【原创】USP-<921>水分测定法的翻译

Many Pharmacopeial articles either are hydrates or contain water in adsorbed form. As a result, the determination of the water content is important in demonstrating compliance with the Pharmacopeial standards. Generally one of the methods given below is called for in the individual monograph, depending upon the nature of the article. In rare cases, a choice is allowed between two methods. When the article contains water of hydration, the Method I (Titrimetric), the Method II (Azeotropic), or the Method III (Gravimetric) is employed, as directed in the individual monograph, and the requirement is given under the heading Water.
The heading Loss on drying (see Loss on Drying 731 ) is used in those cases where the loss sustained on heating may be not entirely water.
药典中的某些物质可能是水合化合物也可能包含着吸附水。因此，水分含量的测定对于验证样品与药典标准的一致性是很重要的。通常在各论中所使用的下面所给出的方法是由样品的本质所决定的。某些特殊情况下，允许选择两个方法。当样品含有结晶水时，如各论所示，方法1（滴定分析法），方法11（共沸法），或者方法111（重量分析法）常被使用，在标题下给出了必要的条件。
干燥失重（参见干燥失重<731>）用于以下情况，当持续加热时失去的不完全是水。

METHOD I (TITRIMETRIC)
Determine the water by Method Ia, unless otherwise specified in the individual monograph.
Method Ia (Direct Titration)
Principle— The titrimetric determination of water is based upon the quantitative reaction of water with an anhydrous solution of sulfur dioxide and iodine in the presence of a buffer that reacts with hydrogen ions.
方法I（滴定分析法）
除另有规定外，使用方法Ia检测水分。
方法Ia（直接滴定法）
原理---水分滴定测定法是基于水与二氧化硫和碘的无水溶液，在能与氢离子反应的缓冲溶液下发生的定量反应。

In the original titrimetric solution, known as Karl Fischer Reagent, the sulfur dioxide and iodine are dissolved in pyridine and methanol. The test specimen may be titrated with the Reagent directly, or the analysis may be carried out by a residual titration procedure. The stoichiometry of the reaction is not exact, and the reproducibility of a determination depends upon such factors as the relative concentrations of the Reagent ingredients, the nature of the inert solvent used to dissolve the test specimen, and the technique used in the particular determination. Therefore, an empirically standardized technique is used in order to achieve the desired accuracy. Precision in the method is governed largely by the extent to which atmospheric moisture is excluded from the system. The titration of water is usually carried out with the use of anhydrous methanol as the solvent for the test specimen; however, other suitable solvents may be used for special or unusual test specimens.
在最初的滴定溶液里，已知的是卡尔费休试剂，二氧化硫和碘溶解在吡啶和甲醇中。待测样品可能会被卡尔试剂直接滴定，或者采用回滴定法完成分析。反应的化学计量并不存在，水分测定的重现性是由这些因素例如卡尔试剂成分的相对浓度、溶解待测样品的惰性溶剂的性质和一些特殊测定中使用的技巧决定的。然而，为了获得理想的准确度，一种以经验为主的标准化的技巧被使用。方法的精密度由系统与大气中的水分隔离程度所决定。水分的滴定通常是用无水甲醇作待测物质的溶剂来完成的。当然，对于特殊物质或者不常见的待测物质，其他适合的溶剂也会被使用。

Apparatus— Any apparatus may be used that provides for adequate exclusion of atmospheric moisture and determination of the endpoint. In the case of a colorless solution that is titrated directly, the endpoint may be observed visually as a change in color from canary yellow to amber. The reverse is observed in the case of a test specimen that is titrated residually. More commonly, however, the endpoint is determined electrometrically with an apparatus employing a simple electrical circuit that serves to impress about 200 mV of applied potential between a pair of platinum electrodes immersed in the solution to be titrated. At the endpoint of the titration a slight excess of the reagent increases the flow of current to between 50 and 150 microamperes for 30 seconds to 30 minutes, depending upon the solution being titrated. The time is shortest for substances that dissolve in the reagent. With some automatic titrators, the abrupt change in current or potential at the endpoint serves to close a solenoid-operated valve that controls the buret delivering the titrant. Commercially available apparatus generally comprises a closed system consisting of one or two automatic burets and a tightly covered titration vessel fitted with the necessary electrodes and a magnetic stirrer. The air in the system is kept dry with a suitable desiccant, and the titration vessel may be purged by means of a stream of dry nitrogen or current of dry air.
仪器----可以使用能与大气水分适当的隔离、并能指示终点的装置。当直接滴定无色溶液时，可以在视觉上观察到从淡黄色到红棕色的颜色改变。回滴定时，待测样品观察到的颜色变化是相反的。然而，更常见的是用电量测定的方法，使用一个带有简单电路的装置，给浸泡在待滴定溶液中的双铂电极之间加上200mV应用电势来指示终点。在滴定到终点时，卡尔试剂的稍微过量，在30秒到30分钟内电流将增加至50~150微安培，取决于被滴定的溶液。在溶剂中完全溶解的样品耗时最短。对一些自动滴定仪来说，电流或电势在终点的突然改变可以关闭螺旋管操作阀，它是控制滴定管释放滴定液的。市售仪器普遍由一个封闭系统组成，包括一个或两个自动滴定管，一个紧密的有盖的滴定容器，装有必须的电极和一个磁力搅拌器。系统里的空气用合适的干燥剂保持着干燥，滴定容器（中的液体）可能被干燥的氮气流或者空气流排尽。

