The counter- and coion influence on the interaction between sodium hyaluronate and tetradecyltrimethylammonium bromide

The minimum concentration of salt (critical electrolyte concentration, CEC) required to suppress precipitation/coacervation in an aqueous solution of sodium hyaluronate (NaHy) and tetradecyltrimethylammonium bromide (TTAB) ha s been studied and CEC diagrams constructed for a set of inorganic salts, a s a function of TTAB concentration. An initial rapid increase in the CEC is observed for low TTAB concentrations at the onset of the coacervation regi on. When the TTAB concentration is increased, a CEC plateau is reached at a certain TTAB concentration. Thereafter, the CEC value stays fairly constan t, independent of TTAB concentration, until finally the CEC value starts to decrease at a sufficiently high TTAB concentration. The CEC plateau value and the onset of the decrease of CEC are shown to depend strongly on the va lence of the ions constituting the salt. For ions of equal valency, ion-spe cific effects are observed.