Gas-liquid chromatographic determination of vitamin D in tuna liver and vitamin D resin oils.

Gas-liquid chromatographic (GLC) determination of vitamin D3 in tuna liver and vitamin D3 resin oils was investigated and a routine method slightly modified from the previously reported methods (1, 2) was established. Since both tuna liver and vitamin D3 resin oils contained large amounts of sterols, digitonin-Celite column chromatography according to SHEPPARD et al.(4) was used to remove the sterol influence from the unsaponifiable matters of the oils. After collecting the eluate and evaporating the solvent, the residue was subjected to thin-layer chromatography (TLC) using Kieselgel GF254 as an adsorbent and a mixture of n-hexane-ethyl acetate (4: 1) as a developing solvent. The scraped zones corresponding to vitamin D3 and pre-D3 were trimethylsilylated and then applied to the GLC using 1.5% OV-17 packed on Shimalite W (80-100 mesh) as a stationary phase. Trimethylsilylation of the gas chromatograms was an essential procedure, because the peaks of unknown substances in tuna liver oils and lumisterol in vitamin D3 resin oils could not be separated from the peak of pyro-D3 without trimethylsilylation. When the proposed method was applied to the samples, satisfactory results were obtained.