USP翻译

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. ]

本检验是用来测定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，其检测结果不得超过专论中规定的重金属限度供试品中铅的百分比（重量比），该检验是通过与标准铅溶液配制的对照进行视觉比较来得出结论的（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、无色供试品的检测；方法II用于方法I规定条件下的非澄清、无色供试品，自身对硫化物离子存在干扰，或者是固化物和挥发性油状物的检测；方法III湿法消解，用于方法一与方法二均不适合使用时的检测

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10.0mL，加水稀释至100.0mL。每1mL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25mL，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。混匀。

标准品：用移液管取标准铅溶液2 mL（含20 μg的铅），置50mL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：取按照专论中所述制备的供试液25 mL，置50mL比色管中；或当专论有规定时，使用指定体积的酸溶解按下列公式计算的供试品的数量（单位g）并用水稀释至25 mL，

2.0/(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：取按照供试品溶液配制方法所述制备的溶液25 mL，置于第三只50mL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 Preparation. [NOTE—If the color of the Monitor Preparation is lighter than that of the Standard Preparation, use Method II instead of Method I for the substance being tested. ]

步骤：在标准品、供试品和监控品中各加pH 3.5醋酸盐缓冲液2 mL，然后加硫代乙酰胺-甘油基底试液1.2 mL，用水稀释至50 mL，混匀，静置2分钟，置一白色表面上，自上向下观察：供试品与标准品的溶液颜色比较，不得更深；监控品与标准品的溶液颜色比较，应

相当或颜色更深。[注意：如果监控品溶液的颜色比标准品溶液的颜色更浅，使用方法II代替方法I来检测该供试品。]

METHOD II

NOTE—This method does not recover mercury.

pH 3.5 Acetate Buffer— Prepare as directed under Method I.

Standard Preparation— Prepare as directed under Method I.

方法II

注意：该方法不包含汞。

pH 3.5醋酸盐缓冲液：按照方法I所述配制。

标准品：按照非方法II所述配制。

Test Preparation—Use a quantity, in g, of the substance to be tested as calculated by the formula:

2.0 / (1000L)

供试品：使用按下公式计算的供试品的数量（单位g）：

2.0/(1000L)

in which L is the Heavy metals limit, in percentage. Transfer the weighed quantity of the substance to a suitable crucible, add sufficient sulfuric acid to wet the substance, and carefully ignite at a low temperature until thoroughly charred. (The crucible may be loosely covered with a suitable lid during the charring.) Add to the carbonized mass 2 mL of nitric acid and 5 drops of sulfuric acid, and heat cautiously until white fumes no longer are evolved. Ignite, preferably in a muffle furnace, at 500 to 600, until the carbon is completely burned off. Cool, add 4 mL of 6 N hydrochloric acid, cover, digest on a steam bath for 15 minutes, uncover, and slowly evaporate on a steam bath to dryness. Moisten the residue with 1 drop of hydrochloric acid, add 10 mL of hot water, and digest for 2 minutes. Add 6 N ammonium hydroxide dropwise until the solution is just alkaline to litmus paper, dilute with water to 25 mL, and adjust with 1 N acetic acid to a pH between 3.0 and 4.0, using short-range pH indicator paper as an external indicator. Filter if necessary, rinse the crucible and the filter with 10 mL of water, combine the filtrate and rinsing in a 50-mL color-comparison tube, dilute with water to 40 mL, and mix.

公式中，L是重金属限度，以百分量计。取准确称量的一定量被测样品至合适的坩埚中，加适量硫酸以润湿样品，低温小心灼烧直至完全碳化。（在碳化过程中，可以给坩埚盖一个合适的盖子，但不要盖得太严实。）向已碳化的残渣中加入2mL硝酸和5滴硫酸，小心加热直至硫酸烟雾挥发完全。于马费炉中灼烧，温度为500～600°，直至碳完全燃烧。冷却，加入4mL 6N盐酸，盖上盖子，在蒸汽浴中水解15分钟，移开盖子，于蒸汽浴中蒸发至干。用1滴盐酸润湿残渣，加10mL热水，水解2分钟。滴加6N氢氧化铵直至溶液刚好显碱性（用石蕊试纸检查），用水稀释至25mL，用1N冰乙酸调节至pH3.0～4.0，可使用短范围pH 试纸作外部指示剂。如果有需要，可过滤，用10mL水洗涤坩埚和过滤器，滤液与洗液合并至50mL比色管中，用水稀释至40mL，摇匀。

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.

