bluuebunny/crossref_metadata_2025_split huggingface dataset:
Carbonate Sensors Based on 4‐Hexyltrifluoroacetophenone Modified by Acceptor Substituents in Phenyl Ring
Authors: Makarychev‐Mikhailov Sergey , Goryacheva Olga , Mortensen John , Legin Andrey , Levitchev Sergey , Vlasov Yuri 
Published: September 2003

AbstractCarbonate sensors based on 4‐hexyltrifluoroacetophenone (Hex‐TFA) and its 3‐nitro‐ and 3‐bromo‐derivatives (NO2‐TFA and Br‐TFA) were studied. The acceptor substituents in phenyl ring of Hex‐TFA increase Lewis acidity of fluoroketone group and provide better carbonate selectivity of ionophore against lipophilic anions. The sensors containing hexyl trifluoroacetylbenzoate (HE) were used as reference. Variation of membrane composition and plastisizer were performed to optimize the selectivity. Potentiometric properties of carbonate sensors such as sensitivity, selectivity, detection limit (DL) and pH‐dependence of sensor response were studied. The sensors based on NO2‐TFA demonstrated significantly better selectivity than the sensors based on unmodified Hex‐TFA, the effect was up to three orders of magnitude for salicylate and nitrate, more than four orders for thiocyanate. However, NO2‐TFA sensors exhibited higher pH‐dependence of sensor response and higher detection limits. The sensors based on Br‐TFA showed the properties similar to that of HE‐based sensors. These results allow recommending trifluoroacetophenone derivatives with acceptor substituents in phenyl ring as promising ionophores for carbonate sensors.
The Use of Hexaamineruthenium(III) Redox Marker for the Characterization of SAM‐Au Amperometric Sensors
Authors: Rondinini Sandra , Vertova Alberto , Pilan Luisa 
Published: September 2003

AbstractChemically modified electrodes (CME's) by self‐assembled monolayers (SAM's) of alkanethiols are extensively studied because of their potential applications in many fields from surface chemistry, to biochemistry, to electroanalytical chemistry. The layer defectivity is one of the most critical feature that affects the reproducibility of the final sensors, hence a careful electrode design and preparation is required. In the present work the preparation and characterization of long chain thiol Au‐SAM's of controlled defectivity is described. In particular, the apparent standard rate constants of the Ru(NH3)63+/2+ redox couple are determined as a function of the degree of coverage for three different linear chain alkylthiols (n‐decane‐, n‐dodecane‐ and n‐octadecane‐thiol). The results are discussed in term of the electron transfer model at partially blocked surfaces.
Comparison of 2‐Mercaptoethane Sulfonate and Mercaptoacetic Acid Disorganized Monolayer‐Coated Electrodes for the Detection of Copper via Underpotential Deposition‐Stripping Voltammetry
Authors: Herzog Grégoire , Arrigan Damien W. M. 
Published: September 2003

AbstractThe presence of electrode‐passivating compounds in many natural samples constitutes a challenge for analytical detection therein using electrochemical techniques. This work reports the spontaneous adsorption of short‐chain thiols onto a gold surface to form a thin and porous film which protects the electrode surface from the adsorption of surfactants while simultaneously allowing the underpotential deposition and stripping of metals. A direct comparison of two disorganized monolayer films (2‐mercaptoethane sulfonate, MES, and mercaptoacetic acid, MAA) for the detection of copper by voltammetric stripping of underpotential deposits and for the protection of the electrode surface from surfactants is presented. These modified electrodes present similar behaviors, both fulfilling the disorganized monolayer approach requirements of surfactant exclusion while maintaining analyte accessibility to the underlying electrode.
Lower Rim Substituted tert‐Butyl Calix[4]Arenes (Part IV). Calix[4]Arene‐Crown Ethers as Ionophores in Plasticized PVC‐Membrane Electrodes
Authors: Bocheńska Maria , Zielińska Anna , Pomećko Radosław , Kravtsov Victor Ch. , Gdaniec Maria 
Published: September 2003

AbstractWe present the synthesis and characterization of p‐tert‐butylcalix[4]arene‐crown ethers (compounds 2–4) with different length of the polyethylenoxy bridge between the distal phenolic OH groups. The studied compounds show selectivity for sodium, potassium or cesium ions. The correlation was made between the stereochemical structure of the ligands and potentiometrically determined ion‐selectivity and complex formation constants. The crystal and molecular structure of the p‐tert‐butylcalix[4]arene‐crown‐5 complex with potassium iodide have been determined by single crystal X‐ray diffraction study.
Recognition of Anions Using Metalloporphyrin‐Based Ion‐Selective Membranes: State‐of‐the‐Art
Authors: Górski Łukasz , Malinowska Elżbieta , Parzuchowski Paweł , Zhang Wei , Meyerhoff Mark E. 
Published: September 2003

