Buffer compleximetric titrations

Buffer solutions find many applications in quantitative analysis, e.g. many precipitations are quantitative only under carefully controlled conditions of pH, as are also many compleximetric titrations numerous examples of their use will be found throughout the book. 

Buffers can also be composed of weak bases and their salts examples include ammonia buffer, used to control the pH of compleximetric titrations (see Chapter 6) and the common biological buffer TRIS (or tris(hydroxymethylaminomethane), C4HnN03), used to control the pH of protein solutions. 

Disodium edetate has the structure shown in Figure 6.5 and ionises with the release of two H+ ions. For this reason, compleximetric titrations involving disodium edetate require an alkaline pH and a buffer to ensure that the released protons do not lower the pH. The usual buffer is ammonia solution, which buffers to around pH 10. Careful choice of buffer conditions can allow the assay of several different metal ions in the same sample for example, in the assay of Intraperitoneal Dialysis Solution BPC, both Ca2+ and Mg2+ are assayed by titration with 0.02 m disodium edetate. 

Finally, a method for the determination of total salt content of natural waters, compleximetric and precipitation titrations monitoring were reported by Yao et al (119,120). Analytes at concentrations down to 10M were determined. Several metal ions were titrated with EDTA in the absence of buffer and competing ligands, in buffered media, in acidic solutions and in presence of competing ligands. 

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