, Volume 176, Issue 1-2, pp 229-234
Date: 27 Oct 2011

A novel pH sensing membrane based on an ionic liquid-polymer composite

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A novel pH sensing membrane was developed that consists of the ionic liquid n-cetylpyridinium hexafluorophosphate (CPFP), poly(vinyl chloride), and quinhydrone. The membrane is stable and flexible and can be easily deposited on the electrode. Electrochemical impedance spectroscopy was used to study the interfacial charge transfer of this membrane. Compared to a traditional plasticizer-based membrane electrode, the new electrode possesses excellent potentiometric characteristics for monitoring pH, such as a response time of less than 10 s, high sensitivity, stability, and reproducibility. The response is almost Nernstian, with a slope of −57.5 ± 0.2 mV pH−1 in the pH range from 2 to 9.5. The new electrode was used for direct monitoring of pH in real food samples.


A novel pH sensing membrane consisted of ionic liquid n-cetylpyridinium hexafluorophosphate, poly(vinyl chloride) and quinhydrone was developed. This membrane was stable and flexible, which could be easily deposited onto the electrode surface. Electrochemical impedance spectroscopy study shows that the ionic liquid-based membrane possesses fast charge transfer. Compared to the traditional plasticizer-based membrane electrode, the ionic liquid-based membrane electrode possessed very excellent potentiometric characteristics for pH monitoring. The pH sensor exhibited an almost Nernstian response with the slope of -57.5 mV pH-1 in the pH range from 2 to 9.5. Furthermore, the developed electrode was successfully applied to measure pH in the packaged beverages. Using ionic liquid as a novel plasticizer for preparation of polymer-based pH sensing membrane with excellent potentiometric performance