半微量测定法 欧洲药典

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. Apparatus The apparatus consists of a titration vessel with: 2 identical platinum elect

2、rodes; 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

3、 according 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 electrod

4、es either 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

5、 automatic 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的

6、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。 Standardisation. To the titration vessel, add methanol R, dried if 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 suitab

8、le 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 recom

9、mended 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论中

10、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 carry

11、 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, with

12、stirring. Titrate the excess of reagent using methanol R or the prescribed solvent, containing an accurately known quantity of water. 方法B。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 accuracy o

13、f 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 chosen

14、. 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: = Wamount of water added, in milligrams; 1 =

15、Wamount of water found, in milligrams. 2Calculate 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 the extrapolated calibration line with the x-axis (d). Calculate the percentage mean recov

16、ery (). Calculate the percentage errors (e and e) 21using the following expressions: ? ? y-axis intercept, in milligrams of water; a = the -axis intercept, in milligrams of water; the d = xwater content of the substance, in milligrams of water. = M The reagent/solvent system is considered to be acceptable if: are not greater than 2.5 per cent; and 2.5 per cent); b is between 0.975 and 1.025 (deviation is between 97.5 per cent and 102.5 per cent. 如样品滴定所选的滴定剂对所检测物质的准确性需查清楚。以下操作，稳定性。 2.5-25mg水分是合适的。中含有溶剂系统。随后，将水以合适的形式加入已知/检测物质的含水量用所选的试剂 按照以下公式计算恢复率：量的水（至少滴定5次）。累计每次滴定的水的含量。 = W; 加入水的含