Indicator and Test Papers
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Tóm tắt nội dung
This article is compiled based on the United States Pharmacopeia (USP) – 2025 Edition
Issued and maintained by the United States Pharmacopeial Convention (USP)
1 DEFINITION
Indicator and test papers are strips of paper of suitable dimension and grade impregnated with an indicator or a reagent to provide a convenient form of the impregnated substance.
Some test papers may be obtained from commercial sources of laboratory supplies. Alternatively, they may be prepared in the laboratory.
2 PREPARATION OF INDICATOR AND TEST PAPERS
Wet white filter paper completely with hydrochloric acid, and wash with water until the last washing does not produce a red color when treated with methyl red TS. Then treat with ammonia TS, and wash again with water until the last washing does not produce a red color when treated with phenolphthalein TS.
Carefully dry in still air, unless otherwise specified, by suspending it from rods of glass or other inert material in a space free from acid, alkali, and other fumes, saturate the paper with the proper strength or concentration of indicator solution, and carefully dry using the same drying procedure.
Cut the paper into strips of convenient size, and store the papers in well-closed containers, protected from light and moisture.
