Recent collaborative research done by the Chinese Center for Disease Control and Prevention (Beijing, China) and Zhengzhou University (Zhengzhou, China) used ultrahigh-performance liquid chromatography–tandem mass spectrometry (UHPLC–MS/MS) to quantify amino-polycyclic aromatic hydrocarbons in urine samples of workers exposed to diesel exhaust. Their findings were published in the Journal of Chromatography B (1).
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Nitrated polycyclic aromatic hydrocarbons (nitro-PAHs) are derivatives of polycyclic aromatic hydrocarbons (PAHs) that include molecules with at least two interconnected benzene rings and 1–2 nitro substituent. Nitro-PAHs can be emitted directly from incomplete fossil fuel combustion, such as diesel, or formed through secondary reactions that involve parent PAHs and mediators like NO2 and NO3− under specific conditions. According to the International Agency for Research on Cancer (IARC), diesel exhaust is classified as a Group 1 human carcinogen. As of the publication of this study, 15nitro-PAHs have been evaluated and classified by IARC for carcinogenic potential, the researchers wrote (1).
Once present in the body, nitro-PAHs are metabolized and typically excreted via body fluids in individuals exposed to diesel exhaust emissions (DEE). Metabolites produced from nitro-PAHs through nitro reduction and subsequent hydrogenation are known as amino-PAHs. Urinary amino-PAHs have been identified as reliable biomarkers for assessing nitro-PAH exposure in people exposed to DEE. Currently, 1-nitronaphthalene, 2-nitronaphthalene, 1-nitropyrene, 9-nitrophenanthrene, and 2-nitrofluorene are predominantly studied. Despite being classified as carcinogens by IARC, no detection methods have been reported for the detection of 6-nitrochrysene and 5-nitroacenaphthene.
In this study, a reliable ultrahigh-performance liquid chromatography–tandem mass spectrometry (UHPLC–MS/MS) method was developed, incorporating solid-phase extraction (SPE) pretreatment for detecting 11 amino-PAHs in urine samples from workers exposed to nitro-PAHs. This list includes 1-aminonaphthalene, 2-aminonaphthalene, 5-aminoacenaphthene, 2-aminofluorene, 9-aminophenanthrene, 1-aminoanthracene 2-aminoanthracene, 3-aminofluoranthene, 4-aminopyrene, 1-aminopyrene and 6-aminochrysen. Further, the method was evaluated and validated for sensitivity, accuracy, precision, and matrix effects using urine samples from workers exposed to diesel exhaust.
Samples were enzymatically hydrolyzed, purified using SPE extraction, and analyzed with the optimized UHPLC–MS/MS method. To best optimize the method, two solid-phase extraction (SPE) columns were tested to minimize matrix effects. Effective separation of the amino-PAHs was achieved with reversed-phase HSS PFP columns with a gradient elution of 0.1% formic acid in water and acetonitrile. Improved MS/MS conditions were established to achieve sufficient sensitivity using positive ion electrospray ionization (ESI), with limits of quantification (LOQs) ranging from 0.009 to 0.378 μg L−1. Utilizing two isotopically labeled internal standards (1-Aminonaphthalene-d7 and 1-Aminopyrene-d9), the method was optimized for linearity, accuracy, precision, and matrix effects. A coefficient of variation (CV) of less than 11% was found, with recovery rates between 82.0% and 106.9%.
The optimized method was applied to urine samples from tunnel construction workers provided important data on exposure levels to amino-PAHs in high diesel exhaust environments. The detection rates of different amino-PAHs varied significantly, highlighting the complexity involved in assessing environmental and occupational exposures. Amino-PAHs were detected in every tested sample, though some contained less than 20% of amino-PAHs. This can reflect differences in exposure levels or metabolic processes between workers. These differences can be influenced by physiological factors, changes in work environment, or different routes of exposure.
The assay developed in this study effectively separated amino-PAHs, showing excellent selectivity and precision while minimizing interference from matrix effects. These findings show the method’s potential as a tool for future bioassays, especially for populations exposed to diesel exhaust.
(1) Li, H.; Cui, S.; Zhou, X.; Improvement of an Ultra-High Liquid Chromatography-Tandem Mass Spectrometry Method for the Simultaneous Quantification of Eleven Amino-Polycyclic Aromatic Hydrocarbons in Human Urine. J. Chromatogr. B 2025, 1262, 124649. DOI: 10.1016/j.jchromb.2025.124649
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