The Experts below are selected from a list of 2085 Experts worldwide ranked by ideXlab platform
Alaa S Amin - One of the best experts on this subject based on the ideXlab platform.
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utilization of a triacetylcellulose membrane to immobilize 5 2 4 dimethylphenylazo 6 hydroxypyrimidine 2 4 dione for erbium determination in real samples
Journal of Industrial and Engineering Chemistry, 2018Co-Authors: Zakia Almallah, Alaa S AminAbstract:Abstract A membrane Optode formed by physical inclusion of a chromophore 2-amino-6-(1,3-thiazol-2yldiazenyl)phenol (ATDP) into a plasticized cellulose triacetate (CTA) matrix was investigated for preconcentration, extraction and colorimetric determination of Er(III) from aqueous samples. The Optode was examined for erbium uptake in borate buffer medium (∼125 ng mL−1) at pH 8.5–9.0. The inclusion of an anion-exchanger tri-isooctylamine (TiOA) was found to be necessary for the formation of Er(III)–ATDP complex in the Optode matrix, resulting into distinct color change of the Optode from red to violet color after erbium sorption. The composition of the Optode was prepared by varying the amounts of different plasticizers and TiOA to obtain minimum response time towards Er(III) in borate buffer medium. The effects of different experimental parameters involved in the detection and quantification of Er(III) using Optode were optimized. The Optode analytical performance was performed in terms of interference of cations and anions, reusability, equilibration time, detection limit, etc. and compared with the conventional colorimetric method for Er(III) using different chromophores. The Optode developed in the present study was tested in real samples with good results comparing to the GF-AAS method.
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application of a triacetylcellulose membrane with immobilizated of 5 2 4 dimethylphenylazo 6 hydroxypyrimidine 2 4 dione for mercury determination in real samples
Sensors and Actuators B-chemical, 2015Co-Authors: Alaa S AminAbstract:Abstract The fabrication of an optical sensor membrane is described for the determination of Hg 2+ ions based on the immobilization of 5-(2′,4′-dimethyl-phenylazo)-6-hydroxypyrimidine-2,4-dione (DMPAHPD) on a triacetyl-cellulose membrane. The membrane responds to mercury ions by changing color reversibly from orange to deep red in thiel buffer solution at pH 8.5. Under optimum conditions, the proposed membrane displayed a linear range of 1.0–80 ng/mL with a limit of detection of 0.3 ng/mL at a wavelength of 594 nm. The response time of the Optode was about 3.0–5.0 min, depending on the concentration of Hg 2+ ions. The coefficient of variation (CV) of the sensor response for 40 ng/mL of Hg 2+ was 1.2% and the CV between seven membranes was 1.45%. The Optode is fully reversible and the selectivity of Optode to Hg 2+ ions is relatively good with Ni 2+ ions as interferences. The proposed Optode was applied successfully for the determination of Hg 2+ ions in real samples.
Wilhelm Simon - One of the best experts on this subject based on the ideXlab platform.
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theoretical aspects of bulk Optode membranes
Analytica Chimica Acta, 1992Co-Authors: K Seiler, Wilhelm SimonAbstract:Abstract The principles of Optodes, which are based on a reversible mass transfer of analyte from the sample into the bulk of the sensing layer, have been elucidated in detail. It is demonstrated that the sensor response of many different types of bulk Optode membranes described in the literature can be related to the same formalism. A universal description is given that is independent of the type of the optical transduction process and can be based on absorption (transmission or attenuated total reflection mode) or on fluorescence. The theoretical performance of bulk Optodes based on plasticized PVC is described in terms of selectivity, response time, dynamic measuring range, sensitivity and lifetime, and whatever a comparison with experimental data is given. The geometrical arrangement and optimization of the membrane composition for a set of specific requirements are discussed in detail. By means of the spin-on technique, a simple manufacture of very thin Optode membranes is described. With this technique, highly homogeneous membranes of thickness from 0.5 to to μm can be produced in only a few seconds.