AbstractThe principles, recent achievements and challenges related to the use of metalloporphyrins as ionophores in the development of polymeric anion‐selective membranes are reported. The advantages and disadvantages of dimer‐monomer equilibria existing within the membrane phase when using certain metalloporphyrins are discussed with respect to their effect on the response characteristics of the resulting anion sensors. The influence of membrane composition and pH of sample solution on these equilibria is described. The possibility of employing both potentiometric and optical transduction modes for anion recognition with metalloporphyrin doped polymer membranes is shown.
Electronic Effects on the Selectivity of Mercuracarborand Ionophores in Ion‐Selective Electrodes and Membrane Formulations for Their Use in High Protein Concentration Environments
Authors: Johnson R. Daniel , Badr Ibrahim H. A. , Diaz Martin , Wedge Timothy J. , Hawthorne M. Frederick , Bachas Leonidas G. 
Published: September 2003

AbstractIon‐selective electrodes based on the ionophore [9]mercuracarborand‐3 (MC3) have been demonstrated in the past to be highly selective for the chloride ion. This ionophore is macrocyclic and possesses Lewis acidic mercury centers, both of which result in enhanced ionophore binding to spherical anions. Like their charge‐reverse analogs, crown ethers, mercuracarborands offer the possibility to tune binding selectivity through changes in cavity size and/or via the incorporation of functional groups onto the cavity framework. Indeed, this article outlines the effect on ionophore selectivity that results from the addition of methyl groups to the MC3's carborane cages. Our results indicate that this simple functionalization leads to significant changes in selectivity that can be attributed to electronic effects. Furthermore, since MC3‐based electrodes and optodes have previously shown sufficient selectivities to perform physiological analysis, the effect of protein backgrounds and mild exposure to human whole blood on the response of mercuracarborand ISEs is also reported.
Optimization of the Composition of Interfaces in Miniature Planar Chloride Electrodes
Authors: Paciorek Renata , van der Wal Peter D. , de Rooij Nicolaas F. , Maj‐Żurawska Magdalena 
Published: September 2003

AbstractDifferent solid contact arrangements for miniature screen‐printed electrodes and silicon based electrodes for chloride ions were investigated. As an inner contact the electrochemically deposited gold on screen‐printed silver and platinum (silicon based electrodes) were used. As the ion‐exchanger for chloride methyl‐tri‐n‐tetradecylammonium chloride with PVC or Tecoflex as the polymer matrix was used. The influence of different intermediate layers between inner contact and the ion selective membrane was studied. The best characteristic of the electrode was obtained for electrodes containing gold contact and conductive polymer (poly‐3‐octylthiophene) with adhesive admixture between the inner contact and the proper ion selective membrane.
Soft Metal Ion‐Selective Electrodes Based on π‐Coordinate Calixarene Derivatives
Authors: Yajima Setsuko , Yoshioka Norio , Tanaka Mutsuo , Kimura Keiichi 
Published: September 2003

AbstractCalix[4]arene derivatives incorporating ω‐unsaturated alkenyl groups or saturated alkyl groups and their monomeric analogues were used as π‐coordinate neutral carriers for ion‐selective electrodes (ISEs) of soft metals [silver and thallium(I)] ions. The EMF responses were excellent for most of the ISEs, among which there was no significant difference in the response. The ion selectivities of the ISEs depend on the structure of neutral carriers employed. 1H NMR study explains the difference in the ion selectivity. In the metal‐ion complexation by the π‐coordinate calixarene derivatives, thallium ion is likely to interact with the calixarene skeleton, while silver ion tends to interact with both of the calixarene skeleton and the ω‐unsaturated alkenyl groups.
Rotating Ion‐Selective Membrane Electrodes for Trace‐Level Measurements
Authors: Vigassy Tamás , Gyurcsányi Robert E. , Pretsch Ernö 
Published: September 2003

