Binding properties of (+/-)[3H]benidipine hydrochloride to rat heart membranes

A simple routine method for the gas chromatographic determination of methylamine, dimethylamine, ethylamine and methylethylamine in urine is presented. The method is based on a two-phase derivatization procedure with isobutyl chloroformate as reagent. The reaction is quantitative in 10 min. We found no artifact formation of either choline or trimethylamine (dietary amine compounds) or of dimethylethylamine or triethylamine (catalyst amines in the industrial setting). The chromatographic behaviour of the amine carbamates was excellent. The recoveries of methylamine, dimethylamine, ethylamine and methylethylamine in spiked urine samples were 82, 89, 100 and 96%, respectively, and the precision (the relative standard deviation) was 3.6, 1.8, 3.3 and 2.0%, respectively. The method was linear for the studied amine carbamates up to 250 mg/l. The endogenous amine concentrations in urine samples from ten normal subjects were: methylamine, 0.9 mg/l (mean; range 0.3-1.5); dimethylamine, 14.7 mg/l (mean; range 4.6-27.6); ethylamine, 0.8 mg/l (mean; range 0.2-2.3); methylethylamine, less than 0.02 mg/l.