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lead selective bulk Optodes based on neutral ionophores with subnanomolar detection limits
Analytical Chemistry, 1992Co-Authors: Markus Lerchi, Eric Bakker, Bruno Rusterholz, Wilhelm SimonAbstract:An optical sensor (Optode) based on a plasticized poly(vinyl chloride) (PVC) bulk membrane incorporating a metal ion-selective ionophore, a proton-selective chromoionophore, and lipophilic anionic sites for the measurement of lead is presented. Different ionophores (ETH 322, ETH 5428, ETH 295, ETH 5435) and chromoionophores (ETH 2439, ETH 5418, ETH 5315, ETH 5294) were used to design a new Optode for environmental sensing properties. The present Optode system shows an especially excellent selectivity over alkali and alkaline-earth metals. The measuring range for lead was found to be 5.0×10 -9 to 5.0×10 -3 M at pH 5.68 with a corresponding detection limit of 3.2×10 -12 M
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characterization of an Optode membrane for zinc ii incorporating a lipophilized analogue of the dye 4 2 pyridylazo resorcinol
Analyst, 1992Co-Authors: Kemin Wang, Kurt Seiler, Bruno Rusterholz, Wilhelm SimonAbstract:A chemical optical sensing system (Optode) for ZnII based on a lipophilized metal ion indicator dye [1-octadecyloxy-4-(2-pyridylazo)resorcinol; ETH 2464] dissolved in a plasticized poly(vinyl chloride) membrane has been developed. In the measuring range from 1 × 10–6 to 3 × 10–3 mol dm–3 Zn2+(pH 4.8), the absorbance response shows a good correlation with the theoretically derived formulae. The Optode membranes were found to reach 95% of the final signal within 5 min (t95). When exposed to a continuous sample flow (1 ml min–1), the Optode membrane did not lose a perceptible amount of the indicator over a period of 10 h. The selectivity of the Optode membrane for the response towards Zn2+ ions in pH-buffered solutions is described.
Eric Bakker - One of the best experts on this subject based on the ideXlab platform.
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Ion selective Optodes: from the bulk to the nanoscale
Analytical and Bioanalytical Chemistry, 2015Co-Authors: Eric BakkerAbstract:This review describes recent advances in the miniaturization of ion selective Optodes into microscale and nanoscale sensors. The topics include a comparison between film-based and miniaturized ion Optodes, equilibrium and exhaustive detection modes, recent preparation methodologies and applications of microscale and nanoscale ion Optodes, criteria for the design of Optode sensors, and other future perspectives. Graphical Abstract Ion selective Optodes are attractivre optical sensing tools for ionic species. This review highlights recent advances with this class of ion selective optical sensors with a focus on miniaturization, characteristics and applications of micrometer and nanometer sized Optode sensors
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ph independent nano Optode sensors based on exhaustive ion selective nanospheres
Analytical Chemistry, 2014Co-Authors: Xiaojiang Xie, Jingying Zhai, Eric BakkerAbstract:Bulk Optode-based ion selective optical sensors work on the basis of extraction equilibria, and their response toward the analyte ion is known to dependent on the sample pH. This pH dependence has been one of the major disadvantages that have hampered the broad acceptance of bulk Optodes in chemical sensing. We present here for the first time the use of exhaustive Ca2+-selective nanosensors that may overcome this pH dependent response. The nanosensors were characterized at different pH and the same linear calibration was obtained in the Ca2+ concentration range from 10–7 M to 10–5 M.
