USP29-231 重金属EN+CN(精品).doc

231 HEAVY METALS 重金属This test is provided to demonstrate that the content of metallic impurities that are colored by sulfide ion, under the specified test conditions, does not exceed the Heavy metals limit specified in the individual monograph in percentage (by weight) of lead in the test substance, as determined by concomitant visual comparison (see Visual Comparison in the section Procedure under Spectrophotometry and Light-Scattering 851) with a control prepared from a Standard Lead Solution. [NOTE—Substances that typically will respond to this test are lead, mercury, bismuth, arsenic, antimony, tin, cadmium, silver, copper, and molybdenum.] 提供本检验来证明与硫化物离子作用显色的金属杂质含量，在规定检验条件下，不得超过各论中规定的重金属限度供试品中铅的百分比（重量比），如同通过与标准铅溶液配制的对照进行视觉比较决定的（参看分光光度法和光散射法<851>中规程部分的视觉比较）。

[注意：与本检验起反应的代表性物质为铅、汞、铋、砷、锑、锡、镉、银、铜和钼]Determine the amount of heavy metals by Method I, unless otherwise specified in the individual monograph. Method I is used for substances that yield clear, colorless preparations under the specified test conditions. Method II is used for substances that do not yield clear, colorless preparations under the test conditions specified for Method I, or for substances that, by virtue of their complex nature, interfere with the precipitation of metals by sulfide ion, or for fixed and volatile oils. Method III, a wet-digestion method, is used only in those cases where neither Method I nor Method II can be used.除各论另有规定外，用方法I测定重金属含量。

方法I用于规定条件下的澄清、无色供试品，方法II用于方法I规定条件下的非澄清、无色供试品，或者，方法III湿法消解Special Reagents Lead Nitrate Stock Solution— Dissolve 159.8 mg of lead nitrate in 100 mL of water to which has been added 1 mL of nitric acid, then dilute with water to 1000 mL. Prepare and store this solution in glass containers free from soluble lead salts. Standard Lead Solution— On the day of use, dilute 10.0 mL of Lead Nitrate Stock Solution with water to 100.0 mL. Each mL of Standard Lead Solution contains the equivalent of 10 µg of lead. A comparison solution prepared on the basis of 100 µL of Standard Lead Solution per g of substance being tested contains the equivalent of 1 part of lead per million parts of substance being tested. 专用试剂硝酸铅贮备液：取硝酸铅159.8 mg，加已加硝酸1 mL的水100 mL，溶解，加水稀释至1000 mL。

于不含可溶铅盐的玻璃容器中配制和贮存该溶液标准铅溶液：使用当天，取硝酸铅贮备液10.0 mL，加水稀释至100.0 mL每1 mL标准铅溶液相当于10 µg的铅对照溶液用100 µL标准铅溶液，METHOD I pH 3.5 Acetate Buffer— Dissolve 25.0 g of ammonium acetate in 25 mL of water, and add 38.0 mL of 6 N hydrochloric acid. Adjust, if necessary, with 6 N ammonium hydroxide or 6 N hydrochloric acid to a pH of 3.5, dilute with water to 100 mL, and mix. Standard Preparation— Into a 50-mL color-comparison tube pipet 2 mL of Standard Lead Solution (20 µg of Pb), and dilute with water to 25 mL. Using a pH meter or short-range pH indicator paper as external indicator, adjust with 1 N acetic acid or 6 N ammonium hydroxide to a pH between 3.0 and 4.0, dilute with water to 40 mL, and mix. pH 3.5醋酸盐缓冲液：取醋酸铵25.0 g，加水25 mL，加6 N盐酸38.0 mL，溶解。

如有需要，用6 N氨水或6 N盐酸调整pH 为3.5，用水稀释至100 mL标准品：用移液管取标准铅溶液（20 µg的铅）2 mL，置50 mL比色管中，用水稀释至25 mL使用pH计或短范围pH试纸作为外指示剂，用1 N醋酸或6 N氨水调整pH至3.0与4.0之间，用水稀释至40 mL，混匀Test Preparation— Into a 50-mL color-comparison tube place 25 mL of the solution prepared for the test as directed in the individual monograph; or, using the designated volume of acid where specified in the individual monograph, dissolve in and dilute with water to 25 mL the quantity, in g, of the substance to be tested, as calculated by the formula: 2.0/(1000L),in which L is the Heavy metals limit, as a percentage. Using a pH meter or short-range pH indicator paper as external indicator, adjust with 1 N acetic acid or 6 N ammonium hydroxide to a pH between 3.0 and 4.0, dilute with water to 40 mL, and mix. 供试品：取如各论所述制备的供试液25 mL，置50 mL比色管中；或当各论有规定时，使用指定体积的酸溶解按下公式计算的供试品的数量（单位g）并用水稀释至25 mL2.0/(1000L),公式中，L是重金属限度，作为一个百分数。

使用pH计或短范围pH试纸作为外指示剂，用1 N醋酸或6 N氨水调整pH至3.0与4.0之间，用水稀释至40 mL，混匀Monitor Preparation— Into a third 50-mL color-comparison tube place 25 mL of a solution prepared as directed for Test Preparation, and add 2.0 mL of Standard Lead Solution. Using a pH meter or short-range pH indicator paper as external indicator, adjust with 1 N acetic acid or 6 N ammonium hydroxide to a pH between 3.0 and 4.0, dilute with water to 40 mL, and mix. 监控品：取如供试品所述制备的溶液25 mL，置50 mL比色管中，加标准铅溶液2.0 mL，使用pH计或短范围pH试纸作为外指示剂，用1 N醋酸或6 N氨水调整pH至3.0与4.0之间，用水稀释至40 mL，混匀。

Procedure— To each of the three tubes containing the Standard Preparation, the Test Preparation, and the Monitor 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, and the color of the solution from the Monitor Preparation is equal to or darker than that of the solution from the Standard Preparatio。