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叶酸(C_(19)H_(19)N_7O_6)是二元有机弱酸,中国药典用分光光度法测定含量。但该法操作十分烦琐费时,还须用叶酸标准品作对照。因此有必要寻求较简便的测定方法。叶酸可以与Ag NO_3定量生成沉淀,但沉淀为桔红色,与Ag_2CrO_4的颜色相似,因而不能用Mohr法直接滴定。如果用交流示波极谱确定滴定终点,就可以不受有色物质的干扰。叶酸本身是极谱活性物质,在pH7.5～8.0的硼酸盐缓冲液中,它在dE/dt～E示波图上有敏锐切口(图1).用该切口的消失指示AgNO_3直接滴定叶酸的终点,测定结果准确,而比现行药典采用的分光光度法或高效液相层析法简便得多。
Folic acid (C_ (19) H_ (19) N_7O_6) is a binary organic weak acid, Chinese Pharmacopoeia spectrophotometric determination of content. However, the method is very cumbersome and time-consuming operation, but also with folate standard for control. Therefore, it is necessary to seek a more convenient method of determination. Folic acid can be precipitated with AgNO_3 quantitatively, but the precipitate is orange-red, which is similar to the color of Ag_2CrO_4 and therefore can not be directly titrated by the Mohr method. If you use the AC oscilloscope to determine the titration end point, you can not subject to the interference of colored materials. Folic acid itself is a polarographic active substance and has a sharp incision in the dE / dt-E oscillogram in a borate buffer pH 7.5 to 8.0 (Figure 1). The disappearance of the incision indicates that AgNO 3 is directly titrated The end point of folic acid, accurate determination of the results, but more than the current Pharmacopoeia using spectrophotometry or HPLC more simple and convenient.