A rapid synergistic cloud point extraction for nine alkylphenols in water using high performance liquid...

A rapid synergistic cloud point extraction for nine alkylphenols coupled with high performance liquid chromatography and fluorescence detection was developed. The non-ionic surfactant polyethylene glycol 6000 (PEG 6000) was selected as the extractant. Acetonitrile was used as a revulsant and synergistic reagent with Na₂SO₄ to lower the cloud point temperature of extractant to room temperature. These two reagents allowed a cloudy solution to form without heating. The affecting factors were optimized by multiple response optimization with a Box-Behnken design and the desirability function. The optimum conditions found were PEG 6000, 4% (m/v); acetonitrile, 1.5 mL; Na₂SO₄, 0.6 mol L^-1; no pH adjustment or bathing and dilution; centrifugation for 3 min at 3500 rpm and less 8 min for the throughout sample pretreatment procedure. The extraction efficiencies of the nine alkylphenols ranged from 91.4% to 99.5%. These values varied by less than 2.78% from those predicted by the multiple response optimization model. Good linearity (r > 0.994) was obtained in the ranges of 0.6-200 μg L^-1 for eight alkylphenols and 1.8-600 μg L^-1 for nonylphenol. Simultaneously, the method showed low limit of detection (0.17-0.39 μg L^-1) and excellent repeatability at 50 μg L^-1 for eight alkylphenols and 150 μg L^-1 for nonylphenol (Intraday and Interday of RSD <4.98%, n = 6). The proposed method was successfully applied to determination of the nine alkylphenols in environmental water samples with good recoveries (95.2-106%) and precision values (RSD <5.51%, spiked two levels of 10 and 100 μL of mixed standard, respectively).