Multi-class determination of undesirables in aquaculture samples by gas chromatography/tandem mass spectrometry with atmospheric pressure chemical ionization: A novel approach for polycyclic aromatic hydrocarbons

Simultaneous determination of anthracene and phenanthrene using a poly-alizarin red S/carbon paste electrode

A polymer-based carbon paste electrode was constructed by electropolymerized Alizarin Red S (ARS) film on the carbon paste electrode (CPE) surface. The electrochemical properties of poly-ARS/CPE were characterized by cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS). Scanning electron microscopy (SEM) was utilized for electrode characterization. The electropolymerization cycles for the construction of the sensor and the supporting electrolyte were optimized. With 0.1 M LiClO₄ as a supporting electrolyte, poly-ARS/CPE was able to generate oxidation peaks for anthracene (ANT) and phenanthrene (PHE), that were clearly defined and easily distinguished from one to another when operating in square wave voltammetry (SWV). In the simultaneous detection the linear ranges of ANT and PHE were within 80-1000 μM, with detection limits of 24 μM. The variation of peak parameters with scan rate was investigated to determine the nature of electrooxidation and the number of electrons involved in the electrode process. Poly-ARS/CPE was successfully utilized for the detection of ANT and PHE in different water samples and the obtained results suggested the selectivity, stability and reproducibility of the modified electrode.

Benefits of Ion Mobility Separation in GC-APCI-HRMS Screening: From the Construction of a CCS Library to the Application to Real-World Samples

The performance of gas chromatography (GC) combined with the improved identification properties of ion mobility separation coupled to high-resolution mass spectrometry (IMS-HRMS) is presented as a promising approach for the monitoring of (semi)volatile compounds in complex matrices. The soft ionization promoted by an atmospheric pressure chemical ionization (APCI) source designed for GC preserves the molecular and/or quasi-molecular ion information enabling a rapid, sensitive, and efficient wide-scope screening. Additionally, ion mobility separation (IMS) separates species of interest from coeluting matrix interferences and/or resolves isomers based on their charge, shape, and size, making IMS-derived collision cross section (CCS) a robust and matrix-independent parameter comparable between instruments. In this way, GC-APCI-IMS-HRMS becomes a powerful approach for both target and suspect screening due to the improvements in (tentative) identifications. In this work, mobility data for 264 relevant multiclass organic pollutants in environmental and food-safety fields were collected by coupling GC-APCI with IMS-HRMS, generating CCS information for molecular ion and/or protonated molecules and some in-source fragments. The identification power of GC-APCI-IMS-HRMS for the studied compounds was assessed in complex-matrix samples, including fish feed extracts, surface waters, and different fruit and vegetable samples.

High-Throughput Mega-Method for the Analysis of Pesticides, Veterinary Drugs, and Environmental Contaminants by Ultra-High-Performance Liquid Chromatography-Tandem Mass Spectrometry and Robotic Mini-Solid-Phase Extraction Cleanup + Low-Pressure Gas Chromatography-Tandem Mass Spectrometry, Part 2: Catfish

The goal of this study was to develop and validate a new method for simultaneous determination of 106 veterinary drugs and 227 pesticides and their metabolites plus 16 polychlorinated biphenyls (PCBs) at and below their regulatory levels established for catfish muscle in the European Union and U.S.A. To do this, two different QuEChERS-based methods for veterinary drugs and pesticides and PCBs were modified and merged into a single mega-method dubbed "QuEChERSER" (more than QuEChERS), which is presented here for the first time. The mega-method was validated in catfish at four different spiking levels with 10 replicates per level. Sample extraction of 2 g test portions was made with 10 mL of 4:1 (v/v) acetonitrile/water, and then an aliquot was taken for ultra-high-performance liquid chromatography-tandem mass spectrometry (UHPLC-MS/MS) analysis of 106 veterinary drugs and 125 pesticides, including metabolites. The remaining extract after salting out was subjected to automated mini-solid-phase extraction cleanup (Instrument Top Sample Preparation) for immediate injection in low-pressure gas chromatography-tandem mass spectrometry (LPGC-MS/MS). The cleanup was conducted in parallel with the 10 min LPGC-MS/MS analysis for 167 PCBs, pesticides, and metabolites, which was conducted in parallel with the 10 min UHPLC-MS/MS analysis for 231 analytes to increase sample throughput (49 analytes were included in both techniques). In MS/MS, three ion transitions were monitored for nearly all targeted analytes to provide unambiguous identification as well as quantification. Satisfactory recoveries (70-120%) and relative standard deviations of ≤20% were achieved for 98 (92%) of the veterinary drugs and their metabolites and for 222 (91%) of pesticides, metabolites, and PCBs, demonstrating that the developed method is applicable for the analysis of these contaminants in fish as part of regulatory monitoring programs and other purposes.

