Wetting film liquid-liquid microextraction in a sequential injection system for spectrofluorimetric determination of bisphenol A in tap waters

Bisphenol A (BPA) shows estrogenic effects for humans and concentrations in the μg L-1 range have been found in tap waters of some countries, including Brazil, thus requiring fast and reliable procedures for its monitoring. A flow-based liquid-liquid microextraction procedure was developed for separation and preconcentration of BPA, aiming at the determination based on its native fluorescence, which significantly increases in organic media. Extraction was carried out in a sequential injection system (Figure 1) by means of a film of the extractor (1-octanol) reproductively formed on the walls of a hydrophobic tube (wetting film approach), followed by elution of the extract with ethanol. An enrichment factor of 15.5 was achieved with only 1.5 mL of sample and 30 μL of 1-octanol. The consumptive index of 0.097 mL and concentration efficiency of 2.6 min-1 indicate that the proposed approach is highly efficient for analyte preconcentration. A linear response was observed from 5.0 to 100 μg L-1 with a detection limit of 1.8 μg L-1, sampling rate of 10 h-1 and coefficient of variation of 2.3% (n = 10). Recoveries of BPA spiked to tap water samples were in the range 96-108%. The procedure was successfully applied to tap water samples (BPA concentrations within 6.7 and 13.4 μg L-1) and the results agreed with those obtained by the HPLC reference method at the 95% confidence level. Because analyte derivatization and the use of toxic solvents are avoided, the proposed procedure is a more environmental friendly alternative for BPA determination.