RAPID PK MEASUREMENTS FOR MULTIBASIC WEAK ACIDS BY GRADIENT FLOW-INJECTION TITRATION

pK values of phthalic acid, phosphoric acid and EDTA (pK2, pK3 and pK4 only) have been determined by rapid gradient flow injection titration . Key factors in experimental design have been investigated, viz. pH r ange of the titration, direction of titration, flow-rate and weak acid concentration. Under optimum conditions the technique is well suited to the determination of pK values with a precision of 0.01-0.05 pK and in good agreement with literature values. It is less well suited than conventional batch titration to the determination of very low or high pK values at low weak acid concentrations.