N-methyl pyrrolidone (NMP) is a substance widely used for its strong and selective solvent capacity. The strong potential NMP has for skin absorption makes biological monitoring ideal for exposure assessment. This study looked at brief exposures to NMP in aqueous solutions over a range of concentrations. Two volunteers placed one hand in NMP solutions ranging from 5 to 25% for as long as 15 min followed by urine collection for 48 h. The analyte of interest (analysed by GC-MS) was the NMP metabolite 5-hydroxy-N-methyl pyrrolidone (5-HNMP). Excretion of 5-HNMP was plotted against time and this showed that urine concentrations were at a maximum after about 10 h and 5-HNMP excretion continued for 48 h after exposure. The half-life of excretion was found to be approximately 11 h. The mean correlation between exposure (as a measure of exposure duration and solution concentration) and total 5-HNMP excreted was 0.9297.
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