ISSN:
1040-0397
Keywords:
pH electrode
;
Quinhydrone
;
Sensor
;
Modified graphite
;
Chemistry
;
Polymer and Materials Science
Source:
Wiley InterScience Backfile Collection 1832-2000
Topics:
Chemistry and Pharmacology
Notes:
A solid composite pH sensor can be made from quinhydrone, solid paraffin and surface-modified graphite powder. It exhibits an almost theoretical slope of the potential-pH dependence (-57.7 mV at 25°C), a formal potential E0′ = 0.6922V (vs. NHE), low standard deviations for repeated measurements (0.04 pH units), fast potential response (15s) and a working range up to pH 9.5. The sensor can be used in moderately concentrated mineral acids and, unlike the conventional quinhydrone electrode, it is also applicable for measurements in milk. The sensor shows the same salt effect and sensitivity towards strong oxidants and reductants as the conventional quinhydrone electrode. The surface modified graphite was prepared by boiling graphite powder with concentrated nitric acid. By voltammetry it was shown that the surface of the modified graphite contains surface-confined redox centers similar to those in quinhydrone, which can catalyze the electron transfer of the quinhydrone on the surface of the sensor.
Additional Material:
7 Ill.
Type of Medium:
Electronic Resource
URL:
http://dx.doi.org/10.1002/elan.1140070917
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