GAS-CHROMATOGRAPHY NEGATIVE-ION CHEMICAL-IONIZATION MASS-SPECTROMETRYOF HYDROLYZED HUMAN URINE AND BLOOD-PLASMA FOR THE BIOMONITORING OF OCCUPATIONAL EXPOSURE TO 4,4'-METHYLENEBISANILINE

A gas chromatographic-mass spectrometric (GC-MS) method for the biolog ical monitoring of 4,4'-methylenebisaniline (MDA), is presented, MDA w as determined in urine and plasma after hydrolysis and analysed as the pentafluoropropionic anhydride derivative. High sensitivity and selec tivity were achieved using negative-ion chemical ionization with ammon ia as the reagent gas. The hydrolysis procedures for urine and plasma samples Here studied under alkaline and acidic conditions. Alkaline co nditions gave the highest recovery for both urine and plasma samples, Hydrolyses of urine at 80 degrees C and of plasma at 100 degrees C for 16 h were selected owing to the good recovery and precision achieved. Ten analyses of a urine sample containing 11 nmol l(-1) of MDA gave r elative standard deviations (s(r)) within and between assays of 2 and 6%, respectively. The determination of MDA in a plasma sample containi ng 8 nmol l(-1) of MDA gave s(r) = 4 and 6% within and between assays, respectively (n = 5). For the preparation of samples spiked to 10 nmo l l(-1) of MDA, the recovery was 97 +/- 3% for urine samples and 96 +/ - 2% for plasma samples, The detection limit, defined as the blank plu s three times the standard deviation of the blank, was 0.2 nmol l(-1) for aquous solutions containing an internal standard. Determinations o f MDA in urine and plasma from exposed workers showed that the method is appropriate for biomonitoring.