1. Simultaneous determination of 25-hydroxy- and 1,25-dihydroxyvitamin D from a single sample by dual-cartridge extraction.
- Author
-
Kao PC and Heser DW
- Subjects
- Absorption, Animals, Calcifediol blood, Calcitriol blood, Chickens, Female, Finland, Humans, Male, Reference Values, Seasons, Texas, Calcifediol isolation & purification, Calcitriol isolation & purification, Chromatography, High Pressure Liquid methods
- Abstract
With this dual-cartridge system we extract 25-hydroxyvitamin D [25(OH)D] and 1,25-dihydroxyvitamin D [1,25(OH)2D] from a single serum sample by using a nonpolar octadecylsilanol silica cartridge to adsorb the vitamin D metabolites and other nonpolar substances; the polar substances wash through the cartridge. The eluted material is then applied to a second alkylamine cartridge, which adsorbs the relatively polar hydroxylated metabolites; the less-polar substances are washed from the second cartridge. Elution from the second cartridge purifies and also separates 25(OH)D and 1,25(OH)2D with analytical recoveries near 90%. The monohydroxyl metabolites are determined by "high-performance" liquid chromatography (HPLC); the dihydroxyl metabolites are further purified by HPLC and determined by radioreceptor assay according to established procedures. Mean (+/- SD) winter normal values (34 subjects of both sexes; blood drawn in mid-April) were 18 +/- 5 micrograms/L for 25(OH)D and 25 +/- 7 ng/L for 1,25(OH)2D. In nine laboratory volunteers, the mean increase in the serum 25(OH)D3 value 5 h after ingestion of 50 micrograms of 25-hydroxycholecalciferol (Calderol) was 9 (SD 4) micrograms/L.
- Published
- 1984