What is the main purpose of TRIS solution?

Document ID

Document ID TE11924

Published Date

Published Date 30/10/2019
Question
What is the main purpose of TRIS solution?
Summary
The TRIS buffer maintains the pH at a value around 9 for the hardness titration.
Answer
The titration is performed at pH 8-9, at these values the complexation constant difference between EDTA-Ca and EDTA-Mg is the greater so that the two inflections are well separated.
The complexation constant of EDTA-Ca being higher than the EDTA-Mg, the first inflection point corresponds to Ca and the second to Mg.
The titration is done in a buffered medium to keep the pH stable, as the reaction of complexation liberates H+ ions and leads to acidify the solution.
The TRIS & acetylacetone buffer solution allows better separation between Calcium and Magnesium when a Calcium selective electrode is used as measuring electrode.