Graphite screen printed electrodes for the electrochemical sensing of chromium(vi)

Abstract

We demonstrate that graphite screen printed macroelectrodes allow the low ppb sensing of chromium(VI) in aqueous solutions over the range 100 to 1000 microg L(-1) with a limit of detection of 19 microg L(-1). The underlying electrochemical mechanism is explored indicating an indirect process involving surface oxygenated species. The drawbacks of using hydrochloric acid as a model solution to evaluate the electrochemical detection of chromium(VI) are also pointed out. The analytical protocol is shown to be applicable for the sensing of chromium(VI) in canal water samples at levels set by the World Health Organisation. The protocol is simplified over existing analytical methodologies and given its analytical performance and economical nature, holds promise for the de-centralised screening of chromium(VI).

Screen-printed electrodes for electroanalytical sensing, of chromium VI in strong acid media

“…Thus, as already reported in other cases [13,34], no need for Cr(VI) ionophore is required: the surface provides the conditions for the reduction. In agreement, the band centered at +150 mV do not appears when only Cr(III), but not Cr(VI), is present (CrCl 3 ·nH 2 O was used).…”

“…For instance, Svancara et al [33] reported Cr(VI) sensor working at pH between 1 and 3 based on synergistic preconcentration of the chromate anion at a carbon paste electrode modified in situ with quaternary ammonium salts. Hallam et al [34] described screen printed electrodes (SPE) with platforms based on graphite for Cr(VI) sensors, working at pH 1 obtaining a limit of detection (LOD) about 0.4 µM, a limit of quantification (LOQ) of 2 µM, but in short range for linear response (up to 20 µM). Welch et al [13] found that Cr(VI) in pH 1 solutions can undergo chemically irreversible reduction on the surface of diamond electrodes, doped with gold, glassy carbon and boron with an LOD of 4 µM.…”

Electroanalytical Sensor Technology

“…The resulting electrodes exhibited low background current and decreased double layer charging in comparison to macroelectrodes, which coupled with their low surface area and capacitance resulted in fast response times in comparison to metal ultramicroelectrodes making them suitable for a variety of applications [94]. Similarly other groups report the application of printed electrodes in environmental and biological analysis [95,96] The work of Banks et al highlights the advantages of miniaturised SPEs over conventional carbon electrodes, specifically in terms of cost and time efficiency. SPEs have been shown to possess a greater ease of use, scale of economies and are disposable in nature, requiring reduced volumes of the analyte (l).…”

A Versatile Environmental Impedimetric Sensor for Ultrasensitive Determination of Persistent Organic Pollutants (POPs) and Highly Toxic Inorganic Ions

“…Gold nanofilm, Au(111)‐like Au electrode, 3D gold nanodendrite network, silver nanoparticles, polymer film platinum nanocomposite, and highly ordered platinum‐nanotube array electrode were therefore designed and fabricated in a complicated way aiming at a more sensitive electroanalysis of such inorganic ions 4. Meanwhile, strongly acidic media (e.g., HCl, H 2 SO 4 , HClO 4 , and HNO 3 ) were mainly employed as electrolytes,[[qv: 4e]],5 which could cause the problems of hydrogen evolution and ­undesirable corrosion. Considering the severe adverse toxic effects of persistent toxic substances (PTS) including POPs and highly toxic inorganic ions in environment and human health, such as genotoxicity, tumor promotion, lung cancer, skin allergy, and arsenicosis,6 it is critically challenging and necessary to explore the novel and simple electrochemical method on their determination.…”