ with preconcentration factors between 150 and 230 in biological and environmental samples, respectively. The intraday precision was less than 8% (n = 5) and the interday precision was less than 9% (n = 5). The applicability and accuracy of the method were tested by the analysis of spiked real samples. The obtained results indicated that the developed method could be an efficient analytical method for analysis of biological and environmental samples.

Graphical Abstract