Britton–Robinson buffer

{{Short description|Universal pH buffer used for the pH range from 2 to 12}}

The Britton–Robinson buffer (BRB or PEM) is a "universal" pH buffer used for the pH range from 2 to 12. It has been used historically as an alternative to the McIlvaine buffer, which has a smaller pH range of effectiveness (from 2 to 8).{{cite journal|journal=Annali di Chimica|first1=Carlos|last1=Mongay|first2=Víctor |last2=Cerdà|title=A Britton-Robinson Buffer of Known Ionic Strength|volume=64|date= January 1974|url=https://www.researchgate.net/publication/285064939}}

Universal buffers consist of mixtures of acids of diminishing strength (increasing pK_a), so that the change in pH is approximately proportional to the amount of alkali added. It consists of a mixture of 0.04 M boric acid, 0.04 M phosphoric acid and 0.04 M acetic acid that has been titrated to the desired pH with 0.2 M sodium hydroxide. Britton and Robinson also proposed a second formulation that gave an essentially linear pH response to added alkali from pH 2.5 to pH 9.2 (and buffers to pH 12). This mixture consists of 0.0286 M citric acid, 0.0286 M monopotassium phosphate, 0.0286 M boric acid, 0.0286 M veronal and 0.0286 M hydrochloric acid titrated with 0.2 M sodium hydroxide.

The buffer was invented in 1931 by the English chemist Hubert Thomas Stanley "Kevin" Britton (1892–1960) and the New Zealand chemist Robert Anthony Robinson (1904–1979).{{cite journal |title=The use of the antimony–antimonous oxide electrode in the determination of the concentration of hydrogen ions and in potenliometric titrations. The Prideaux–Ward universal buffer mixture |url=https://pubs.rsc.org/en/content/articlelanding/1931/jr/jr9310000458 |journal=Journal of the Chemical Society (Resumed) |year=1931 |publisher=Royal Society of Chemistry|doi=10.1039/JR9310001456|pages=747–748 |last1=Britton |first1=Hubert Thomas Stanley |last2=Robinson |first2=Robert Anthony |url-access=subscription }}