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.
View Article and Find Full Text PDFThe utilisation of British Currency (GBP) as an electrode substrate is demonstrated for the first time. Termed Regal electrochemistry, a 5 pence (5p) coin (GBP) is electrically wired using a bespoke electrochemical cell and is electrochemically characterised using the outer-sphere redox probe hexaammineruthenium(III) chloride. The electroanalytical utility of the 5p coin electrode is demonstrated towards the novel, proof-of-concept sensing of lead(II) ions using square-wave voltammetry in model buffer solutions over the linear range 5-2000 nM exhibiting a limit of detection (3σ) of 1.
View Article and Find Full Text PDFPhosphorus is one of the key indicators of eutrophication levels in natural waters where it exists mainly as dissolved phosphorus. Various analytical protocols exist to provide an offsite analysis, and a point of site analysis is required. The current standard method recommended by the Environmental Protection Agency (EPA) for the detection of total phosphorus is colorimetric and based upon the color of a phosphomolybdate complex formed as a result of the reaction between orthophosphates and molybdates ions where ascorbic acid and antimony potassium tartrate are added and serve as reducing agents.
View Article and Find Full Text PDFA novel indirect electrochemical protocol for the electroanalytical detection of phenols is presented for the first time. This methodology is demonstrated with the indirect determination of the target analytes phenol, 2-chlorophenol, 4-chlorophenol and 2,4-dichlorophenol through an electrochemically adapted optical protocol. This electrochemical adaptation allows the determination of the above mentioned phenols without the use of any oxidising agents, as is the case in the optical method, where pyrazoline compounds (mediators) chemically react with the target phenols forming a quinoneimine product which is electrochemically active providing an indirect analytical signal to measure the target phenol(s).
View Article and Find Full Text PDFIt has recently been demonstrated that 2-aminoacetophenone (2-AA) is a chemical indicator in exhaled air/breath of Pseudomonas aeruginosa infection associated with progressive life threatening decline of lung function in cystic fibrosis sufferers [Scott-Thomas et al., BMC Pulm. Med.
View Article and Find Full Text PDFThe detection of creatinine via an enzymeless electrochemical method is reported through an indirect electrochemical system in which the picrate anion consumed upon the reaction with creatinine is electrochemically measured. After careful optimisation it is found that in pH 13 two linear analytical ranges are possible utilising an Edge Plane Pyrolytic Graphite (EPPG) electrode: 0-6 mM and 7.5-11.
View Article and Find Full Text PDFThe electroanalytical sensing of Rohypnol® (flunitrazepam) is reported for the first time utilising screen-printed graphite electrodes without the requirement for any additional pre-treatment or modification. The methodology is shown to be useful for quantifying low levels (μg mL(-1)) of Rohypnol® in not only buffered solutions but also two internationally favoured drinks: Coca Cola™ and the alcopop WKD™ without any sample pre-treatment. The current analytical approaches for the sensing of Rohypnol® are also summarised within this paper.
View Article and Find Full Text PDFA newly synthesised type of graphene, Q-Graphene, has been physically and electrochemically characterised with Scanning and Transmission Electron Microscopy (SEM, TEM), X-ray Photoelectron Spectroscopy (XPS) and Cyclic Voltammetry (CV). Interpretation of SEM, TEM and XPS data reveal the material to consist of hollow carbon nanospheres of multi-layer graphene (viz. graphite), which exhibit a total oxygen content of ca.
View Article and Find Full Text PDFThe use of graphene, a one atom thick individual planar carbon layer, has exploded in a plethora of scientific disciplines since it was reported to possess a range of unique and exclusive properties. Despite graphene being explored theoretically since the 1940s and known to exist since the 1960s, the recent burst of interest from a large proportion of scientists globally can be correlated with work by Geim and Novoselov in 2004/5, who reported the so-called "scotch tape method" for the production of graphene in addition to identifying its unique electronic properties which has escalated into graphene being reported to be superior in a superfluity of areas. Consequently, many are involved in the pursuit of producing new methodologies to fabricate pristine graphene on an industrial scale in order to meet the current world-wide appetite for graphene.
View Article and Find Full Text PDFWe explore the use of surfactant free graphene towards the electroanalytical sensing of cadmium(II) ions via anodic stripping voltammetry. In line with literature methodologies, we modify an electrode substrate which exhibits relatively fast electron transfer with commercially available graphene which is free from surfactants. Surprisingly, we find that graphene reduces the analytical performance and hence inhibits the electrochemical detection of cadmium(II) ions, with calibration plots in model aqueous solutions revealing no advantages of employing graphene in this analytical context.
View Article and Find Full Text PDFConvincing evidence is presented demonstrating that the electro-catalytic nature of graphene resides in electron transfer from the edge of graphene which structurally resembles the behaviour of edge plane (rather than basal plane) of highly ordered pyrolytic graphite. The impact of surfactants intrinsic to graphene on the electrochemical response is highlighted.
View Article and Find Full Text PDFWe 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.
View Article and Find Full Text PDFGold-nanoparticle-modified electrodes find wide and diverse applications in the area of electrochemistry. We demonstrate for the first time that gold-nanoparticle-modified electrodes can provide mechanistic information and we exemplify this with the electrochemical deposition of arsenic(III). Our approach of using nanoparticle ensembles is a facile and economical methodology that provides an alternative to using expensive gold single-crystal electrodes that require careful surface preparation before each measurement.
View Article and Find Full Text PDFThe cathodic stripping voltammetry of lead at disposable screen printed shallow recessed microelectrode arrays has been developed for the first time. The array comprises 6 microdiscs which have radii of 116 (+/-6) microns which are recessed by 4 microns and are separated by 2500 microns from their nearest neighbour in a hexagonal arrangement. The electroanalytical determination of lead was explored in 0.
View Article and Find Full Text PDFThe first example of a copper(ii) oxide screen printed electrode is reported which is characterised with microscopy and explored towards the electrochemical sensing of glucose, maltose, sucrose and fructose. It is shown that the non-enzymatic electrochemical sensing of glucose with cyclic voltammetry and amperometry is possible with low micro-molar up to milli-molar glucose readily detectable which compares competitively with nano-catalyst modified electrodes. The sensing of glucose shows a modest selectivity over maltose and sucrose while fructose is not detectable.
View Article and Find Full Text PDFWe demonstrate, with the example of the electroanalytical sensing of chromium(vi) using ultra-microelectrode arrays, that a larger number of microelectrodes comprising an array do not necessarily provide improved electroanalytical performance. Using a low density array, which consists of 256 microdiscs where each microdisc comprising the array has a radius of 10 microns in a cubic arrangement separated from their nearest neighbour by 100 microns, the electroanalytical sensing of chromium(vi) is shown to be possible over the range 13-428 microM with a limit of detection of 3.4 microM readily achievable.
View Article and Find Full Text PDFWe explore the possible use of screen printing technology for fabricating disposable electrochemical platforms for the sensing of pH. These screen printed pH sensors incorporate the pH sensitive phenanthraquinone moiety which undergoes a Nernstian potential shift with pH, and the pH insensitive dimethylferrocene which acts as an internal reference. This generic approach offers a calibration-less and reproducible approach for portable pH measurements with the possibility of miniaturisation allowing incorporation into existing sensing devices.
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