title: Automatic determination of chlorine without standard solutions using a biamperometric flow-batch analysis system.
abstract: This study presents an automatic analysis system that does not require the use of standard solutions. The system uses an electrochemical flow cell for in line generation of the standards, and operates under the standard addition technique. The versatility of this system was demonstrated by the development of a one key touch fully automatic method for the determination of total available chlorine in real samples. The extremely simple, accurate and inexpensive method was based simply on the biamperometric monitoring of the well known redox reaction of chlorine with iodide ions in a flow-batch system, where the produced iodine (triiodide ions) generates an electrical current proportional to the chlorine concentration in the sample. The flow-batch parameters were optimized to maximize the sensitivity without losses on the precision of the analysis. An excellent linear dependence between the biamperometric signal and the chlorine concentration for the standard additions and a good agreement between the proposed approach and a reference method were obtained. The method was successfully applied to determine chlorine in several different bleach and chlorinated water samples (r=0.9995, LOD=8.261 x 10(-7) mol L(-1)) and could be easily extended to other oxidants and samples. Comparison to a reference method and recoveries close to 100% demonstrated the reliability of the proposed method. In addition, low residue disposal and reagent consumption, allied with high accuracy and precision, make it very promising for routine applications.
authors.affiliation: Universidade Federal Rural de Pernambuco, Departamento de Química, 52171-030, Recife, PE, Brazil. valberes@dq.ufrpe.br
authors.forename: Valberes B
authors.initials: VB
authors.lastname: Nascimento
authors.forename: Thiago M G
authors.initials: TM
authors.lastname: Selva
authors.forename: Elaine C S
authors.initials: EC
authors.lastname: Coelho
authors.forename: Francyana P
authors.initials: FP
authors.lastname: Santos
authors.forename: Jadielson L S
authors.initials: JL
authors.lastname: Antônio
authors.forename: José R
authors.initials: JR
authors.lastname: Silva
authors.forename: Edvaldo N
authors.initials: EN
authors.lastname: Gaião
authors.forename: Mário C U
authors.initials: MC
authors.lastname: Araújo
mesh_terms: D001331:Automation; D002713:Chlorine / Q000032:analysis*; D004563:Electrochemistry; D017022:Flow Injection Analysis / Q000379:methods* / Q000592:standards; D012015:Reference Standards; D012996:Solutions
chemical_list: D012996:Solutions; D002713:Chlorine