#0059 Simple and reliable method to simultaneously determine urinary 1- and 2-naphthol using in-situ derivatization and gas chromatography-mass spectrometry for biological monitoring of naphthalene exposure in occupational health practice
Simple, Reliable Method to Measure Exposure to Naphthalene
Naphthalene, a white volatile chemical compound, is widely used in the manufacture of synthetic resins, explosives, insect repellants, and dyes. It has been classified as a potential carcinogen (ie, a cancer-causing compound), and thus, long-term exposure to naphthalene can be detrimental.
Of the thirty metabolites of naphthalene identified in mammals, 1-naphthol (1-NAP) and 2-naphthol (2-NAP) have been used as biomarkers for assessing exposure to naphthalene. Individuals who are exposed to naphthalene as part of their profession are recommended to undergo periodic medical tests wherein urinary levels of 1-NAP and 2-NAP may be measured at the physician’s discretion. However, several mass spectrometry analytical techniques reported for the simultaneous detection of 1-NAP and 2-NAP from urine samples are not practically feasible in clinical settings due to their lengthy and complex protocols of sample preparation.
To this end, we sought to develop an easier yet accurate method for the estimation of urinary 1-NAP and 2-NAP, which can be incorporated in routine clinical practice. For this, we first used enzymatic treatment to break down complex conjugates of NAPs in the urine sample and obtained their acetyl derivatives by treating them with acetyl anhydride. Acetylation, or the addition of an acetyl functional group to NAPs, decreases their polarity or charge, thereby enhancing their chromatographic analysis. However, a majority of the chemicals used for acetylation require a time-consuming evaporation step, in which much of the target compound can be lost. To avoid this, we chose acetic anhydride, as the reaction takes place in an aqueous phase and, owing to the hydrophobic nature of the derivative, its extraction becomes easier in hydrophobic solvents like N-hexane. Next, we analyzed the processed samples using gas chromatography mass spectrometry. Samples from healthy volunteers who did not smoke and were not occupationally exposed to naphthalene were considered as baseline.
The limits of detection and quantification, which represent three and ten times the baseline value for each NAP. were found to be 0.30 and 1.00 μg/L respectively. We observed a recovery of 90.8%-98.1% using the aforementioned extraction method. We also evaluated the intra- and inter-day precision of our method by analyzing three different sample concentrations in replicates over the same day and over consecutive days and observed good reproducibility. Moreover, we validated our results with known standard concentrations of NPA.
Overall, our method provides a simple and reliable way to quantify and monitor occupational naphthalene exposure and can help inform recommendations and assess its hazardous effects.
Link to the original journal article:
https://onlinelibrary.wiley.com/doi/10.1002/1348-9585.12144
Title of the paper:
Simple and reliable method to simultaneously determine urinary 1- and 2-naphthol using in situ derivatization and gas chromatography-mass spectrometry for biological monitoring of naphthalene exposure in occupational health practice
Authors:
Akito Takeuchi, Sadao Nakamura, Akira Namera, Tomoaki Kondo, Hiroyuki Onuki, Shinobu Yamamoto, Shingo Okamura, Osamu Nishinoiri, Yoko Endo Hiroyuki Miyauchi, Ginji Endo
