Development of dispersive solid-liquid extraction method based on organic polymers followed by deep eutectic solvents elution; application in extraction of some pesticides from milk samples prior to their determination by HPLC-MS/MS.

An effective extraction procedure based dispersive solid phase extraction was developed for the extraction of different pesticides (dimethoate, imidacloprid, pirimicarb, carbaryl, fenitrothion, hexythiazox, and phosalone) from milk samples. The analytes were determined by high performance liquid chromatography-tandem mass spectrometry. In this method, an organic polymer (polystyrene) was dissolved in a water-miscible organic solvent (tetrahydrofuran) and it was injected into the aqueous phase obtained from milk sample after deprotonation. By this action the sorbent (polymer) was precipitated and dispersed in the solution as tiny particles. By doing so, the pesticides were adsorbed onto the sorbent. After that, the sorbent was separated by centrifugation and the adsorbed analytes were eluted by tetrabutylammonium chloride: dichloroacetic acid deep eutectic solvent. After optimization, the method validation was followed according to Food and Drug Administration and International Research Council guidelines and the results showed that wide linear ranges (0.93-500 ng/mL) and low limits of detection (0.09-0.27 ng/mL) and quantification (0.31-0.93 ng/mL) were obtained. Extraction recoveries and extraction and enrichment factors were in the ranges of 81-94% and 162-188, respectively. Relative standard deviations were less than 9% for intra- (n = 6) and inter-day (n = 6) precisions at three concentration of 2, 5, and 25 ng mL-1 of each analyte. The developed method was successfully applied to twenty cow milk samples for determination of the pesticides.

In-situ formation/decomposition of deep eutectic solvent during solidification of floating organic droplet-liquid-liquid microextraction method for the extraction of some antibiotics from honey prior to high performance liquid chromatography-tandem mass spectrometry.

A new liquid-liquid microextraction approach by applying a deep eutectic solvent was adopted for the extraction of four antibiotics (penicillin G, dihydrostreptomycin, enrofloxacin, and ciprofloxacin) from honey samples. The enriched analytes were analyzed by HPLC-MS/MS. The procedure was carried out by synthesis of tetrabutylammonium chloride: p-cresol deep eutectic solvent in the sample solution and then its decomposition in the presence of an acid. In-solution formation of deep eutectic solvent provided wide contact areas among the extractant and sample solution, and accelerated sample preparation. Also, its decomposition enabled collection of the final extraction phase without centrifugation. Low LODs (0.55-0.79 ng/g) and LOQs (1.9-2.6 ng/g), high ERs (70-92%), and suitable RSDs (≤ 6.9%) were obtained. After performing the method on real samples, dihydrostreptomycin was found in several honey samples.

A polymer-based dispersive solid phase extraction combined with deep eutectic solvent based-dispersive liquid-liquid microextraction for the determination of four hydroxylated polycyclic aromatic hydrocarbons from urine samples.

A new and efficient extraction procedure was proposed and used for the simultaneous extraction of four hydroxylated metabolites polycyclic aromatic hydrocarbons from urine samples. The extraction procedure was started by dissolving an organic polymer into a water-miscible organic solvent (iso-propanol) and its injection into the sample solution. The sorbent was re-precipitated in all parts of the solution as tiny particles and the analytes were adsorbed onto the sorbent. After that, the sorbent was separated and the adsorbed analytes were eluted by choline chloride: dichloroacetic acid deep eutectic solvent. The elution solvent was mixed with choline chloride-3,3-dimethyl butyric acid deep eutectic solvent and the mixture was applied in dispersive liquid-liquid microextraction procedure for more concentration of the analytes. After optimization, the method validation was followed according to International Council Harmonization guidelines and the results showed that wide linear ranges (26-500 000 ng/L) and low limits of detection (3.6-7.2 ng/L) and quantification (11-26 ng/L) were obtained. Satisfactory enrichment factors (435-475) and extraction recoveries (87-95%), and acceptable relative standard deviations (equal or less than 8.6%) were obtained. Finally, the introduced method was successfully applied for determination of the analytes in urine samples obtained from tobacco smokers.