Potentiometric flow injection determination of cadmium in waste waters including in-line ion-exchange separation/concentration

A flow injection system including an ion exchange resin minicolumn was proposed for potentiometric determination of cadmium. The analyte was preferential and quantitatively retained as chlorocomplex by a strongly basic anion exchange resin (AG 1-X8, 200-400 mesh, chloride form) minicolumn (2.0 cm height, 1.85 mm i.d.) whereas other metallic cations and inert components of the samples were wasted. The retained complexes were further eluted towards detection. The flow-through detector was a cadmium homogeneous crystalline double membrane tubular electrode of increased sensitivity; summation of the potentials related to each membrane was performed by means of an external electronic device. The system was applied to analysis of residual waste waters with cadmium contents within 0.056 and 56.2 mg l(-1). Precise results (r.s.d. about 7%) in agreement with those obtained by flame atomic absorption spectrometry were obtained at a rate of 15-20 determinations per hour. (C) 1998 Elsevier Science B.V. All rights reserved.