Automated SPE-HPLC-UV methodology for the on-line determination of plasticisers in wastewater samples

An automated methodology (SPE-HPLC-UV) is proposed in this work for the determination of plasticisers in water samples collected at different stages of two wastewater treatment plants (WWTPs). Bisphenol A (BPA) and 4-tert-butylphenol (4tBP) were chosen as model pollutants. The 3(3-1) fractional factorial experimental design (FFED) was used to determine more significant variables associated with the preconcentration procedure. The factors studied were the adsorbent composing the SPE membrane disk, sample volume and pH of the sample. Three SPE membranes disks were evaluated: (1) C18 octadecyl bonded silica (C18), (2) styrenedivinylbenzene-extra clean (SDB-XC) copolymer, and (3) styrenedivinylbenzene-reversed-phase sulphonated (SDB-RPS) copolymer. The preconcentration conditions selected were the SDB-RPS membrane disk as the sorbent, a sample volume of 30 mL and a solution pH of 7. HPLC-UV analysis was achieved isocratically using a C18 column with CH3CN:H2O, 60:40% v v(-1), at a flow rate of 1.0 mL min(-1). The linearity range was between 5 and 80 mu g L-1 with determination coefficients (R-2) higher than 0.9989. The limits of detection (LODs) were 0.77 and 1.46 mu g L-1 for BPA and 4tBP, respectively. Furthermore, the intraday and interday precisions expressed in terms of relative standard deviation (RSD) were found between 2.5-5.0% and 4.6-6.0%, respectively. Excellent recovery rates (72.2-99.8%) were demonstrated by spiking known concentrations of BPA and 4tBP in the WWTP samples. The proposed methodology was successfully applied to determine BPA and 4tBP in water samples of two WWTPs from the metropolitan area of Monterrey, Mexico. BPA was found in wastewater influent ranging from 5.9 to 16.6 mu g L-1, while 4tBP was detected in samples from different stages of WWTPs in concentrations ranging from 4.9 to 21.5 mu g L-1.

Automated summary

In this study, an automated methodology was proposed for the determination of plasticisers in water samples collected from wastewater treatment plants. The methodology combined solid-phase extraction with high-performance liquid chromatography and ultraviolet detection. The selected preconcentration conditions and analysis parameters were optimized. The proposed methodology was successfully applied to detect Bisphenol A and 4-tert-butylphenol in water samples from two wastewater treatment plants.