Search

We investigated the electroanalytical determination of dissolved oxygen using low-cost disposable screen-printed bulk modified electrodes based on nanostructures. A nanostructure based on gold nanoparticles functionalized with an anthraquinone derivative and cysteamine was prepared. The nanostructured material was characterized morphologically using transmission electron microscopy and further physical characterization was carried out by energy-dispersive X-ray spectrometry. The prepared material was incorporated into a screen-printable graphite ink to develop the technology for the economic mass production of the next generation of field sensors. The electroanalytical determination of dissolved oxygen was possible in the range 0.2–6.1 mg L−1 with a detection limit of 0.131 mg L−1 (based on 3σ). We demonstrate proof-of-concept that this approach provides a rapid and inexpensive sensing strategy for the determination of dissolved oxygen in contaminated water samples.

Corrosion inhibitors are widely used in the water industry for steam condensate treatment. Due to their application into the food industry, the Food and Drug Administration (FDA) legislate that such inhibitors are not to exceed 10 mg L−1. Various analytical protocols exist to provide an offsite analysis and a point of site analysis is required. Consequently, the first example has been reported for the indirect electroanalytical determination of cyclohexylamine and morpholine, two important corrosion inhibitors using disposable and economical screen-printed graphite macroelectrodes. These two analytes have been demonstrated to have no measureable direct electrochemical signatures in aqueous solutions using carbon and noble metal based macroelectrodes and we propose, for the first time, an indirect electrochemical sensing protocol which utilises screen-printed graphite macroelectrodes. This indirect approach utilises an EC type-mechanism using the compounds, N,N′-(1,4-phenylene)dibenzenesulfonamide and N-(4-amino-2-methyl-phenyl)-benzenesulfonamide as mediators. In this approach the mediators are electrochemically oxidised which then chemically react with the target analytes, cyclohexylamine and morpholine; the products of these reactions are then electrochemically interrogated and provide an indirect electroanalytical signal with which to quantify cyclohexylamine and morpholine. The two mediators are required for the two analytes as one mediator cannot measure both analytes. It is demonstrated that this indirect sensing protocol allows the electroanalytical detection of cyclohexylamine and morpholine over the range 1 to 10 mg L−1 in pH 10 carbonate buffer utilising cyclic voltammetry. This indirect electroanalytical protocol is found to exhibit a limit of detection (3σ) of 0.9 and 1 mg L−1 for cyclohexylamine and morpholine respectively which are significantly below the FDA sanctioned levels. This indirect electroanalytical protocol utilising screen-printed sensors has the potential to be applied into-the-field enabling the measurement of these two neutralizing amines to ensure they do not exceed FDA guidelines.

We report the fabrication of paper-based graphite screen printed electroanalytical sensors. Consideration is taken as to determine the most suitable paper-based material enabling reproducible, robust and low cost effective sensor development, after which the paper-based sensor is electrochemically characterised and utilised for the sensing of the important model analytes NADH and nitrite. The analytical performance of the sensors are compared and contrasted to that of commercially available graphite based screen printed sensors fabricated upon traditional polyester substrates. It is found that the paper-based screen printed sensors offers competitive analytical performance when compared with traditional screen printed sensors and other graphite based electrodes offering limits of detection of 1.8 μM and 15.1 μM for NADH and nitrite respectively. As such, these screen printed paper-based analytical devices offer a innovative alternative to the well-established screen printing history of electrodes for use in electroanalytical sensing; the ability to fabricate screen printed electroanalytical sensors which are highly flexible provides the potential for a new class of point-of-care diagnostic devices that are ultra-low-cost, easy to use, and can be designed specifically for use in developing countries.

Correction for ‘Quantification of corrosion inhibitors used in the water industry for steam condensate treatment: the indirect electroanalytical sensing of morpholine and cyclohexylamine’ by Athanasios V. Kolliopoulos et al., Environ. Sci.: Water Res. Technol., 2015, 1, 40–46.

We report a novel electrode composite comprising zinc phosphate within a multiwalled carbon nanotube paste electrode matrix which is applied for the detection of trace amounts of captopril (CAP) via square-wave adsorptive anodic stripping voltammetry (SWAdASV); to the best of our knowledge this is the first report on such a composite electrode. Under optimum experimental conditions, the peak current of CAP was found to be linear over the concentration range from 3.7 to 67 μmol L−1 with a limit of detection of 0.1 μmol L−1. The proposed method was applied for the successful determination of CAP in commercial tablet excipients and biological samples using the electroanalytical protocol evaluated against the laboratory standard iodometric procedure. Excellent comparability between the two is found suggesting that the former can replace the latter within laboratory settings or can be applied to in-the-field applications.

The electroanalytical determination of selenium(IV) via anodic stripping voltammetry is shown to be possible for the first time using screen printed graphite electrodes. The deposition potential and time was optimised allowing a linear range from 10 to 1000 μg L−1 in 0.1 mol L−1 HClO4 to be realised with a limit of detection (3σ) found to correspond to 4.9 μg L−1. Utilising these screen printed graphite electrodes, the detection of selenium(IV) in drinking (tap) water is shown to be feasible allowing a detection limit (3σ) of 19.2 μg L−1 to be realised which is below the levels set by the United States Environmental Protection Agency. Such an approach suggests the possibility of a disposable screening tool for selenium(IV) in drinking water samples.

