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 strong ly basic anion exchange resin (AG 1-X8, 200-400 mesh, chloride form) m inicolumn (2.0 cm height, 1.85 mm i.d.) whereas other metallic cations and inert components of the samples were wasted. The retained complex es were further eluted towards detection. The flow-through detector wa s 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 c ontents 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 spectr ometry were obtained at a rate of 15-20 determinations per hour. (C) 1 998 Elsevier Science B.V. All rights reserved.