WATERCONDUCTIVITY水的电导率

<645> WATER CONDUCTIVITY 水的电导率

Electrical conductivity in water is a measure of the ion-facilitated electron flow through it. Water molecules dissociate into ions as a function of pH and temperature and result in a very predictable conductivity.

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。

Some gases, most notably carbon dioxide, readily dissolve in water and interact to form ions, which predictably affect conductivity as well as pH. For the purpose of this discussion, these ions and their resulting conductivity can be considered intrinsic to the water.

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。

Water conductivity is also affected by the presence of extraneous ions. The extraneous ions used in modeling the conductivity specifications described below are the chloride and sodium ions. The conductivity of the ubiquitous chloride ion (at the theoretical endpoint concentration of 0.47 ppm when it was a required attribute test in USP XXII and earlier revisions) and the ammonium ion (at the limit of 0.3 ppm) represent a major portion of the allowed water impurity level. A balancing quantity of cations, such as sodium ions, is included in this allowed impurity level to maintain electroneutrality. Extraneous ions such as these may have significant impact on the water's chemical purity and suitability for use in pharmaceutical applications. The procedure in the section Bulk Water is specified for measuring the conductivity of waters such as Purified Water, Water for Injection, Water for Hemodialysis, and the condensate of Pure Steam. The procedure in the section Sterile Water is specified for measuring the conductivity of waters such as Sterile Purified Water, Sterile Water for Injection, Sterile Water for Inhalation, and Sterile Water for Irrigation.

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。

Online conductivity testing provides real-time measurements and opportunities for real-time process control, decision, and intervention. Precaution should be taken while collecting water samples for off-line conductivity measurements. The sample may be affected by the sampling method, the sampling container, and environmental factors such as ambient carbon dioxide concentration and organic vapors.

在线电导率检测提供了一种实时测量，可以有机会进行实时过程控制、决策和干预。在取样进行离线电导率测量时，需要注意样品可能会受到取样方法的影响，取样容器、环境因素如空气中二氧化碳浓度和有机蒸汽等。

INSTRUMENT SPECIFICATIONS AND OPERATING PARAMETERS 仪器标准和操作参数Water conductivity must be measured accurately using calibrated instrumentation. The conductivity cell constant, a factor that represents the geometrical properties of the conductivity sensor, must be known within ±2%. The cell constant can be verified directly by using a solution of known or traceable conductivity, or indirectly by comparing the instrument reading taken with the conductivity sensor in question to readings from a conductivity sensor of known or traceable cell constant.

水的电导率测量应使用经过校正的仪器进行准确测量。电导率电极常数，代表电导率电极的几何级性能，误差必须在±2%内。电极常数可以直接采用已知可追溯的电导率溶液确认，或间接地通过将待确认电极在仪器中的读数与已知或可追溯常数的电导率电极读数进行比较来确认。Meter calibration is accomplished by replacing the conductivity sensor with NIST (or equivalent local national authority) -traceable precision resistors (accurate to ±0.1% of the stated value) or an equivalently accurate adjustable resistance device, such as a Wheatstone Bridge, to give a predicted instrument response. Each scale on the meter may require separate calibration prior to use. The frequency of recalibration is a function of instrument design, degree of use, etc. However, because some multiple-scale instruments have a single calibration adjustment, recalibration may be required between each use of a different scale. Excluding the conductivity sensor cell constant accuracy, the instrument accuracy must be ±0.1 μS/cm.