Quantitation of ultra-trace nitrated polycyclic aromatic hydrocarbons isomers in water by online solid-phase extraction coupled-liquid chromatography-mass spectrometry

Insight into the environmental photochemistry of nitrated polycyclic aromatic hydrocarbons in water and in ice: kinetics, pathways and photo-modified toxicity

Nitrated polycyclic aromatic hydrocarbons (nitro-PAHs) are contaminants of emerging concern due to their various sources and widespread existence in the environment. This study demonstrated an in-depth comparison of the aqueous and ice photochemistry of three nitro-PAHs: 1-nitropyrene (1-Npyr), 2-nitrofluorene (2-Nflu) and 9-nitrophenanthrene (9-Nphe). Upon exposure to the simulating solar irradiation (λ > 290 nm), their apparent photolysis followed pseudo-first-order kinetics, with apparent quantum yields (Φs) and half-lives (t1/2) depending on the chemical structures or the reaction media (water/ice). Based on the ROS scavenging experiments, 1-Npyr was found to suffer from self-sensitized photo-oxidation by hydroxyl radicals (·OH), while 2-Nflu and 9-Nphe underwent singlet-oxygen (1O2) mediated self-sensitized photolysis. Moreover, the contributions of the self-sensitized photolysis via ·OH/1O2 in ice were lower than in water for all the nitro-PAHs (p < 0.05), which may be ascribed to the lower fluidity of the molecules in ice and insufficient ·OH/1O2 generated to participate in the reactions. The product identification by HPLC-MS/MS indicated that the main photodegradation pathways involved photoinduced hydroxylation, photooxidation and isomerization. Interestingly, isomerization reaction only occurred in the ice phase, attributing to the freezing concentration effect that led to the enrichment of solutes at the crystal boundaries of the ice crystals and facilitated the generation of isomers in ice. Furthermore, the photo-modified toxicities of the nitro-PAHs to Vibrio fischeri were examined in the two phases, indicating that the higher or comparable toxicities persisted in their intermediates. The toxicities of the individual intermediates to multiple trophic-level organisms were further assayed by the ECOSAR software, indicating consistency with the results of the bioassay using Vibrio fischeri. These results showed that the similarities and differences between aqueous and ice photochemistry of nitro-PAHs, which has crucial implications for how we undertake assessments of environmental persistence for the group of chemicals in cold regions.

A Novel Column-Switching Method Coupled with Supercritical Fluid Chromatography for Online Analysis of Bisphenol A Diglycidyl Ether and Its Derivatives in Canned Beverages

Bisphenol A diglycidyl ether (BADGE) and its related derivatives (BADGEs for short) are reactive epoxides condensed from bisphenol A (BPA) and epichlorohydrin. Nowadays, they are heavily used as additives in the production process of food and beverage contacting materials. However, BADGEs are considered as emerging organic pollutants due to their high toxicity including cytotoxicity, mutagenicity, and genotoxicity. In this work, an online analytical method integrated column-switching technique with supercritical fluid chromatography (SFC) was proposed for the simultaneous determination of bisphenol A diglycidyl ether and its derivatives. In this process, a homemade column was utilized in the first dimension of the column-switching SFC system to preconcentrate the analytes as well as eliminate interferences online. Under the optimal conditions, the obtained calibration curves for BADGEs showed good linearity ranging from 0.02 μg/mL to 10.00 μg/mL, while the values of LOD and LOQ were in the range of 0.0024-0.0035 μg/mL and 0.0080-0.0116 μg/mL, respectively. The optimized method exhibited a good recovery ranging from 85.6% to 105.5% with relative standard deviations less than 11.8%. The developed method provides an eco-friendly and effective way for the rapid and automated analysis of BADGEs at trace levels in canned beverages and can be applied to the high-throughput analysis of other similar matrices.

