title: Preconcentration and determination of mercury(II) at a chemically modified electrode containing 3-(2-thioimidazolyl)propyl silica gel.
abstract: A mercury-sensitive chemically modified graphite paste electrode was constructed by incorporating modified silica gel into a conventional graphite paste electrode. The functional group attached to the (3-chloropropyl) silica gel surface was 2-mercaptoimidazole, giving a new product denoted by 3-(2-thioimidazolyl)propyl silica gel, which is able to complex mercury ions. Mercury was chemically adsorbed on the modified graphite paste electrode containing 3-(2-thioimidazolyl)propyl silica (TIPSG GPE) by immersion in a Hg(II) solution, and the resultant surface was characterized by cyclic and differential pulse anodic stripping voltammetry. One cathodic peak at 0.1 V and other anodic peak at 0.34 V were observed on scanning the potential from -0.1 to 0.8 V (0.01 M KNO3; v = 2.0 mV s(-1) vs. Ag/AgCl). The anodic peak at 0.34 V show an excellent sensitivity for Hg(II) ions in the presence of several foreign ions. A calibration graph covering the concentration range from 0.02 to 2 mg L(-1) was obtained. The detection limit was estimated to be 5 microg L(-1). The precision for six determinations of 0.05 and 0.26 mg L(-1) Hg(II) was 3.0 and 2.5% (relative standard deviation), respectively. The method can be used to determine the concentration of mercury(II) in natural waters contaminated by this metal.
authors.affiliation: Departamento de Física e Química, Universidade Estadual Paulista, Ilha Solteira, SP, Brazil. nldias@dfq.feis.unesp.br
authors.forename: Newton L
authors.initials: NL
authors.lastname: Dias Filho
authors.forename: Devaney R
authors.initials: DR
authors.lastname: do Carmo
authors.forename: Laércio
authors.initials: L
authors.lastname: Caetano
authors.forename: André H
authors.initials: AH
authors.lastname: Rosa
mesh_terms: D002138:Calibration; D002412:Cations / Q000737:chemistry; D004563:Electrochemistry / Q000295:instrumentation / Q000379:methods; D005031:Ethylenethiourea / Q000031:analogs & derivatives* / Q000737:chemistry; D005618:Fresh Water / Q000032:analysis; D006108:Graphite / Q000737:chemistry; D006863:Hydrogen-Ion Concentration; D007093:Imidazoles / Q000737:chemistry; D017736:Ion-Selective Electrodes; D008628:Mercury / Q000032:analysis* / Q000737:chemistry; D010084:Oxidation-Reduction; D015203:Reproducibility of Results; D012623:Seawater / Q000032:analysis; D058428:Silica Gel; D012822:Silicon Dioxide / Q000737:chemistry*
chemical_list: D002412:Cations; D007093:Imidazoles; D005031:Ethylenethiourea; D058428:Silica Gel; D012822:Silicon Dioxide; D006108:Graphite; C077232:2-mercaptoimidazole; D008628:Mercury