645 WATER CONDUCTIVITY水的电导率

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1、<645>WATERCONDUCTIVITY 水的电导率Electricalconductivityinwaterisameasureoftheion-facilitatedelectronflowthroughit.WatermoleculesdissociateintoionsasafunctionofpHandtemperatureandresultinaverypredictableconductivity.水的电导能力是对水中离子化电子的一种测量。离解为离子的水分子是pH值、温度的函数，它导致可预期的电导率。Somegases,mostnotablycar

2、bondioxide,readilydissolveinwaterandinteracttoformions,whichpredictablyaffectconductivityaswellaspH.Forthepurposeofthisdiscussion,theseionsandtheirresultingconductivitycanbeconsideredintrinsictothewater.一些气体，特别是二氧化碳，容易溶于水中并产生反应形成离子，对电导率产生影响。在本讨论中，这些离子和其对电导率的影响结果可以认为是水的内在本质。Waterconduct

3、ivityisalsoaffectedbythepresenceofextraneousions.Theextraneousionsusedinmodelingtheconductivityspecificationsdescribedbelowarethechlorideandsodiumions.Theconductivityoftheubiquitouschlorideion(atthetheoreticalendpointconcentrationof0.47ppmwhenitwasarequiredattributetestin USPXXII andea

4、rlierrevisions)andtheammoniumion(atthelimitof0.3ppm)representamajorportionoftheallowedwaterimpuritylevel.Abalancingquantityofcations,suchassodiumions,isincludedinthisallowedimpurityleveltomaintainelectroneutrality.Extraneousionssuchasthesemayhavesignificantimpactonthewater'schemicalpur

5、ityandsuitabilityforuseinpharmaceuticalapplications.Theprocedureinthesection BulkWater isspecifiedformeasuringtheconductivityofwaterssuchasPurifiedWater,WaterforInjection,WaterforHemodialysis,andthecondensateofPureSteam.Theprocedureinthesection SterileWater isspecifiedformeasuringtheco

6、nductivityofwaterssuchasSterilePurifiedWater,SterileWaterforInjection,SterileWaterforInhalation,andSterileWaterforIrrigation.水的电导率还受到外来离子的影响，下面所述的包括在电导率质量标准中的外来离子包括氯离子和钠离子。无所不在的钠离子（根据USP22和更早版本测试其理论终点浓度0.47ppm）和铵离子（限度为0.3ppm时）的电导率代表了水中允许杂质的主要组成部分。阳离子数量平衡，例如钠离子，包括在允许杂质水平内以保持电中性。象这些外来离子对

7、水的化学纯度和水在制药用途适用性可能具有显著的影响。在“散装水”部分的检测程序用于测量以下水的电导率，如纯化水、注射水、透析用水、纯蒸汽冷凝水。在“无菌水”部分中的检测程序用于测量以下水的电导率，如无菌纯化水、注射用无菌水、吸入剂用无菌水和冲洗剂用无菌水。Onlineconductivitytestingprovidesreal-timemeasurementsandopportunitiesforreal-timeprocesscontrol,decision,andintervention.Precautionshouldbetakenwhilecollec