Buffers are of primary importance in many fields, from biology to geochemistry as a scientific notion, but they also are used in technological applications-among many, one can cite water treatment , catalytic reduction , drug solubility , control of enzyme activity , polarography and, in analytical chemistry, atomic absorption spectrophotometry , chromatography , electrophoresis -in particular the use of immobilized pH gradients in electrophoresis , binary buffers for cell electrophoresis or as an important parameter influencing peak spreading . In all these practical uses, it is important to obtain as good a control as possible over the buffer index, sometimes across several pH units.