Disinfection of drinking water is critical to prevent waterborne diseases. An unexpected consequence of water disinfection is the formation of disinfection by-products by the interaction of disinfectants with organic matter (natural or anthropogenic) and halides, which present significant toxicological effects and carcinogenic risks. As an emerging disinfection by-product, halobenzoquinones (HBQs) have attracted increasing attention owing to their severe toxicity and high detection rates. The credible determination of HBQs is essential for further studies on their occurrence, toxicity, and control measures; however, HBQs are usually detected in drinking water at trace levels. Therefore, accurate and efficient analytical techniques are critical for HBQ determination and quantitation. In this study, a method based on solid phase extraction (SPE) combined with ultra performance liquid chromatography-triple quadrupole mass spectrometry (UPLC-MS/MS) was developed to determine 13 HBQs, including six chlorobenzoquinones, six bromobenzoquinones, and one iodobenzoquinone, in drinking water. One-liter water samples were added with 2.5 mL of formic acid, and 500 mL of each sample was collected for further enrichment. Pretreatment optimization mainly focused on the SPE column, washing solvent, and nitrogen blowing temperature. After extraction using Plexa SPE columns (200 mg/6 mL), the samples were washed with ultrapure water containing 0.25% formic acid combined with 30% methanol aqueous solution containing 0.25% formic acid, eluted with 6 mL of methanol containing 0.25% formic acid, and then nitrogen blown at 30 ℃. The UPLC-MS/MS parameters were optimized by comparing the results of two reversed-phase columns (BEH C18 and HSS T3) and various concentrations of formic acid in the mobile phase, as well as by establishing the best instrumental conditions. The separation of 13 HBQs was performed using an HSS T3 column (100 mm×2.1 mm, 1.8 μm) via gradient elution with a mixture of 0.1% formic acid aqueous solution and methanol as the mobile phase for 16 min. The 13 HBQs were detected using a triple quadrupole mass spectrometer equipped with a negative electrospray ionization source (ESI-) in multiple reaction monitoring (MRM) mode. Matrix-matched calibration curves were used to quantify the HBQs owing to intense matrix inhibitory effects. The results reflected the good linear relationships of the 13 HBQs and yielded correlation coefficients (r) greater than 0.999. The method detection limits (MDLs, S/N=3) were 0.2-10.0 ng/L, while the method quantification limits (MQLs, S/N=10) were 0.6-33.0 ng/L. The recoveries of the 13 HBQs were 56%-88% at three spiked levels (10, 20, 50 ng/L), and the relative standard deviations (RSDs, n=6) were less than or equal to 9.2%. The optimization method was applied to analyze HBQs in five drinking water samples. Four HBQs, namely, 2,6-dichloro-1,4-benzoquinone (2,6-DCBQ), 2,5-dibromo-1,4-benzoquinone (2,5-DBBQ), 2,6-dibromo-1,4-benzoquinone (2,6-DBBQ), and 2,6-dibromo-3,5-dimethyl-1,4-benzoquinone (2,6-DBDMBQ), were detected in the samples with detection rates of 100%, 20%, 80%, and 20%, respectively. The most frequently detected HBQ, 2,6-DCBQ, also exhibited the highest content (15.0-56.2 ng/L). The method showed high sensitivity, stability, accuracy, and efficiency, rendering it suitable for the analysis of 13 HBQs in drinking water. Compared with previous methods that mainly focused on 2,6-DCBQ and 2,6-DBBQ, the developed method achieved higher throughput and enabled the simultaneous analysis of 13 HBQs. The method presented in this study provides an opportunity to explore different types and concentrations of HBQs in drinking water, offers a deeper understanding of the occurrence of HBQs, and facilitates further studies on the health risks and control measures of these compounds.
卤代苯醌作为一类新检出的消毒副产物,在饮用水中检出率高但含量较低。为准确、高效、高通量分析饮用水中的卤代苯醌,本文基于固相萃取前处理和超高效液相色谱-三重四极杆质谱,建立了同时检测饮用水中13种卤代苯醌(6种氯代苯醌、6种溴代苯醌、1种碘代苯醌)的方法。在1 L水样中加入2.5 mL甲酸混匀,取500 mL水样经Plexa固相萃取柱(200 mg/6 mL)富集浓缩后,进行超高效液相色谱-三重四极杆质谱检测。以HSS T3色谱柱(100 mm×2.1 mm, 1.8 μm)分离,甲醇-0.1%甲酸水溶液为流动相进行梯度洗脱,采用电喷雾负离子模式电离、多反应监测模式检测,基质匹配外标法定量。以饮用水为基质考察方法的精密度和准确度,结果表明,13种卤代苯醌在各自的线性范围内呈现良好的线性关系,相关系数(r)均大于0.999,方法检出限(MDL, S/N=3)和方法定量限(MQL, S/N=10)分别为0.2~10.0 ng/L和0.6~33.0 ng/L。不同加标水平(10、20、50 ng/L)下13种卤代苯醌的回收率为56%~88%,相对标准偏差(RSD, n=6)均≤9.2%。利用该方法分析了5份实际饮用水样品,共检出4种卤代苯醌,分别是2,6-二氯-1,4-苯醌、2,5-二溴-1,4-苯醌、2,6-二溴-1,4-苯醌和2,6-二溴-3,5-二甲基-1,4-苯醌。单一样品中若以任一卤代苯醌检出为标准,则卤代苯醌总检出率为100%。其中2,6-二氯-1,4-苯醌的含量最高,为15.0~56.2 ng/L。本方法具有良好的灵敏度、准确度和精密度,分析时间短,覆盖目标物种类多,适合饮用水中卤代苯醌类消毒副产物的测定,同时为研究饮用水中卤代苯醌的分布特征、健康风险及控制措施提供了有力支撑。
Keywords: disinfection by-products (DBPs); drinking water; halobenzoquinones (HBQs); solid phase extraction (SPE); ultra performance liquid chromatography-triple quadrupole mass spectrometry (UPLC-MS/MS).