Congener-specific determination of hydroxylated polychlorinated biphenyls by polar-embedded reversed-phase liquid chromatography-tandem mass spectrometry

Analytical challenges and opportunities in the study of endocrine disrupting chemicals within an exposomics framework

Exposomics aims to measure human exposures throughout the lifespan and the changes they produce in the human body. Exposome-scale studies have significant potential to understand the interplay of environmental factors with complex multifactorial diseases widespread in our society and whose origin remain unclear. In this framework, the study of the chemical exposome aims to cover all chemical exposures and their effects in human health but, today, this goal still seems unfeasible or at least very challenging, which makes the exposome for now only a concept. Furthermore, the study of the chemical exposome faces several methodological challenges such as moving from specific targeted methodologies towards high-throughput multitargeted and non-targeted approaches, guaranteeing the availability and quality of biological samples to obtain quality analytical data, standardization of applied analytical methodologies, as well as the statistical assignment of increasingly complex datasets, or the identification of (un)known analytes. This review discusses the various steps involved in applying the exposome concept from an analytical perspective. It provides an overview of the wide variety of existing analytical methods and instruments, highlighting their complementarity to develop combined analytical strategies to advance towards the chemical exposome characterization. In addition, this review focuses on endocrine disrupting chemicals (EDCs) to show how studying even a minor part of the chemical exposome represents a great challenge. Analytical strategies applied in an exposomics context have shown great potential to elucidate the role of EDCs in health outcomes. However, translating innovative methods into etiological research and chemical risk assessment will require a multidisciplinary effort. Unlike other review articles focused on exposomics, this review offers a holistic view from the perspective of analytical chemistry and discuss the entire analytical workflow to finally obtain valuable results.

Development of an Ultra-Performance Liquid Chromatography-Tandem Mass Spectrometry Method for Hydroxylated Polychlorinated Biphenyls in Animal-Derived Food

Hydroxylated polychlorinated biphenyls (OH-PCBs) are a group of metabolites biotransformed from polychlorinated biphenyls by animals with higher toxicities than their parent compounds. The present work developed and validated an analytical method for determinating penta-, hexa-, and hepta-chlorine substituted OH-PCBs in animal-derived food based on ultra-performance liquid chromatography-tandem mass spectrometry (UPLC-MS/MS) with isotope-dilution. The target analytes were extracted with a 50% n-hexane/dichloromethane (v/v), purified by sulfuric acid-silica gel, and separated by 5% hydrated silica gel, achieving a final concentration of 100 times before injection to LC-MS/MS. The limits of detection (LOD) and quantification (LOQ) for target OH-PCBs were within the ranges of 0.003-0.010 μg/kg and 0.009-0.030 μg/kg, respectively. Average recoveries ranged between 76.7% and 116.5%, with relative standard deviations of less than 18.4%. The proposed method is simple, time-saving, sensitive, and accurate, making it a powerful tool for risk monitoring of OH-PCBs in animal-derived food.

[Simultaneous determination of 29 pesticides residues in bayberry by pass-through solid-phase extraction and ultra-performance liquid chromatography-high resolution mass spectrometry]

A rapid and accurate analysis method based on PRiME HLB pass-through solid-phase extraction (SPE) and ultra-performance liquid chromatography-high resolution mass spectrometry (UPLC-HRMS) was developed for the determination of 29 pesticide residues in bayberry samples. The bayberry samples were first extracted using acetonitrile by vortexing; then, the extract solution was salted out and purified by PRiME HLB pass-through solid-phase extraction (SPE) cartridges. Chromatographic separation was subsequently carried out on a Waters ACQUITY UPLC HSS T₃ column (100 mm×2.1 mm, 1.8 μm) using 5 mmol/L ammonium acetate in water and acetonitrile as the elution solvent. The electrospray ion source in positive (ESI⁺) mode and full mass-data-dependent MS² (full mass-ddMS²) mode were used for quantification by the matrix-matched external standard method. The LC conditions were first optimized, and two analytical columns, Waters ACQUITY UPLC HSS T₃ and Waters ACQUITY UPLC BEH C₁₈, were investigated for the 29 pesticides. The results indicated that the Waters ACQUITY UPLC HSS T₃ column showed better chromatographic retention. Moreover, composites of the mobile phase were also studied. Compared to the acetonitrile-formic acid aqueous solution system and acetonitrile-formic acid-ammonium acetate aqueous solution system, the acetonitrile-ammonium acetate aqueous solution system used as the mobile phase exhibited much better chromatographic behavior for most of the 29 pesticides. In particular, the MS responses of some of the target pesticides were significantly improved when using the ammonium acetate-acetonitrile system as the mobile phase. In addition, the sample pretreatment conditions for the 29 pesticides in bayberry samples were systematically optimized. The matrix effect (ME) for three different types of purification methods were applied to evaluate the purification efficiency for the 29 pesticides in the bayberry samples. The following results were obtained from the post-spiking experiments: (1) For graphitized carbon (GCB) SPE, the post-spiking recoveries of 29 pesticides in the bayberry samples were generally low, less than 60%. (2) For the QuEChERS method, the recoveries of most target pesticides improved. The pesticide ratio with recoveries ranging from 70% to 120% was found to be 41%; however, the pesticide ratio with recoveries of less than 60% was still high (35%). (3) For the PRiME HLB-based pretreatment method, the recoveries of the 29 pesticides obviously improved. The pesticide ratio with recoveries between 70% and 120% was up to 76%, while the pesticide ratios were only 14% and 10% for post-spiking recoveries of 60%-70% and >120%, respectively. Meanwhile, the recoveries of all 29 pesticides were found to be more than 60%. Therefore, the PRiME HLB-based method was better than the GCB SPE and QuEChERS methods for pretreatment of the 29 pesticides in the bayberry samples. In addition, the PRiME HLB-based pretreatment process does not require tedious operation processes such as activation, balance, and elution, and thus, the sample pretreatment time is greatly shortened. Under the optimal conditions, the 29 target pesticides showed good linearity in the range of 1.0-200.0 μg/L, with correlation coefficients (R²) higher than 0.999. The limits of detection (LODs) were 2.0 μg/kg for the 29 target pesticides. The recoveries of the pesticides spiked in the bayberry samples were in the range of 69.2%-135.6% at 6, 200, and 400 μg/kg, respectively, while the relative standard deviations (RSDs) in the range of 0.7%-14.6%. The proposed method based on PRiME HLB-pass through SPE-UPLC-HRMS was adopted to determine these 29 pesticides in 30 bayberry samples purchased from local and online markets. According to the results, pesticides such as methamidamine, difenoconazole, and tebuconazole were frequently detected in the bayberry samples. However, the maximum residue limits (MRLs) of methamidamine, difenoconazole, and tebuconazole in bayberry samples were not provided in GB 2763-2019. In summary, the developed method is fast, simple, sensitive, and accurate, and it can be applied for daily monitoring of pesticides in bayberry samples.