Stability issues in the determination of 19 urinary (free and conjugated) monohydroxy polycyclic aromatic hydrocarbons

Abstract

Data on the stability of monohydroxy polycyclic aromatic hydrocarbons (OH-PAHs; metabolites of PAHs) in urine are needed in order to effectively study the effects of PAHs in the body, but the relevant data are not available in the literature. Therefore, in this work, we investigated the stability of OH-PAHs in urine. For each OH-PAH studied, the free form (as opposed to the conjugated form) comprised <10 % of the total OH-PAH in urine samples obtained from a normal population, except for 9-OH-phenanthrene (where the free form represented 22.2 % of the total 9-OH-phenanthrene). 1-Naphthol and 9-OH-phenanthrene were found to be less stable in their free forms in urine than in their conjugated forms when the urine samples were stored at 4 °C or room temperature. Free 3-OH-fluoranthene was also very unstable at 4 °C or room temperature. The conjugated forms of the OH-PAHs were more stable than their corresponding free forms. However, the free and conjugated forms of all the OH-PAHs were stable in urine at -20 °C and -80 °C. A freeze and thaw assay also revealed that freezing and thawing had minimal impact on the stability of the OH-PAHs in urine. For the derivatized extracts, storing the samples under an argon atmosphere at 4 °C was found to maintain sample integrity. In order to measure the stabilities of 19 hydroxylated metabolites of PAHs in urine, we developed a method with sensitivity in the low pg/mL range using nine labeled internal standards. This method combined enzymatic deconjugation with liquid-liquid extraction, derivatization with N-methyl-N-(trimethylsilyl)trifluoroacetamide (MSTFA), and gas chromatography/tandem mass spectrometry (GC-MS/MS). Graphical abstract Stability of the conjugated forms of the OH-PAHs versus free forms (e.g. 1-naphthol).

The influence of demographic and lifestyle factors on urinary levels of PAH metabolites—empirical analyses of Cycle 2 (2009–2011) CHMS data

“…The dataset contains 6395 participants ranging in age from 3 to 79-years-old; a randomly selected subsample of the total sample population was selected for PAH metabolite analysis and only those 16 years old and older were included in this study. Analyses of the various PAH metabolites were conducted using enzymatic deconjugation and derivatization, followed by GC-MS/MS [26].…”

Cross-validation of biomonitoring methods for polycyclic aromatic hydrocarbon metabolites in human urine: Results from the formative phase of the Household Air Pollution Intervention Network (HAPIN) trial in India

“…In addition, 2NAP and 1PYR selected for the HAPIN trial represents inhalation and ingestion pathways of exposure to PAHs in humans. The conjugated forms of 2NAP and 1PYR are the two predominant OH-PAHs and constitute more than 95% compared to free forms in urine and are stable for more than a year when stored under −20 °C [24] . Because PAH metabolites are highly sensitive to fluorescence detection, the HPLC-FLD is a cost-effective and easy to adopt analytical technique in the absence of LC-MSMS system to reliably determine levels of PAH metabolites in large scale human biomonitoring studies such as the HAPIN trial.…”

“…Because of biological half-lives in the range of hours to days, high specificity to parent PAHs and ease of measurement in urine, OH-PAHs are regarded as reliable biomarkers of PAH exposure in large scale population studies examining health effects of air pollution. Among the several OH-PAH metabolites, 2-naphthol (2NAP) and 1-hydroxypyrene (1PYR) are the two predominant urinary metabolites commonly detected in humans experiencing varying ranges of PAH sources and exposures [22] , [23] , [24] , [25] , [26] .…”

Implementation of human biomonitoring in the Dehcho region of the Northwest Territories, Canada (2016–2017)

“…Lastly, because smoking can contribute substantially to cadmium exposure, cotinine, the predominant metabolite of nicotine was also measured, yielding information regarding potential sources of cadmium exposure among study participants. These analyses were conducted in the laboratory of the Centre de Toxicologie du Québec (CTQ) [ 44 , 45 ]. Finally, hair metals were analysed at University of Montreal using the ICP-MS method described above.…”