NMR spectroscopic analysis of 2-mercapto-5-methyl-1,3,4-thiadiazole in cefazolin.
A rapid, sensitive, and accurate method for the quantitative analysis of 2-mercapto-5-methyl-1,3,4-thiadiazole in cefazolin is presented. The method utilizes NMR spectroscopy and is based on the difference in the chemical shift of the methyl protons on free thiadiazole and the thiadiazole moiety of cefazolin.
NMR analysis of mestranol bulk drug.
A double assay procedure for mestranol is described. The method is based upon measurement of the NMR spectrum of mestranol in pyridine, using diphenylacetic acid as an internal standard. The signals chosen are those from the methoxyl and ethinyl groups. Three commercial lots of the steroid were studied, and a TLC study of each lot is described. The impurities are tentatively identified.
THE IRON-ACETOCARMINE METHOD OF FIXING AND STAINING CHROMOSOMES
A short description of this procedure was given in Vol. 55 of the American Naturalist, pp. 573â€”574. The method has now been used almost daily for five years, and certain improvements have suggested themselves. The solution can be prepared by mixing about equal volumes of glacial acetic acid and water. To this is added powdered carmine in excess. The liquid is then â€ ? just brought to boil, cooled, and decanted. To the red solution there are then added a few drops of a solution of ferric hydrate in 50 per cent. acetic acid, to act as a mordant. The amount of iron varies with different objects. Too much produces a precipitate in a short time. The more