Measurement of vitamin D in foods and nutritional supplements by liquid chromatography/tandem mass spectrometry.

Vitamin D is a fat-soluble vitamin with great nutritional interest. An HPLC/MS/MS method was developed to measure vitamin D with atmospheric pressure chemical ionization. Under the experimental parameters used, the LOQ was 0.018 IU/g or 0.45 ng/g, which greatly enhances the capability of measurement of vitamin D at low levels in foods and supplements. This method was validated with spike recovery of 100 +/- 15% and the RSD of less than 10% for most sample matrixes, including infant formula, cheese, cereal and cereal-based foods, multivitamin supplements, and pet foods. The results for vitamin D were compared with those obtained by other methods.