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phosphate selective fluorescent sensing microspheres based on uranyl salophene ionophores
Analytica Chimica Acta, 2008Co-Authors: Katarzyna Wygladacz, Eric Bakker, Wojciech WroblewskiAbstract:Optical dihydrogen phosphate-selective sensors that function on the basis of bulk Optode principles and are based on two different uranyl salophene ionophores are reported here for the first time. The influence of the Optode composition and measuring conditions such as sample pH on the Optode response are characterized, along with sensor selectivity and long-term stability. Three plasticizers of different polarity are considered for Optode fabrication: bis(2-ethylhexyl)sebacate (DOS), dodecyl 2-nitrophenyl ether (o-NPDDE), o-nitrophenyloctylether (o-NPOE). The compounds 9-(diethylamino)-5-(octadecanoylimino)-5H-benzo[a]phenoxazine (ETH 5294, chromoionophore I) and 9-(diethylamino)-5-[(2-octyldecyl)imino]benzo[a]phenoxazine (ETH 5350, chromoionophore III) are used as H+-selective fluoroionophores that also act as reference ionophores. The resulting Optode-based sensors are compared with their ion-selective electrode (ISE) counterparts, and it is revealed that Optodes are better suited for operation at physiological pH. The best Optode performance was found for the two component Optode sensors doped with ETH 5350 and phosphate ionophore(I). The linear range of these sensor was log a = −6.0 to −2.6. Dihydrogen phosphate-selective Optode sensors of optimized composition are fabricated in microsphere format and preliminary measurements in diluted sheep blood samples are presented.
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multiplexed flow cytometric sensing of blood electrolytes in physiological samples using fluorescent bulk Optode microspheres
Analytical Chemistry, 2007Co-Authors: Katarzyna Wygladacz, Robert Retter, Michael Bell, Eric BakkerAbstract:Polymeric bulk Optode microsphere ion sensors in combination with suspension array technologies such as analytical flow cytometry may become a power tool for measuring electrolytes in physiological samples. In this work, the methodology for the direct measurement of common blood electrolytes in physiological samples using bulk Optode microsphere sensors was explored. The simultaneous determination of Na+, K+, and Ca2+ in diluted sheep blood plasma was demonstrated for the first time, using a random suspension array containing three types of mixed microsphere bulk Optodes of similar size, fabricated from the same chromoionophore without additional labeling. Sodium ionophore X, potassium ionophore III, and grafted AU-1 in poly(butyl acrylate) were the ionophores used in the bulk Optode microsphere ion sensors for Na+, K+, and Ca2+, respectively, in combination with the cation-exchanger NaTFPB (sodium tetrakis-[3,5-bis(trifluoromethyl)phenyl]borate) and the same concentration of the chromoionophore ETH 5294 ...
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lead selective bulk Optodes based on neutral ionophores with subnanomolar detection limits
Analytical Chemistry, 1992Co-Authors: Markus Lerchi, Eric Bakker, Bruno Rusterholz, Wilhelm SimonAbstract:An optical sensor (Optode) based on a plasticized poly(vinyl chloride) (PVC) bulk membrane incorporating a metal ion-selective ionophore, a proton-selective chromoionophore, and lipophilic anionic sites for the measurement of lead is presented. Different ionophores (ETH 322, ETH 5428, ETH 295, ETH 5435) and chromoionophores (ETH 2439, ETH 5418, ETH 5315, ETH 5294) were used to design a new Optode for environmental sensing properties. The present Optode system shows an especially excellent selectivity over alkali and alkaline-earth metals. The measuring range for lead was found to be 5.0×10 -9 to 5.0×10 -3 M at pH 5.68 with a corresponding detection limit of 3.2×10 -12 M
A V R Reddy - One of the best experts on this subject based on the ideXlab platform.