High-sensitive detection of fluorene by ambient ionization mass spectrometry

High sensitive analysis for fluorene at the sub-ng L⁻¹ level in real water samples was achieved by nebulization-dielectric barrier discharge ionization.

Novel ionization reagent for the measurement of gas-phase ammonia and amines using a stand-alone atmospheric pressure gas chromatography (APGC) source

RATIONALE

Contaminants present in ambient air or in sampling lines can interfere with the target analysis through overlapping peaks or causing a high background. This study presents a positive outcome from the unexpected presence of N-methyl-2-pyrrolidone, released from a PALL HEPA filter, in the analysis of atmospherically relevant gas-phase amines using chemical ionization mass spectrometry.

METHODS

Gas-phase measurements were performed using a triple quadrupole mass spectrometer equipped with a modified atmospheric pressure gas chromatography (APGC) source which allows sampling of the headspace above pure amine standards. Gas-phase N-methyl-2-pyrrolidone (NMP) emitted from a PALL HEPA filter located in the inlet stream served as the ionizing agent.

RESULTS

This study demonstrates that some alkylamines efficiently form a [NMP + amine+H]⁺ cluster with NMP upon chemical ionization at atmospheric pressure. The extent of cluster formation depends largely on the proton affinity of the amine compared with that of NMP. Aromatic amines (aniline, pyridine) and diamines (putrescine) were shown not to form cluster ions with NMP.

CONCLUSIONS

The use of NMP as an ionizing agent with stand-alone APGC provided high sensitivity for ammonia and the smaller amines. The main advantages, in addition to sensitivity, are direct sampling into the APGC source and avoiding uptake on sampling lines which can be a significant problem with ammonia and amines.

Aquaculture Contributes a Higher Proportion to Children's Daily Intake of Polycyclic Aromatic Hydrocarbons Than to That of Adults in Eastern China

Asia, especially China, shares a large proportion of global aquaculture production. Consequently, aquaculture food quality and safety with regard to contamination with polycyclic aromatic hydrocarbons (PAHs) were assessed in eastern China, which is a typical area of aquaculture. The concentrations of ∑PAHs ranged from 42 to 600 ng/g dry weight in a variety of dietary species from farm ponds in eastern China. With regard to the total daily intake of PAHs estimated based on the literature data on urinary hydroxy-PAHs in this region, there was a significant difference between children (mean = 130 ng/kg/d) and adults (mean = 600 ng/kg/d for pregnant women, 1700 ng/kg/d for women, and 2300 ng/kg/d for men). Furthermore, we provided a novel estimation on the fractional contribution of aquatic products to the overall human daily intake of PAHs. Specifically, the contribution of aquatic foodstuffs to total daily intake for children and pregnant women reached more than 50 and 10%, respectively, indicating that children and pregnant women were more vulnerable to the PAH-contaminated aquaculture foodstuffs. Meanwhile, no significant region-specific pattern between different provinces was observed. In summary, these results suggested that sensitive subpopulations were vulnerable to exposure to PAH-contaminated aquatic products, and it is necessary to pay attention to the dietary intake pattern of these sensitive subgroups in eastern China. Environ Toxicol Chem 2019;00:1-9. © 2019 SETAC.