We present the electroanalytical sensing of atropine using disposable and economic screen printed graphite sensors. The electroanalytical determination of atropine is found to be possible over the concentration range of 5 μM to 50 μM with a detection limit of 3.9 μM (based on 3-sigma) found to be possible. We demonstrate proof-of-concept that this approach provides a rapid and inexpensive sensing strategy for determining the molecule of murder atropine in diet Coca-Cola samples.

The electroanalytical determination of antimony(III) is explored using disposable and economical unmodified screen printed graphite macro-electrodes. These sensors are found to allow the sensing of antimony(III) via anodic stripping voltammetry over the range of 1 to 910 μg L−1 in pH 3.5 acetate buffer solutions with a limit of detection found to correspond to 0.58 μg L−1. The analytical protocol is applied to the sensing of antimony(III) in drinking water samples where a limit of detection was found to correspond to 1.2 μgL−1. The observed detection limits are well below those recommended by the US Environmental Agency and World Health Organisation for antimony(III) concentrations in drinking water. The effects of interferences on the electroanalytical protocol are also explored, where only copper(II) ions are found to be problematic due to the close proximity of the antimony and copper stripping peaks. Proof-of-concept is demonstrated that the interference from copper(II) ions can be eliminated through the application of a complexing agent.

We report the fabrication of novel carbon based screen printed disc-shaped recessed electrodes (250 μm radius) which are electrochemically characterised and contrasted to other screen printed sensors previously reported upon within the literature. In these circumstances, the electrode is fabricated entirely through screen printing and the electrode geometry is defined by the dielectric (inert polymer) producing shallow recessed electrodes. In comparison to co-planar carbon screen printed electrodes, the shallow recessed screen printed electrodes exhibit a greater current density over the former. The potential electroanalytical applications of these carbon based disc-shaped shallow recessed electrodes are explored through the sensing of NADH and nitrite exhibiting analytically relevant limits of detection (3σ) of 5.2 and 7.28 μM respectively. Additionally, the electroanalytical sensing of nitrite is further trialled in a canal water sample demonstrating the robust nature of the sensors analytical performance. Furthermore we explore the potential improvement of the shallow recessed electrodes through the fabrication of pentagon-shaped carbon based shallow recessed electrodes, which are compared and contrasted with shallow recessed disc electrodes towards the electroanalytical sensing of manganese(II); we believe this to be the first example of such an electrode geometry. In comparison of the observed current density the disc-shaped shallow recessed electrode offers greater sensitivity over co-planar screen printed electrode, whilst in addition to this, a pentagon-shaped recessed electrode offers improved sensitivity over even that of the disc-shaped shallow recessed screen printed electrode. The ultra-low nM sensing of manganese(II) is shown to be possible at both the disc and pentagon shallow recessed electrodes exhibiting limits of detection (3σ) found to correspond to 63 and 36 nM respectively. Both the disc and pentagon-shaped shallow recessed screen printed electrodes are determined to offer greater analytical sensitivity as determined within this study and in comparison with previous literature using graphitic electrodes. The fabrication methodology of the shallow recessed electrodes is shown to be generic in nature such that the underlying carbon layer, which defines the composition of the shallow recessed working electrode, can be replaced with electrocatalytic surfaces. We demonstrate this with the fabrication of platinum disc-shaped shallow recessed screen printed electrodes, which are electrochemically characterised and explored towards the sensing of hydrazine and hydrogen peroxide displaying limits of detection (3σ) of 26.3 and 44.3 μM respectively, which are found to be analytically useful.

We report the fabrication of platinum screen printed electrodes which are electrochemically characterised and evaluated as to their potential analytical application towards the sensing of hydrazine and hydrogen peroxide. In the case of hydrazine a linear range of 50 to 500 μM is possible with a limit of detection (3σ) of 0.15 μM achievable using cyclic voltammetry which can be reduced to 0.12 μM using chronoamperometry. The novelty of these platinum screen printed electrodes is highlighted in that the platinum on the screen printed electrode surface resides as an oxide, which is favourable for the electrochemical oxidation of hydrazine, which need to be formed via extensive potential cycling when using a traditional platinum electrode hence the platinum screen printed sensors alleviate these requirements. The electroanalytical reduction of hydrogen peroxide is shown to be feasible with a linear range over 100 and 1000 μM with a limit of detection (3σ) of 0.14 μM which is competitive with other reported analytical protocols.

The crystal and molecular structure of the title compound have been determined by X-ray diffraction methods from photographic data. Crystals are monoclinic tablets, space group C2/c, with Z= 8 in a cell with a= 25.46, b= 11.62, c= 8.25 A, and β= 109.8°. The structure has been solved by Patterson and Fourier methods, and refined by least-squares techniques to R 0.087 7 for 660 reflections. The manganese is bonded to the heterocyclic rina; one of the carbonyl grouos is trans to the nitrogen atom. The root-mean-square deviation from planarity for the atoms of the heterodyclic ring is 0.04 A.