Simultaneous determination of betaine and N,N-dimethylglycine in urine

A method is described for the determination of betaine and its metabolite N,N-dimethylglycine in human urine. The method involves a deamination step and a solid-phase extraction to isolate both substances from urine followed by high performance liquid chromatography (HPLC) separation on a 5-microns SCX column with UV absorbance detection. Limit of detection is about 0.9 micrograms for both substances. Recoveries were > 85%. The method appears to be suitable for monitoring betaine and its metabolite in urine of patients undergoing therapy with betaine.