Multiwalled carbon nanotube modified electrodes for the adsorptive stripping voltammetric determination and quantification of curcumin in turmeric

A sensitive electrochemical method for the determination and quantification of curcumin using adsorptive stripping voltammetry (AdsSV) at a multiwalled carbon nanotube modified basal plane pyrolytic graphite electrode (MWCNT-BPPG electrode) is presented exploiting the high surface area of the latter. Next the voltammetric behaviour of curcumin on the modified electrode is examined and AdsSV shown to be a sensitive method for quantifying curcumin. The adsorption of curcumin on the electrode surface is evidenced to follow a Langmuir adsorption isotherm. Linear calibration for curcumin in the range of 2 – 100 µM was obtained with a detection limit of 0.45 µM and a limit of quantification of 1.49 µM. For application to real samples of turmeric, a one-step sample preparation in ethanol has developed providing a simple and rapid extraction procedure. The MWCNT-BPPG electrode with AdsSV allowed the determination of curcumin equivalent in turmeric powder sample with recoveries in the range of 92-108%. This facile and fast method will be useful for monitoring the quality of curcumin containing in commercial turmeric products

Optimising amperometric pH sensing in blood samples: an iridium oxide electrode for blood pH sensing

Amperometric pH sensing in blood samples has been studied using iridium oxide electrodes. The iridium oxide electrodes are made by electrodeposition of iridium oxide onto an iridium micro-disc electrode from an alkaline solution of iridium(iii) oxide. The response of the electrode is studied in aqueous solutions and authentic samples of sheep's blood employing both cyclic voltammetry and square wave voltammetry. Uncertainties of pH measurement in blood samples via cyclic voltammetry (±0.07 pH units) were improved by a factor of two using square wave voltammetry (±0.03 pH units). Limitations of amperometric pH sensing in blood samples are considered as caused by the uncertainty of the required reference measurements (via a conventional glass electrode) and also the use of matrix-free and low ionic strength buffers to calibrate a standard glass electrode for the measurement of blood pH

Rapid electrochemical detection of vanillin in natural vanilla

A commercially available and disposable multiwalled carbon nanotube screen‐printed electrode (CNT‐SPE) was employed to detect and determine vanillin compounds in natural vanilla. The voltammetric behaviour of vanillin at the CNT‐SPE is examined and shown to be a sensitive method for quantifying vanillin. Linear calibration for vanillin in the range of 2.5–750 μM was obtained with a detection limit of 1.03 μM and a quantification limit of 3.44 μM. The developed method comprises a simple sample preparation method and a sensitive electrochemical detection for the quantification of vanillin in vanilla pods and is an easy and simple procedure for manufacturers and consumers

Optimising amperometric pH sensing in blood samples: an iridium oxide electrode for blood pH sensing

Amperometric pH sensing in blood samples has been studied using iridium oxide electrodes. The iridium oxide electrodes are made by electrodeposition of iridium oxide onto an iridium micro-disc electrode from an alkaline solution of iridium(iii) oxide. The response of the electrode is studied in aqueous solutions and authentic samples of sheep's blood employing both cyclic voltammetry and square wave voltammetry. Uncertainties of pH measurement in blood samples via cyclic voltammetry (±0.07 pH units) were improved by a factor of two using square wave voltammetry (±0.03 pH units). Limitations of amperometric pH sensing in blood samples are considered as caused by the uncertainty of the required reference measurements (via a conventional glass electrode) and also the use of matrix-free and low ionic strength buffers to calibrate a standard glass electrode for the measurement of blood pH

Electrochemical detection and quantification of gingerol species in ginger (Zingiber officinale) using multiwalled carbon nanotube modified electrodes

We demonstrate the potential of electrochemical detection for the analysis of the 'strength' of ginger in ginger sample. This facile and fast detection method is aimed at the quality control in food industry. Specifically, we report adsorptive stripping voltammetry (AdsSV) as a technique for detection of gingerol compounds, the pungent components of ginger rhizome. Among the gingerols, 6-gingerol is the most abundant and is chosen as a model to characterise the behaviour of a wider range of related compounds. Multiwalled carbon nanotube modified basal plane pyrolytic graphite electrodes (MWCNT-BPPG electrode) are employed to enhance the sensitivity of the measurement. A linearity range from 1 μM to 50 μM with limit of detection of 0.21 μM and limit of quantification of 0.71 μM is obtained. Further, the simple and rapid extraction procedure by simply vortexing the ginger sample with ethanol is developed for extraction of gingerol related species

