Metabolites from NVP sorted out by correct GC

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  • Published: Nov 15, 2017
  • Author: Ryan De Vooght-Johnson
  • Channels: Gas Chromatography
thumbnail image: Metabolites from NVP sorted out by correct GC

Biomarkers needed for 1-vinyl-2-pyrrolidone

1-Vinyl-2-pyrrolidone (also known as N-vinylpyrrolidone, NVP or VP) is used in a wide variety of applications, being a co-polymer in inks, coatings and adhesives. Its polymer, polyvinylpyrrolidone (PVP), has many applications, such as being used in pharmaceutical formulations and personal care products. There are therefore a number of possible exposure routes for the general public, while those working with the compound in industry would probably be exposed to a greater extent. 1-Vinyl-2-pyrrolidone is generally thought to be of relatively low toxicity, but long-term inhalation studies in rats led to an increased incidence of nasal and liver cancer. Although the risk to humans is likely to be low, there is a need to examine the metabolites of 1-vinyl-2-pyrrolidone and to select reliable biomarkers to estimate exposure.

The Aachen team examined the detection of six likely metabolites of 1-vinyl-2-pyrrolidone by GC-MS/MS, using human urine spiked with these compounds. Rats were exposed 1-vinyl-2-pyrrolidone and their urine examined using the new GC method.

Metabolites of 1-vinyl-2-pyrrolidone assayed by GC-MS/MS

Six suspected metabolites of 1-vinyl-2-pyrrolidone were used to spike pooled human urine from non-smokers; deuterated versions of two of these metabolites were added as internal standards (no deuterated material was available for the remaining four metabolites). The samples were freeze dried, then taken up into ethyl acetate and derivatised with N-tert-butyldimethylsilyl-N-methyl-trifluoroacetamide (MTBSTFA) over 1 hour at 110 °C in sealed vials to give volatile tert-butyldimethylsilyl derivatives. Acetonitrile was added and the samples were dried under nitrogen. The residue was taken up in ethyl acetate, the bulk of which was removed to a fresh vial, leaving insoluble material behind. This was extracted again with ethyl acetate, then combined with the previous solution. After volume reduction, the solution was injected onto the GC.

GC was carried out with an Agilent 7890A instrument fitted with an Agilent DB-35ms column. The temperature was taken from 50 to 280 °C in a series of ramps, separating the six potential metabolites. Mass spectrometry employed an Agilent 7000 triple quadrupole instrument. It was found that all the six compounds had been successfully derivatised, some twice. Quantifying and qualifying transitions were found for each suspected metabolite.

Examination of the results from the spiked samples showed acceptable precision. The limits of detection (LODs) were mostly low (2 to 50 μg/L), apart from one suspected metabolite that gave 200 μg/L. In the same manner, the limits of quantification (LOQs) were mostly low (6 to 150 μg/L), with the compound with the high LOD giving an LOQ of 600 μg/L. It was found that the prepared samples gave poor stability in a cooled autosampler for 24 hours or when subjected to repeated freezing and thawing; it was concluded that samples had to be injected as soon as possible after being prepared.

1-Vinyl-2-pyrrolidone was dermally applied to rats, while a control group was untreated. Urine samples were taken 6 hours before and after treatment/non-treatment for both groups. All six suspected metabolites were detected after treatment with the compound. However, three of the metabolites were seen in the treated group prior to treatment and also in the control group at both time points. Another metabolite appeared in the control group after, but not before, ‘non-treatment’. These results are unexplained. The authors stated that exposure from the cages or water flasks was unlikely. It may be that the background levels of the metabolites could arise from the related compound N-ethylpyrrolidone (NEP), which is widely used for many applications. Overall, only 1% of the 1-vinyl-2-pyrrolidone used for the exposure was accounted for by the six metabolites examined.

GC-MS/MS measures NVP metabolites, but questions remain

The authors have successfully developed a GC-MS/MS method for measuring NVP metabolites, some of which could be used as biomarkers. However, further work is needed to explain the positive results from untreated rats before this method can be more widely applied.

Related Links

Rapid Communications in Mass Spectrometry, 2017, 31, 1851-1858. Bertram et al. Quantification of six potential unspecific human biomarkers of 1-vinyl-2-pyrrolidone exposure in Sprague-Dawley rat urine using gas chromatography coupled with triple mass spectrometry.

Wikipedia, Triple Quadrupole Mass Spectrometer

Wikipedia, N-Vinylpyrrolidone

Article by Ryan De Vooght-Johnson

The views represented in this article are solely those of the author and do not necessarily represent those of John Wiley and Sons, Ltd.

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