Detection of chlorinated quinones using interdigitated electrodes coupled with capillary electrophoresis

Abstract

An array of eight interdigitated microband gold electrodes (IDEs) has been developed together with electrophoretic separation for analysis of chlorinated hydroquinones (ClHQs) and benzoquinones (ClBQs). The IDE chip positioned very close to the separation capillary outlet served as an amplification/detection system without the requirement for frequent "capillary-electrode" alignment. ClHQs, electrophoretically migrating to the IDE surface, were oxidized at +1.1 V by seven electrodes of the array and then detected by the remaining electrode, poised at -0.1 V. Conversely, ClBQs were detected at +1.1 V by the detecting electrode after having been reduced at the 7 adjacent electrodes poised at -0.1 V. There was an amplification effect on both the detecting electrode as well as the adjacent electrodes because of the recycle between ClHQs and ClBQs. The detecting "amplification" current response was dependent on the potentials applied, the position of the detecting electrode on the array, the number of adjacent electrodes being used for recycling and the distance between the oxidative and reductive electrodes. Micellar electrokinetic chromatography (MEKC) separation of the analytes was achieved using 30 mM sodium dodecyl sulfate (SDS) with a detection limit in the range of 2-20 micro M. In addition to a facile "capillary-electrode" alignment, the important aspect described here was the capability of detecting through recycling a reduced compound (in the case of ClHQs) at a negative potential to circumvent fouling and electroactive interferences. An appealing feature was also the concurrent oxidation/reduction detection for each compound to ascertain peak assignment, as interfering compounds are less likely to exhibit the same oxidative/reductive characteristics and electrophoretic mobilities as the target analytes.

Generation–Collection Electrochemistry Inside a Rotating Droplet

“…In this work, we further explore the RD technique and discuss generation–collection electrochemistry in this new hydrodynamic volume-limited environment. Numerous generation–collection systemswhere the signal recorded on one electrode (generator) is amplified due to the reversed reaction on a second electrode (collector)have been studied, ranging from static interdigitated electrodes − or nanogap electrodes − through microfluidic channels − and rotating ring disk electrodes, − but none of them has dealt with both small droplet confinement and droplet rotation. Here, we discuss the effect of the generator–collector distance and counter electrode reactions on the total current recorded on the generator.…”

A Combined Experimental and Computational Investigation on the Unusual Molecular Mechanism of the Lossen Rearrangement Reaction Activated by Carcinogenic Halogenated Quinones

“…2-Chloro-5-hydroxy-1,4-benzoquinone (CBQ-OH), 2,3-dichloro-1,4-benzoquinone (2,3-DCBQ), and 2,3,5-trichloro-1,4-benzoquinone (TrCBQ) were synthesized by our research group according to the literature methods. 38 , 39 …”

“…2,5-Dichloro-1,4-benzoquinone (2,5-DCBQ), 2,6-dichloro-1,4-benzoquinone (2,6-DCBQ), 2-chloro-1,4-benzoquinone (2-CBQ), tetrachloro-1,4-benzoquinone (TCBQ), benzohydroxamic aicd (BHA), phenyl isocycanate (Ph-NCO), N , N ′-diphenylurea, and aniline were used as purchased. 2-Chloro-5-hydroxy-1,4-benzoquinone (CBQ-OH), 2,3-dichloro-1,4-benzoquinone (2,3-DCBQ), and 2,3,5-trichloro-1,4-benzoquinone (TrCBQ) were synthesized by our research group according to the literature methods. , …”

MEKC as a powerful growing analytical technique

“…Other detection approaches which have been hyphenated to MEKC, however, with fewer reported applications include: electrochemical detection 160, 219–224, FTIR detection 225, 226, and chemiluminescence detection 227–230.…”