pH Paper and Buffers
pH papers, pH strips, pH sticks and pH test kits are used in laboratory, industrial and educational environments to qualitatively assess pH levels or monitor acid-base titrations in a range of sample types. pH buffer reference standards are used for the accurate calibration of pH meters and monitors for far more precise and quantitative pH measurement.
pH test papers are supplied either as rolls, tear-off strips, or sticks. They are impregnated with indicator dyes which change colour when dipped into the solution under test. In some products, the indicator dyes are covalently linked to the cellulose fibres to avoid bleed-out (leaching) and contamination of the test samples.
Some pH papers indicate simple acid or base conditions with a single red-blue colour change (also called litmus papers). Universal pH papers and strips contain a mix of indicator dyes which cover a range of pH values up to and including 0 to 14 in a single test. The observed colour change is checked against a comparison chart normally supplied with the papers.
Alternatively, for accurate assessment of pH, standard (reference) pH buffers are manufactured to very high degrees of precision and are used for the quantitative calibration of pH meters, electrodes and other electrochemical sensors. Standard buffers are:
- Typically supplied at fixed values of pH4.01, pH7.00 and pH10.01
- May be colour-coded for easy and quick identification
- Certified to their nominal pH and accuracy at a specified temperature (typically 20°C)
- Supplied as ready-to-use solutions or concentrates
- Contain antifungals for extended shelf life