title: Novel bilirubin-based PVC calcium sensors.
abstract: Poly(vinyl chloride) membrane sensors for Ca(II) ions were constructed based on bilirubin (1,3,6,7-tetramethyl-4,5-dicarboxyethy-2,8-divinyl-[b-13]-dihydrobilenone) as a neutral carrier in the presence of various plasticizers (o-nitrophenyloctyl ether, dioctyl phethalate and dibutyl sebacate), which were used as solvent mediators to incorporate the carrier into the membranes. The role of plasticizers as a medium of complexation was demonstrated. The influences of an anionic excluder, the pH and foreign ions were investigated. The selectivity coefficients were measured by a separate solution method. Among the plasticizers used, o-nitrophenyloctyl ether gave the best selectivity in the presence of large concentrations of alkali and alkaline earth's metal ions. Using sensor number I, a linear calibration graph with a good Nernstian slope of 29.5 +/- 0.8 mV was obtained for Ca(II) concentrations of 5 x 10(-7)-10(-2) mol l(-1) with a detection limit of 3 x 10(-7) mol l(-1) (12 ppb). The sensor can be used for more than 3 months with good reproducibility and a fast response time of 10 s. The developed sensor has been successfully applied to the analysis of some pharmaceutical formulations, baby-food products and human plasma. Moreover, it can be used as an indicator sensor in the potentiometric titration of Ca(II) with EDTA.
authors.affiliation: Department of Chemistry, Faculty of Science, Ain Shams University, Abassia, Cairo, 11566, Egypt.
authors.forename: Wagiha H
authors.initials: WH
authors.lastname: Mahmoud
mesh_terms: D001663:Bilirubin; D015374:Biosensing Techniques / Q000379:methods*; D002118:Calcium / Q000032:analysis* / Q000097:blood; D006801:Humans; D007223:Infant; D007225:Infant Food; D015394:Molecular Structure; D004364:Pharmaceutical Preparations / Q000737:chemistry; D011143:Polyvinyl Chloride
chemical_list: D004364:Pharmaceutical Preparations; D011143:Polyvinyl Chloride; D001663:Bilirubin; D002118:Calcium