Determination of N-nitrosodiethanolamine in urine by gas chromatography thermal energy analysis: application in workers exposed to aqueous metalworking fluids |
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Authors: | P Ducos R Gaudin J M Francin |
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Institution: | (1) Institut National de Recherche et de Sécurité, Avenue de Bourgogne, F-54501 Vandoeuvre Cedex, France e-mail: ducos@inrs.fr Tel.: +33 3 83 50 20 00; Fax: +33 3 83 50 20 96, FR |
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Abstract: | Objective: The aim of this study was to describe a detailed and validated methodology designed for the analysis of carcinogenic N-nitrosodiethanolamine (NDELA) down to sub-μg/l levels in urine and its application to a number of workers exposed to NDELA-contaminated
aqueous metalworking fluids (MWF). Methods: Following a work-up procedure based on solid-phase extraction of NDELA, the urinary extracts were analysed without derivatization
by gas chromatography on a polar wide-bore column with chemiluminescent detection using a thermal energy analyser (TEA). N-Nitroso-(2-hydroxypropyl)amine was used as an internal standard. The method was applied to 12 workers using “nitrite-free”
or “nitrite-formulated” MWF and to 15 unexposed subjects. The NDELA content of the MWF was also determined using a similar,
but simpler method able to easily quantify NDELA down to at least 0.1 mg/l. Results: Contamination by NDELA traces of some chemicals used for the sample preparation, particularly ethyl formate, must be carefully
checked since it can give rise to false-positive results of up to 1 or 2 μg/l. The response was linear in the range of 0–500 μg/l.
Between 0.5 and 10 μg/l, the recovery rate was close to 95%, while repeatability ranged from 12.5 to 6.4% (n = 5). The detection limit was 0.3 μg/l (Signal/noise = 3). No detectable NDELA could be observed in the control workers.
There was no significant increase in NDELA levels at the end of shift spot samples from an exposed worker over 1 week. Higher
NDELA concentrations were found in two workers (4.3 and 10.7 μg/l) exposed to “nitrite-formulated” fluids (contaminated with
65 and 18 mg NDELA per l, respectively) than in nine workers (range, 0.4–1.3 μg/l exposed to “nitrite-free” fluids with lower
levels of NDELA (range, 0.5–6.6 mg/l). Conclusion: The detailed methodology described in this work and applied to a limited industrial situation was found to be suitable for
monitoring NDELA in the urine of workers exposed to aqueous MWF. A much larger screening has been undertaken with the aim
of obtaining better information on the real exposure of workers sometimes exposed to “nitrite-formulated” fluids that are
still used.
Received: 8 December 1998 / Accepted: 3 April 1999 |
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Keywords: | N-Nitrosodiethanolamine Urine Metalworking fluids Nitrite |
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