Direct High-Performance liquid chromatography method for determination of glycine betaine and its metabolite,N,N-dimethylglycine,in pharmacokinetic studies

摘要

A simple and direct. without derivatization, method for the routine analysis of glycine betaine and its metabolite N ,N - dimethylglycine in body fluids, serum or urine, is described. Low wavelength ultraviolet detection is achieved at 198 nm using 20 mmol/L KH_2PO_4 at a flow rate of 1.2 mL/min as a mobile phase and a Nucleosil 100-10 SA (10 #mu#m, 250 x 4.6 mill) as an analytical column. The limit of detection is 7.5 ng for both com- pounds and the limit of quantitation is 25 ng when 50 ILL is in- jected onto the column. A rectilinear relationship is observed up to 120 ng/ILL. Method validation perfonned by day-to-day (n = 8) and within-day (n = 8) precision assays gave relative standard de- viation values in the range of 5.1-10.5% for glycine betaine and 3.6-9.0% for N ,N -dimethylglycine. 7-Methylxanthi,ne is used as the internal standard at a concentration of 0.2 ng/#mu#.L. Analysis time is approximately 6 min. The method developed is applied to the analysis of glycine betaine in a commercial pharmaceutical prepara- tion with high accuracy and precision results, as well as to the mon- itoring of glycine betaine and its metabolite N ,N -dimethylglycine levels in body fluids, serum and urine, as their levels are indicative of renal disorder. Mean recdvel"y of glycine betaine in the ph~r- maceutical formulation, assayed at different concentration levels, is 102.~('!c Percel1tage recovery values of analytes in ~piked serum samples ral1ge from 90.9 to 106.6 0% for N .N -dimethylglycine and from 95.6 to 100.3% for glycine betaine. while the respective val- ues in spiked urine samples are in the range of 93.6-106.2% and . 100.9-103.9%After the appropriate dilution of biological fluid ' samples, any matrix interference is eliminated. The niethod appears to be suitable for monitoring glycine betaine and its metabolite in body tluid, especially in urine of patients undergoing therapy with . betaine.