A new potentiometric electrode incorporating functionalized β-cyclodextrins for diclofenac determination

This paper reports the preparation of diclofenac-selective membrane electrodes incorporating β-cyclodextrins: (2-hydroxypropyl)-β-cyclodextrin, heptakis(2,3,6-tri-O-methyl)-β-cyclodextrin, and heptakis(2,3,6-tri-O-benzoyl)-β-cyclodextrin. Several plasticized poly(vinyl chloride) membranes of different compositions were tested with the best electrode being the one incorporating heptakis(2,3,6-tri-O-benzoyl)-β-cyclodextrin with the membrane plasticized with 2-nitrophenyloctyl ether. The electrode is characterized by a near-Nernstian response slope of − 60.0 mV decade− 1 over the linear range of 5.0 × 10− 5 − 1.0 × 10− 2 mol L− 1 and a limit of detection of 1.4 × 10− 5 mol L− 1. The proposed electrode can easily discriminate diclofenac ions from several inorganic and organic interferents and some common drug excipients. The electrode has a response time of 10 s and can be used within a pH range of 6.2–8.5 over 10 months without any considerable deterioration. The electrical properties of the membrane electrode were studied by impedance spectroscopy. The notable advantages of the diclofenac-selective electrode include its high sensitivity, selectivity, cost-effectiveness, and comfortable application in drug and urine analysis.