Reagent— Prepare the Karl Fischer Reagent as follows. Add 125 g of iodine to a solution containing 670 mL of methanol and 170 mL of pyridine, and cool. Place 100 mL of pyridine in a 250-mL graduated cylinder, and, keeping the pyridine cold in an ice bath, pass in dry sulfur dioxide until the volume reaches 200 mL. Slowly add this solution, with shaking, to the cooled iodine mixture. Shake to dissolve the iodine, transfer the solution to the apparatus, and allow the solution to stand overnight before standardizing. One mL of this solution when freshly prepared is equivalent to approximately 5 mg of water, but it deteriorates gradually; therefore, standardize it within 1 hour before use, or daily if in continuous use. Protect from light while in use. Store any bulk stock of the reagent in a suitably sealed, glass-stoppered container, fully protected from light, and under refrigeration.
试剂—如下准备卡尔费休试剂。将125g的碘加至含有670ml甲醇和170ml吡啶的溶液中，放冷。将100ml的吡啶至250ml的量筒中，使吡啶在冰浴中保持冷，加干燥的二氧化硫直至体积达到200ml。振摇中缓缓加该溶液至已放冷的碘混合液中。振摇使碘溶解，将卡尔溶液转移至仪器中，标定前使卡尔溶液放置过夜。新鲜配制的卡尔溶液溶液1ml相当于大约5mg的水，但是它会逐渐变质，因此，在使用前1小时内标定，如果连续使用则每天标定。使用时避光。将大批量的试剂储存在一个适当封口的，带玻璃塞的容器中，避光冷藏。

A commercially available, stabilized solution of Karl Fischer type reagent may be used. Commercially available reagents containing solvents or bases other than pyridine or alcohols other than methanol may be used also. These may be single solutions or reagents formed in situ by combining the components of the reagents present in two discrete solutions. The diluted Reagent called for in some monographs should be diluted as directed by the manufacturer. Either methanol or other suitable solvent, such as ethylene glycol monomethyl ether, may be used as the diluent.
可使用市售、稳定的卡尔费休试剂。也可以使用吡啶以外的碱性物质和甲醇以外的醇类的市售卡氏试剂。这些试剂可能是单组分试剂，也可能是由两个单独的溶液中的试剂成分混合形成的卡氏试剂。一些各论中所要求稀释的卡尔试剂将会被生产商如各论所示稀释。可能是甲醇或者其他合适的溶剂，例如二乙醇甲醚，可以用做稀释剂。

我曾搜集过美国药典的相关翻译，但是没有看到水分滴定法的翻译，再者，我发出来的目的不是加精或者加分什么的，因为我本人英文不是很好，该篇文章我翻译了很长时间，而且也反复翻译校正了好几遍，但是仍然存在很多自己感觉不是很好的地方，希望大家多多指教。

请楼主不要误会，您的本意我也知道的。不过我加精一般都是要过几天才加，几乎每个帖子都这样的。
另外你的翻译已经很专业，很棒

Test Preparation— Unless otherwise specified in the individual monograph, use an accurately weighed or measured amount of the specimen under test estimated to contain 2 to 250 mg of water. The amount of water depends on the water equivalency factor of the Reagent and on the method of endpoint determination. In most cases, the minimum amount of specimen, in mg, can be estimated using the formula:
FCV / KF
in which F is the water equivalency factor of the Reagent, in mg per mL; C is the used volume, in percent, of the capacity of the buret; V is the buret volume, in mL; and KF is the limit or reasonable expected water content in the sample, in percent. C is between 30% and 100% for manual titration, and between 10% and 100% for the instrumental method endpoint determination.
测试样本---除另有规定外，准备一份准确称量或测量的一定量待测样品，估计含有2~250mg的水。水的数量是由水与卡尔试剂的等价因子和终点判断的方法决定的。在大多数情况下，样品的最少量，以mg计，可以用以下公式估算：FCV/KF。其中，F是水与卡尔试剂的等价因子，单位是mg/ml；C是滴定管的总体积中被使用的体积，用百分数计；V是滴定管体积，以ml计；KF是限度或者样品中合理期望的水的含量，以百分数计。手动滴定时C是在30%到100%之间；仪器分析确定终点的方法，C是在10%到100%之间。