Catanionic surfactant ambient cloud point extraction and high-performance liquid chromatography for simultaneous analysis of organophosphorus pesticide residues in water and fruit juice samples

A mixed anionic–cationic surfactant cloud point extraction (CPE) has been developed using sodium dodecyl sulfate (SDS) and tetrabutylammonium bromide (TBABr) for the extraction and preconcentration of organophosphorus pesticides (OPPs) at ambient temperature before analysis by high-performance liquid chromatography. The studied OPPs were azinphos-methyl, parathion-methyl, fenitrothion, diazinon, chlorpyrifos, and prothiophos. The optimum conditions of the mixed anionic–cationic CPE were 50 mmol L⁻¹ SDS, 100 mmol L⁻¹ TBABr, and 10% (w/v) NaCl. The extracted OPPs were successfully separated within 11 min using the conditions of a Waters Symmetry C8 column, a flow rate of 0.8 mL min⁻¹, a gradient elution of methanol and water, and detection at 210 nm. Linearity was found over the range 0.05–5 μg mL⁻¹, with the correlation coefficients higher than 0.996. The enrichment factor of the target analytes was in the range 6–11, which corresponds to their limits of detection from 1 to 30 ng mL⁻¹. High precisions (intra-day and inter-day) were obtained with relative standard deviation <1.5% (t _R) and 10% (peak area). Accuracies (% recovery) of the different spiked OPP concentrations were 82.7–109.1% (water samples) and 80.3–113.3% (fruit juice samples). No contamination by the OPPs was observed in any studied samples.