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development of a visual Optode sensor for onsite determination of hg ii
Sensors and Actuators B-chemical, 2015Co-Authors: Neha Thakur, Ashok K Pandey, Sanjukta A Kumar, K Ajish S Kumar, Sangita D Kumar, A V R ReddyAbstract:Abstract A color changeable cellulose triacetate (CTA) membrane-based Optode has been developed for the highly selective and sensitive determination of Hg(II) ions in aqueous solutions. The sensing layer of the Optode consists of phenylthiosemicarbazide derivative of rhodamine 6G immobilized in a plasticized CTA membrane. The colorless Optode film on reaction with Hg(II) turned pink, in color, and the intensity of the color was found to be directly proportional to the amount of Hg(II). The sensing mechanism is based on the mercury-induced spirolactum ring opening followed by its cyclization to form highly conjugated system which leads to the development of pink color. Various experimental parameters such as pH, Optode composition and response time have been optimized. Under these conditions, the sensor showed a wide linear dynamic range of 10–5000 ng mL−1 Hg(II), with a detection limit of 1.3 ng mL−1. In addition to its stability and reproducibility, Optode showed a high selectivity toward Hg(II) ions as compared to other coexisting ions in real water samples. The developed Optode is suitable for rapid and onsite detection of Hg(II) ions in a variety of aqueous samples. The sensor was successfully applied for the determination of Hg(II) ions in groundwater samples.
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membrane Optode for mercury ii determination in aqueous samples
Journal of Hazardous Materials, 2009Co-Authors: Y Kalyan, Ashok K Pandey, P R Bhagat, R Acharya, V Natarajan, G R K Naidu, A V R ReddyAbstract:Abstract A color changeable Optode for Hg(II) was prepared by the immobilization of a dye 4-(2-pyridylazo)resorcinol (PAR) and a liquid ion-exchanger trioctylmethylammonium chloride (Aliquat-336) in the tri-(2-ethylhexyl) phosphate plasticized cellulose triacetate matrix. Hg(II) and CH 3 Hg + from aqueous samples could be quantitatively preconcentrated in this transparent Optode producing a distinct color change ( λ max = 520 nm) within 5 min equilibration time in bicarbonate aqueous medium or 30 min in natural water. Whereas Optode sample without Aliquat-336 did not change its color corresponding to Hg–PAR complex on equilibrium with the same aqueous solution containing Hg(II) ions. The uptake of Hg(II) was found to be pH dependant with a maximum (>90%) at a pH 7.5. The uptake of ions like Cu(II), Fe(II), Zn(II) and Pb(II) was negligible in the Optode where as the uptake of Cd(II) and Zn(II) ions was 10–15% at pH 7.5. The Optode developed in the present work was studied for its analytical application for Hg(II) in the aqueous samples by spectrophotometry, radiotracer ( 203 Hg), Energy Dispersive X-ray Fluorescence (EDXRF) analyses and Instrumental Neutron Activation Analysis (INAA). The minimum amount of Hg(II) required to produce detectable response by spectrophotometry, INAA and EDXRF were found to be 5.5, 1 and 12 μg, respectively. This Optode showed a linear increase in the absorbance at λ max = 520 nm over a concentration range of 0.22–1.32 μg/mL of Hg(II) ions in aqueous solution for 5 min. The preconcentration of Hg(II) from large volume of aqueous solution was used to extend the lower limit of concentration range that can be quantified by the spectrophotometry of Optode. It was observed that preconcentration of 11 μg Hg(II) in 100 mL (0.11 μg/mL) in aqueous samples gives a distinct color change and absorbance above 3 σ of the blank absorbance. The Optode developed in the present work was found to be reusable.
