title: Optical acetylcholine sensor based on free base porphyrin as a chromoionophore.
abstract: In this work, the possibility of application of free base porphyrin as a lipophilic pH chromoionophore for the preparation of optical cation-selective sensors was investigated. The properties of polymeric membranes, containing porphyrins of different structures, namely tetraphenylporphyrin (TPP) and octaethylporphyrin (OEP), were compared. Changes in equilibrium between protonated and deprotonated form of porphyrin, resulting from variations in ACh concentration, were evaluated. The influence of various factors (kind and quantity of anionic additive and porphyrin in the membrane phase, pH of sample solution) on initial equilibrium was studied. The best membrane composition was chosen as: TPP 3 wt.%, KTFPB 175 mol.% relative to ionophore, PVC:o-NPOE (1 : 4) and measuring buffer solution: 0.05 M MES, pH 4.5. Selectivity, response stability, reversibility and repeatability tests were carried out for chosen sensor. Developed sensor allowed for the determination of a model analyte, acetylcholine, at the concentration range of 10(-5) to 10(-2) M, both in stationary and flow-injection system. Sensor response was reversible and repeatable in the mentioned concentration range.
authors.affiliation: Warsaw University of Technology, Faculty of Chemistry, Institute of Biotechnology, Department of Microbioanalytics, 00-664 Warsaw, Poland.
authors.forename: Monika
authors.initials: M
authors.lastname: Mroczkiewicz
authors.forename: Mariusz
authors.initials: M
authors.lastname: Pietrzak
authors.forename: Łukasz
authors.initials: Ł
authors.lastname: Górski
authors.forename: Elżbieta
authors.initials: E
authors.lastname: Malinowska
mesh_terms: D000109:Acetylcholine / Q000032:analysis*; D002412:Cations / Q000737:chemistry; D017022:Flow Injection Analysis; D006863:Hydrogen-Ion Concentration; D011143:Polyvinyl Chloride / Q000737:chemistry; D011166:Porphyrins / Q000737:chemistry*; D013056:Spectrophotometry, Ultraviolet; D055672:Static Electricity
chemical_list: D002412:Cations; D011166:Porphyrins; C488938:octaethylporphyrin; C409084:tetraphenylporphyrin; D011143:Polyvinyl Chloride; D000109:Acetylcholine