Determination of L-threonate in calcium L-threonate preparations by capillary electrophoresis with indirect UV detection.

A validated capillary electrophoresis method with indirect UV detection for the determination of L-threonate in a calcium L-threonate (Ca-Th) chewable tablet and dry syrup was described. The 2,6-naphthalenedicarboxylic acid (NDC) was used as the background carrier ion and the tetradecyltrimethylammonium bromide (TTAB) was used as electroosmotic flow modifier. The running buffer contained 2 mM NDC, 6 mM disodium carbonate and 0.2 mM TTAB. The detection wavelength was set at 240 nm. A linear calibration range of 50-500 microg/mL was obtained (r = 0.9996). The limit of detection and limit of quantitation were found to be 6 microg/mL and 20 microg/mL, respectively. The recovery was 99.45% (RSD = 0.57%, n = 5) and 99.12% (RSD = 0.48%, n = 5) for the tablet and dry syrup preparation, respectively. Repeatability tests on the migration times or peak areas proved that the results were of high precision. The RSD of peak area ratio was lower than 1% (0.74%, n = 5). The factors influencing quantitation were discussed and three batches of chewable tablet and also of dry syrup were assayed by the proposed method.