Corticosteroids (CSs) are widely used to treat various inflammatory and immune diseases in humans and animals, such as arthritis and lupus. Thus far, CSs have been frequently detected in diverse pollution sources, such as in the influent and effluent of traditional wastewater treatment plants, livestock farms, and aquaculture. Owing to incomplete removal or limited treatment, CSs can enter the water environment and eventually be adsorbed in the sediment. Due to hydrodynamic effects, CSs can re-enter the surface water through the resuspension of sediments, and pose a hazard to the ecosystem and human health via the enrichment of aquatic organisms and transmission through the food chain. Therefore, trace analysis of CSs in sediments is significant for exploring their prevalence and behavior in multiple environments. However, existing research mainly focuses on the determination of glucocorticoids in water samples, and studies on the systematic quantitative analysis of CSs in environmental solid samples with more complex matrices are scarce. Moreover, majority of previous investigations focused on a limited number of glucocorticoids, making it important to widen the range of target compounds to be studied, including mineralocorticoids. In this study, the main factors which could influence the accuracy and sensitivity in the determination of 24 target CSs were systematically optimized in the sample pretreatment and instrument analysis. A novel method based on ultrasonic extraction coupled with solid phase extraction (SPE) for sample pretreatment was developed for the simultaneous determination of the 24 CSs in sediments using ultra-performance liquid chromatography-tandem mass spectrometry (UPLC-MS/MS). The sediment sample was ground to homogenize the particle sizes after freeze-drying. The analytes from 2.0 g of the sample were ultrasonicated and extracted with methanol-acetone (1∶1, v/v). After concentrating and diluting each extract, SPE was performed. The water sample was extracted and purified using hydrophile-lipophile balance (HLB) cartridges, following which the extract was further purified with LC-NH2 cartridges. The extracts were concentrated using a rotary evaporator, dried under a gentle stream of nitrogen, and re-dissolved in methanol for instrumental analysis. Chromatographic separation was conducted on an Agilent ZORBAX Eclipse Plus C8 column (100 mm×2.1 mm, 1.8 μm), with a column flow rate of 0.3 mL/min and a gradient of mobile phases A (water with 0.1% acetic acid) and B (acetonitrile). The column temperature was set to 30 ℃ and the injection volume was fixed at 5 μL. Electrospray ionization MS in the dynamic multiple reaction monitoring (DMRM) and selected ion monitoring (SIM) modes were performed in the positive mode for the qualitative and quantitative analysis of the target compounds. Quantitation of the target compounds was carried out using the internal standard method. The effects of different extraction solvents, purification conditions, and MS conditions on the recoveries of the target compounds were investigated. The limits of detection (LODs) (S/N≥3) and limits of quantification (LOQs) (S/N≥10) of all 24 compounds were in the ranges of 0.14-1.25 μg/kg and 0.26-2.26 μg/kg, respectively. The correlation coefficients of linear calibration curves were higher than 0.995 in the range of 1.0-100 μg/L. The recoveries of the 24 CSs at 5, 20, and 50 μg/kg spiked levels ranged from 64.9% to 125.1% with relative standard deviations of 0.4%-12.6% (n=5). The developed method was applied to analyze the CSs in three sediment samples from the rivers of the Pearl River Delta. In all, 11 target compounds were detected in these samples, with contents in the range of 1.25-29.38 μg/kg. The characteristic of this method is efficient, sensitive, reliable, and suitable for the trace determination of varieties of natural and synthesized CSs in environmental sediments.
沉积物中皮质类固醇激素(CSs)的痕量分析对探究其在环境多介质中的赋存状况和环境行为具有重要意义。然而目前相关研究主要集中在水样中糖皮质激素的测定,对基质更为复杂的环境固体样品中CSs的定量分析研究仍十分有限亦缺乏针对性、系统性,且目标物未能覆盖大多数常见常用的糖/盐CSs。本研究系统地优化了样品前处理过程和仪器分析中影响24种CSs测定准确性和灵敏度的条件,建立了采用超声波提取联合固相萃取技术对样品进行前处理,利用超高效液相色谱-串联质谱(UPLC-MS/MS)同时测定沉积物中24种CSs的分析方法。沉积物经冷冻干燥、研磨后,取2.0 g样品采用甲醇-丙酮(1:1, v/v)超声提取,HLB固相萃取柱富集、净化,LC-NH2小柱二次净化,甲醇定容。目标物经Agilent ZORBAX Eclipse Plus C8反相色谱柱(100 mm×2.1 mm, 1.8 μm)分离,柱温30 ℃,进样量5 μL,以乙腈和0.1%(v/v)乙酸水溶液作为流动相进行梯度洗脱,流速0.3 mL/min。在电喷雾正离子模式(ESI+)下采用动态多反应(DMRM)选择离子监测(SIM)方式测定24种目标化合物,内标法定量。结果表明,24种CSs的方法检出限(LOD, S/N≥3)和定量限(LOQ, S/N≥10)分别为0.14~1.25 μg/kg和0.26~2.26 μg/kg,工作曲线在1.0~100 μg/L范围内具有良好的线性关系(R2>0.995)。在5、20、50 μg/kg的基质加标水平下,24种CSs的平均回收率为64.9%~125.1%,相对标准偏差为0.4%~12.6%(n=5)。应用该方法测定了3份珠江三角洲河流沉积物,其中有11种目标物被检出,含量范围为1.25~29.38 μg/kg。该方法净化效率高,灵敏可靠,适用于环境沉积物中多种天然和合成CSs的痕量检测。
Keywords: corticosteroids; sediments; solid phase extraction (SPE); ultra performance liquid chromatography-tandem mass spectrometry (UPLC-MS/MS); ultrasonic extraction.