Electrochemical impedance spectroscopy measurements for determination of derivatized aldehydes in several matrices

Electrochemical Sensors for Determination of Bromate in Water and Food Samples-Review

The application of potassium bromate in the baking industry is used in most parts of the world to avert the human health compromise that characterizes bromates carcinogenic effect. Herein, various methods of its analysis, especially the electrochemical methods of bromate detection, were extensively discussed. Amperometry (AP), cyclic voltammetry (CV), square wave voltammetry (SWV), electrochemiluminescence (ECL), differential pulse voltammetry and electrochemical impedance spectroscopy (EIS) are the techniques that have been deployed for bromate detection in the last two decades, with 50%, 23%, 7.7%, 7.7%, 7.7% and 3.9% application, respectively. Despite the unique electrocatalytic activity of metal phthalocyanine (MP) and carbon quantum dots (CQDs), only few sensors based on MP and CQDs are available compared to the conducting polymers, carbon nanotubes (CNTs), metal (oxide) and graphene-based sensors. This review emboldens the underutilization of CQDs and metal phthalocyanines as sensing materials and briefly discusses the future perspective on MP and CQDs application in bromate detection via EIS.

Hemostasis-On-a-Chip: Impedance Spectroscopy Meets Microfluidics for Hemostasis Evaluation

In the case of vascular injury, a complex process (of clotting) starts, involving mainly platelets and coagulation factors. This process in healthy humans is known as hemostasis, but when it is deregulated (thrombosis), it can be the cause of important cardiovascular diseases. Nowadays, the aging of the population and unhealthy lifestyles increase the impact of thrombosis, and therefore there is a need for tools to provide a better understanding of the hemostasis mechanisms, as well as more cost-effective diagnosis and control devices. This study proposes a novel microflow chamber, with interchangeable biomimetic surfaces to evaluate global hemostasis, using reduced amounts of blood sample and reagents, and also a minimized time required to do the test. To validate the performance of this novel device, a study on the new oral anticoagulant Apixaban (APIX) has been performed and compared to previous conventional techniques. The test shows an excellent agreement, while the amount of the required sample has been reduced (only 100 µL is used), and the amount of reagent as well. An imprinted electrode embedded in the chamber in order to measure the impedance during the coagulation process. This approach distinguishes the impedance behavior of plasma poor in platelets (PPP) and plasma rich in platelets (PRP) for the first time.

Impedance Spectroscopy-Based Reduced Graphene Oxide-Incorporated ZnO Composite Sensor for H2S Investigations

Electrochemical impedance spectroscopy (EIS) has been applied to measure the H₂S gas response of the sensor fabricated on reduced graphene oxide (rGO)-incorporated nano-zinc oxide (n-ZnO) composites. These nanocomposites were prepared by a facile one-step solution route at room temperature. The structural, surface morphological, and elemental analyses of the composite material have been investigated. EIS was carried out to study the H₂S gas-sensing properties of fabricated sensors. The developed sensor showed an optimal H₂S gas response to various concentrations ranging from 2 to 100 ppm at 90 °C. The H₂S gas-sensing performances of pure n-ZnO and various concentrations of rGO-incorporated n-ZnO were evaluated. The H₂S gas-sensing results showed that n-ZnO/rGO composites exhibited high response when compared to pure n-ZnO. The enhanced H₂S response was speculated to be ascribed due to two factors. First, rGO creates reactive sites for H₂S molecule adsorption. Second, rGO has great electrical conductivity compared to n-ZnO that enables the active transport of electrons from H₂S gas on interaction with the sensing layer, resulting in enhanced gas response at 90 °C temperatures.

Rapid electrochemical device for single-drop point-of-use screening of parathyroid hormone

Aim: Novel electrochemical point-of-use biosensing device for rapid assessment of parathyroid hormone (PTH) levels has been developed. Materials & methods: The analytical nanobiosensor was designed by integrating unique high density semiconducting nanostructured arrays on a flexible sensing surface. Surface modification technique was tailored for enhancing the interaction of nanostructure–biological interface to capture the target PTH level. Results & conclusion: We demonstrate a rapid nanobiosensor to detect PTH in human serum, plasma and whole blood with a limit of detection of 1 pg/ml and a clinically relevant dynamic range from 1 to 1000 pg/ml. This is the first demonstration of detecting PTH as a point-of-use device devoid of sample pretreatment suitable in a surgical setting with high specificity to PTH.

Design and Finite Element Model of a Microfluidic Platform with Removable Electrodes for Electrochemical Analysis

A microfluidic platform for hydrodynamic electrochemical analysis was developed, consisting of a poly(methyl methacrylate) chip and three removable electrodes, each housed in 1/16" OD polyether ether ketone tube which can be removed independently for polishing or replacement. The working electrode was a 100-μm diameter Pt microdisk, located flush with the upper face of a 150 μm × 20 μm × 3 cm microchannel, smaller than previously reported for these types of removable electrodes. A commercial leak-less reference electrode was utilized, and a coiled platinum wire was the counter electrode. The platform was evaluated electrochemically by oxidizing a potassium ferrocyanide solution at the working electrode, and a typical limiting current behavior was observed after running linear sweep voltammetry and chronoamperometry, with flow rates 1-6 μL/min. While microdisk channel electrodes have been simulated before using a finite difference method in an ideal 3D geometry, here we predict the limiting current using finite elements in COMSOL Multiphysics 5.3a, which allowed us to easily explore variations in the microchannel geometry that have not previously been considered in the literature. Experimental and simulated currents showed the same trend but differed by 41% in simulations of the ideal geometry, which improved when channel and electrode imperfections were included.