ADVANTAGES OF PAPER-CHROMATOGRAPHY AS A PREPARATIVE STEP IN THE ASSAYOF 1,25-DIHYDROXYVITAMIN-D

Ether extraction and paper chromatography were used to separate the ma in metabolites of vitamin D in plasma [25-(OH), 24,25-(OH)(2) and 1,25 -(OH)(2) vitamin D] prior to radio receptorassay. The overall procedur al loss of the 1,25-(OH)(2) vitamin D was 58 +/- 5% (n = 40), correcte d for by tracer addition. The sensitivity of the assay was 0.5 fmol/tu be, corresponding to 4 pmol/l, and the intra- and inter-assay coeffici ents of variation were 10.5% and 11.5%, respectively. The range of val ues measured in healthy controls was 80-200 pmol/l(n = 60), which is i n agreement with findings reported in the literature. A comparison of the results of the present procedure with those obtained with a proced ure employing C-18 purification, disclosed a correlation coefficient o f 0.92 (p less than or equal to 0.0001), a slope of 0.89 (p less than or equal to 0.0001) and a small non-significant intercept of 5.0 pmol/ l (n = 53).