The determination of uric acid in human saliva by liquid chromatography with electrochemical detection

A method employing high-performance liquid chromatography with electrochemical detection (LC-ED) has been successfully developed for the determination of uric acid in human salvia. The optimal chromatographic conditions were found to comprise a mobile phase containing 5 % methanol, 95 % 50 mM trichloroacetic acid, adjusted to pH 2.7, in conjunction with a Hypersil C18 250 mm x 4.6 mm column at a flow rate of 0.6 mL min-1. Hydrodynamic voltammetric studies were undertaken to optimize the operating potentials required for electrochemical detection. It was found that an applied potential of +1.2 V was optimum for the determination of uric acid. The proposed method was evaluated by carrying out replicate uric acid determinations on spiked and unspiked human saliva samples (%CV = 8.8 %). The data suggest that the method holds promise for clinical applications

Development of an electrochemical assay for the illegal “fat burner” 2,4-dinitrophenol and its potential application in forensic and biomedical analysis

The illegal use of 2,4-dinitrophenol (24DNP) as a diet aid has increased markedly resulting in a number of deaths. This paper describes the development of a simple voltammetric method for the measurement of 24DNP in serum at glassy carbon electrode (GCE). It is believed that this is the first report on the voltammetric determination of 24DNP in any biological sample. Initial investigations were undertaken using cyclic voltammetry to characterise the redox behaviour of 24DNP. Over the pH range 2 to 10 four pH dependent reduction peaks were recorded on the initial negative going scan, concluded to result from the reduction of the two nitro groups to the corresponding hydroxylamines. On the return positive going scan two oxidation peaks were recorded, resulting from the oxidation of the hydroxylamine (O1) formed on the initial negative scan and the direct oxidation of the phenol group (O2). At pH 6, the peak potential of the oxidation process O1 occurred at a potential close to 0 V and was chosen for investigation. The optimum voltammetric conditions required were identified to be supporting electrolyte of 0.1 M pH 6.0 phosphate buffer containing 10 % acetonitrile. Using differential pulse voltammetry, the calibration plot was found to be linear from 180 ng/mL to 184 µg/mL (R2= 0.9996), with a detection limit of 98.4 ng/mL (based on a signal-to-noise ratio of 3). The optimised method was evaluated by carrying out 24DNP determinations on spiked and unspiked serum samples. Using an external calibration technique, mean recoveries of 79.2 % were obtained and coefficients of variation of 7.4 % were calculated for a forensically relative con-centration of 36.8 µg/mL. The performance characteristics show that the method holds promise and reliable data may be obtained for 24DNP in forensics and bioanalysis

Screen-printed electrochemical sensors and biosensors for monitoring metal pollutants

The present review (with 231 references) focuses on developments made in the area of screen-printed biosensors and sensors for the determination of metal ions in industrial, environmental and biomedical applications. The year 2012 represents the twentieth anniversary of the first reported application of screen-printed electrodes for the determination of metal ions. Focus is placed on fabrication techniques, operating details and performance characteristics for the selected applications. The greater proportion of articles have utilised the technique of stripping voltammetry, gaining detection limits in the low ng/mL (ppb) region. An increasing percentage of these have explored bismuth as an alternative to mercury for the modification of the carbon electrode surface. However, a steady number of applications have shown the possibility of utilising the unmodified screen-printed carbon, gold or silver electrode surface. More recently the alternative approach of electrochemical biosensors has become a growing area. The majority of these have exploited the inhabitation metal ions exhibit on the enzyme activity of urease, acetylcholinesterase and glucose oxidase gaining detection limits in the sub µg/mL region, however recent applications utilising thiol-functionalised oligonucleotides have been shown the possibility of gaining detection limits as low as 120 ng/L for Hg2+

Recent developments in the stripping voltammetric determination of indium

The determination of indium has become increasingly more important as the demand for this metal has greatly increased in recent years for the manufacture of touch screen devices, photovoltaic and semi-conductor devices. Concentrations of In generally reported in the environmental are very low requiring highly sensitive techniques such as stripping voltammetry to obtain the detection limits required. This present review focuses on the past and present applications of stripping voltammetry for the determination of In. The majority of applications have utilized Hg working electrodes, either as hanging Hg drop or as thin-film electrodes for use in either anodic stripping voltammetry or adsorptive stripping voltammetry. Detection limits in the low ng/mL range have been generally been reported. The major issue with In determination has been its very low concentrations and interferences from elements such as Pb and Cd, which are generally found in much greater concentrations. More recently alternatives such as Sb and Bi thin film electrodes have been reported and shown to give similar or superior performance characteristics

Underpotential deposition of lead at silver electrodes manufactured from compact discs and its determination in environmental water samples

