Abstract:

Chromatography combined with mass spectrometry is the most commonly used detection technology, and it offers the advantages of high sensitivity and high selectivity. However, the contents of bisphenols (BPs) in water samples are at the ng/L level. Even if the BPs contents are determined by mass spectrometry, the samples must be pretreated and enriched. A quick, easy, inexpensive, effective, rugged, and safe technique (QuEChERS) can offer advantages such as cost effectiveness and time efficiency. The application of QuEChERS is currently extended to the analysis of contaminants in food and water samples. In this work, QuEChERS coupled with ultra performance liquid chromatography-tandem mass spectrometry (UPLC-MS/MS) was proposed for the determination of eight BPs in surface water. Method optimization was carried out in terms of process efficiency (PE), which included the matrix effect (ME) and extraction recovery (RE). First, the water samples were extracted with 10 mL ethyl acetate and cleaned with 50 mg primary secondary amine (PSA) and 50 mg graphitized carbon black (GCB). Then, the organic layer was collected and evaporated to dryness under nitrogen flow (40 ℃). Finally, the extracts were redissolved in 0.5 mL of a methanol-water (1∶1, v/v) mixture and subjected to UPLC-MS/MS analysis. Chromatographic separation was accomplished on a Waters ACQUITY UPLC BEH C₁₈ column (100 mm×2.1 mm, 1.7 μm) with gradient elution. Methanol and 0.1 mmol/L ammonium bicarbonate aqueous solution were used as the mobile phases. The eight BPs were analyzed by MS/MS with negative electrospray ionization (ESI^-) and in the multiple reaction monitoring (MRM) mode. The matrix matching external standard method was used for quantitative determination. The eight compounds could be analyzed within 8 min. Under the optimized conditions, the calibration curves showed good linearities for the eight BPs, and the coefficients of determination (R²) were greater than 0.9990. The limits of detection (LODs, S/N=3) and limits of quantification (LOQs, S/N=10) were in the ranges of 0.1-2.3 ng/L and 0.3-6.1 ng/L, respectively. The average recoveries of the eight BPs in river water samples were 78.8%-116.6%, and the corresponding relative standard deviations (RSDs) were 1.8%-9.0% (n=6). This method was applied to the analysis of BPs pollution in Guangyuan section of Jialing river and its tributaries, and widespread pollution was confirmed. The detection rate of BPA was 100% with a content of 6.15-90.03 ng/L, and the detection rate of BPS was 91%, with the contents being in the range not detected (nd) to 4.63 ng/L. The method established in this study allowed for the rapid enrichment and purification of the eight BPs in water. With its advantages of simplicity, rapidness, high sensitivity, and low cost, the method can be used for the rapid determination of trace BPs in surface water such as lake water and river water.

Key words: ultra performance liquid chromatography-tandem mass spectrometry (UPLC-MS/MS), QuEChERS, bisphenols (BPs), surface water