Determination of parabens in human urine by optimal ultrasound-assisted emulsification microextraction and on-line acetylation gas chromatography–mass spectrometry

An effective and solvent-less method for the rapid determination of four commonly detected parabens (methyl-, ethyl-, propyl- and butyl-) in human urine samples is described. This method employed ultrasound-assisted emulsification microextraction (USAEME) before identification and quantitation of the parabens via on-line acetylation gas chromatography-mass spectrometry (GC–MS). Urine samples were enzymatically de-conjugated with β-glucuronidase and then extracted by an optimal USAEME procedure for the measurement of total concentrations of target analytes. The optimal USAEME parameters for one mL of urine sample (containing 0.1-g of sodium chloride), according to the Box-Behnken design method, are thus described: extractant of 200-μL of ethyl acetate, and ultrasonication for 1.0 min and centrifugation at 7000 rpm (3 min). The supernatant was collected and evaporated until dry. Then the residue was re-dissolved in methanol (100-μL), and the extract was subjected to on-line acetylation GC–MS analysis. The limits of quantitation (LOQs) were less than 0.06 ng/mL. Precisions for both intra- and inter-day analysis were calculated, and were less than 8%. Mean extraction recovery (known as trueness) was between 83 and 101% on three concentration levels. In human urine, the total concentrations of the four selected parabens, according to preliminary results, range from 0.3 to 124.5 ng/mL for male, and from 27.2 to 246.3 ng/mL for female. Female urine samples showed higher concentrations for the target parabens, which may indicate higher exposure due to lifestyle. This method permits accurate and high-throughput analysis of parabens for epidemiological studies.