Abstract:

Halobenzoquinones (HBQs), which are emerging chlorinated disinfection byproducts (DBPs), have attracted increasing attention because they are frequently detected in treated tap water, entrainment water, etc. These compounds are mainly generated during the water treatment process using chlorine, chloramine, and chlorine dioxide as disinfectants, and display more toxic effects than regulated DBPs, such as trihalomethane and haloacetic acid. HBQs have been recognized as potential bladder carcinogens and are harmful to the nervous system. Additionally, they can exert genotoxic effects and cause oxidative damage to DNA and proteins. The risk of HBQs in aquatic products is expected to rise because the disinfection of public facilities has significantly increased in recent years. Therefore, developing a sensitive and accurate analytical method to detect HBQs in aquatic products is of great importance. Several analytical methods, including gas chromatography, gas chromatography-mass spectrometry, electrochemical methods, liquid chromatography, and liquid chromatography-tandem mass spectrometry, can be used to identify and quantify HBQs in water. However, to the best of our knowledge, no reports on the determination of HBQ levels in aquatic products are yet available. Further, pretreatment is essential for HBQ determination because of the complex matrix effects of aquatic products. Herein, a sensitive and accurate method based on the QuEChERS technique coupled with ultra performance liquid chromatography-tandem mass spectrometry (UPLC-MS/MS) was developed for the simultaneous determination of five HBQs in aquatic products. For the QuEChERS procedure, the pretreatment conditions, such as the extraction solvent and adsorbent species, were systematically optimized. The sample was extracted with 10 mL of 10% methanol acetonitrile solution (containing 0.1% formic acid), dehydrated, and centrifuged with sodium chloride and anhydrous magnesium sulfate. The supernatant was purified using a QuEChERS packing material consisting of 50 mg N-propylethylenediamine (PSA), 30 mg of graphitized carbon black (GCB), and 30 mg of neutral alumina (Al₂O₃), dried with nitrogen, and concentrated. The five HBQs were separated on a Waters ACQUITY UPLC BEH C₁₈ column (100 mm×2.1 mm, 1.7 μm) using 0.25% acetonitrile formate solution and 0.25% formic acid aqueous solution as the mobile phase under a gradient elution program and then detected using UPLC-MS/MS with negative electrospray ionization (ESI^-) under multiple reaction monitoring (MRM) mode. Quantitative analysis was performed using a matrix-matched external standard method. The five HBQs achieved rapid separation within 6 min, indicating that the proposed method has a much shorter separation time compared with previous studies. The matrix effect was evaluated by establishing a matrix-matched calibration curve. The results showed that 2,5-dichloro-1,4-benzoquinone (2,5-DCBQ) presented a matrix-enhancing effect, whereas the other HBQs displayed matrix-inhibiting effects. In particular, tetrachlorobenzoquinone (TCBQ) exhibited strong inhibitory effects. Under the optimized experimental conditions, the five HBQs demonstrated good linear relationships in the range of 1.0-50.0 μg/L, with correlation coefficients (r)≥0.9992. The detection limits of the method were 0.15-0.8 μg/kg, and the recoveries of the target compounds were 85.9%-116.5%. The relative standard deviations were 1.4%-8.2%, which indicates good reproducibility. The proposed method was successfully applied to actual sample detection, and 2,6-dichloro-3-methyl-1,4-benzoquinone (2,6-DCMBQ) was detected in grass carp. The proposed method is convenient, sensitive, accurate, and suitable for the simultaneous determination of five HBQs in aquatic products. Moreover, the developed method provides a reliable reference for the routine monitoring of trace HBQs in food samples.

Key words: QuEChERS, ultra performance liquid chromatography-tandem mass spectrometry (UPLC-MS/MS), halobenzoquinones (HBQs), aquatic products