A simple and reliable enzymatic assay for the determination of formic acid in urine.

A simple, reliable and efficient enzymatic assay for the analysis of formic acid in urine is described. The principle of the method is the quantitative oxidation of the acid with the enzyme formate dehydrogenase (FDH) in the presence of NAD. The detection limit was 0.5 mg/l, the recovery rates ranged from 66% to 74% and the coefficient of variation was 5%. The results obtained with this method correlated well with the values measured with two different gas chromatographic procedures. Normal formic acid excretion in urine is between 2.0 and 30.0 mg/l, with a mean of 13.0 +/- 7.4 mg/l and between 1.2 and 17.5 mg/g creatinine, the mean being 7.7 +/- 4.0 mg/g creatinine. The determination of formic acid concentration in urine may be an important means to quantify the degree of exposure to or intoxication of persons with methanol, formaldehyde and acetone.