The present paper describes the facile manufacture of silver electrodes from compact discs for the anodic stripping voltammetric determination of lead. The voltammetric behaviour of Pb in 0.1 M HCl was examined by cyclic voltammetry. Using a starting potential of 0.0 V and switching potential of -0.60 V a distinct underpotential deposition (UPD) process was recognizable resulting in a reduction process at -0.43 V, with a corresponding stripping peak at -0.37 V on the return positive going scan. If a more negative switching potential of -0.90 V was used a further stripping peak is seen with an Ep of -0.49 V, indicative of the stripping of a bulk deposited Pb layer. The possibility of using this UPD behaviour for the determination of trace levels using this medium was examined by anodic stripping voltammetry using the differential pulse waveform in the measurement step. The developed method was evaluated by carrying out Pb determinations on spiked and unspiked roof drainage water. The unfortified sample was found to contain 99.6 ng /mL. The percentage recovery gained for the same sample fortified with 100 ng/mL was calculated to be 95 % with an associated coefficient of variation of 2.7 %

A rapid, green high performance anion-exchange chromatographic assay for saccharin and its determination in environmental water samples

A green, rapid and sensitive high performance anion-exchange chromatographic (HPAEC) method for the determination of saccharin in environmental water samples is reported. A linear range of 5 μg/L to 28.2 μg/mL was found with a theoretical limit of detection of 5 μg/L based on a signal-to-noise ratio of three. No interferences were seen for sodium cyclamate, acesulfame K, aspartame, nitrite, nitrate and chlorate. Following a simple filtration sample pre-treatment a percentage recovery of 92.9 % and an associated coefficient of variation of 3.8 % was found for a sample fortified with 28.2 ng/mL saccharin. Separation was achieved within 2.5 minutes using a SAP 100 mm × 4.6 mm, 8 μm strong anion exchange analytical column with a mobile phase of 0.1 M NaCl at a flow rate of 1.5 mL/min. The develop method avoids the use of potentially environmentally hazardous reagents and minimises the production of waste

Cheap and disposable gold and silver electrodes: Trends in the application of compact discs and digital versatile discs for electroanalytical chemistry

© 2017 Increasingly more reports have focused on the use of digital versatile discs (DVDs) and compact discs (CDs) for the fabrication of electrodes. The majority of discs use Al to reflect the laser. However, a notable percentage utilise Au or Ag. This layer can be mechanically or chemically exposed allowing for the economic fabrication of otherwise expensive Ag and Au electrodes. Cleaning steps are not required due to the layer's mirror like surface. Mass production of these discs means they are available, reproducible and disposable. Modifications can be made by laser, inkjet printing, etching or xurography. Self-assembled monolayers and the attachment of functional groups can also be made. This review (97 references and 6 figures) is divided into four sections. The first describes the development of these electrodes and their fabrication and modification. The next three sections focused on applications for the determination of metal ions, biomedical and environmental analysis

Review of electroanalytical-based approaches for the determination of benzodiazepines

The benzodiazepine class of drugs are characterised by a readily electrochemically reducible azomethine group. A number are also substituted by other electrochemically active nitro, N-oxide, and carbonyl groups, making them readily accessible to electrochemical determination. Techniques such as polarography, voltammetry, and potentiometry have been employed for pharmaceutical and biomedical samples, requiring little sample preparation. This review describes current developments in the design and applications of electrochemical-based approaches for the determination of the benzodiazepine class of drugs form their introduction in the early 1960s to 2019. Throughout this period, state-of-the-art electroanalytical techniques have been reported for their determination. Polarography was first employed focused on mechanistic investigations. Subsequent studies showed the adsorption of many the benzodiazepines at Hg electrodes allowed for the highly sensitive technique of adsorptive stripping voltammetry to be employed. The development and introduction of other working electrode materials such as carbon led to techniques such as voltammetry to become commonly reported, and the modification of these electrodes has now become the most commonly employed approach using molecularly imprinting and nanotechnology

Electrochemical (bio) sensors for environmental and food analyses

© 2018 by the authors. In recent years, great progress has been made in the development of sensors and biosensors to meet the demands of environmental and food analysis. In this Special Issue, the state of art and the future trends in the field of environmental and food analyses have been explored. A total of seven papers (three research and four review papers) are included. These are focused on the fabrication and detection of contaminates such as heavy metals, pesticides and food components, including uric acid and 3-hydroxybutyrate. Included in this Issue is a paper dedicated to the experimental determination of the electroactive area of screen-printed electrodes, an important parameter in the development of such sensors

Amperometric determination of hydrogen peroxide at a silver electrode fabricated from a recycled compact disc

This present study investigates the utilisation of Ag electrodes fabricated from recycled recordable compact discs (CD-R) for the amperometric determination of hydrogen peroxide. The analytical curve was linear up to at least 30 mM hydrogen peroxide with a sensitivity of 21.89 μA/mM over this range. A corresponding detection limit of 17.7 μM, based on a signal-to-noise ratio of three was recorded. The developed electrode represents a simple, inexpensive, reliable method for the determination of hydrogen peroxide, avoiding extended and complex multi-step fabrication as it is readily fabricated from recycled materials. It has a number of potential applications, including environmental, industrial, physiological and home security, especially where single use and disposability could be beneficial