Graphite Screen-Printed Electrodes Applied for the Accurate and Reagentless Sensing of pH

Abstract

A reagentless pH sensor based upon disposable and economical graphite screen-printed electrodes (GSPEs) is demonstrated for the first time. The voltammetric pH sensor utilizes GSPEs which are chemically pretreated to form surface immobilized oxygenated species that, when their redox behavior is monitored, give a Nernstian response over a large pH range (1-13). An excellent experimental correlation is observed between the voltammetric potential and pH over the entire pH range of 1-13 providing a simple approach with which to monitor solution pH. Such a linear response over this dynamic pH range is not usually expected but rather deviation from linearity is encountered at alkaline pH values; absence of this has previously been attributed to a change in the pKa value of surface immobilized groups from that of solution phase species. This non-deviation, which is observed here in the case of our facile produced reagentless pH sensor and also reported in the literature for pH sensitive compounds immobilized upon carbon electrodes/surfaces, where a linear response is observed over the entire pH range, is explained alternatively for the first time. The performance of the GSPE pH sensor is also directly compared with a glass pH probe and applied to the measurement of pH in "real" unbuffered samples where an excellent correlation between the two protocols is observed validating the proposed GSPE pH sensor.

Electrochemical performance of activated screen printed carbon electrodes for hydrogen peroxide and phenol derivatives sensing

“…The content of C-C graphitic clearly lowered, while O-C=O groups appeared in the activated electrodes, except for treatment 1Na (Figure 5A). The binding energy of 286.4 eV could also be ascribed to the presence of the C-Cl bond, as proven by the presence of the Cl 2p core level depicted in the survey scan (data not shown), which was chemically attributed to the presence of the Cl element used to manufacture carbonaceous inks, as indicated in the previous XPS analysis of SPCEs[44].…”

A prototype device of microliter volume voltammetric pH sensor based on carbazole–quinone redox-probe tethered MWCNT modified three-in-one screen-printed electrode

“…A regular variation in the redox potentials, E pa and E pc against changes up to pH 11 after that plateau in the response was noticed indicating a limitation in the proton-coupled electron-transfer mechanism of the redox reaction in the window, pH 2–11. A pKa (~ pH = 13) of the Car-HQ is the likely reason for the termination in the E pa value 27 . A plot of E pa versus pH showed a linear line in a window, pH 2–11 with a slope and regression coefficient values of − 45.2 ± 1 mV pH −1 and 0.9997 respectively (Fig.…”

“… 13 , is a serious issue. Alternately, pH-sensitive redox probes, like hydroquinone (HQ) 18 , 19 , anthraquinone (AQ) 20 , 21 , phenanthroline–quinone 22 , 23 , quinone functionalized graphitic edge-planes 24 – 27 etc., based voltammetric pH-sensing approach have been reported as an alternate choice. Nevertheless, the part of the above-mentioned problems like potential drift due to the mediated electrochemical oxidation and reduction reactions by the redox probes (Table 1 ) couldn’t be completely eliminated 1 , 3 , 25 .…”

Hybrid Carbon Film Electrodes for Electroanalysis

“…Glassy carbon (GC) electrodes have been employed for basic electrochemical measurements. In contrast, printed electrodes using carbon inks have been studied for use in practical biosensors and wearable sensing devices because of their low cost and simple fabrication process 3,4 .…”