Conductometric detection of anions of weak acids in chemically suppressed ion chromatography

A commercial micromembrane suppressor, usually used to chemically suppress eluent conductance in ion chromatography, has been successfully used to effect ion replacement reactions in suppressed eluent streams, For 10 mM fluoride and 100 mu M acetate, there were net decreases in conductance upon conversion of the acids to the sodium salts, showing that these concentrations were below their critical point concentrations (CPCs), defined here as the formal concentration above which a specified conjugate salt has a higher conductance than the same formal concentration of the weak acid, For 10 mM carbonate and 10 mu M berate, there were net increases in conductance, showing that these concentrations were above their respective CPCs, The most effective of several ion replacement reagents investigated was EDTA at pH 11, which, for 5.0 mM berate, produced 250- and 1400-fold increases in peak height and peak area, respectively, compared with a normal IC system and low background conductance, The applicability of the system used in this work to cation and anion replacement reactions in general is discussed.