What are the buffers used for biological and clinical measurements? State the properties of each buffer and the limitations to its applications.
Two common buffers used for biological and clinical measurements are:
- PBS (Phosphate-buffered saline). It consists of disodium hydrogen phosphate, sodium chloride, and potassium chloride and potassium dihydrogen phosphate. The osmolarity and ion concentrations of PBS is the same as in the human body. It is non-toxic to cells, its pH changes little with temperature. The pH of PBS is ~7.4. Limitation: Can be contaminated with micro-organisms and tends to form precipitates in the presence of calcium ions.
- TBS (Tris-buffered saline). It consists of Tris(hydroxymethyl)aminomethane, shows good buffering capacity at higher pH required for some tissues, physiologically inert. Limitation: pH changes with temperature, pH must be measured with a certain electrode.