Ultrasound-Assisted Surfactant-Enhanced Emulsification Micro-Extraction Followed by HPLC for Determination of Preservatives in Water, Beverages and Personal Care Products

An ultrasound-assisted surfactant-enhanced emulsification micro-extraction (UASEME) procedure has been developed for pre-concentration of benzoic acid (BA) and paraben preservatives, including methylparaben, ethylparaben, propylparaben and butylparaben, prior to high-performance liquid chromatography-ultraviolet (HPLC-UV) analysis. Separations were performed on a Lichrospher RP-18 endcapped 5 µm, using an isocratic mobile phase of 40% acetonitile, at a flow rate of 1 mL min−1. The selected UASEME conditions comprised the use of 10 mL sample extract, 125 µL 1-octanol as extraction solvent and 0.05 mmol L−1 Tween 20 as emulsifier, 0.5% sodium chloride, ultrasonication time of 6 min and centrifugation time of 10 min. Method performance demonstrated wide linear range between 0.5 and 7,000 µg L−1 (R2 > 0.9903) and limits of detection between 0.03 and 10 µg L−1, which providing the enrichment factors of 15–184. The method precision (relative standard deviation) was <7%. The developed UASEME coupled with HPLC-UV has been successfully applied to determine four paraben preservatives in various sample matrices such as water, beverages and personal care products. The recoveries in the range of 70–138.1% were obtained. However, BA could not be determined in real sample extracts.