Gas chromatographic assay for N,N-dimethylglycine in urine

A gas chromatographic method for the determination of N,N-dimethylglycine in urine has been developed. After clean-up by cation-exchange, N,N-dimethylglycine was derivatized with ethanol and hydrochloric acid to form the corresponding ethyl ester. After evaporation of solvent, N,N-dimethylglycine ethyl ester was extracted into methylene chloride and chromatographed on a gas chromatograph equipped with a packed column containing 10% Carbowax 20 M. The detection limit of the method is 0.01 mM N,N-dimethylglycine in urine. This method has been used to detect N,N-dimethylglycine in urine from healthy subjects as well as in urine from patients with metabolic disorders. These findings were verified by gas chromatography-mass spectrometry.