BIOLOGICAL MONITORING OF WORKERS EXPOSED TO N,N-DIMETHYLFORMAMIDE .1.METHODS OF ANALYSIS

Some methods for analysing N,N-dimethylformamide and its metabolites [ hydroxymethyl-N-methylformamide, hydroxymethylformamide and N-acetyl-S -(N-methylcarbamoyl)cysteine] in the urine of exposed workers are desc ribed. Unchanged dimethylformamide was measured after pretreatment of urine (2 ml) with silica gel cartridges and elution with methanol. The gas chromatographic analysis using a nitrogen phosphor detector made it possible to detect N,N-dimethylformamide in urine even when workers were exposed to low concentrations of the solvent (about 1 mg/m(3)). N-Hydroxymethyl-N-methylformamide and N-hydroxymethylformamide were an alysed as N-methylformamide and formamide respectively after direct in jection of urine into the gas chromatograph. The injection port temper ature played an important role in the gas chromatographic determinatio n of these products. Reliable results were obtained when direct or spl it injections were performed at 250 degrees C. The splitless injection gave the same reliable results at 150 degrees C. In urine samples fro m occupationally non-exposed persons, N-methylformamide could not be d etected. In contrast, formamide (or its precursor, hydroxymethylformam ide) was present in every urine sample. Our results in respect of 19 u rine samples analysed with the injection port of the gas chromatograph at 250 degrees C gave a mean of 8.6 mg/l of formamide. N-Acetyl-S-(N- methylcarbamoyl)cysteine was determined using a modified method for an alysing organic acid in urine samples. The metabolite was extracted wi th ethyl ether in an acid environment, treated with a silylating reage nt and measured by gas chromatography/mass spectrometry.