【国外标准】 Standard Practice for Estimating pH to Verify Status of Aqueous Samples

5.1 This practice is intended for use by samplers, technicians, or analysts to verify that samples are preserved or at the proper pH specified in analytical procedures.5.2 The pH is indicated within about 1 pH unit for wide-range paper and within 0.5 pH units for narrow-range paper.5.3 Unless stated otherwise in the test method, a wide-range paper estimating pH within 1 unit is suitable.5.4 A narrow-range pH paperstrip may be used for test methods with tighter pH requirements; however, accuracy better than ±0.5 pH units of the estimate should not be implied.5.5 Rapid pH tests allow users to make spot determinations directly without auxiliary equipment.1.1 This practice provides information on verifying the pH of aqueous samples before analysis. This practice is not intended to be used for non-aqueous samples like oil or grease.1.2 This practice may also be used in adjusting pH of samples during various analytical steps.1.3 Wide-range pH papers/strips are used for a rapid indication of pH to within about 1 pH unit, and narrow-range pH papers/strips are used to indicate pH within about 0.5 pH units.1.4 In some instances, a universal liquid indicator may be used.1.5 Units—The values stated in SI units are to be regarded as standard. No other units of measurement are included in this standard.1.6 This practice offers a set of instructions for performing one or more specific operations. This document cannot replace education or experience and should be used in conjunction with professional judgment. Not all aspects of this practice may be applicable in all circumstances. This ASTM International standard is not intended to represent or replace the standard of care by which the adequacy of a given professional service must be judged, nor should this document be applied without consideration of a project’s many unique aspects. The word “Standard” in the title means only that the document has been approved through the ASTM consensus process.1.7 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, health, and environmental practices and determine the applicability of regulatory limitations prior to use.1.8 This international standard was developed in accordance with internationally recognized principles on standardization established in the Decision on Principles for the Development of International Standards, Guides and Recommendations issued by the World Trade Organization Technical Barriers to Trade (TBT) Committee.