A Glass Capillary Ultramicroelectrode with an Electrokinetic Sampling Ability

Abstract

A glass capillary ultramicroelectrode (tip diameter ≈1.2 µm) having an electrokinetic sampling ability is described. It is composed of a pulled glass capillary filled with an inner solution and three internal electrodes (Pt working and counter electrodes and an Ag/AgCl reference electrode). The voltammetric response of the capillary electrode is based on electrokinetic transport of analyte ions from the sample solution into the inner solution across the conical tip. It was found that the electrophoretic migration of analytes at the conical tip is faster than electroosmotic flow, enabling electrokinetic transport of analyte ions into the inner solution of the electrode. By using [Fe(CN) 6 ] 4-and (ferrocenylmethyl)trimethylammonium (FcTMA + ) ions as model analytes, differential pulse voltammetric responses of the capillary electrode were investigated in terms of tip diameter of the capillary, sampling voltage, sampling time, detection limit and selectivity. The magnitude of the response depends on the size and charge of analyte ions. With a capillary electrode having a ≈1.2-µm tip diameter, which minimizes non-selective diffusional entry of analytes, the response after 1 h sampling at +1. Detection of ions and molecules with ultramicroelectrodes is one of the most useful approaches for knowing local and dynamic concentration changes in biological fluids in tissues, slices and cells.

Mercury-induced hepatotoxicity in zebrafish: in vivo mechanistic insights from transcriptome analysis, phenotype anchoring and targeted gene expression validation

“…The environmental limit of inorganic mercuric from the United States Environmental Protection Agency (US EPA) in drinking water is below 2 ppb (2 μg/L) http://www.epa.gov/ogwdw000/contaminants/dw_contamfs/mercury.html. Mercury content in human blood is normally within the range of 0.87 to 3.51 μg/L [34,35] and the warning level of mercury in human blood is 22.8 to 30 μg/L [34,36]. The reproducible, rapid and dose-dependent responsiveness of these genes to a range of HgCl 2 concentrations from 10 to 200 μg/L suggested that these genes can be potentially used as robust biomarkers in combination with analytical chemistry detection of mercury for investigating and assessing the severity of mercury exposure.…”

A Glass Capillary Microelectrode Based on Capillarity and Its Application to the Detection of l-Glutamate Release from Mouse Brain Slices

“…8 Improvements of the spatial dissolution of L-glutamate measurements by miniaturizing the size of sampling probe and/or that of enzyme-based electrodes are important, because the neuronal activity that releases and metabolizes L-glutamate is a very fast event, 10 and hence the concentration of Lglutamate detected at a sensing probe depends on the location and distance of the probe from the neurons. For the purpose of miniaturizing the size of the sensing probes, pulled glass capillaries 27,28 have a unique feature: the tip diameters range from submicro-to several µm, and the glass surface has an affinity to lipids and biocompatibility.…”

Oxidation of dopamine on multi-walled carbon nanotubes

“…It must be mentioned that on MWCNT-based films, well-defined CV curves of [Fe (CN) 6 ] 3−/4− were obtained with peak-to-peak potential separation equal to that which corresponds to Nernstian oneelectron transfer reaction (ΔE p ≈0.059 V) [24]. Furthermore, the detection limit of MWCNT-based films on [Fe (CN) 6 ] 3−/4− was determined to be about 0.80 μM, which was much better compared to that determined on other electrodes reported in literature [25]. SEM was used for the analysis of the structure and surface of MWCNT-based films.…”