Conductivity measurements are typically made on samples of moderate to high ionic strength where contamination of open samples in routine laboratory handling is negligible. Under those conditions, standard temperature compensation using coefficients of 1 to 3 % of reading per degree Celsius over wide concentration ranges is appropriate. In contrast, this test method requires special considerations to reduce trace contamination and accommodates the high and variable temperature coefficients of pure water samples that can range as high as 7 % of reading per degree Celsius. In addition, measuring instrument design performance must be proven under high purity conditions.

This test method is applicable for detecting trace amounts of ionic contaminants in water. It is the primary means of monitoring the performance of demineralization and other high purity water treatment operations. It is also used to detect ionic contamination in boiler waters, microelectronics rinse waters, pharmaceutical process waters, etc., as well as to monitor and control the level of boiler and power plant cycle chemistry treatment chemicals. This test method supplements the basic measurement requirements for Test Methods D 1125, D 2186, and D 4519.

At very low levels of alkaline contamination, for example, 0–1 μg/L NaOH, conductivity is suppressed, and can actually be slightly below the theoretical value for pure water. (13,14) Alkaline materials suppress the highly conductive hydrogen ion concentration while replacing it with less conductive sodium and hydroxide ions. This phenomenon is not an interference with conductivity or resistivity measurement itself but could give misleading indications of inferred water purity in this range if it is not recognized.

1. Scope

1.1 This test method covers the determination of electrical conductivity and resistivity of high purity water samples below 10 μS/cm (above 0.1 Mohm-cm). It is applicable to both continuous and periodic measurements but in all cases, the water must be flowing in order to provide representative sampling. Static grab sampling cannot be used for such high purity water. Continuous measurements are made directly in pure water process lines, or in side stream sample lines to enable measurements on high temperature or high pressure samples, or both.

1.2 The values stated in SI units are to be regarded as standard. No other units of measurement are included in this standard.

1.3 This standard does not purport to address all of the safety concerns, if any, associated with its use. It is the responsibility of the user of this standard to establish appropriate safety and health practices and determine the applicability of regulatory limitations prior to use.

2. Referenced Documents (purchase separately) The documents listed below are referenced within the subject standard but are not provided as part of the standard.

ASTM Standards

D1066 Practice for Sampling Steam

D1125 Test Methods for Electrical Conductivity and Resistivity of Water

D1129 Terminology Relating to Water

D1192 Guide for Equipment for Sampling Water and Steam in Closed Conduits

D1193 Specification for Reagent Water

D2186 Test Methods for Deposit-Forming Impurities in Steam

D2777 Practice for Determination of Precision and Bias of Applicable Test Methods of Committee D19 on Water

D3370 Practices for Sampling Water from Closed Conduits

D3864 Guide for Continual On-Line Monitoring Systems for Water Analysis

D4519 Test Method for On-Line Determination of Anions and Carbon Dioxide in High Purity Water by Cation Exchange and Degassed Cation Conductivity

Keywords

cation; conductivity; high purity water measurements; resistivity; specific conductance; specific resistance; Conductance and conductivity (electrical)--water; Contamination--water; High-purity water; Instrumental measurement--water; Ionic contamination; Resistance and resistivity (water); Sampling water analysis applications; Specific conductance; Specific resistance (resistivity);

ICS Code

ICS Number Code 13.060.60 (Examination of water for physical properties)

Citing ASTM Standards

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