Facile construction of magnetic solid-phase extraction of polyaniline blend poly(amidoamine) dendrimers modified graphene oxide quantum dots for efficient adsorption of polycyclic aromatic hydrocarbons in environmental water

An efficient magneto-adsorbent composed of polyaniline blend poly(amidoamine) dendrimers modified graphene oxide quantum dots and magnetic Fe3O4 particles (Fe3O4@PANI-PSS/PAMAM-QGO) for magnetic solid-phase extraction (MSPE) of polycyclic aromatic hydrocarbons (PAHs) in environmental water was synthesized. Fe3O4@PANI-PSS/PAMAM-QGO exhibited exceptional adsorption property for most PAHs analytes. The nanocomposite sorbent demonstrated a ferromagnetic behavior of 17.457 emu g-1, which is adequate for subsequent use in MSPE. Key parameters affecting the processes of adsorption and desorption, including the sorbent amount, vortex adsorption time, vortex extraction time, sample volume, a solvent for desorption and the solvent volume were all examined and optimized. The performance of MSPE using Fe3O4@PANI-PSS/PAMAM-QGO as adsorbent for four PAHs, including fluoranthene, acenaphthene, phenanthrene and pyrene were studied through high performance liquid chromatography equipped with spectrofluorometer. Under the optimal conditions, Fe3O4@PANI-PSS/PAMAM-QGO showed a wide linearity of 10-1,000 ng mL-1, low detection limit (LOD) ranging from 1.92 to 4.25 ng mL -1 and high accuracy (recoveries of 93.6-96.5 %). Enrichment factors up to 185 were achieved. Furthermore, Fe3O4@PANI-PSS/PAMAM-QGO exhibited good recyclability (10 times, RSDs ≤ 5.35%), while maintaining its high efficiency in the extraction of PAHs. The proposed method was successfully applied for environmental samples. Recoveries ranging from 81.2 to 106.2 % were obtained, indicating a low matrix effect and the robustness of the optimized MSPE method. Based on these features and under the optimal extraction conditions, Fe3O4@PANI-PSS/PAMAM-QGO was demonstrated to be a successful tool for the rapid and sensitive extraction of PAHs in the samples.

Graphene oxide modified magnetic polyamidoamide dendrimers based magnetic solid phase extraction for sensitive measurement of polycyclic aromatic hydrocarbons

In this study, graphene oxide modified magnetic polyamidoamine dendrimers (MNPs@PAMAM-G2.0@GO) nanoparticles were successfully prepared by amidation method. The obtained MNPs@PAMAM-G2.0@GO nanocomposites were examined by fourier transform infrared spectroscopy (FT-IR), X-ray diffraction (XRD), vibrating sample magnetometer (VSM), scanning electron microscope (SEM) and transmission electron microscopy (TEM), etc. MNPs@PAMAM-G2.0@GO exhibited excellent adsorption property and was investigated for magnetic solid phase extraction (MSPE) of polycyclic aromatic hydrocarbons (PAHs) from water. The detection of extracted PAHs was accomplished by high performance liquid chromatography (HPLC) and gas chromatography tandem mass spectrometry (GC-MS/MS). The target PAHs included anthracene (ANT), pyrene (PYR), fluoranthene (FLT), carbazole (CB), 7-methylquinoline (7-MQL), 9-methylcarbazole (9-MCB), dibenzothiophene (DBT) and 4,6-dimethyldibenzothiophene (4,6-DBT). Important operation parameters for MSPE that could affect the extraction efficiencies of PAHs were investigated in detail. Under optimal parameters, the constructed method demonstrated excellent linear range with 0.001-10 μg L^-1 for analytes and low limits of detection within the range of 0.11-0.9 ng L^-1. The spiked average recoveries of PAHs in natural water samples ranged from 92.5% to 105.2%. The promising results indicated that MNPs@PAMAM-G2.0@GO could be employed to efficiently extract PAHs from aqueous samples.

Triazine-based covalent organic polymer: A promising coating for solid-phase microextraction

Advancement of novel coating materials for solid-phase microextraction is highly needed for sample pretreatment. Herein, a triazine-based covalent organic polymer was constructed from the monomers of cyanuric chloride and trans-stilbene via the Friedel-Crafts reaction and thereafter used as a solid-phase microextraction fiber coating for the extraction of polycyclic aromatic hydrocarbons and their nitrated and oxygenated derivatives. The newly-developed solid-phase microextraction method coupled with gas chromatography/flame ionization detection gives enhancement factors of 548-1236 and limits of detection of 0.40-2.81 ng/L for the determination of polycyclic aromatic hydrocarbons and their derivatives. The one fiber precision for five replicate determinations of the analytes and the fiber-to-fiber precision with three parallel prepared fibers, expressed as relative standard deviations, was in the range of 4.6-9.4% and 6.2-10.9%, respectively. The relative recoveries of the analytes for environmental water samples were in the range of 88.6-106.4% with the relative standard deviations ranging from 4.0 to 11.7% (n = 5).