A simplified ultrasound-assisted cloud-point extraction method coupled with high performance liquid chromatography for residue analysis of benzimidazole anthelmintics in water and milk samples

Abstract

A simple ultrasound-assisted cloud point extraction (UA-CPE) method combined with high performance liquid chromatography-photodiode array (PDA) detection has been developed for the extraction, preconcentration and determination of benzimidazole anthelmintics (e.g., thiabendazole, oxfendazole, mebendazole, albendazole, and fenbendazole) residues in water and milk samples. Parameters affecting the extraction efficiency, such as concentration of surfactant, content of salt additive, incubation temperature and time, and centrifugation were investigated and optimized. The optimum conditions of UA-CPE were 0.75% (w/v) Triton X-114, 7% (w/v) sodium acetate, 2 min ultrasonication, and 10 min centrifugation. The surfactant-rich phase (SRP) was analyzed by subjecting it to HPLC under gradient condition of 1% (v/v) acetic acid and methanol, an Inertsil ODS column (4.6 × 150 mm, 5 μm), a flow rate of 1.0 mL min⁻¹, and photodiode array detection at 296 nm. Under the optimum conditions, linearity was obtained in the range of 0.1–100 μg L⁻¹ with the correlation coefficients (r²) higher than 0.996. A high preconcentration factor of up to 164 was obtained, corresponding to limits of detection (LOD) in the range of 0.005–0.1 μg L⁻¹. Intra-day (n = 5) and inter-day (n = 3 × 3) precisions were obtained with relative standard deviation (RSD) for retention time and peak area lower than 2.0 and 7.0%, respectively. The recoveries for the spiked target anthelmintics at different concentrations in water (3, 10, and 70 μg L⁻¹) and milk (20, 50 and 100 μg L⁻¹) were in the ranges 81.6–111.4% and 75.3–111.4%, respectively. The proposed UA-CPE method has been demonstrated to be simple, effective, and reliable for the analysis of analytes in the samples studied. In addition, the developed method can be used as an alternative technique to the conventional CPE.