Microdetermination of ergocalciferol (vitamin D2) in pharmaceutical preparations by differential spectroscopy using trifluoroacetic acid in the absence of vitamin A.
A differential spectroscopy method for the determination of microgram quantities of ergocalciferol, using trifluoroacetic acid and hydrogen peroxide, was applied to commercially available pharmaceutical preparations. Tablets were powdered and extracted with methanol after being made basic with diethylamine. The methanol was concentrated, chloroform was added, and the mixture was chromatographed on neutral alumina using chloroform as the eluent. Ergocalciferol was determined in an aliquot of the eluate by differential spectroscopy and was compared with a reference ergocalciferol standard treated similarly. The method applied to low potency formulations (2.5-6 mug/tablet) is simple and quantitative, needs less than 5 hr for completion, and has a precision of less than +/- 2%. A simple and accurate chromatographic method for the determination of ergocalciferol in stabilized powders and high potency tablets, which precludes the necessity of solvent-solvent extraction, was also developed. The results are comparable with those obtained by the rat bioassay and the USP XVIII chemical assay.
Separation of fat-soluble vitamins by gel filtration. VII. Determination of vitamin D in the presence of vitamin A and -tocopherol.
An analytical method for the determination of vitamin D in the presence of vitamin A and α-tocopherol was investigated. After saponifying preparations, extracting the unsaponifiable matters and dissolving in iso-propanol, the solution was subjected to the column chromatography using Amberlyst A-26 as a strongly basic anion exchange resin. Vitamin A alcohol and vitamin D were eluted with iso-propanol, whereas α-tocopherol was remained in the column. After evaporating solvent from the eluate, the residue was dissolved in chloroform and then treated with gel filtration through a Sephadex LH-20 column to eliminate vitamin A alcohol and α-tocopherol degradation products accompanied with vitamin D. The vitamin A degradation products still accompanied with vitamin D were removed by means of the adsorption chromatography through a Florex XXS column. Then, vitamin D was determined by Nield's antimony trichloride color reaction applying Wilkie's color inhibitor method. When this proposed method was applied to the model preparations made by mixing vitamin D2, vitamin A palmitate and α-tocopheryl acetate, satisfactory results were obtained. It was also confirmed that this method was available for the determination of vitamin D in pharmaceutical preparations.
Total Lobbying : What Lobbyists Want (and How They Try to Get It)
1. Studying lobbyists and lobbying 2. Lobbying and lobbyists in the United States: a primer 3. Public policy lobbying, part 1 4. Public policy lobbying, part 2 5. Land-use lobbying 6. Procurement lobbying 7. Summary and conclusions.