AbstractIon‐selective solvent polymeric membrane electrodes (ISEs) are shown to exhibit improved response characteristics in a rotating electrode configuration. With a rather concentrated internal electrolyte solution of primary (analyte) ions, which induces their leaching from the membrane into the sample, the detection limit of the ISEs rotating at 3000 rpm is found to be better by about one order of magnitude than that of the analogous conventional ones in a stirred solution. On the other hand, with an internal solution inducing a strong inward flux of primary ions (i.e., from the sample to the ISE membrane), the apparent super‐Nernstian response due to depletion of primary ions from the analyte solution near the membrane surface is shifted by about one order of magnitude to lower concentrations. Membranes of about 0.8 mm diameter positioned eccentrically with respect to the rotation axis give a further shift of the apparent super‐Nernstian response step by about 0.3 logarithmic units. Simultaneously, the use of rotating electrodes substantially lowers the response time at submicromolar activities. An eccentrically placed Pb2+‐selective membrane on a rotating disk electrode with optimized internal solution shows a lower detection limit of aPb=6.3×10−11 M.
Scanning Electrochemical Microscopy Inside the Biocatalytic Layer of Biosensors, Investigation of a Double Function Complex Multienzyme Reaction Layer
Authors: Csóka Balázs , Kovács Barna , Nagy Géza 
Published: September 2003

AbstractAs the continuation of the work started earlier, this article deals with the scanning electrochemical microscopic (SECM) study of the function of complex enzyme sensors. In this case reaction layer of the sensor is made of two different parts. One is for interference elimination and the other for selective molecular recognition and measurement. As Scheller's group described this sucrose electrode, the inner that is the measuring layer contains three enzymes: invertase, mutarotase and glucose oxidase while the outer, the eliminating one, uses glucose oxidase and catalase. In our work the concentration profiles of oxygen and hydrogen peroxide were recorded inside the two different enzyme layers with the SECM. The dependence of these profiles on the working parameters such as enzyme activity and activity ratios, reaction layer thickness, sucrose and glucose concentration were observed and compared with the results of model calculations. Method of finite differences was used for the model calculations.
Separation of Escherichia coli 055:B5 lipopolysaccharide and detoxified lipopolysaccharide by high‐performance capillary electrophoresis
Authors: Volpi Nicola 
Published: September 2003

AbstractA rapid, highly sensitive and reproducible high‐performance capillary electrophoresis (HPCE) method (electrokinetic chromatography with sodium dodecyl sulfate) is described for the determination of the lipopolysaccharide (LPS) and detoxified LPS (D‐LPS), produced by both alkaline treatment in anhydrous conditions and mild acid hydrolysis, from Escherichia coli 055:B5 bacteria. LPS and D‐LPS are separated and readily determined within 25 min on an uncoated fused‐silica capillary using normal polarity at 20 kV and detection at 200 nm. A linear relationship (correlation coefficient greater than about 0.97) was found for the LPS and the two D‐LPS species over a wide range of concentrations, from approximately 120 to 360 ng, with a detection sensitivity less than about 100 ng. Furthermore, HPCE was able to separate several molecular species mainly due to the presence of populations with O‐specific polysaccharides of distinct and increasing mean chain lengths. This approach could be of great importance for the quantitative determination of LPS and D‐LPS during the purification and preparation processes, also considering the importance of D‐LPS in the preparation of human vaccines, and for the qualitative evaluation of the heterogeneity of LPS and the O‐polysaccharide components.
Improved separation of double‐stranded DNA fragments by capillary electrophoresis using poly(ethylene oxide) solution containing colloids
Authors: Huang Ming‐Feng , Huang Chih‐Ching , Chang Huan‐Tsung 
Published: September 2003

AbstractThe analysis of double‐stranded (ds) DNA fragments by capillary electrophoresis (CE) using poly(ethylene oxide) (PEO) solution containing gold nanoparticles (GNPs) is presented, focusing on evaluating size dependence of the GNPs and PEO on resolution and speed. To prevent the interaction of the capillary wall with DNA, the capillary was dynamically coated with polyvinylpyrrolidone. Using different PEO solutions containing GNPs ranging in diameter from 3.5 to 56 nm, we have achieved reproducible, rapid, and high‐resolution DNA separations. The results indicate that the sizes of PEO and GNPs as well as the concentration of PEO affect resolution. The separation of DNA ranging in size from 8 to 2176 base pairs (bp) was accomplished in 5 min using 0.2% PEO (8 MDa) containing 56 nm GNPs. We have also demonstrated the separations of the DNA fragments ranging from 5 to 40 kbp using 0.05% PEO (2 MDa) containing 13 nm GNPs or 0.05% PEO (4 MDa) containing 32 nm GNPs. With very low viscosity (< 15 cP), automatic replacement of the sieving matrices is easy, indicating a great potential for high‐throughput DNA analysis using capillary array electrophoresis systems.
A quantitative study of continuous flow‐counterbalanced capillary electrophoresis for sample purification
Authors: McLaren David G. , Chen David D. Y. 
Published: September 2003

