Chemosphere Volume 163, November 2016, Pages 99-107
A sensitive method for simultaneous determination of 20 trace organic chemicals (TOrCs, including preservatives, antioxidants, disinfectants, oestrogens, alkyl-phenols and bisphenol-A) in surface water and wastewater has been developed and validated based on the optimisation of solid-phase extraction (SPE) followed by liquid chromatography-mass spectrometry (LC-MS) analysis. 500 mL acidified (pH=2.5) water samples were pre-concentrated by Supel-Select HLB cartridge (200 mg, 6 mL) and eluted with 12 mL mixture of acetonitrile and ethyl acetate (50:50, v/v). This optimised SPE procedure could provide >75% recoveries for the majority of TOrCs. The instrumental methods were developed using two different LC-MS systems: a triple-quadrupole MS (QqQ-MS) and a hybrid quadrupole Orbitrap high resolution MS (Q-Orbitrap-HRMS). Both showed good performance data, but the former system provided better linearity and method precision, with the latter system providing 2–33 times lower detection limits. Different matrix effects were observed for both systems: No remarkable matrix effects were observed for Q-Orbitrap-HRMS but significant matrix effects were found in influent and river water samples for the QqQ-MS. This analytical method was subsequently employed to analyse the TOrCs in river waters and wastewaters from China successfully, which confirmed its applicability to environmental samples.
Preservatives, antioxidants, disinfectants, oestrogens, alkyl-phenols and bisphenol-A are among the trace organic chemicals (TOrCs) that are often present in house and personal care products and pharmaceuticals and discharged to the aquatic environment across the world. As a result, attention has been paid to their potential long-term effects on human health and wildlife. Monitoring the concentrations of these chemicals and studying their fate and behaviour in aquatic environment enables an assessment of their potential transport through food chains and an evaluation of potential risks on ecosystems and human health.
Many of the analytical methods for these chemicals in water samples have been developed based on pre-treatment, normally solid-phase extraction (SPE), followed by instrumental determination by gas chromatography-mass spectrometry (GC-MS) or liquid chromatography-tandem mass spectrometry (LC-MS/MS). With the rapid development of the technology, LC-MS/MS techniques have become the preferred analytical method for polar and/or non-volatile TOrCs, which have advantages such as high selectivity, sensitivity and throughput, reduced analytical time and do not require derivatisation as some GC-MS procedures do. This has led to their widespread application for water/wastewater sample analysis. More recently, LC systems equipped with high resolution MS (LC-HRMS), such as time-of-flight (TOF) and Orbitrip MS, are increasingly popular as it is beneficial for both quantifying target analytes and identifying non-target analytes.
A considerable amount of research has been conducted to determine certain TOrCs, such as preservatives, antioxidants, disinfectants, oestrogens or alkyl-phenols, in different matrixes (water/wastewater, sludge, cosmetics, foodstuffs, biota) using LC-MS/MS, but few studies have provided their simultaneous determination. Furthermore, few studies have conducted a comparative evaluation for conventional LC-MS/MS (triple-quadrupole MS) and LC-HRMS, such an assessment would be of great interest for laboratories that have access to one or the other instrument setup.
Therefore, the aims of this study were to 1) develop and optimise a rapid and sensitive method for the simultaneous extraction and determination of 20 TOrCs (preservatives, antioxidants, disinfectants, oestrogens, alkyl-phenols and bisphenol-A) by SPE and LC-MS/MS, 2) compare the performance of two different LC-MS systems: a triple-quadrupole MS (QqQ-MS) system and a hybrid quadrupole Orbitrap high resolution MS (Q-Orbitrap-HRMS) system for these chemicals, and 3) apply this analytical method to determine the occurrence of these substances in river water and municipal wastewater collected from a city in Central China.
Twenty typical chemicals from 6 groups of TOrCs (preservatives, antioxidants, disinfectants, oestrogens, alkyl-phenols and bisphenol-A) were selected for analysis in this study. High purity standards of these compounds, including six preservatives and one of their metabolites (methylparaben (MEP), ethylparaben (ETP), propylparaben (PRP), butylparaben (BUP), benzylparaben (BEP), heptyl paraben (HEP) and 4-hydroxybenzoic acid (PHBA)), two antioxidants (butylated hydroxyanisole (BHA) and butylated
To optimise the LC separation and ESI ionisation, different organic mobile phases and the effect of mobile phase additives were studied. ACN was selected as the major organic mobile phase, because it could provide better separation and lower column pressure than MeOH. A small proportion (2.5%) of MeOH and MQ water was added into organic mobile phase to enhance the solubility of additives.
Acid additives such as FA in the mobile phases are known to strongly suppress the signal in ESI negative
A sensitive and reliable analytical method has been developed for the simultaneous determination of preservatives, antioxidants, disinfectants, oestrogens, alkyl-phenols and BPA in surface water and wastewater samples by SPE followed by LC-MS analysis. SPE optimisation showed that extraction of 500 mL acidified (pH 2.5) water samples with Supel-Select HLB tubes (200 mg, 6 mL) followed by elution with 12 mL acetonitrile and ethyl acetate (50:50, v/v) mixture could provide good SPE recoveries
The authors thank Dr. Yue'e Peng and Miss Qing Chang and Miss Conghui Shan for assistance in LC-HRMS operation, and Dr. Yuan Zhang, Dr. Xinli Xing, Mr Xiaoyu Jiang, Mr. Yang Min, Miss Hongyan Xiang, Dr. Xiaoping Liao, Miss Yanying Li, Dr. Junyi Li and Dr. Shizhen Zhao for sample collection and pre-treatment. The authors would also like to thank the Safety and Environmental Assurance Centre, Unilever, for the financial support of this study and the Chinese Scholarship Council (CSC, 2011641016)
