SIMPLE METHOD FOR THE ROUTINE DETERMINATION OF BETAINE AND N,N-DIMETHYLGLYCINE IN BLOOD AND URINE

A simple and convenient method using commercially available derivatiza tion reagents is described for the measurement of betaine and N,N-dime thylglycine (DMG) in blood and urine. Precolumn derivatization of plas ma or urine is performed directly in acetonitrile without extraction w ith p-bromophenacyl bromide and crown ether as catalyst. The p-bromoph enacyl ester derivatives are then separated by high-performance liquid chromatography, using an isocratic system of acetonitrile and water c ontaining choline. Effluent was monitored at 254 nm. The limit of dete ction was 5 mu mol/L for betaine and 2 mu mol/L for DMG. Analytical re covery was >97% for both analytes. Total and within-day CVs were 2.0-4 .4% and 0.9-2.2% for DMG. For betaine, the total and within-day CVs we re 1.3-5.3% and 0.4-3.8%, respectively. The method is precise and cost -effective and has been used successfully to determine the concentrati ons of DMG and betaine in human plasma and urine.