AbstractA systematic evaluation of continuous flow‐counterbalanced capillary electrophoresis for microscale preparative applications is presented. The success of the technique was found to depend on the specific nature of the analyte and background electrolyte and was most heavily influenced by factors such as solution conductivity and rate of buffer depletion. The performance of the technique for the system studied was ultimately limited by contamination arising from changes in analyte mobilities during extended run times. Marked improvements in both purification rate and yield were observed using the zwitterionic buffer 2‐(N‐cyclohexylamino)ethanesulfonic acid when compared to similar runs carried out using a borate background electrolyte. A quantitative evaluation of the technique was performed for the analytes studied and the performance of the technique has been compared to fraction collection methods. The highest recovery achieved was 5.2% of the fastest migrating component present in the original sample with a resolution of 9 to the adjacent peak and required 100 min under optimized conditions. Recovery could be further increased to 9.0% in 120 min for the same analyte using pressure‐ramped flow‐counterbalanced capillary electrophoresis.
An insight into the phenomena involved in a multiple‐function stationary phase for the capillary electrochromatographic separation of 2'‐, 3'‐, and 5'‐monophosphorylated nucleoside isomers
Authors: Lin Shu‐Yu , Liu Chuen‐Ying 
Published: September 2003

AbstractThe electrochromatographic separations of 2'‐, 3'‐ and 5'‐monophosphates of adenosine, guanosine, cytidine, and uridine were carried out with an open‐tubular capillary column which was wall‐coated with a highly selective reagent, 28‐membered macrocyclic polyamine, 4, 8, 12, 18, 22, 26‐hexaaza‐1,15‐dioxacyclooctaeicosane ([28]ane‐N6O2). The effects of pH, composition and concentration of background electrolyte (BGE), applied voltage, column length, and the additive of the BGE, such as metal ions, borate, β‐cyclodextrin and organic solvent on the separation of these monophosphorylated nucleotide isomers were investigated. The results suggested that the interactions between analytes and the bonded groups on the wall predominantly comprise anion coordination and anion exchange in addition to the electrophoresis. A well‐resolved electrochromatogram was obtained with the capillary column of 100 cm (75 cm effective length)×75 μm inside diameter (ID), citrate buffer (20 mM, pH 3.99), applied voltage of −22 kV and detection at 254 nm. Column efficiency was found with the average theoretical plate numbers of 119 500/m and a low detection limit of 0.01 μM level could be achieved for the separation of these isomers.
Evaluation of teicoplanin chiral stationary phases of 3.5 and 5 μm inside diameter silica microparticles by polar‐organic mode capillary electrochromatography
Authors: Catarcini Paolo , Fanali Salvatore , Presutti Carla , D'Acquarica Ilaria , Gasparrini Francesco 
Published: September 2003

AbstractDifferent types of fused‐silica capillaries of 75 μm inside diameter (ID) were packed, namely type A and B, and evaluated for the direct resolution of racemates of several basic compounds by enantioselective capillary electrochromatography (e‐CEC). Type A was packed with a chiral stationary phase (CSP) containing teicoplanin (TE) mixed with silica microparticles (3:1 w/w) while type B contained only the TE‐CSP. In both cases, particles of different sizes (3.5 and 5 μm ID) were employed. A polar‐organic mobile phase containing methanol‐acetonitrile (60–40% v/v and 0.05% w/v ammonium acetate was used. Several β‐blockers (alprenolol, oxprenolol, metoprolol, pindolol, salbutamol, propranolol, atenolol, acebutolol) were baseline‐enantioresolved with both capillary types, in very short times.
Violet light emitting diode‐induced fluorescence detection combined with on‐line sample concentration techniques for use in capillary electrophoresis
Authors: Tsai Chih‐Hsin , Huang Hsuan‐Ming , Lin Cheng‐Huang 
Published: September 2003

