Vitamin D analysis in plasma by high performance liquid chromatography (HPLC) with C(30) reversed phase column and UV detection--easy and acetonitrile-free.

Two physiologically important forms of vitamin D exist: vitamin D(2) and vitamin D(3), which by liver based hydroxylase enzymes are converted to 25-hydroxyvitamin D(2) and 25-hydroxyvitamin D(3), respectively. These hydroxylated metabolites of vitamin D are measured in plasma to assess the vitamin D status of animals and humans. Therefore cheap and reliable analytical methods are very much in demand in nutritional and physiological research. After saponification and extraction of plasma or serum samples the current method uses reverse phase high performance liquid chromatography on a C(30) column and with UV detection at 265nm for quantifying vitamin D(2), vitamin D(3), 25-hydroxyvitamin D(2), and 25-hydroxyvitamin D(3). The method proved versatile with respect to plasma lipid content, sample amount, and plasma concentration of the vitamin D metabolites as it was tested using plasma from six different species: cattle, pigs, poultry, mink, horses, and humans. In cattle plasma recoveries were between 86.6 and 101.0%, within day error between 0.9 and 5.9%, and between day error between 0.2 and 1.7%. However, depending on species and sample amount error percentages varied. When running the method on standard reference material® 972 "Vitamin D in human serum" from the National Institute of Standards and Technology (NIST) (Gaithersburg, USA) the results for 25-hydroxyvitamin D(2) and 25-hydroxyvitamin D(3) concentrations were within the boundaries provided by NIST, reflected by Z-scores between 0.1 and 0.9.