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巴比妥、茶硷、甲基硫脲嘧啶等pK值为7～8,故为弱酸,各国药典所用的定量方法均比较繁琐。本文以二甲替甲酰胺作溶剂,丙醇钾作滴定剂进行非水滴定测定,方法简便,结果准确。二甲替甲酰胺具有较好的溶剂性能,介电常数较高,为惰性溶剂,而且所具极性对多数有机酸及其盐均有良好的溶解度。缺点是对水灵敏,在水存在下遇碱即水解。滴定剂也可用四丁基氢氧化铵溶液,但稳定性较差,而且价昂。
The pK value of barbiturate, theophylline, methylthiouracil and the like is 7 to 8, so it is a weak acid, and the quantitative methods used in the pharmacopoeias of various countries are relatively complicated. In this paper, dimethyl formamide as a solvent, potassium propoxide as a titrant for non-aqueous titration, the method is simple and accurate. Dimethyl formamide has better solvent properties, higher dielectric constant, an inert solvent, and the polarity of most of the organic acids and their salts have good solubility. The disadvantage is sensitive to water, in the presence of water that is alkaline hydrolysis. Titrant can also be used tetrabutylammonium hydroxide solution, but the stability is poor, and the price is high.