操作程序——分别含标准溶液和供试品溶液的两个比色管中，各加2 mL pH3.5醋酸盐缓冲溶液，然后各加入1.2 mL硫代乙酰胺-甘油碱试液，用水稀释至50mL，摇匀，静置2分钟，置于白色平面向下观察：供试品溶液所显颜色不得比标准溶液所显颜色更深。

METHOD III

方法三

pH 3.5 Acetate Buffer— Prepare as directed under Method I.

pH 3.5的醋酸盐缓冲液——按方法一中的方法配制。

Standard Preparation— Transfer a mixture of 8 mL of sulfuric acid and 10 mL of nitric acid to a clean, dry, 100-mL Kjeldahl flask, and add a further volume of nitric acid equal to the incremental volume of nitric acid added to the Test Preparation. Heat the solution to the production of dense, white fumes; cool; cautiously add 10 mL of water; and, if hydrogen peroxide was used in treating the Test Preparation, add a volume of 30 percent hydrogen peroxide equal to that used for the substance being tested. Boil gently to the production of dense, white fumes. Again cool, cautiously add 5 mL of water, mix, and boil gently to the production of dense, white fumes and to a volume of 2 to 3 mL. Cool, dilute cautiously with a few mL of water, add 2.0 mL of Standard Lead Solution (20 μg of Pb), and mix. Transfer to a 50-mL color-comparison tube, rinse the flask with water, adding the rinsing to the tube until the volume is 25 mL, and mix.

标准溶液的制备——取硫酸8ml和硝酸10ml的混合液，置洁净干燥的100ml凯氏烧瓶中，再加硝酸适量，加入量与供试品溶液中加入的硝酸量相当。加热使产生浓的白烟，冷却，小心加水10ml，若处理供试品需用过氧化氢，则加30%过氧化氢适量，加水量相当于供试品中消耗的过氧化氢量。继续煮沸至产生浓的白烟，再冷却，小心地加水5ml，混匀，缓缓煮沸至产生浓的白烟，浓缩至提及2~3ml。冷却，小心加水数毫升稀释，加标准铅溶液2.0ml （20μg的铅），混匀，移入50ml比色管中，用水洗涤烧瓶，洗液并入比色管中，并稀释至25ml，混匀。

Test Preparation— Unless otherwise indicated in the individual monograph, use a quantity, in g, of the substance to be tested as calculated by the formula:

供试品溶液的准备：除非在各论中另有提及，否则将被测物质的质量（以克计算）按下式计算：

2.0/(1000L)

in which L is the Heavy metals limit, as a percentage.

在公式中，L是重金属的限量，以百分比表示。

If the substance is a solid— Transfer the weighed quantity of the test substance to a clean, dry, 100-mL Kjeldahl flask. [NOTE—A 300-mL flask may be used if the reaction foams excessively. ] Clamp the flask at an angle of 45, and add a sufficient quantity of a mixture of 8 mL of sulfuric acid and 10 mL of nitric acid to moisten the substance thoroughly. Warm gently until the reaction commences, allow the reaction to subside, and add portions of the same acid mixture, heating after each addition, until a total of 18 mL of the acid mixture has been added. Increase the amount of heat, and boil gently until the solution darkens. Cool, add 2 mL of nitric acid, and heat again until the solution darkens. Continue the heating, followed by addition of nitric acid until no further darkening occurs, then heat strongly to the production of dense, white fumes. Cool, cautiously add 5 mL of water, boil gently to the production of dense, white fumes, and continue heating until the volume is reduced to a few mL. Cool, cautiously add 5 mL of water, and examine

the color of the solution. If the color is yellow, cautiously add 1 mL of 30 percent hydrogen peroxide, and again evaporate to the production of dense, white fumes and a volume of 2 to 3 mL. If the solution is still yellow, repeat the addition of 5 mL of water and the peroxide treatment. Cool, dilute cautiously with a few mL of water, and rinse into a 50-mL color-comparison tube, taking care that the combined volume does not exceed 25 mL.

