USP35-231重金属

USP35 <231> HEAVY METALS
<231>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.]
本检验用以证实供试品中与硫离子作用显色的金属杂质含量，在规定检验条件下，不超过个论中规定的供试品重金属限度，以铅百分含量（重量比）计，与用标准铅溶液配制的对照进行目测比较（参看分光光度法和光散射法<851>中操作步骤部分的视觉比较）测定。

[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.
除个论另有规定外，用方法I测定重金属含量。

方法I用于规定条件下可生成无色的、透明的制品的物质。

方法II适用于在方法I规定条件下无法生成无色透明制品的物质，或由于自身复杂特性，会对硫离子生成的金属沉淀造成干扰的
物质，以及不挥发油和挥发油。

方法III湿消化法，仅在方法I和方法II均不适用时使用。

Special Reagents
专用试剂
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.
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。

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.
标准铅溶液：使用当天配制。

取硝酸铅贮备液10.0 mL，加水稀释至100.0 mL。

每mL标准铅溶液相当于10 µg的铅。

以每g供试品100µL标准铅溶液为基准制备的参比溶液相当于每一百万份供试品中含有一份铅。

METHOD I
方法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.
pH 3.5醋酸盐缓冲液：取醋酸铵25.0 g，加水25 mL，溶解，加6 N盐酸38.0 mL。

如有需要，用6 N氨水或6 N盐酸调节pH 为3.5，用水稀释至100 mL。

混匀。

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.
标准溶液：用移液管取标准铅溶液2 mL（20 µg的铅），置50 mL比色管中，用水稀释至25 mL。

使用pH计或窄范围pH试纸作外部指示剂，用1 N醋酸或6 N氨水调节pH至3.0-4.0，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.
供试溶液：取如个论所述制备的供试液25 mL，置50 mL比色管中；或当个论另有规定时，使用个论中规定体积量的酸溶解，并用水稀释至25 mL。

按下公式计算供试品的量（单位g），
2.0/(1000L),
公式中，L是重金属限度，以百分数计。

使用pH计或窄范围pH试纸作外部指示剂，用1 N醋酸或6 N氨水调节pH至3.0-4.0，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.
监控溶液：取如供试溶液所述制备的溶液25 mL，置50 mL比色管中，加标准铅溶液2.0 mL，使用pH计或窄范围pH试纸作外部指示剂，用1 N醋酸或6 N氨水调节pH至3.0-4.0，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.]
操作：在标准溶液、供试溶液和监控溶液中各加pH 3.5的醋酸盐缓冲液2 mL，然后加硫代乙酰胺-甘油烧碱试液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：供试溶液与标准溶液的颜色比较，不得更深；监控溶液与标准溶液的颜色比较，相当或更深。

[注意：如果监控溶液的颜色比标准溶液的颜色更浅，使用方法II代替方法I来检测该供试品。

]
METHOD II
方法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.
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。

标准溶液：按照方法I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)
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 500to 600, until the carbon is completely burned off. Cool, add 4mL of 6 N hydrochloric acid, cover, digest on a steam bath for 15minutes, uncover, and slowly evaporate on a steam bath to dryness. Moisten the residue with 1 drop of hydrochloric acid, add 10mL of hot water, and digest for 2 minutes, Add 6N 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-rang 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 40mL, and mix.
供试溶液：取按下述公式计算所得供试品的量（单位g）
2.0/(1000L)
式中，L是重金属限度，以百分数计。

精密称定后转移至适宜坩埚中，加足量硫酸润湿供试品，在低温下小心炽灼至完全炭化。

（炭化时可用一适宜盖子松盖于坩埚上。

）向炭化物加硝酸2 mL，硫酸5滴，小心加热至不再产生白色烟雾。

最好用马弗炉于500-600℃进行炽灼，直至炭完全燃尽。

放冷，加6N盐酸4 mL，盖盖，在蒸汽浴中煮解15分钟。

打开盖子，在蒸汽浴上缓慢蒸发至干。

用1滴盐酸润湿残渣，加10ml热水，并煮解2分钟，滴加6N的氨水，直到溶液恰呈碱性（用石蕊试纸检查），用水稀释至25ml，用1N的醋酸调节pH值为3.0-4.0，用窄范围的pH试纸作外指示剂。

