A new sensitive optical bulk test-system for thallium based on pyridylazo resorcinol

A color changeable optode for thallium(III) ions in aqueous solutions was prepared by physical inclusion of 4-(2-pyridylazo)-resorcinol into a plasticized PVC film. The increase in the absorbance of the optode at 524 nm is proportional to thallium(III) concentration. Different parameters effecting the sensitivity such as sample parameters and composition of the membrane were optimized. The response times of the prepared test-system are found to be 230, 210, and 180 s for 4.8 × 10^?6, 4.8 × 10^?5, and 4.8 × 10^?4 M Tl(III), respectively. The analytical performance of the optode was evaluated, obtaining a linear concentration range of two decades of concentration, 3.1 × 10^?6 ? 4.7 × 10^?4 M Tl(III), with a limit of detection of 1.8 × 10^?6 M Tl(III). Selectivity of the optode is also studied. Application of the optode to the determination of Tl(III) in some aqueous samples yields good results.     

A novel optical sensor for uranium determination

A metal ion indicator, Alizarin Red S, was tested for its potential use in uranium selective optode membrane. The water-soluble indicator was lipophilized in the form of an ion pair with tetraoctylammonium bromide, and subsequently immobilized on a triacetyl cellulose membrane. The membrane responds to uranium ions, giving a color change from yellow to violet in acetate buffer pH 5. This optode has a linear range of (1.70-18.7) × 10⁻⁵ M of UO₂²⁺ ions with a limit of detection of 5 × 10⁻⁶ M. The response time of optode was within 6 min depending on the concentration of UO₂²⁺ ions. The sensor can readily be regenerated with hydrochloric acid solution (0.01 M). The optode is fully reversible.     

Design of a Novel Gadolinium Optical Sensor Based on Immobilization of (Z)-N′-((Pyridine-2-yl) Methylene) Thiophene-2-carbohydrazide on a Triacetylcellulose Membrane and Its Application to the Urine Samples

Abstract

In this work, for the first time we report a highly selective and sensitive Gd(III) optical sensor based on immobilization of (Z)-N′-((pyridine-2-yl) methylene) thiophene-2-carbohydrazide (PMTC) on a triacetylcellulose membrane. This optode exhibits a linear range 5.0 × 10^?8 to 2.0 × 10^?5 M of Gd(III) ion concentration with a detection limit of 1.1 × 10^?8 M. The response time of the newly designed optode was within 1–2 min, depending on the Gd(III) ion concentration. The response of the sensor is independent of the pH solution in the range of 2.0–9.0. It manifests advantages of low detection limit, fast response time, and most significant, very good selectivity with respect to a number of lanthanide ions (La, Ce, Sm, and Eu ions). The proposed sensor could be successfully regenerated with a thiourea solution. Its response was reversible and reproducible (RSD less than 1.3%). This optode was applied to the determination of Gd(III) in synthetic and real samples.     

A new procedure for the construction of flow-through optodes. Application to determination of copper (II)

A new procedure for constructing an optical fibre reflectance, bulk optode membrane type, sensor is presented. The optode membrane consists of a plasticized poly (vinyl chloride) membrane in which the ionophore is dissolved, entrapped in a cellulose support. The new optode with the dye indicator 1-(2-pyridylazo)-2-naphthol (PAN) was incorporated in a new flow-through cell and the injection system was optimized to determine Cu (II) at 567 nm in the range 5 x 10(-5)-10(-3) M. The response was reproducible and the optode can be regenerated using 10(-2) M EDTA followed by water. The method was applied to the determination of copper in real samples.     

Design and evaluation of a thorium (IV) selective optode

A novel optical sensor has been proposed for sensitive determination of thorium (IV) ion in aqueous solutions. The thorium sensing membrane was prepared by incorporating 4-(p-nitrophenyl azo)-pyrocatechol (NAP) as ionophore in the plasticized PVC membrane containing tributyl phosphate (TBP) as plasticizer. The membrane responds to thorium ion by changing color reversibly from yellow to red-brown in glycine buffer solution at pH 3.5. The proposed sensor displays a linear range of 8.66 × 10⁻⁶-2.00 × 10⁻⁴ M with a limit of detection of 6 × 10⁻⁶ M. The response time of the optode was about 8.8-12.5 min, depending on the concentration of Th (IV) ions. The selectivity of optode to Th (IV) ions in glycine buffer is good. The sensor can readily be regenerated by exposure to a solution mixture of sodium fluoride and 5-sulfosalicylic acid (dihydrate) (0.01 M each). The optode is fully reversible. The proposed optode was applied to the determination of thorium (IV) in environmental water samples.     

