title: Screen-printed sensor for batch and flow injection potentiometric chromium(VI) monitoring.
abstract: A disposable screen-printed electrode was designed and evaluated for direct detection of chromium(VI) in batch and flow analysis. The carbon screen-printed electrode was modified with a graphite-epoxy composite. The optimal graphite-epoxy matrix contains 37.5% graphite powder, 12.5% diphenylcarbohydrazide, a selective compound for chromium(VI), and 50% epoxy resin. The principal analytical parameters of the potentiometric response in batch and flow analysis were optimized and calculated. The screen-printed sensor exhibits a response time of 20 +/- 1 s. In flow analysis, the analytical frequency of sampling is 70 injections per hour using 0.1 M NaNO(3) solution at pH 3 as the carrier, a flow rate of 2.5 mL.min(-1), and an injection sample volume of 0.50 mL. The sensor shows potentiometric responses that are very selective for chromium(VI) ions and optimal detection limits in both static mode (2.1 x 10(-7) M) and online analysis (9.4 x 10(-7) M). The disposable potentiometric sensor was employed to determine toxicity levels of chromium(VI) in mineral, tap, and river waters by flow-injection potentiometry and batch potentiometry. Chromium(VI) determination was also carried out with successful results in leachates from municipal solid waste landfills.
authors.affiliation: Departamento de Química Analítica y Análisis Instrumental, Facultad de Ciencias, Universidad Autónoma de Madrid, Avda. Francisco Tomás y Valiente, 7, 28049, Madrid, Spain.
authors.forename: Raúl A
authors.initials: RA
authors.lastname: Sánchez-Moreno
authors.affiliation: Departamento de Química Analítica y Análisis Instrumental, Facultad de Ciencias, Universidad Autónoma de Madrid, Avda. Francisco Tomás y Valiente, 7, 28049, Madrid, Spain. mariajesus.gismera@uam.es.
authors.forename: M Jesús
authors.initials: MJ
authors.lastname: Gismera
authors.affiliation: Departamento de Química Analítica y Análisis Instrumental, Facultad de Ciencias, Universidad Autónoma de Madrid, Avda. Francisco Tomás y Valiente, 7, 28049, Madrid, Spain.
authors.forename: M Teresa
authors.initials: MT
authors.lastname: Sevilla
authors.affiliation: Departamento de Química Analítica y Análisis Instrumental, Facultad de Ciencias, Universidad Autónoma de Madrid, Avda. Francisco Tomás y Valiente, 7, 28049, Madrid, Spain.
authors.forename: Jesús R
authors.initials: JR
authors.lastname: Procopio