关于USP重金属2法的检验

rgdhh316

关于USP重金属2法的检验

求教：USP重金属检验中2法，为什么标准铅的使用量为4ml，而一法中为2ml？

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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：用移液管取标准铅溶液4mL，置一适宜试管中，加6 N盐酸10 mL。

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

4.0/(1000L),

in which L is the Heavy metalslimit, as a percentage. Transfer the weighed quantity of the substance to asuitable crucible, add sufficient sulfuric acid to wet the substance, andcarefully ignite at a low temperature until thoroughly charred. (The cruciblemay be loosely covered with a suitable lid during the charring.) Add to thecarbonized mass 2 mL of nitric acid and 5 drops of sulfuric acid, and heatcautiously until white fumes no longer are evolved. Ignite, preferably in amuffle furnace, at 500° to 600°, until the carbon is completely burned off(no longer than 2 hours). If carbon remains, allow the residue to cool, add afew drops of sulfuric acid, evaporate, and ignite again. Cool, add 5 mL of 6 Nhydrochloric acid, cover, and digest on a steam bath for 10 minutes. Cool, andquantitatively transfer the solution to a test tube. Rinse the crucible with asecond 5-mL portion of 6 N hydrochloric acid, and transfer the rinsing to thetest tube.

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 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— Pipet 4 mL of the StandardLead Solution into a crucible identical to that used for the TestPreparation and containing a quantity of the substance under test that isequal to 10% of the amount required for the Test Preparation. Evaporateon a steam bath to dryness. Ignite at the same time, in the same muffle furnace,and under the same conditions used for the Test Preparation. Cool, add 5mL of 6 N hydrochloric acid, cover, and digest on a steam bath for 10 minutes.Cool, and quantitatively transfer to a test tube. Rinse the crucible with asecond 5-mL portion of 6 N hydrochloric acid, and transfer the rinsing to thetest tube.

监控品：取标准铅溶液4mL，置一坩埚中（该坩埚为供试品使用过并含有相当于制备供试品所需量10%的供试品），于蒸气浴上蒸干，然后在与炽灼供试品时使用的同一马弗炉、相同时间及相同条件下炽灼，冷却，加6 N盐酸5 mL，盖盖，于蒸气浴上煮解10分钟，冷却，取全部至试管，用6 N盐酸5 mL清洗坩埚，取清洗液至试管。

Procedure— Adjust the solution in each of thetubes containing the Standard Preparation, the Test Preparation, andthe Monitor Preparation with ammonium hydroxide, added cautiously anddropwise, to a pH of 9. Cool, and adjust with glacial acetic acid, addeddropwise, to a pH of 8, then add 0.5 mL in excess. Using a pH meter orshort-range pH indicator paper as external indicator, check the pH, and adjust,if necessary, with 1 N acetic acid or 6 N ammonium hydroxide to a pH between3.0 and 4.0. Filter, if necessary, washing the filter with a few mL of water,into a 50-mL color-comparison tube, and then dilute with water to 40 mL. Add 2mL of pH 3.5 Acetate Buffer, then add 1.2 mL of thioacetamide–glycerinbase TS, dilute with water to 50 mL, mix, allow to stand for 2 minutes, andview downward over a white surface*: the color of the solution fromthe Test Preparation is not darker than that of the solution from the StandardPreparation, and the color of the solution from the Monitor Preparationis equal to or darker than that of the solution from the StandardPreparation. [NOTE—If thecolor of the solution from the Monitor Preparation is lighter than thatof the solution from the Standard Preparation, proceed as directed for MethodIII for the substance being tested.]

规程：取标准品、供试品和监控品试管，缓慢滴加氨水，调整pH至9，冷却，滴加冰醋酸，调整pH至8，然后再过量加0.5 mL。使用pH计或短范围pH试纸作为外指示剂，检查pH值，如果需要，加1 N醋酸或6 N氨水调整pH至3.0与4.0之间。如果需要，滤过，置一50 mL比色管中，用少许mL水清洗滤器，将清洗液置该比色管中，然后用水稀释至40 mL。加pH 3.5醋酸盐缓冲液2 mL，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。[注意：如果监控品溶液的颜色比标准品溶液的颜色更浅，如方法III所述来检测该供试品。]”

总统特使

谢谢楼主分享

咕咕

呃，没用过USP。
@巴西木 @雪峰 @vabs @hongwei2000  

梦蕾馨

为什么你不计算它的浓度，标准溶液浓度多少，样品重量多少，药典不是有公式吗？
重金属限量=标准溶液体积*标准溶液浓度/样品质量*100%

rgdhh316

{:soso_e100:}

hongwei2000

我不知道楼主是怎么查的，我查到即使是到还没生效的USP36，重金属检验方法中标准铅的取样量一直是2ml，供试品的取样量公式也量2.0/(1000L)

歪说歪有李

楼主，问题解决了吗？

歪说歪有李

咕咕 发表于 2013-3-8 17:55
呃，没用过USP。
@巴西木 @雪峰 @vabs @hongwei2000

见7楼的回复，可能楼主使用的标准有问题。

饮水泉

{:soso_e127:}