A Novel Optical Sensor for Determination of Thiocyanate

Abstract

A novel optical sensor (optode) is described for the determination of thiocyanate using methyltrioctylammonium chloride immobilized on triacetylcellulose membrane. The response to thiocyanate is the result of adsorption of [Co(SCN)₄]^2? on sensing membrane, which caused the colorless membrane to change to blue. This optode can readily be regenerated by using 0.02 mol/l sodium oxalate solution. The linear range of the method was 3.44×10^?5 to 8.61×10^?4 mol/l of thiocyanate with a limit of detection 1.51×10^?5 mol/l. The relative standard deviation for eight replicate measurements of 8.61×10^?5 and 4.30×10^?4 mol/l of thiocyanate was 3.45 and 1.23%, respectively. The sensor was successfully applied for the determination of thiocyanate in saliva of smokers, nonsmokers and various water samples.     

A simple optical sensor for cadmium ions assay in water samples using spectrophotometry

A new simple and inexpensive optical chemical sensor for cadmium(II) ions is presented. The cadmium sensing system was prepared by incorporating 2-amino-cyclopentene-1-dithiocarboxylic acid (ACDA) on a triacetylcellulose membrane. The absorption spectra of the optical sensor membrane in Cd(II) solution showed a maximum peak at 430 nm. The proportionality in intensity of the membrane color on the optode to varying amounts of Cd(II) suggests its potential applications for screening Cd(II) in aqueous samples by visual colorimetry. The sensor provided a wide concentration range of 3.0 × 10⁻⁶–3.4 × 10⁻⁴ M of Cd(II) ions with a detection limit of 1.0 × 10⁻⁶ M (0.2 μg/mL). The relative standard deviations for eight replicate measurements of 8.0 × 10⁻⁶ and 5.0 × 10⁻⁵ M Cd(II) were 2.7 and 2.3%, respectively. The response time of the optode was 6 min. The influence of interfering ions on the determination of 1.0 × 10⁻⁵ M Cd(II) was studied and the main interferences were removed by extraction method. The sensor was applied to the determination of Cd(II) in water samples.     

Design of a novel optical sensor for determination of trace amounts of copper by UV–visible spectrophotometry in real samples

A new optical chemical sensor is established for sensitive and selective spectrophotometric detection of copper based on the immobilization of 3‐(2‐methyl‐2,3‐dihydro‐1,3‐benzothiezol‐2‐yl)‐2H‐chromen‐2‐one on a triacetylcellulose membrane. Copper ions react with the immobilized ligand and cause an increase in the absorption of the membrane at 550 nm in universal buffer solution at pH = 6. The effects of pH, indicator concentration and reaction time on the immobilization of the ligand were studied. This optode exhibits a linear range of 7.0 × 10^?7 to 1 × 10^?4 mol l^?1 of copper ion concentration with a limit of detection of 3.0 × 10^?7 mol l^?1. The response time of the newly designed optode is within 3 min. The effect of different possible interfering species was investigated and it was found that the sensor has very good selectivity. The proposed sensor benefits from advantages such as low cost, high stability, low detection limit, fast response time, reproducibility, relatively long lifetime, and good selectivity for Cu²⁺ ion determination among a large number of alkali, alkaline earth, transition and heavy metal ions. The sensor can readily be regenerated with thiourea solution and its response is reversible and reproducible (relative standard deviation < 1.4%). The proposed optode was applied successfully for the determination of Cu(II) in various samples.     

Development of a new fluorimetric bulk optode membrane based on 2,5-thiophenylbis(5-tert-butyl-1,3-benzexazole) for nickel(II) ions

A highly sensitive and selective fluorimetric optode membrane for the determination of ultra trace amounts of Ni²⁺ ions was prepared. The plasticized PVC-membrane incorporating potassium tetrakis(p-chlorophenyl)borate (KTpClPB) and 2,5-thiophenylbis(5-tert-butyl-1,3-benzexazole) (TTBB), as a highly fluorescent chromoionophore, displays a calibration response for Ni²⁺ ions over a wide concentration range of 1.0×10⁻³ to 1.0×10⁻⁸ M. It has a relatively fast response of <40 s. In addition to high stability and reproducibility, and relatively long working lifetime, the sensor possesses good selectivity for nickel ions over several common diverse ions. The fluorescence signal of the optode membrane can be easily recovered by immersion in EDTA solution. The optode was applied successfully to the determination of traces of Ni²⁺ ion in edible oil and a wastewater sample from nickel electroplating industries.     

