A solid composite pH sensor based on quinhydrone

Düssel, Heike; Komorsky‐Lovrić, Šebojka; Scholz, Fritz

doi:10.1002/elan.1140070917

Cited by 39 publications

(21 citation statements)

References 15 publications

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“…Also, E f E 1 E 2 a2. It has been shown previously that under potentiometric conditions the formal potential of solid quinhydrone in a graphite powder composite electrode is E f 0.692±0.058 pH V vs SHE [70]. So, at pH 2 the formal potential is E f 0.37 V vs Ag | AgCl | 3 M KCl.…”

Section: Resultsmentioning

confidence: 83%

Voltammetry of Organic Microparticles

1999

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Solid microparticles of several different insoluble organic compounds were mechanically immobilized on the surface of graphite electrodes and immersed into a liquid electrolyte in order to study their electrochemical reactions. Cyclic staircase voltammetry and square-wave voltammetry were used. Quinhydrone was found to be a stable intermediate in the reversible redox reaction of solid quinone and hydroquinone on the electrode surface. The reaction occurs on the surface of the solid particle which is in contact with water. Indigo can be reduced to leucoindigo and oxidized to dehydroindigo in two separate reversible redox reactions. In strongly basic medium indigo dissolves in water upon electroreduction. A hydroacridine radical was detected as a stable intermediate in the electrochemically irreversible redox reaction of acridine and dihydroacridine. Famotidine can be electrooxidized and the product of this reaction can be electroreduced in two separate chemically irreversible reactions. Probucol is oxidized to a semiquinone radical which can be re-reduced in an electrochemically irreversible redox reaction. Propylthiouracil can be also oxidized to an unknown product which can be re-reduced in a chemically reversible, but slow solid state surface redox reaction. Reductions of solid thionicotinoylanilide and nicotinoylanilide are totally irreversible.

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Section: Resultsmentioning

confidence: 83%

Voltammetry of Organic Microparticles

1999

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“…The cathodic and anodic peaks appear at 0.2 V and 0.32 V (vs. AgyAgCly3 M KCl), respectively, with a median at 0.26 V. This phenomenon was investigated previously [17], and it was shown that the median potential depended linearly on pH of the solution, with a slope of À59 mVypH. It was also demonstrated that this pair of peaks originated from the reversible reaction of the surface bound redox couple.…”

Section: Resultsmentioning

confidence: 89%

Voltammetric Determination of Cocaine Microparticles

Komorsky‐Lovrić¹,

Galić²,

Penovski³

1999

Electroanalysis

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A voltammetric method for the qualitative detection of cocaine powder traces on solid substrates is described. A paraf®n-impregnated graphite electrode is rubbed over the contaminated substrate and microparticles of cocaine are mechanically transferred onto its surface. Using square-wave voltammetry in 1 M KNO 3 at pH 2, the presence of cocaine is indicated by the peak at 0.36 AE 0.01 V (vs. AgyAgCly3 M KCl).

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“…It has been shown in earlier studies [12], that composite electrodes based on quinhydrone are useful for calibration free measurements in solutions with pH values up to 8.5. These electrodes have the same properties as a conventional quinhydrone electrode but additionally they can be used in emulsions and they can be produced as very robust electrodes.…”

Section: Introductionmentioning

confidence: 97%

A New Calibration Free pH‐Probe for In Situ Measurements of Soil pH

Kahlert

Steinhardt

Behnert³

et al. 2004

Electroanalysis

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A new pH-probe was developed for in situ determination of soil pH. It consists of a stainless steel tube with a plastic inset containing the indicator electrode, the reference electrode and a temperature sensor at the end of the tube. The indicator electrode is a quinhydrone composite electrode that does not need to be calibrated, because it acquires almost the theoretical predicted potential and has a constant formal potential and slope under all fabrication conditions. The pH-probe has a low standard deviation (AE 4 mV or 0.07 pH units). The response time is short (5 s). To characterize its function the soil pH-probe was used to analyse pond and arable soil samples. The results were compared with those obtained with a conventional combined glass electrode. To evaluate the results, measurements were performed (i) in natural wet soil samples (in situ conditions), (ii) after drying and moistening the soil samples (moistened samples) and (iii) after drying the soil samples and mixing with bidistilled water (soil solutions; generally accepted method in laboratories). The minimum water content required to obtain stable potentials in soil samples was 10%. The influence of S 2À , NO À 3 and Fe 3þ as naturally available reducing and oxidising agents on the potential response of the pH-probe was investigated. All the obtained results demonstrate that the developed pH-probe is a powerful tool to measure the pH of a soil sample under in situ conditions without a calibration step.

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A solid composite pH sensor based on quinhydrone

Cited by 39 publications

References 15 publications

Voltammetry of Organic Microparticles

Voltammetry of Organic Microparticles

Voltammetric Determination of Cocaine Microparticles

A New Calibration Free pH‐Probe for In Situ Measurements of Soil pH

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