Investigation of pH-switchability of hydrophobic deep eutectic solvents for the extraction and preconcentration of triazine herbicides in water samples

Abstract

An environmental friendly, fast, easy, inexpensive and dispersive-solvent-free liquid–liquid microextraction (LLME) based on pH-switchable hydrophobic deep eutectic solvent (HDES) procedure was developed and combined with high performance liquid chromatography–ultraviolet (HPLC − UV) detection for the extraction and analysis of triazine herbicides in water samples. In this method, 10 different DESs were prepared and then their pH-switchability was investigated. DESs that could be switched with pH were employed for separation and preconcentration of triazine herbicides in water samples. In this method, dispersing the extractant phase in the aqueous solution and subsequent phase separation is done only by changing the pH. Important parameters affecting extraction, such as type of DES and its volume, concentration of KOH, volume of HCL, effect of salt and extraction time were investigated and optimum conditions were obtained. In optimized conditions, the values of relative standard deviations (RSDs) for intra-day and inter-day of the procedure based on seven replicate analysis of 100 μg L–1 of triazines in water samples were 1.9–4.4 and 2.7–6.2%, respectively. The calibration graphs were linear ranging from 0.5 to 350 μg L–1 with correlation coefficients (r2) better than 0.990. The limit of detections (LODs) and limit of quantifications (LOQs) were 0.2–0.5 and 0.5–1.5 μg L–1, respectively. The relative recoveries (RRs) of real water samples which have been spiked with different levels of triazines were 91–107.8%.