Determination of phylloquinone and cholecalciferol encapsulated in granulates formed by melt extrusion

Vitamin K1 (phylloquinone) and vitamin D3 (cholecalciferol) play a dominant role in bone metabolism. Both vitamins are sensitive to ultraviolet radiation, oxygen and other environmental influences. For this reason a special extrusion technology was developed, that enables an encapsulation of these sensitive substances in a matrix of carbohydrates and hydrogenated carbohydrates. To exclude decomposition products possibly originating under process conditions quantitative analysis was carried out by HPLC/UV using a modified method based on United States Pharmacopoeia. Under the used chromatographic conditions it has to be possible to separate cis-phylloquinone, trans-phylloquinone and phylloquinone 2,3-oxide, as well as pre-cholecalciferol, cis-cholecalciferol and trans-cholecalciferol. A silica column as stationary phase and a mixture of n-hexane and 1-amyl alcohol as mobile phase were used for quantification. UV detection ensued at 254 nm. A linear relationship between peak area and concentration was found over almost two orders of magnitude for cis-phylloquinone, trans-phylloquinone and cholecalciferol. The detection limits (S/N 3) on column were 0.1 μg for phylloquinone and 0.4 μg for cholecalciferol. Analytical results showed that the vitamins were encapsulated sufficiently in the used carbohydrate matrix and that they were protected against environmental influences. After granulation process all of the samples tested met the pharmacopoeial requirements.