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Fluorometric assay of 25-hydroxyvitamin D3 and 24R,25-dihydroxyvitamin D3 in plasma
1Institute for Medical and Dental Engineering, Tokyo Medical and Dental University, Japan.
Abstract:
The first practical fluorometric assay of plasma 25-hydroxyvitamin D3 (25-OH-D3) and 24R,25-dihydroxyvitamin D3 (24,25-(OH)2D3) is described. The method uses a highly fluorescent dienophile, 4-[2-(6,7-dimethoxy-4-methyl-3-oxo-3,4-dihydroquinoxalyl)ethyl]-1, 2,4- triazoline-3,5-dione (DMEQ-TAD), to fluorescence-label vitamin D. Vitamin D metabolites were roughly purified with a short cartridge column followed by HPLC, labeled with DMEQ-TAD, and the product was analyzed on HPLC. In the assay of 25-OH-D3 the new fluorometric method was compared with the HPLC-uv method and was confirmed to be as accurate and reliable (CV, 4-5%) as the HPLC-uv method. Plasma 24,25-(OH)2D3 was accurately assayed by the HPLC-FL method, where the standard addition method was successfully used to calculate the overall recovery.