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chemically selective membrane Optode for cr vi determination in aqueous samples
Analytica Chimica Acta, 2004Co-Authors: Yogesh Scindia, Ashok K Pandey, A V R Reddy, S B ManoharAbstract:Abstract A methodology for simultaneous preconcentration and determination of Cr(VI) from aqueous samples was developed using a membrane Optode formed by physical inclusion of a Cr(VI) selective chromophore 1,5-diphenylcarbazide (DPC) into a plasticized cellulose triacetate matrix. The inclusion of an anion exchanger (Aliquat-336) was found to be effective for immobilization of both DPC and Cr(VI)–DPC complex in the Optode matrix itself. The proportionality in intensity of the magenta color on the Optodes loaded with varying amounts of Cr(VI) suggests its potential applications for screening of Cr(VI) in aqueous samples by visual colorimetry. On loading high amounts of Cr(VI) in the membrane Optode, its color changes from magenta to yellow, which indicates the possibility of using it as a threshold detector for Cr(VI). The membrane Optode was optimized in terms of obtaining maximum preconcentration efficiency for Cr(VI) and subsequent stable optical response proportional to the amount of Cr(VI) in the membrane Optode sample. The membrane Optodes were tested for Cr(VI) determination in tap water and seawater samples. Using this Optode, Cr(VI) even at levels of 13.6 ppb could be quantitatively detected. The Optodes developed in the present work were found to be stable, cost effective, easy to prepare and efficient for direct preconcentration and determination of Cr(VI) in a variety of aqueous samples using spectrophotometry. However, this membrane Optode is for one time use only as the reaction of Cr(VI) with DPC is irreversible.
Koji Suzuki - One of the best experts on this subject based on the ideXlab platform.
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Implementation of a plasticized PVC-based cation-selective Optode system into a paper-based analytical device for colorimetric sodium detection
Analyst, 2018Co-Authors: Hiroyuki Shibata, Terence G. Henares, Kentaro Yamada, Koji Suzuki, Daniel CitterioAbstract:On the example of a colorimetric sodium assay, this work demonstrates the implementation of a classical cation-exchange Optode relying on an ionophore-doped plasticized PVC membrane into a paper-based analytical device (PAD). An ion-selective Optode (ISO) system has been arranged into a vertically-assembled PAD (vPAD) integrating a pH-buffering function. Capillary force-driven sample liquid transportation through the paper matrix enabled pH-adjustment prior to the optical detection of the analyte cation. Functionalized paper layers with inkjet-deposited ISO membranes were combined with whole device lamination to attain a stable ion-exchange equilibrium required for the theoretical behavior of ISOs. Whole device lamination limited rapid evaporation of sample liquid on vPADs to avoid an increase of target concentration. Sigmoidal response curves between 10−5 and 1 M of Na+ at pH 5.0–7.0 have been confirmed on vPADs, following the theory defined by the cation-exchange equilibrium reaction. Finally, the influence of the cellulosic paper substrate matrix acting as a cation-exchanger on the Optode response behavior has been evaluated and compared with conventional plastic film Optodes.
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determination of blood potassium using a fouling resistant pvdf hfp based Optode
RSC Advances, 2016Co-Authors: Mizuki Tenjimbayashi, Jonathan P Hill, Hirokazu Komatsu, Waka Nakanishi, Masaaki Akamatsu, Koji Suzuki, Seimei Shiratori, Katsuhiko ArigaAbstract:Monitoring potassium levels in blood is a significant aspect of clinical analysis. For this reason, polymeric bulk Optodes have received much attention for their use in portable and easy-to-use analysis systems in situ determination without additional calibration. However, blood contamination on the detection area of the sensor can hinder accurate sensing and also increases risk of infection from the wounds. In this paper, we report a system for determination of potassium in blood which has the additional advantage of being blood-fouling resistant. We have replaced the generally used poly(vinyl chloride) (PVC) with hydrophobic fluorinated poly(vinylidene fluoride–hexafluoropropylene) (PVDF–HFP) for preparation of a polymeric bulk Optode. Sensing ability in the visual range of the polymeric bulk Optode was retained despite the variation of the polymer matrix. These polymeric bulk Optodes are suitable for potassium determination in blood with the PVDF–HFP-based Optode possessing better blood antifouling properties than the PVC-based Optode. The blood monitoring system described here represents the basis for functionalization of the Optode toward safe and easily implementation in blood and in situ sensing applications.