若供试品为固体——按各论中的规定称取供试品适量，置洁净干燥的100ml凯氏烧瓶中[注意——若反应泡沫过多，可用300ml的烧瓶]，夹住烧瓶使成45○角，加入硫酸8ml和硝酸10ml的混合液适量，其量应足以使样品完全润湿，缓缓加热，至反应开始后停止加热，待反应平息，再分数次加入上述剩余的酸混合液，每次加酸后再加热，直至18ml酸混合液完全加完。继续加热至沸腾，直至溶液变黑，冷却，加硝酸2ml，再加热至溶液变黑。继续加热，再加硝酸，直至溶液不再变黑，然后加强热使产生浓的白烟，冷却，小心地加入水5ml，缓缓加热至产生弄得白烟，继续加热直至提及仅剩数毫升，冷却，小心地加水5ml，观察溶液颜色，若呈黄色，则小心地加入30%的过氧化氢1ml，再蒸发至产生浓的白烟且提及仅剩2~3ml，若溶液仍呈黄色，可重复加水5ml及过氧化氢处理。冷却，小心地加水数毫升稀释，并洗入50ml比色管中，注意合并洗液后的体积不得超过25ml。

If the substance is a liquid— Transfer the weighed quantity of the test substance to a clean, dry, 100-mL Kjeldahl flask. [NOTE—A 300-mL flask may be used if the reaction foams excessively. ] Clamp the flask at an angle of 45, and cautiously add a few mL of a mixture of 8 mL of sulfuric acid and 10 mL of nitric acid. Warm gently until the reaction commences, allow the reaction to subside, and proceed as directed for If the substance is a solid, beginning with “add portions of the same acid mixture.”

若供试品为液体——取各论中规定量的供试品，置一洁净干燥的100ml凯氏烧瓶中[注——若反应泡沫过多，可用300ml烧瓶]，夹住烧瓶使成45度角，小心地加入硫酸8ml与硝酸10ml的混合液数毫升，缓缓温热至反应开始，待反应渐止，按固体项下自“分数次加入上述相同的酸混合液”开始，同法处理。

Monitor Preparation—Proceed with the digestion, using the same amount of sample and the same procedure as directed in the subsection If the substance is a solid in the section Test Preparation, until the step “Cool, dilute cautiously with a few mL of water.” Add 2.0 mL of Lead Standard Solution (20 μg of lead), and mix. Transfer to a 50-mL color comparison tube, rinse the flask with water, adding the rinsing to the tube until the volume is 25 mL, and mix.

监控品：如果反应物为固体使用相同量的样品和相同的步骤将消化液继续反应，直到“冷却，用少量水稀释”这个步骤。加入2.0ml标准铅溶液（含20μg铅），混合。转移至50-ml的比色管中，用水冲洗烧瓶，将洗涤的水加入至试管中加至体积为25ml，混合。Procedure— Treat the Test Preparation, the Standard Preparation, and the Monitor Preparation as follows. Using a pH meter or short-range pH indicator paper as external indicator, adjust the solution to a pH between 3.0 and 4.0 with ammonium hydroxide (a dilute ammonia solution may be used, if desired, as the specified range is approached), dilute with water to 40 mL, and mix. To each tube 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 Test Preparation is not darker than that of the Standard Preparation, and the color of the Monitor Preparation is equal to or darker than that of the Standard Preparation.

规程：按下述方法处理供试品、标准品和监控品。使用一pH计或小范围的pH试纸作为指示，用氢氧化铵将溶液pH调节至3.0至4.0之间（如果要达到精确的范围则可能要用稀释

的铵溶液），用水稀释至40ml，混合。在每个试管中加入2mlpH3.5 的醋酸盐缓冲液，然后加硫代乙酰胺-甘油基底试液1.2 mL，用水稀释至50 mL，混匀，静置2分钟，置一白色表面上，自上向下观察：供试品与标准品的溶液颜色比较，不得更深；监控品与标准品的溶液颜色比较，相当或颜色更深。

In those countries orjurisdictions where thioacetamide cannot be used, add 10 mL of freshly prepared hydrogen sulfide TS to each of the tubes, mix, allow to stand for 5 minutes, and view downward over a white surface.

在硫代乙酰胺不能使用的国家或地区则可以在每个试管中加入10ml新配制的硫化氢试液，混合，放置5分钟，置于一白色表面上，自上向下观察。