Potentiometric and spectrophotometric flow-injection determinations of metal ions with use of metal ion buffers

Potentiometric and spectrophotometric flow-injection determinations of metal ions, based on metal ion buffers, are described. A copper(II) ion-selective electrode and copper(II) ion buffers containing nitrilotriacetic acid (NTA) or ethylenebis(oxyethylenedinitrilo)tetraacetic acid (EGTA) are used for determination of ca. 10^?3 M transition metal ions or of calcium in the presence of magnesium. Spectrophotometric determination of transition metal ions is achieved by using a zinc ion buffer solution containing NTA and xylenol orange as indicator. Zinc concentrations up to 2 M can be determined by using large dispersion in the manifold. The factors influencing the sensitivity of the proposed methods are discussed.