Amperometric micro pH measurements in oxygenated saliva

An amperometric micro pH sensor has been developed based on the chemical oxidation of carbon fibre surfaces (diameter of 9 µm and length of ca. 1 mm) to enhance the population of surface quinone groups for the measurement of salivary pH. The pH analysis utilises the electrochemically reversible two-electron, two-proton behaviour of surface quinone groups on the micro-wire electrodes. A Nernstian response is observed across the pH range 2-8 which is the pH range of many biological fluids. We highlight the measurement of pH in small volumes of biological fluids without the need for oxygen removal and specifically the micro pH electrode is examined by measuring the pH of commercial synthetic saliva and authentic human saliva samples. The results correspond well with those obtained by using commercial glass pH electrodes on large volume samples

Amperometric micro pH measurements in oxygenated saliva

An amperometric micro pH sensor has been developed based on the chemical oxidation of carbon fibre surfaces (diameter of 9 µm and length of ca. 1 mm) to enhance the population of surface quinone groups for the measurement of salivary pH. The pH analysis utilises the electrochemically reversible two-electron, two-proton behaviour of surface quinone groups on the micro-wire electrodes. A Nernstian response is observed across the pH range 2-8 which is the pH range of many biological fluids. We highlight the measurement of pH in small volumes of biological fluids without the need for oxygen removal and specifically the micro pH electrode is examined by measuring the pH of commercial synthetic saliva and authentic human saliva samples. The results correspond well with those obtained by using commercial glass pH electrodes on large volume samples

Electrochemical detection and quantification of gingerol species in ginger (Zingiber officinale) using multiwalled carbon nanotube modified electrodes

We demonstrate the potential of electrochemical detection for the analysis of the 'strength' of ginger in ginger sample. This facile and fast detection method is aimed at the quality control in food industry. Specifically, we report adsorptive stripping voltammetry (AdsSV) as a technique for detection of gingerol compounds, the pungent components of ginger rhizome. Among the gingerols, 6-gingerol is the most abundant and is chosen as a model to characterise the behaviour of a wider range of related compounds. Multiwalled carbon nanotube modified basal plane pyrolytic graphite electrodes (MWCNT-BPPG electrode) are employed to enhance the sensitivity of the measurement. A linearity range from 1 μM to 50 μM with limit of detection of 0.21 μM and limit of quantification of 0.71 μM is obtained. Further, the simple and rapid extraction procedure by simply vortexing the ginger sample with ethanol is developed for extraction of gingerol related species

Chemical analysis in saliva and the search for salivary biomarkers – a tutorial review

Biomarkers refer to analytes that can be used in the diagnosis of diseases or disorders. In saliva, there are many components that are potential biomarkers, and an increasingly research has focussed on the development of saliva as a diagnostic fluid. This review summarizes existing uses of salivary biomarkers and highlights the importance of the choice of saliva collection as well as the storage procedures. A case study on the effect of collection tools on the concentrations of one of the potential biomarkers, glutathione, is highlighted. Moreover, molecular diagnosis requires reliable measurement assays. This review presents electroanalytical methods for the detection of salivary biomarkers. It further reviews approaches that can be taken to improve the selectivity of the electroanalytical assays without the use of biologically selective materials, notably without the use of enzymes or antibodie

Multiwalled carbon nanotube modified electrodes for the adsorptive stripping voltammetric determination and quantification of curcumin in turmeric

A sensitive electrochemical method for the determination and quantification of curcumin using adsorptive stripping voltammetry (AdsSV) at a multiwalled carbon nanotube modified basal plane pyrolytic graphite electrode (MWCNT-BPPG electrode) is presented exploiting the high surface area of the latter. Next the voltammetric behaviour of curcumin on the modified electrode is examined and AdsSV shown to be a sensitive method for quantifying curcumin. The adsorption of curcumin on the electrode surface is evidenced to follow a Langmuir adsorption isotherm. Linear calibration for curcumin in the range of 2 – 100 µM was obtained with a detection limit of 0.45 µM and a limit of quantification of 1.49 µM. For application to real samples of turmeric, a one-step sample preparation in ethanol has developed providing a simple and rapid extraction procedure. The MWCNT-BPPG electrode with AdsSV allowed the determination of curcumin equivalent in turmeric powder sample with recoveries in the range of 92-108%. This facile and fast method will be useful for monitoring the quality of curcumin containing in commercial turmeric products