High-performance liquid chromatography determination of nitrated polycyclic aromatic hydrocarbons by indirect fluorescence detection

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

An online solid-phase extraction (SPE)-coupled liquid chromatography-mass spectrometry (LC-MS) method was established for the determination of 10 nitrated polycyclic aromatic hydrocarbons (nitro-PAHs) in water. Water samples were mixed with methanol to generate 40% methanol solutions (v/v), and filtered by 0.45 μm membrane. The filtration with polytetrafluoroethylene(PTFE) membrane got higher recovery rates than nylon membrane, especially for 4-ring and 5-ring nitro-PAHs. 2.5 mL solution was directly injected into online SPE flow path to allow for online purification and enrichment of target analytes in the SPE column. The nitro-PAHs eluted from the SPE column were automatically transferred to the analytical flow path by a well-designed valve-switching system. With the optimization of LC and MS condition, ten nitro-PAH isomers was separated and detected from each other by LC-MS/MS with negative atmospheric pressure chemical ionization (APCI). It was firstly found that nitro-PAHs could produce strong [M-H]^- precursor ions in the primary MS besides [M+e]^- and [M+15]^-. In the secondary MS, the precursor ions mainly lose NO neutral molecule (30 Daltons) to produce daughter ions. The online SPE and LC-MS analysis process was completed in 15.5 min. The linear correlation coefficients of 10 nitro-PAH standard curves were higher than 0.99. The detection limits of nitro-PAHs were about 1.2~22.2 ng/L (S/N=3). The intra-day and inter-day reproducibility (RSD, n=6) were 1.6%~8.4% and 5.3%~16.9%, respectively. The recoveries of 10, 40 and 200 ng/L in tap water were 71.7%~106.4%, 79.7%~100.9% and 73.0%~105.5%, with the corresponding RSD of 2.4%~10.5%, 2.1%~8.6% and 2.7%~6.2%, respectively.

Nitrated polycyclic aromatic hydrocarbons (nitro-PAHs) in the environment - A review

Nitrated polycyclic aromatic hydrocarbons (nitro-PAHs) are derivatives of PAHs with at least one nitro-functional group (-NO₂) on the aromatic ring. The toxic effects of several nitro-PAHs are more pronounced than those of PAHs. Some nitro-PAHs are classified as possible or probable human carcinogens by the International Agency for Research on Cancer. Nitro-PAHs are released into the environment from combustion of carbonaceous materials (e.g. fossil fuels, biomass, waste) and post-emission transformation of PAHs. Most studies on nitro-PAHs are about air (gas-phase and particulate matter), therefore less is known about the occurrence, concentrations, transport and fate of nitro-PAHs in soils, aquatic environment and biota. Studies on partition and exchange of nitro-PAHs between adjacent environmental compartments are also sparse. The concentrations of nitro-PAHs cannot easily be predicted from the intensity of anthropogenic activity or easily related to those of PAHs. This is because anthropogenic source strengths of nitro-PAHs are different from those of PAHs, and also nitro-PAHs have additional sources (formed by photochemical conversion of PAHs). The fate and transport of nitro-PAHs could be considerably different from their related PAHs because of their higher molecular weights and considerably different sorption mechanisms. Hence, specific knowledge on nitro-PAHs is required. Regulations on nitro-PAHs are also lacking. We present an extensive review of published literature on the sources, formation, physico-chemical properties, methods of determination, occurrence, concentration, transport, fate, (eco)toxicological and adverse health effects of nitro-PAHs. We also make suggestions and recommendations about data needs, and future research directions on nitro-PAHs. It is expected that this review will stimulate scientific discussion and provide the basis for further research and regulations on nitro-PAHs.

Combination of precolumn nitro-reduction and ultraperformance liquid chromatography with fluorescence detection for the sensitive quantification of 1-nitronaphthalene, 2-nitrofluorene, and 1-nitropyrene in meat products

Carcinogenic nitropolycyclic aromatic hydrocarbons (nitro-PAHs) are ubiquitous in the ambient environment. They are emitted predominantly from internal combustion engines and by reacting polycyclic aromatic hydrocarbons with nitrogen oxide. The emerging evidence that nitro-PAHs are taken up by plants and bioaccumulatd in the food chain has aroused worldwide concerns for the potential of chronic poisoning through dietary intake. Therefore, analytical methods of high sensitivity are extremely important for assessing the risk of human exposure to nitro-PAHs. This paper describes the development of a simple and robust ultraperformance liquid chromatography coupled fluorescence detector (UPLC-FLD) method for the sensitive determination of nitro-PAHs in meat products. The method entails precolumn reduction of the otherwise nonfluorescent nitro-PAHs to amino-PAHs which strongly fluoresce for their determination by UPLC-FLD analysis. The developed method was validated for extraction efficiency, accuracy, precision, and detection limit and has been successfully applied in quantifying 1-nitronaphthalene (1-NN), 2-nitrofluorene (2-NF), and 1-nitropyrene (1-NP) in fresh and cured meat products. The results showed that the combination of Fe/H(+)-induced nitro-reduction and UPLC-FLD analysis allows sensitive quantification of 1-NN, 2-NF, and 1-NP at detection limits of 0.59, 0.51, and 0.31 μg/kg, respectively, which is at least 10 times lower than those of the existing analytical methods.