Perihan Caglar

IMMOBILISED REAGENTS FOR OPTICAL HEAVY METAL IONS SENSING

Abstract Many ligands such as 1-nitroso-2-naphthol (NN), 4-(2-pyridylazo)resorcinol (PAR), 2,4-dinitrosoresorcinol (DNR) and 1-(2-pyridylazo)-2-naphthol (PAN) have been investigated in the development of optical sensors for heavy metal ions found in aquatic environments which include Co2+, Cu2+, Ni2+, Fe3+, Cd2+, Zn2+, Pb2+ and Hg2+. The reagents were immobilised by physical adsorption on to polymeric materials such as XAD-4, XAD-7 and Dowex ion-exchange resins, and were found to exhibit chromic characteristics in the absence and presence of metal ions in solution. Reflectance measurements are used here. Parameters such as pH, measurement wavelength and reagent concentration have been optimised for a given metal ion, and the reversibility/regenerability characteristics of the sensing reagent have been studied together with the limit of detection and the concentration range producing linear response for the metal ion.

Microchip extraction of catecholamines using a boronic acid functional affinity monolith.

A novel solid phase extraction microchip with a boronic acid functional affinity monolithic disc was developed in this work. Vinyl phenylboronic acid-ethylene glycol dimethacrylate co-polymer monoliths, which have pore sizes up to 20 μm, were investigated for extraction of catecholamines using adsorption and desorption studies in a batch system. Desorption yields of greater than 90% were achieved for catecholamines at pH 3 and below. Monolithic discs were then formed in chambers in borofloat glass microfluidic chips using in situ UV polymerization. Adsorption on the monolithic discs was performed via electrokinetic flow, with catecholamines determined via laser-induced native fluorescence (LINF) detection following electrokinetic elution. Microchips containing the boronic acid functional polymer discs worked well for extraction of catecholamines, providing greater than 100 fold concentration enrichment. This study demonstrated that a solid phase extraction microchip, containing an easily prepared monolith disc, will be useful for boronate affinity extraction of cis-diol containing compounds.

Glucose-sensitive polypyrrole/poly(styrenesulfonate) films containing co-immobilized glucose oxidase and (ferrocenylmethyl) trimethylammonium bromide

Abstract Glucose oxidase (GOx) and (ferrocenylmethyl) trimethylammonium bromide (FcBr) were co-immobilized into polypyrrole (PP)/poly(styrenesulfonate) (PSS) films during the electropolymerization of pyrrole. PSS was employed as a partial dopant anion for PP (along with Br−) and as an electrostatic binder for the cationic mediator (FcBr). The electropolymerization of the PP/PSS film was carried out at +0.8 V vs SCE in a 5-cm3 aqueous solution of glucose oxidase (1 mg°Cm−3), FcBr (1 mM), PSS (1 mM), and pyrrole (50 mM) at 5°C. These enzymemediator derivatized electroactive polymer films (ca. 0.5-2 μm thick) coated on Pt electrodes showed sensitivities to glucose without the use of any mediator in solution, and can be used as amperometric glucose sensors. The responses of the resulting electrodes (0.24 cm2 Pt plate with the polymer film) to glucose were measured amperometrically in pH 7, 0.1 M phosphate buffer solution at 5°C, and a constant potential (+0.5 V vs SCE) by using a Pt coil counterelectrode, wit...

Fiber-optic cation determination using crown ether dyes immobilized on polymer membranes ☆

Abstract This study describes the determination and comparison of some cations such as Na+, K+, Ba2+ and Cu2+ in aqueous media by using crown ether dyes immobilized onto thin (0.04 mm) sulfonated kraton polymeric membranes. The studies have been carried out in aqueous solutions first, and in dye–immobilized membrane systems later. The flow-cell system has been found to be more practical in application and had lower response times (30–60 s) as well as detection limits (2.24×10−10–1.19×10-8 mol l−1). The optimum pH range for the formation of ion-dye complexes have been found to be 5 and 9 for the ions above. Since the complexation reactions were reversible it was possible to regenerate the membranes by using HCl solutions and reuse them many times. The same membrane showed high reproducibility and low relative standard deviation. In addition, the interferences of the studied cations to each other and of other various cations during the determinations have also been investigated.

The operational parameters of a new fibre-optic sensor for ferric ions in aqueous media

Abstract An optical ferric ion sensor, based on the use of 2,4-dinitrosoresorcinol (DNR) immobilized on XAD-7 and absorbance spectrometry, has been developed. To determine the sensor response to Fe(III) concentration, a kinetic approach is used, where the absorbance signal is measured at 10 min intervals. Reproducibility of Fe(III) measurements using the same probe (relative standard deviation RSD = 0.05%), and reproducibility of probe construction (RSD = 0.01%) are very good. Linear response is obtained for Fe(III) concentrations between 8.0×10−6 and 1.0×10−4 M with a detection limit of 8.0×10−6 M of ferric ion. The sensor is used successfully for the determination of Fe(III) in simulated seawater samples in the absence and presence of interfering ions. The results are comparable to those obtained by flameless atomic absorption spectrometry and relative errors are 1.30% and 0.98%, respectively, for the samples in the absence and presence of interfering cations by using the method described.

The Immobilization of Ionic and Neutral Crown Ether Dyes to Specific Anionic Polymer Membrane Used as a Chemical Sensor for the Determination of Metal Ions

ABSTRACT In the present study, a neutral crown ether dye (NCED), [4-Nitrophenyl)(4-(4,7,10,13,16-pantaoxa-1 azacyclooctadecyl)phenyl] diazen and an ionic crown ether dye (ICED), 1-Methyl-{2-[4-(4,7,10,13,16-pentaoxa-1 azacyclooctadecyl)phenyl]ethenyl}pyridinium-iodide were synthesized and immobilized on sulfonated hydrocarbon-based block copolymer ionomer to determine Ba2+ and Cu2+ ions in aqueous solution. 5.0×10−2 M ion solutions were used since the best absorbance increase was obtained with this concentration. The increases in absorbances after treating the NCED-immobilized thick polymer membranes (0.20 mm thickness) with Ba2+ and Cu2+ solutions were 0.1488 and 0.2446 in 120 minutes, respectively. The absorbance increases were 0.1664 and 0.3710 during the same time-interval with ICED-immobilized membranes. The response time decreased and absorbance values increased when thin polymer membranes (0.04 mm thickness) were used. The absorbance increases were 0.5088 and 0.8761, respectively in one minute with...