Description
The method is intended for routine determination of cholecalciferol (vitamin D3) in enriched foodstuffs. Ergocalciferol (vitamin D2) is primarily used as an internal standard, but can also be determined quantitatively with cholecalciferol as the internal standard. It is assumed that there is no natural content of vitamin D2 or D3 in either case. The method has been tested on milk, gruel powder, margarine, cooking oil and fish oil. After the addition of an internal standard (vitamin D2/D3) and basic hydrolysis, vitamin D is extracted with n-heptane. The fraction that contains vitamin D3/D2 is separated with preparative straight phase HPLC (Silica). After evaporation and dilution in acetonitrile/methanol vitamin D3 (or D2) is deter-mined quantitatively with reversed phase HPLC (C-18). UV detection is at 265 nm.