Shimizu M, Iwasaki Y, Ishida H, Yamada S
Division of Molecular Biology, Tokyo Medical and Dental University, Japan.
J Chromatogr B Biomed Appl. 1995 Oct 6;672(1):63-71. doi: 10.1016/0378-4347(95)00187-n.
A convenient non-radioactive method for assaying plasma 25-hydroxyvitamin D3 is described. The method uses 22-hydroxytetranorvitamin D3 as an internal standard and includes two-step liquid- and solid-phase extractions and quantification by normal-phase HPLC. The intra- and inter-assay coefficients of variation were 2.2% and 2.4%, respectively, and the analytical recovery of 25-hydroxyvitamin D3 added to plasma was quantitative. Assay linearity was obtained in the range 0.5-4.0 ml of plasma. When compared with the method employing a radioactive 25-hydroxyvitamin D3 tracer, the correlation coefficient was 0.990 (slope 0.999 and intercept 1.19 ng/ml).
