Micromachined Electrophoresis Chips with Thick-Film Electrochemical Detectors

Abstract

A capillary electrophoresis (CE) microsystem, based on the combination of microphotolithographically fabricated separation chips and thick-film electrochemical detector strips, is described. The microsystem consists of a planar screen-printed carbon line electrode mounted perpendicular to the flow direction. Such coupling obviates the need for permanent attachment of the detector, to allow easy and fast replacement of the working electrode. Variables influencing the separation efficiency and amperometric response, including the channel-electrode spacing, separation voltage, or detection potential, are assessed and optimized. The versatility, simplicity, and low-cost advantages of the new design are coupled to an attractive performance, with submicromolar detection limits, and good precision. Applicability for assays of mixtures of nitroaromatic explosives or catecholamines is demonstrated. Such use of screen-printed detectors should also benefit conventional CE systems, particularly in applications requiring a frequent replacement of the working electrode.

Microscale solid-phase extraction system for explosives

“…We, along with various other groups, have been investigating the development of capillary electrophoresis (CE) microchips capable of detecting aromatic explosives in the ng/1 regime to ensure accurate water analysis below toxic levels [5][6][7][8]. Our intent is to develop field portable sensors capable of (1) locating UXOs or land mines present in our ocean's harbors for removal and clean-up, and (2) determining the explosives contamination level of surface and groundwaters in close proximity to munition's practice sites.…”

An end-channel amperometric detector for microchip capillary electrophoresis

“…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

“…Eletrodos impressos de carbono têm sido uma boa alternativa na construção de detectores eletroquímicos em µchips [267][268][269][270][271][272] . Wang e colaboradores [267][268][269][270][271] demonstraram a potencialidade da utilização de eletrodos impressos removíveis, pela facilidade de troca de eletrodos passivados ou modificados, eliminando a necessidade de troca do sistema completo de separação e reduzindo os custos de confecção do sistema total. Materiais diversos têm sido empregados na construção dos µchips, como polímeros 272,273 e cerâ-mica 274 .…”

“…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.…”