Determination of urinary bisphenol A by coacervative microextraction and liquid chromatography-fluorescence detection

Total (free plus conjugated) urinary BPA is currently being used to assess human exposure to this contaminant. This work proposes the use of coacervates made up of reverse micelles of decanoic acid for the microextraction of BPA, prior to its determination by liquid chromatography and fluorescence detection (lambda(ex)=276 nm and lambda(em)=306 nm), with the aim of simplifying sample treatment and reducing analysis time and costs in epidemiologic studies. The procedure involves the enzymatic hydrolysis of 7 mL of urine and then the addition of decanoic acid (100mg) and tetrahydrofurane (1 mL), conditions under which the coacervate (extractant phase, approximately 167 microL) forms in situ and instantaneously. The overall procedure takes about 20 min and several samples can be simultaneously treated using conventional lab equipment (i.e. stirrers and centrifuges). Extractions were independent of the pH and temperature in the ranges studied (1-4 and 25-50 degrees C) rendering the method robust. Recoveries in samples ranged between 88 and 95% and the practical detection limit was 0.197 microgL(-1), which is below the usual concentrations of BPA in urine (ranges reported 0.4-149 microgL(-1)). The actual concentration factor provided by the method was 38. The precision of the method, expressed as relative standard deviation, was 4.5%. The method was successfully applied to the determination of total BPA in urine from eight healthy volunteers. BPA was detected in all the samples at concentrations ranging between 4.03 and 49 microgL(-1).