Integrated Electrophoresis Chips/Amperometric Detection with Sputtered Gold Working Electrodes

Abstract

An on-chip electrochemical detector for micromachined capillary electrophoresis (CE) systems, based on sputtering a gold working electrode directly onto the capillary outlet, is described. The new on-chip detector preparation requires no microfabrication or alignment procedures nor a decoupling mechanism. The attractive performance of the integrated electrophoresis chips/amperometric detection was demonstrated for the anodic detection of neurotransmitters. The response for dopamine was linear from 20 to 200 μM, with a LOD of 1.0 μM and a sensitivity of 52 pA/μM. Such intimate coupling of capillary electrophoresis chips and electrochemical detection facilitates the realization of complete integrated microanalytical devices.

An end-channel amperometric detector for microchip capillary electrophoresis

“…Relative standard deviations (RSDs) of migration times for DA and CA were 1.0 and 1.2%, respectively. RSDs of peak currents (i RSD ) were 5.4 and 6.0% for DA and CA respectively, which were better than reference [23] and some what worse than [19,22]. Although migration times of DA and CA were fast (<80 s), RSDs of migration times (t RSD ) of DA and CA were better compared with reference [22] and slightly better than reference [24].…”

“…The sensitivities of 47.3 and 20.6 pA/M were obtained for DA and CA, respectively. By measuring 5 m DA alone with the same condition, the limit of detection (LOD) of DA was 0.51 m (S/N = 3), which was more sensitive than some works [22,23,25] while higher than reference [16,19,26]. The bigger electrode diameter thus the bigger background (about 20 pA in this work versus 1.6 pA in reference [17]) may partly explain the higher LOD, incomplete decoupling (0.1 V higher detection potential implied) of detection circuit may be another reason.…”

Detecção eletroquímica em eletroforese capilar

“…O sistema de separação, denominado eletroforese em canal, permitiu a resolução em duas dimensões do analito entregue por um capilar de amostragem, posicionado na abertura do canal [261][262][263] . O processo de fabricação dos µchips e sistema de detecção foi primeiramente proposto por Wooley e colaboradores 264 , onde foi demonstrada a separação de três neurotransmissores em 100 s. Wang e colaboradores 265 depositaram por "sputtering" um filme fino de ouro na saída do canal de separação e o utilizaram como eletrodo de trabalho, eliminando os problemas envolvidos no alinhamento. A mesma aproximação foi conduzida por Hilmi e Luong 266 , mas pela utilização de deposição química de ouro catalisada na superfície do substrato de vidro.…”

“…Sistemas duplos de detecção também foram propostos para separações em µchip 273 . As aplicações de µchips com ED estendem-se à separação de neurotransmissores [261][262][263][264][265][266][267][272][273][274] , explosivos nitroaromáticos 266,267,275 , acetaminofeno 268 ácidos úrico 268 e ascórbico 268,273 . Estratégias de reação enzimática 268 e derivatização acoplada ao canal de separação 269 foram empregadas na determinação de glicose e aminoácidos, respectivamente.…”

Development of a High-Density Microplasma Emission Source for a Micro Total Analysis System

“…5,6 The use of such a μ-TAS device enables the miniaturization of analytical systems, the reduction of the amount of samples necessary for analysis, and a decrease in the analysis time because each chemical analytical system element is integrated on a single chip using the micromachining technique. UV absorbance detection, 7 laser-induced fluorescence, 8,9 electrochemical detection 10,11 as well as other techniques have been used as the basis for μ-TAS detectors. Nevertheless, as shown by recent studies, these systems are currently limited by their inability to analyze a wide range of compounds and by their insufficient analytical sensitivity.…”