Dual Photonic-Electrochemical Lab on a Chip for Online Simultaneous Absorbance and Amperometric Measurements

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• 作者：Olga Ordeig ; Pedro Ortiz ; Xavier Mu帽oz-Berbel ; Stefanie Demming ; Stephanus B眉ttgenbach ; C茅sar Fern谩ndez-S谩nchez ; Andreu Llobera
• 刊名：Analytical Chemistry
• 出版年：2012
• 出版时间：April 17, 2012
• 年：2012
• 卷：84
• 期：8
• 页码：3546-3553
• 全文大小：319K
• 年卷期：v.84,no.8(April 17, 2012)
• ISSN：1520-6882

文摘

A dual lab on a chip (DLOC) approach that enables simultaneous optical and electrochemical detection working in a continuous flow regime is presented. Both detection modes are integrated for the first time into a single detection volume and operate simultaneously with no evidence of cross-talk. The electrochemical cell was characterized amperometrically by measuring the current in ferrocyanide solutions at +0.4 V vs gold pseudoreference electrode, at a flow rate of 200 渭L min^鈥?. The experimental results for ferrocyanide concentrations ranging from 0.005 to 2 mM were in good agreement with the values predicted by the Levich equation for a microelectrode inside a rectangular channel, with a sensitivity of 2.059 卤 0.004 渭A mM^鈥? and a limit of detection (LoD) of (2.303 卤 0.004) 脳 10^鈥? mM. Besides, optical detection was evaluated by measuring the absorbance of ferricyanide solutions at 420 nm. The results obtained therein coincide with those predicted by the Beer鈥揕ambert law for a range of ferricyanide concentrations from 0.005 to 0.3 mM and showed an estimated LoD of (0.553 卤 0.001) 脳 10^鈥? mM. The DLOC was finally applied to the analysis of L-lactate via a bienzymatic reaction involving lactate oxidase (LOX) and horseradish peroxidase (HRP). Here, the consumption of the reagent of the reaction (ferrocyanide) was continuously monitored by amperometry whereas the product of the reaction (ferricyanide) was recorded by absorbance. The DLOC presented good performance in terms of sensitivity and limit of detection, comparable to other fluidic systems found in the literature. Additionally, the ability to simultaneously quantify enzymatic reagent consumption and product generation confers the DLOC a self-verifying capability which in turn enhances its robustness and reliability.