Determination of bisphenols in sewage based on supramolecular solid-phase extraction/liquid chromatography/fluorimetry

Supramolecular sorbents (hemimicelles/admicelles) are proposed for the extraction/preconcentration of bisphenols from aqueous environmental samples prior to their liquid chromatography/fluorimetric determination. A comparative study on the use of cetyltrimethylammonium bromide (CTABr)-coated silica and sodium dodecyl sulphate (SDS)-coated γ-alumina as sorbent materials, is presented. Bisphenol A (BPA) and bisphenol F (BPF) were quantitatively retained on CTABr admicelles. Addition of tetrabutylammonium chloride (TBAC) to water samples was required to completely retain bisphenols on SDS-γ-alumina. Retention on both sorbents occurred through hydrophobic and pi-cation interactions between the quaternary ammonium head group of the cationic amphiphile (CTABr or TBAC) and the aromatic rings of the target analytes. TBAC-SDS-γ-alumina was the sorbent selected for the SPE of bisphenols on the basis of the lower elution volume required (1 ml of methanol) and the greater breakthrough volume allowed (400 ml), which permitted to reach practical detection limits of 10 and 15 ng/l for BPF and BPA, respectively. The proposed method was used to quantify bisphenol A and bisphenol B in wastewater samples from four sewage treatment plants. Recoveries obtained ranged between about 99 and 105% for raw wastewater and between 96 and 106% for treated wastewater.