Development and application of a fluorescent sensor for potassium ions based on a calix[6]arene ionophore and a novel cationic dye

A plasticised poly(vinyl chloride) optode membrane incorporated with a calix[6]arene hexaester, a H⁺-selective chromoionophore (3,3′,5,5′-tetramethyl-N,N-dibenzylbenzidine, a novel synthetic cationic dye) and a lipophilic potassium tetrakis(4-chlorophenyl)borate was used as a sensing device for the indirect optical determination of potassium ions. It exhibited a reversible response to the potassium ion in 0.05 mol/l HCl buffer media in the concentration range from 1 × 10^? 6 to 1 × 10^? 2 mol/l. The linear range was from 1.53 × 10^? 5 to 3.20 × 10^? 3 mol/l. The proposed optode sensor exhibited a fast response of less than 1 min, good repeatability (n = 7, RSD = 3.62%) at 5 × 10^? 5 mol/l, and long-term stability with 92% of its initial sensitivity after 1 month of storage. The selectivity of the potassium-selective membrane allows its application for the detection of the potassium concentration in real sample analysis. The result was satisfactory compared with atomic absorption spectrometry.     

A highly selective fluorescent sensor for Cu based on 2-(2′-hydroxyphenyl)benzoxazole in a poly(vinyl chloride) matrix

This paper describes a copper selective optical chemical sensor based on static quenching of the fluorescence of 2-(2′-hydroxyphenyl)benzoxazole entrapped in a poly(vinyl chloride) (PVC) membrane. The effect of the composition of the sensing membrane was studied, and experimental conditions were optimized. The sensors exhibit stable response over the concentration range from 4.0 × 10⁻⁸ M to 5.0 × 10⁻⁵ M Cu²⁺ at pH 4.0-6.5, and a high selectivity. The response time for Cu²⁺ with concentration ≤5 × 10⁻⁶ M is less than 7 min. The optode can be regenerated using 0.1 M HCl and acetate buffer solution. The sensor has been used for direct measurement of copper content in river water samples with a relative error less than 4% with reference to that obtained by atomic absorption spectrometry.     

Zinc-Selective Membrane Electrode Based On 5, 6, 14, 15-Dibenzo-l, 4-Dioxa-8, 12-Diazacyclopentadecane-5, 14-Diene

ABSTRACT

A new PVC membrane for zinc ions based on DBDA15C4 as membrane carrier was prepared. The electrode shows a linear stable response over a wide concentration range (5.0 × 10^?5-1.0 × 10^?1 M) with a slope of 22 mV/decade and a limit of detection of 3.0 × 10^?5 M (2.0 μg/ml). It has a very short response time of less than 5 s and can be use for at least 11 months without any divergence in potential. The zinc ion-selective electrode exhibited very good selectivities with respect to alkali, alkaline earth and some transition and heavy metal ions and could be used in a pH range 1.5-7.0. It was successfully applied for the direct determination of zinc in a pharmaceutical sample and, as an indicator electrode, in potentiometric titration of Zn²⁺ ions.     

Lead-Selective Membrane Potentiometric Sensor Based On A Recently Synthesized Dimethyl Benzo Tetrathia Fulvalene

ABSTRACT

A PVC membrane electrode for lead ion based on dimethyl benzo tetrathia fulvalene(DMBTTF)as membrane carrier was developed. The electrode exhibits a Nernstian response for Pb^2? over a wide concentration range (10^?2?10^?5 M) with a limit of detection of 8^*10^?6M. It has a response time of 20s and can be used for at least 2 months without any considerable divergence in potentials. The proposed membrane sensor revealed good selectivities for Pb^2? over a wide variety of other metal ions and could be used in pH range of 3.0-6.0.     

Fabrication of an optical sensor based on the immobilization of Qsal on the plasticized PVC membrane for the determination of copper(II)

A novel optical sensor has been proposed for sensitive determination of Cu(II) ion in aqueous solutions. The copper sensing membrane was prepared by incorporating Qsal (2-(2-hydroxyphenyl)-3H-anthra[2,1-d]imidazole-6,11-dione) as ionophore in the plasticized PVC membrane containing tributyl phosphate (TBP) as plasticizer. The membrane responds to Cu(II) ion by changing color reversibly from yellow to dark red in acetate buffer solution at pH 4.0. The proposed sensor displays a linear range of 6.3 × 10^?7?1.00 × 10^?4 M with a limit of detection of 3.3 × 10^?7 M. The response time of the optical sensor was about 3?C5 min, depending on the concentration of Cu(II) ions. The selectivity of the optical sensor to Cu(II) ions in acetate buffer is good. The sensor can readily be regenerated by hydrochloric acid (0.1 M). The optical sensor is fully reversible. The proposed optical sensor was applied to the determination of Cu(II) in environmental water samples.     

