Determination of bisphenol A, 4-octylphenol, and 4-nonylphenol in soft drinks and dairy products by ultrasound-assisted dispersive liquid-liquid microextraction combined with derivatization and high-performance liquid chromatography with fluorescence detection.

A novel hyphenated method based on ultrasound-assisted dispersive liquid-liquid microextraction coupled to precolumn derivatization has been established for the simultaneous determination of bisphenol A, 4-octylphenol, and 4-nonylphenol by high-performance liquid chromatography with fluorescence detection. Different parameters that influence microextraction and derivatization have been optimized. The quantitative linear range of analytes is 5.0-400.0 ng/L, and the correlation coefficients are more than 0.9998. Limits of detection for soft drinks and dairy products have been obtained in the range of 0.5-1.2 ng/kg and 0.01-0.04 μg/kg, respectively. Relative standard deviations of intra- and inter-day precision for retention time and peak area are in the range of 0.47-2.31 and 2.76-8.79%, respectively. Accuracy is satisfactory in the range of 81.5-118.7%. Relative standard deviations of repeatability are in the range of 0.35-1.43 and 2.36-4.75% for retention time and peak area, respectively. Enrichment factors for bisphenol A, 4-octylphenol, and 4-nonylphenol are 170.5, 240.3, and 283.2, respectively. The results of recovery and matrix effect are in the range of 82.7-114.9 and 92.0-109.0%, respectively. The proposed method has been applied to the determination of bisphenol A, 4-octylphenol, and 4-nonylphenol in soft drinks and dairy products with much higher sensitivity than many other methods.