231方法II中是对照白色表面往下看,第一段的方法与原来的略有不同,是参照黑色表面观察以及使用0.22微米的耐酸滤膜过滤溶液,不知理解是否对
mjyang 发表:这是盐酸米托蒽醌中关于重金属的要求:
Heavy metals 231— Proceed as directed under Method II, except in the Procedure to filter the final solutions through a suitable acid-resistant membrane filter of 0.22 µm or finer porosity, instead of viewing them over a dark surface: the precipitate on the filter obtained from the Test Preparation is not darker than that obtained from the Standard Preparation. The limit is 0.002%.
这是231 HEAVY METALS 中方法II的操作:
Procedure— To each of the tubes containing the Standard Preparation and the Test Preparation, add 2 mL of pH 3.5 Acetate Buffer, then add 1.2 mL of thioacetamide–glycerin base TS, dilute with water to 50 mL, mix, allow to stand for 2 minutes, and view downward over a white surface*: the color of the solution from the Test Preparation is not darker than that of the solution from the Standard Preparation.
怎么会出现黑色背景?