Use of ultrafiltration on the analysis of low molecular weight complexing molecules. Analysis of iminodiacetic acid at constant ionic strength.

Low molecular weight complexing molecules may be indirectly analyzed by ultrafiltration with the aid of a water-soluble polymer. The theory concerned is developed and the analysis of iminodiacetic acid (IDAA) is performed by ultrafiltration of aqueous solutions containing poly(sodium-4-styrenesulfonate) (PSS), Cu(NO3)2, and IDAA in variable concentrations. The technique allows measuring IDAA in a range of concentrations between 10(-4) M and 10(-5) M when a 1.6 x 10(-4) M Cu2+ solution is ultrafiltered in the presence of PSS and IDAA.