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1、The semi-micro determination of water is based upon the quantitative reaction of water with sulphur dioxide and iodine in a suitable anhydrous medium in the presence of a base with sufficient buffering capacity.ApparatusThe apparatus consists of a titration vessel with: 2 identical platinum electrod
2、es; tight inlets for introduction of solvent and titrant; an inlet for introduction of air via a desiccant; a sample inlet fitted with a stopper or, for liquids, a septum.Inlet systems for introduction of dry nitrogen or for aspiration of solvents may also be fitted.The titration is carried out acco
3、rding to the instrument suppliers instructions. Care is taken throughout the determination to avoid exposure of reagents and solvents to atmospheric moisture. The end-point is determined using 2 identical indicator electrodes connected to an electrical source that maintains between the electrodes ei
4、ther a constant current or a constant voltage. Where direct titration is used (method A), addition of titrant causes either a decrease in voltage where constant current is maintained or an increase in current where constant voltage is maintained, until the end-point is reached. Instruments with auto
5、matic end-point detection are commonly used.水分的半微量测定法是基于水与二氧化硫和碘在无水的具有足够缓冲性能的介 质中的反应。设备该设备是由 2 个相同的铂电极，引入溶剂和滴定剂的密封入口，引入空气的干燥 通道和引入样品的通道(引入固体物质的通道装有塞子，引入液体物质的通道装 有隔膜)。入口系统中也装有引入氮气的通道或引入溶剂的通道。其滴定操作是根据仪器供 应商的说明书执行。整个测定过程需细心以防止试剂或溶剂散入到空气中。其终 端用 2 个相同的检测电极连接电源以保持电极间稳定的电流或稳定的电压。其直 接滴定法见方法A,滴定标准液的加入导致稳定电流下
6、的电压的减少或增加，直 到达到反应终点。将用到自动的终点检测仪器。StandardisatioriTo the titration vessel, add methanol R, dried f necessary, or the solvent recommended by the supplier of the titrant. Where applicable for the apparatus used, eliminate residual water from the measurement cell or carry out a pre-titration. Introduce
7、a suitable amount of water in an appropriate form (water R or a certified reference material) and carry out the titration, stirring for the necessary time. The water equivalent is not less than 80 per cent of that indicated by the supplier. Standardise the titrant before the first use and at suitabl
8、e intervals thereafter. Unless otherwise prescribed, use Method A.标准化。于滴定容器中加入甲醇，如有必要，进行干燥或使用其他的支持滴定的 溶剂。消除设备中的残留水或实行预滴定。以合适的形式引入适量的水来进行滴 定，搅拌一定的时间。第一次使用时，或间隔一段时间后，水的等量不少于标准 滴定的 80%，除运用方法 A 测量以外。Method A. Introduce into the titration vessel methanol R, or the solvent indicated in the monograph or re
9、commended by the supplier of the titrant. Where applicable for the apparatus used, eliminate residual water from the measurement cell or carry out a pre-titration. Introduce the substance to be examined rapidly and carry out the titration, stirring for the necessary extraction time.方法A。在滴定容器中引入甲醇或者专
10、论中所规定的支持滴定的溶剂。除去设备 中的残留水或实行预滴定。迅速引入检测物质并实行滴定，在提取期间实行搅拌。Method B. Introduce into the titration vessel methanol R, or the solvent indicated in the monograph or recommended by the supplier of the titrant. Where applicable for the apparatus used, eliminate residual water from the measurement cell or car
11、ry out a pre-titration. Introduce the substance to be examined rapidly and in a suitable state of division. Add an accurately measured volume of the titrant, sufficient to give an excess of about 1 ml or the prescribed volume. Allow to stand protected from light for 1 min or the prescribed time, wit
12、h stirring. Titrate the excess of reagent using methanol R or the prescribed solvent, containing an accurately known quantity of water.方法Bo于滴定容器中引入甲醇或专论中所规定的支持滴定的溶剂。除去设备中 的残留水或实行预滴定。于合适的位置迅速引入需检测的物质。加入精确量取的 滴定剂，超过所需要的滴定剂的量 1ml 或按照规定的量。避光 1 分钟或一段时间 后，搅拌。用甲醇或规定的溶剂滴定过量的试剂，这包括已知量的水分。Suitability. The acc
13、uracy of the determination with the chosen titrant must be verified for each substance to be examined. The following procedure, given as an example, is suitable for samples containing 2.5-25 mg of water.The water content of the substance to be examined is determined using the reagent/solvent system
14、chosen. Thereafter, sequential known amounts of water R are added in an appropriate form (at least 5 additions) and the cumulative water content determined after each addition. Calculate the percentage recovery (r) at each point using the following expression:W1=amount of water added, in milligrams;
15、W2=amount of water found, in milligrams.Calculate the regression line of the cumulative water determined against the water added. Calculate the slope (b), the intercept with the y-axis (a) and the intercept of theextrapolated calibration line with the x-axis (d).Calculate the percentage mean recover
16、y (冃).Calculate the percentage errors (e1 and e2) using the following expressions:100tj 100a=the y-axis intercept, in milligrams of water;d=the x-axis intercept, in milligrams of water;M=water content of the substance, in milligramsof water.The reagent/solvent system is considered to be acceptable f:一 I I and 丨 I are not greater than 2.5 per cent; b is between 0.975 and 1.025 (deviation 2.5 per cen
