Electroanalytical overview: The pungency of chile and chilli products determinedviathe sensing of capsaicinoids

When you bite into a chile pepper or eat food containing chile (chilli), one might feel heat, or other associated feelings, some good such as the release of endorphins, and some bad. The heat, or pungency, and related feelings from eating chile peppers are the result of their chemical composition,i.e.the concentrations of capsaicinoids. The major components are capsaicin and dihydrocapsaicin, which occur in chiles in the ratio of 6 : 4. Other capsaicinoids occur in smaller concentrations and are known as the “minor” capsaicinoids. Wilbur L. Scoville in 1912 created an organoleptic test, now known as the Scoville scale, which asked a panel of tasters to state when an increasingly dilute solution of the chile pepper in alcohol no longer burned the mouth. Following the Scoville scale, a plethora of analytical techniques later followed. In this overview, we explore the endeavours directed to the development of electrochemical-based sensors for the determination of capsaicin and related compounds, starting from their use in hyphenated laboratory set-ups to their modern use as stand-alone electroanalytical sensors. The latter have the advantage of providing a rapid and sensitive methodology that has the potential to be translated in the field; future trends and issues to be overcome are consequently suggested

Electroanalytical overview: The detection of the molecule of murder atropine

In this overview we explore the electroanalytical determination of the molecule of murder: atropine. Atropine, occurs naturally in various plants of the nightshade family, including the deadly nightshade (Atropa belladonna). On the one hand, atropine, a tropane alkaloid, has medical uses, named on the World Health Organisations list of essential medicines, used for example in resuscitations and as an antidote to certain poison gases and insecticides, but on the other hand, it is fatal in a high enough dose. Atropine derives it names from atropos, one of the three Fates, where in Greek mythology, one of the Fates determining the individuals moment of death. There is clearly a need to analytically determine atropine within clinical and other misdemeanours situations. In this overview, we review the current research directed to the electroanalytical sensing of atropine

The Shono-type electroorganic oxidation of unfunctionalised amides. Carbon-carbon bond formation via electrogenerated N-acyliminium ions

N-acyliminium ions are useful reactive synthetic intermediates in a variety of important carbon–carbon bond forming and cyclisation strategies in organic chemistry. The advent of an electrochemical anodic oxidation of unfunctionalised amides, more commonly known as the Shono oxidation, has provided a complementary route to the C–H activation of low reactivity intermediates. In this article, containing over 100 references, we highlight the development of the Shono-type oxidations from the original direct electrolysis methods, to the use of electroauxiliaries before arriving at indirect electrolysis methodologies. We also highlight new technologies and techniques applied to this area of electrosynthesis. We conclude with the use of this electrosynthetic approach to challenging syntheses of natural products and other complex structures for biological evaluation discussing recent technological developments in electroorganic techniques and future directions

Rapid and portable electrochemical quantification of phosphorus.

Phosphorus 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. Prior to the measurements, all forms of phosphorus are converted into orthophosphates via sample digestion (heating and acidifying). The work presented here details an electrochemical adaptation of this EPA recommended colorimetric approach for the measurement of dissolved phosphorus in water samples using screen-printed graphite macroelectrodes for the first time. This novel indirect electrochemical sensing protocol allows the determination of orthophosphates over the range from 0.5 to 20 μg L(-1) in ideal pH 1 solutions utilizing cyclic voltammetry with a limit of detection (3σ) found to correspond to 0.3 μg L(-1) of phosphorus. The reaction time and influence of foreign ions (potential interferents) upon this electroanalytical protocol was also investigated, where it was found that a reaction time of 5 min, which is essential in the standard colorimetric approach, is not required in the new proposed electrochemically adapted protocol. The proposed electrochemical method was independently validated through the quantification of orthophosphates and total dissolved phosphorus in polluted water samples (canal water samples) with ion chromatography and ICP-OES, respectively. This novel electrochemical protocol exhibits advantages over the established EPA recommended colorimetric determination for total phosphorus with lower detection limits and shorter experimental times. Additionally this electrochemical adaptation allows the determination of dissolved phosphorus without the use of ascorbic acid and antimony potassium tartrate as reducing agents (as used in the colorimetric method). The potential portability of this protocol is demonstrated in the development of the PhosQuant electrochemical device and provides a portable device for the rapid electrochemical detection of dissolved phosphorus using screen-printed electrodes

In situ electrochemical characterisation of graphene and various carbon-based electrode materials: an internal standard approach

We employ an internal standard protocol to simultaneously characterise and utilise electrode materials during their electrochemical implementation. The proposed approach involves ‘spiking’ a solution containing the analyte of interest (namely, β-nicotinamide adenine dinucleotide (NADH)) with a common electrochemical redox probe (such as hexaammine-ruthenium(III) chloride), which consequently allows information on the electrochemical properties of the electrode being utilised to be obtained and monitored throughout its application. This approach is explored using a range of commonly encountered carbonaceous electrode materials, including various graphene configurations, such as monolayer, double- and few-layered graphene electrodes – the latter is reported for the first time. The variability in structural quality and stability of the graphene electrodes used (particularly between batches) highlights the necessity for implementation of such approaches within the literature. This work provides a simple, yet effective option for the in situ electrochemical characterisation of various electrode materials, essential where the quality and composition of a ‘reported’ electrode material can vary greatly depending on its fabrication (batch-to-batch quality) or during the course of experimental use

