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A solid composite pH sensor based on quinhydrone
Author(s) -
Düssel Heike,
KomorskyLovrić Šebojka,
Scholz Fritz
Publication year - 1995
Publication title -
electroanalysis
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.574
H-Index - 128
eISSN - 1521-4109
pISSN - 1040-0397
DOI - 10.1002/elan.1140070917
Subject(s) - quinhydrone electrode , graphite , chemistry , analytical chemistry (journal) , electrode , inorganic chemistry , redox , cyclic voltammetry , reference electrode , nitric acid , absolute electrode potential , potentiometric sensor , electrochemistry , potentiometric titration , chromatography , organic chemistry
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 E 0 ′ = 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.