Flow-Through Bulk Optode for the Spectrophotometric Determination of Perchlorate

A flow-through spectrophotometric bulk optode for the flow-injection determination of perchlorate is described. As active constituents, the optode incorporates the lipophilic pH indicator 5-octadecanoyloxy-2-(4-nitrophenylazo) phenol and methyltridodecyl ammonium chloride, dissolved in a plasticized poly(vinyl chloride) membrane which is entrapped in a cellulose support. The optode is applied in conjunction with the flow injection technique at pH 8.2 (TRIS buffer). The sensor is readily regenerated with a 10^–2M NaOH carrier solution. The analytical characteristics of this optode with respect to response time, dynamic measurement range, reproducibility and selectivity are discussed. The proposed FI method is applied to the determination of perchlorate in waters from different sources.Received December 16, 2002; accepted May 16, 2003 Published online August 8, 2003     

Construction of a New Perbromate-Selective Electrode. Kinetic Study of the Iron(II)- Perbromate Reaction and Microdetermination of Iron

Abstract

A perbromate- selective membrane electrode with a liquid membrane of crystal violet-perbromate dissolved in chlorobenzene is described, The liquid membrane electrode exhibits rapid and near Nernstian response to perbromate activity from 10^?5 to 10^?2 M. The response is unaffected by pH in the range 2–10, Major interferences are periodate and perchlorate. A kinetic study of the iron(II)- perbromate reaction was carried out with the perbromate electrode, A potentiometric method is described for the determination of 50–500 μg of iron (II) with relative errors and standard deviations of 1–2%.     

Solid contact Zn2+ -selective electrode with low detection limit and stable and reversible potential

A new solid contact Zn²⁺ polyvinylchloride membrane sensor with 2-(2-Hydroxy-1-naphthylazo)-1,3,4 -thiadiazole as an ionophore has been prepared. For the electrode construction, ionic liquids, alkylmethylimidazolium chlorides are used as transducer media and as a lipophilic ionic membrane component. The addition of ionic liquid to the membrane phase was found to reduce membrane resistance and determine the potential of an internal reference Ag/AgCl electrode. The electrode with the membrane composition: ionophore: PVC: o-NPOE: ionic liquid in the percentage ratio of (wt.) 1:30:66:3, respectively, exhibited the best performance, having a slope of 29.8 mV decade^?1 in the concentration range 3×10^?7–1×10^?1 M. The detection limit is 6.9×10^?8 M. It has a fast response time of 5–7 s and exhibits stable and reproducible potential. It has a fast response time of 5–7 s and exhibits stable and reproducible potential, which does not depend on pH in the range 3.8–8.0. The proposed sensor shows a good and satisfactory selectivity towards Zn²⁺ ion in comparison with other cations including alkali, alkaline earth, transition and heavy metal ions. It was successfully applied for direct determination of zinc ions in tap water and as an indicator electrode in potentiometric titration of Zn²⁺ ions with EDTA.      

Dioctadecyldimethylammonium Chloride Bilayer Membrane Vesicle-Enhanced and Manganese (II)-Catalyzed Chemiluminescence for Determination of Adrenaline by a Flow-Injection Method

Abstract

A new chemiluminescence system reinforced by use of a surfactant and a metal catalyst is demonstrated for selective determination of adrenaline by a flow-injection method. The weak light emission originating from an aerobic oxidation of adrenaline in an alkaline solution is dramatically enhanced by ordered surfactant molecular assemblies, dioctadecyldimethylammonium chloride bilayer membrane vesicles, with the largest enhancement factor of 1000 which has not ever been realized. The enhanced emission is further increased by a Mn(II) catalyst with an enhancement factor of ca. 40. The limit of determination(S/N=2) is 1×10^?8M (0.2 ng in 100-μ1 injection), the linear range is four ordrers of magnitude, the sample throughput is 100 h^?1. and the relative standard deviation(n=5) is 0.9 % for 5×10^?7M adrenaline. Of other substances including dopamine, noradrenaline, and related compounds, p-hydroxymandelenic acid chemiluminesces most strongly after adrenaline, the 1×10^?3M solution providing a signal 24% of that for 1×10^?6M adrenaline.     

Sequential flow-injection determinations of calcium and magnesium in waters

A tubular PVC membrane electrode for calcium without inner reference solution and a device for location of the reference electrode are described. In the flow-injection system, calcium is determined potentiometrically and then magnesium is determined by atomic absorption spectrometry. The electrode provides linear response to calcium in the range 5 × 10^?5/2-10^?1 M. On-line dilution of the sample allows magnesium determination in the range 0/2-10 mg l^?. Flow rates between 3 and 6 ml min^?1 are possible. The sampling frequency is 60/2-90 h^?1.