Electroanalytical Overview: The Sensing of Mesalamine (5-Aminosalicylic Acid)

Mesalamine, known as 5-aminosalicylic acid, is a medication used primarily in the treatment of inflammatory bowel disease, including ulcerative colitis and Crohn’s disease. 5-Aminosalicylic acid can be measured using various benchtop laboratory techniques which involve liquid chromatography-mass spectroscopy, but these are sophisticated and large, meaning that they cannot be used on-site because transportation of the samples, chemicals, and physical and biological reactions can potentially occur, which can affect the sample’s composition and potentially result in inaccurate results. An alternative approach is the use of electrochemical based sensing platforms which has the advantages of portability, cost-efficiency, facile miniaturization, and rapid analysis while nonetheless providing sensitivity and selectivity. We provide an overview of the use of the electroanalytical techniques for the sensing of 5-aminosalicylic acid and compare them to other laboratory-based measurements. The applications, challenges faced, and future opportunities for electroanalytical based sensing platforms are presented in this review

New electrochemical approach for the measurement of oxidative DNA damageVoltammetric determination of 8-oxoguanine at screen-printed graphite electrodes

© 2017 Elsevier B.V. Simplification and miniaturisation of analytical methods for the direct detection of DNA damage is a challenging area of research and screen-printed electrodes are a promising alternative approach to analytically/electroanalytically monitor the species involved. In this work we demonstrate that screen-printed graphite macroelectrodes (SPEs) provide useful electrochemical signatures to study the behaviour of 8-oxoguanine (8-oxoGua), which is the most frequent and important marker of oxidative DNA damage and it is widely considered as a biomarker, via differential pulse voltammetry (DPV). Under the optimum experimental conditions, the proposed electrochemical sensing protocol towards 8-oxoGua using SPEs is demonstrated to be possible over the concentration range of 0.1–12 μM. The response of the SPEs is superior over routinely utilised glassy carbon electrodes in terms of sensitivity with a limit of detection (3σ) found to correspond to 0.33 μM. Reproducibility and repeatability of the proposed methodology at low and high concentrations were also demonstrated. Quantification of 8-oxoGua in the presence of other nucleobases and different compounds of interest which are present in biological fluids was successfully accomplished. Furthermore, proof-of-concept demonstrating the potential use of the developed SPE based methodology for the detection of 8-oxoGua in real complex samples as demonstrated in simulated biological samples (human semen)

Defining the origins of electron transfer at screen-printed graphene-like and graphite electrodes: MoO2 nanowire fabrication on edge plane sites reveals electrochemical insights

© 2016 The Royal Society of Chemistry .Molybdenum (di)oxide (MoO2) nanowires are fabricated onto graphene-like and graphite screen-printed electrodes (SPEs) for the first time, revealing crucial insights into the electrochemical properties of carbon/graphitic based materials. Distinctive patterns observed in the electrochemical process of nanowire decoration show that electron transfer occurs predominantly on edge plane sites when utilising SPEs fabricated/comprised of graphitic materials. Nanowire fabrication along the edge plane sites (and on edge plane like-sites/defects) of graphene/graphite is confirmed with Cyclic Voltammetry, Scanning Electron Microscopy (SEM) and Raman Spectroscopy. Comparison of the heterogeneous electron transfer (HET) rate constants (k°) at unmodified and nanowire coated SPEs show a reduction in the electrochemical reactivity of SPEs when the edge plane sites are effectively blocked/coated with MoO2. Throughout the process, the basal plane sites of the graphene/graphite electrodes remain relatively uncovered; except when the available edge plane sites have been utilised, in which case MoO2 deposition grows from the edge sites covering the entire surface of the electrode. This work clearly illustrates the distinct electron transfer properties of edge and basal plane sites on graphitic materials, indicating favourable electrochemical reactivity at the edge planes in contrast to limited reactivity at the basal plane sites. In addition to providing fundamental insights into the electron transfer properties of graphite and graphene-like SPEs, the reported simple, scalable, and cost effective formation of unique and intriguing MoO2 nanowires realised herein is of significant interest for use in both academic and commercial applications

Recent advances in 2D hexagonal boron nitride (2D-hBN) applied as the basis of electrochemical sensing platforms

2D hexagonal boron nitride (2D-hBN) is a lesser utilised material than other 2D counterparts in electrochemistry due to initial reports of it being non-conductive. As we will demonstrate in this review, this common misconception is being challenged, and researchers are starting to utilise 2D-hBN in the field of electrochemistry, particularly as the basis of electroanalytical sensing platforms. In this critical review, we overview the use of 2D-hBN as an electroanalytical sensing platform summarising recent developments and trends and highlight future developments of this interesting, often overlooked, 2D material