如有必要，可过滤，用10ml水冲洗坩锅和过滤器，将滤液与冲洗液一并移入50-ml比色管中，用水稀释至40ml，并混匀。

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.
步骤：分别向每个含有标准溶液和供试溶液的试管中加入2mlpH值为3.5
的醋酸盐缓冲液，然后加入1.2ml硫代乙酰胺－丙三醇TS，用水稀释至50ml，混匀，静置2分钟，在一白色表面上自上向下看：供试品溶液的颜色不得深于标准品溶液的颜色。

METHOD III
方法III
pH 3.5 Acetate Buffer— Prepare as directed under Method I.
pH 3.5醋酸盐缓冲液：按照方法I所述配制。

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：取硫酸8mL和硝酸10 mL，置于一清洁干燥的100mL凯氏烧瓶中，再加入与加到供试品中的硝酸等体积的硝酸。

加热溶液至生成浓密的白烟；冷却，小心加水10mL。

如果供试溶液用过氧化氢处理过，则加入与供试溶液所
用等量的30%过氧化氢。

轻微煮沸至生成浓密的白烟。

再次冷却，小心加水5mL，混合，轻微煮沸至生成浓密的白烟，且体积为2-3mL。

冷却，用少许（mL）水小心稀释，加标准铅溶液2.0 mL（20 µg铅），混匀。

转移至50-mL比色管中，用水冲洗烧瓶，将清洗液加至试管中，至体积为25mL，混合。

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:
2.0/(1000L),
in which L is the Heavy metals limit, as a percentage.
供试品：除个论中另有规定外，取用由下述公式计算所得的供试品量（单位g）：
2.0/(1000L)
式中，L是重金属限度，以百分数计。

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.
如果供试品为固体：取供试品，精密称定，转移至一清洁干燥的100-mL凯氏烧瓶中。

[注意：如果反应起泡剧烈，可以使用300-mL烧瓶。

] 于45°角处夹紧烧瓶，加入硫酸8mL和硝酸10 mL的混合液足量，使供试品完全润湿。

轻缓加温至开始反应，使反应平息，加相同的酸混合液，每次加酸后继续加热，直至18mL酸混合液完全加入。

增加加热，缓慢煮沸至溶液变深。

冷却，加硝酸
2mL，再次加热至溶液变深。

继续加热，并加硝酸直至颜色不再进一步加深，剧烈加热至生成浓密的白烟。

冷却，小心加入水5mL，缓慢煮沸至生成浓密的白烟，继续加热直到体积减少至几mL。

冷却，小心加入水5mL，检查溶液颜色。

如果为黄色，小心加入30%过氧化氢1mL，并再次蒸发至生成浓密的白烟，且体积剩2-3mL。

如果溶液仍呈黄色，再次加水5mL，并用过氧化氢处理。

冷却，用少许的水小心稀释，并冲入50 mL比色管中，小心最终体积不得超过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.‖
如果供试品为液体：取精密称定的供试品，置于一清洁干燥的100mL凯氏烧瓶中。

[注意：如果反应起泡剧烈，可以使用300-mL烧瓶。

] 于45°角处夹紧烧瓶，小心加入硫酸8mL和硝酸10 mL的混合液少量。

轻微加温至反应开始，使反应平息，并按“如果供试品是固体：从加相同的酸混合液”处开始进行操作。

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.
监控溶液：进行煮解，样品量与操作与供试品项下“如果供试品是固体”的小节中所述的相同，到“冷却，用少许（ml）的水小心地稀释”为止。

加入2.0ml 铅标准溶液（20 µg铅），并混匀。

转移至50ml的比色管中，用水冲洗烧瓶，将冲洗液加入到试管中至25ml，混匀。

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.
操作步骤：按如下方法处理供试溶液，标准溶液以及监控溶液。

使用pH计或窄范围的pH试纸作外部指示剂，用氨水调节溶液的pH值至3.0-4.0（如需要，可以用稀氨水，按规定的范围进行操作），用水稀释至10ml，混匀。

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.
向每个管中加入2ml pH为3.5的醋酸盐缓冲液，然后加入1.2ml的硫代乙酰胺－丙三醇TS，用水稀释至50ml，混匀，静置2分钟，在一白色表面上，自上向下观察：供试品的颜色不得深于标准品的颜色，并且监控品的颜色不得浅于标准品的颜色。

*In those countries or jurisdictions 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.
在不能使用硫代乙酰胺的国家或管辖区域，向每个试管中加入10ml新配制的硫化氢TS，静置5分钟，在一白色表面上，自上向下观察。