Preparation of Chromium (III) and Copper (II) Liquid Membrane Electrodes using Two Methylcoumarin Derivatives

4-methylcoumarin-7-yloxy-N-4-nitrophenyl acetamide and 4-methylcoumarin-7-yloxy-N-phenyl acetamide were used as effective ionophores for preparation of chromium (III) and copper (II) selective liquid membrane electrodes, respectively. Optimization of the composition of the membranes and the conditions of the analysis was performed, and under the optimized conditions the chromium (III) liquid membrane electrode has a detections limit of 1.0×10-10 with response time 4-6 s and the concentration range 1.0×10-4 to 1.0×10-10 M chromium (III) with a Nernstian slope of 20.25±0.4 mV/decade over the pH range of 4.0–7.5 and copper (II) liquid membrane electrode has a detection limit of 3.0×10-5 with response time about 5 s and the concentration range 1.0×10-1 to 3.0×10-5 M copper (II) with a Nernstian slope of 31.08±0.5 mV/decade over the pH range of 4.5–8. The chromium (III) and copper (II) selective electrodes were stable for about 8 and 5 weeks, respectively. They exhibit good selectivity for two ions. They were successfully applied for the direct determination of chromium (III) and copper (II) in wastewater and as indicator electrodes for potentiometric titration of copper ions and chromium ions with EDTA.