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highly durable double sol gel layer ratiometric fluorescent ph Optode based on the combination of two types of quantum dots and absorbing ph indicators
Analytical Chemistry, 2012Co-Authors: Yuki Hiruta, Daniel Citterio, Naoto Yoshizawa, Koji SuzukiAbstract:Long-term stable ratiometric fluorescent optical pH sensors (Optodes) based on double sol-gel silica layers are prepared with the first layer embedding two types of quantum dots (QDs) and the second layer embedding light-absorbing pH indicators. The sensors are fabricated by a simple general sol-gel spin-coating method. The resulting double-layer pH Optodes are designed as having long Stokes shift as well as ratiometric fluorescence emission response to pH in aqueous solutions of varying pH values. This Optode has high durability against continuous light exposure, even under severe acidic condition (1 M HCl), and the storage stability is over a period of more than 6 months. These results indicate that the double-layer ratiometric fluorescence-based pH Optode allows for long-term pH sensing. When two pH indicators of different pK(a) values with an optimized mixing ratio are embedded into the second layer, a double-layer pH Optode with reproducible linear response in a wide pH range of over 6 pH units (from pH 4 to 10) can be designed and fabricated.
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an oxo bacteriochlorin derivative for long wavelength fluorescence ratiometric alcohol sensing
Analyst, 2010Co-Authors: Kosuke Takano, Daniel Citterio, Shinichi Sasaki, Hitoshi Tamiaki, Koji SuzukiAbstract:A fluorescent ratiometric optical chemical sensor (Optode) for alcohol detection is presented. A lipophilized bacteriochlorin derivative possessing a trifluoroacetyl group at the 3-position was synthesized for alcohol detection. When embedded in a plasticized poly(vinyl chloride) (PVC) membrane, the fluororeceptor shows a significant signal change on exposure to aqueous ethanol solutions both in the absorbance and the fluorescence emission. This Optode allows the determination of ethanol concentrations in aqueous sample solutions by ratiometric fluorometry. The fluorescent indicator responds with increasing fluorescence around 701 nm and decreasing fluorescence around 751 nm towards the presence of ethanol. The Optode response was found to be fully reversible in a dynamic measurement range from 0.3% to at least 25% (v/v) ethanol. The limit of detection (LOD) and the limit of quantification (LOQ) of the sensor for ethanol were estimated to be 0.1% and 0.4% (v/v), respectively. These results indicate that the new Optode can be employed as an ethanol-sensing device with high sensitivity for beverage and industrial analyses.
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an absorption based surface plasmon resonance sensor applied to sodium ion sensing based on an ion selective Optode membrane
Analytical Chemistry, 2002Co-Authors: Kazuyoshi Kurihara, Etsuko Hirayama, Kaori Nakamura, Koji SuzukiAbstract:A surface plasmon resonance (SPR) sodium ion sensor using an ion Optode membrane film was experimentally and theoretically described based on an absorption-based SPR principle proposed in our previous article (Kurihara, K; Suzuki, K. AnaL Chem. 2002, 74, 696-701). The sodium ion concentrations from 10(-6) to 10(-1) have been successfully determined not only by the resonance angle diagnosis of the SPR curve but also by the minimum reflectance one. The ion Optode film was plasticized poly(vinyl chloride) including a neutral sodium ionophore, a pH-sensitive cationic dye, and an anionic additive. Its optical absorption intensity changed with the sodium ion concentrations. The SPR ion sensor physically measured the complex refractive index caused by the absorption in the ion Optode film. We have exhaustively investigated the experimental response behavior of the SPR curve relative to the sodium ion concentrations by comparison with numerically simulated SPR curves using a three-layer Fresnel equation including experimental values for the sodium ion Optode membrane film. As predicted by the absorption-based SPR principle, the SPR curve behavior of the SPR ion sensors depended on two factors: one was the relation between the excitation frequency of the light source and the absorption maximum frequency in the ion Optode film while the other was the gold metallic thickness in the Kretchmann configuration. The concept and practical theory of an absorption-based SPR sensor not only have been proved by the experimental results of the SPR sodium ion sensor but also have successfully allowed flexible ion sensing in an SPR sensor, which would be very difficult without the absorption mechanism in the ion Optode film.
