High-Frequency Impedance Spectroscopy of Platinum Ultramicroelectrodes in Flowing Solutions

Abstract

A method for studying impedance spectroscopy of micrometer-sized electrodes in the frequency range from 5 kHz to 5 MHz has been developed and tested. Details of the electronic circuit and the data processing method are provided. Since the method involves high-speed data acquisition and fast Fourier transformation, the impedance data can be obtained within a 5-ms time window. This enables measurement of changes in the electrode impedance caused by rapid changes in the solution composition. In particular, the method is well suited to studying the performance of electrochemical microdetectors in flowing solutions. The performance of the method was tested in a brief study of the competitive adsorption of hydrogen and methionine on a Pt ultramicroelectrode. It has been shown that proper electrochemical conditioning can prevent any long-term changes in the properties of the electrode caused by its exposure to common organic or inorganic substances. Hence, it provides means for making an ultramicroelectrode with a virtually renewable surface. Alternatively, without electrochemical conditioning, it is possible to construct an adsorbed layer with desired properties by exposing the electrode to one or even several solutions for precisely controlled time periods.

Selective and Non-Selective Determination ofHeavy Metal Ions in Flowing Solutions by Fast Stripping Cyclic Voltammetry

“…14 In Fig. 2, a diagram of the applied potential waveform during cyclic voltammetric measurements is shown.…”

Separation and determination of the macrolide antibiotics (erythromycin, spiramycin and oleandomycin) by capillary electrophoresis coupled with fast reductive voltammetric detection

“…The counter electrode was a Pt wire (surface area about 0.5 mm 2 ) and a saturated KCl calomel electrode (SCE, miniature model; Fisher Scientific, Ottawa, Canada) was used as reference electrode. The working electrode consisted of an Hg-film (6 mm thick)/Au mm-electrode, which was prepared by computer-controlled electrodeposition of a layer of Hg onto a 25 mm Au disk electrode under constant current conditions in a 0.1 mol/L Hg 2 (ClO 4 ) 2 and 1 mol/L HCl 4 solution [18]. The Hg-film electrode was washed with water and operating buffer solution, and then aligned to the capillary outlet at a distance of 30 mm with a micropositioner.…”

Alternating‐Current Measurements in Scanning Electrochemical Microscopy, Part 1: Principle and Theory

“…Some chronoamperometric experiments have been done in SECM, [19][20][21][22] but only a few studies have been reported on SECM in ac mode. [23][24][25][26][27][28][29][30] Schuhmann et al developed an ac-SECM mode for mapping domains of different conductivity or electrochemical reactivity on surfaces. [31][32][33][34] Their approach is different from that presented here, because they applied a frequency perturbation to the probe, whereas in this work the perturbation is applied to the substrate.…”