A novel duloxetine ion-selective poly(vinyl chloride) membrane electrode based on the ion-pair complex of duloxetine with phosphomolybdic acid was prepared with diocyl phthalate as a plasticizer. The electrode exhibits a linear response with a slope of 56.9 mV decade~(-1) of duloxetine concentration at 25 ± 0.1 °C for the optimum electrode prepared with a membrane consisting of 10.0% ion pairs. The electrode response was not sensitive to pH changes from 4.30-8.35 and was not affected by possible interfering species such as common inorganic cations, sugars and amino acids. It has a relatively fast response time less than (15 s) and the lifetime was about 2 months during which it could be used without any measurable divergence. The electrode was successfully used for the potentiometric determination of duloxetine hydrochloride both in pure solutions and in pharmaceutical preparations.
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