title: Construction and electrochemical characterization of microelectrodes for improved sensitivity in paper-based analytical devices.
abstract: This work presents a simple, low cost method for creating microelectrodes for electrochemical paper-based analytical devices (ePADs). The microelectrodes were constructed by backfilling small holes made in polyester sheets using a CO2 laser etching system. To make electrical connections, the working electrodes were combined with silver screen-printed paper in a sandwich type two-electrode configuration. The devices were characterized using linear sweep voltammetry, and the results are in good agreement with theoretical predictions for electrode size and shape. As a proof-of-concept, cysteine was measured using cobalt phthalocyanine as a redox mediator. The rate constant (k(obs)) for the chemical reaction between cysteine and the redox mediator was obtained by chronoamperometry and found to be on the order of 10(5) s(-1) M(-1). Using a microelectrode array, it was possible to reach a limit of detection of 4.8 μM for cysteine. The results show that carbon paste microelectrodes can be easily integrated with paper-based analytical devices.
authors.affiliation: Department of Analytical Chemistry, Institute of Chemistry-UNICAMP, Campinas, SP, Brazil.
authors.forename: Murilo
authors.initials: M
authors.lastname: Santhiago
authors.forename: John B
authors.initials: JB
authors.lastname: Wydallis
authors.forename: Lauro T
authors.initials: LT
authors.lastname: Kubota
authors.forename: Charles S
authors.initials: CS
authors.lastname: Henry
mesh_terms: D002244:Carbon / Q000737:chemistry; D002384:Catalysis; D003545:Cysteine / Q000032:analysis / Q000737:chemistry; D004563:Electrochemistry / Q000295:instrumentation*; D007211:Indoles / Q000737:chemistry; D008839:Microelectrodes; D009942:Organometallic Compounds / Q000737:chemistry; D010209:Paper
chemical_list: D007211:Indoles; D009942:Organometallic Compounds; C063633:cobalt phthalocyanine; D002244:Carbon; D003545:Cysteine