AbstractThe first application of a violet light‐emitting diode (LED) for fluorescence detection in capillary electrophoresis (CE) is described. The utility of violet LED (peak emission wavelength at 410 nm, ∼ 2 mW) for fluorescence detection is demonstrated by examining reserpine and dopamine‐labeled NDA (naphthalene‐2,3‐dicarboxaldehyde), respectively. The detection limit for reserpine was determined to be 2.5×10−6 M by normal micellar electrokinetic capillary chromatography (MEKC) and this was improved to 2.0×10−9 M and 2.0×10−10 M when sweeping‐MEKC and cation‐selective exhaustive injection (CSEI)‐sweep‐MEKC techniques were applied, respectively. In addition, the detection limit of NDA‐labeled dopamine was determined to be 6.3×10−6 M by means of normal MEKC and this was improved to 3.0×10−8 M when the sweeping‐MEKC mode was applied.
A simple and low‐cost electrochemiluminescence detector for capillary electrophoresis
Authors: Chiang Mei‐Tsu , Lu Mei‐Chun , Whang Chen‐Wen 
Published: September 2003

AbstractA simple and cost‐effective electrochemiluminescence (ECL) detector for capillary electrophoresis (CE) has been developed. The detector was constructed by vertically gluing a 0.5 mL plastic sample vial onto a piece of 1.5 cm×1 cm×0.6 mm indium/tin oxide (ITO)‐coated glass plate. End‐column ECL detection was performed in a wall‐jet configuration. Potential control of the ITO electrode was provided using a direct current (DC) battery. Tris(2,2'‐bipyridyl)ruthenium(III) (Ru(bpy)33+)‐based ECL reaction was used for sensitive detection of four trialkylamines (trimethylamine, triethylamine, tripropylamine, tributylamine) and two amino acids (proline, hydroxyproline). With 15 mM sodium borate (pH 9.5) plus 3.5 mM Ru(bpy)32+ present in the detection cell and the ITO electrode biased at 1.7 V (vs. platinum wire reference), the test analytes can be efficiently separated and sensitively detected by the developed CE‐ECL system. Linearity (r ≥ 0.995) over two orders of magnitude and an average number of theoretical plates of 160 000/m were generally obtained. Reproducibility on peak height and migration times (n = 42) was 3.3% and 1.2% for tripropylamine, and 2.4% and 1.5% for proline, respectively. The detection limits were in the range of 2–5 μM (1–2 fmol) for the test analytes.
Investigation of the effects of wall adsorption of the visualization agent on baseline noise characteristics for indirect UV detection in capillary electrophoresis
Authors: Choy Tom M. H. , Huie Carmen W. 
Published: September 2003

AbstractNew insights into the effects of the wall adsorption of the visualization agent on baseline noise characteristics in indirect UV detection in capillary electrophoresis were provided. When compared to relatively small, hydrophilic cationic (1‐(4‐pyridyl)pyridinium chloride hydrochloride) or anionic chromophores (bromide and benzoate), the use of a UV‐absorbing long‐chain cationic surfactant (benzyldimethylhexadecylammonium chloride) as a probe (visualization agent) for studying baseline noise characteristics as a function of various experimental conditions, such as applied voltage, pH or buffer composition, was found to provide noise data that were very different under certain conditions. For cationic visualization agents that have a strong tendency of adsorbing onto the capillary surfaces due to electrostatic and/or hydrophobic interactions, it appeared that the interplay of both thermal as well as adsorption/desorption events occurring within the capillary is likely responsible for a fluctuation of the visualization agent concentration at the detector.
Use of poly(sodium oleyl‐L‐leucylvalinate) surfactant for the separation of chiral compounds in micellar electrokinetic chromatography
Authors: Mwongela Simon , Akbay Cevdet , Zhu Xiaofeng , Collins Sibrina , Warner Isiah M. 
Published: September 2003

AbstractA chiral amino acid‐based monomeric and polymeric surfactant, sodium oleyl‐L‐leucylvalinate) (L‐SOLV) and poly(sodium oleyl‐L‐leucylvalinate) (poly‐L‐SOLV) were synthesized and used for chiral separations in micellar electrokinetic chromatography (MEKC). Poly‐L‐SOLV was used successfully in the separation of various enantiomers of neutral, acidic, and basic analytes such as 1,1'‐bi‐2‐napthol, 1,1'‐binaphthyl‐2,2'‐diamine, benzoin, hydrobenzoin, benzoin methylether, warfarin, and coumachlor obtaining well‐resolved peaks but with only partial separation of temazepam. In addition, the atropisomer 1,1'‐binaphthyl‐2, 2'‐dihydrogen phosphate was chosen to study the applicability of the polymeric surfactant over a wide range of parameters such as concentration, temperature, voltage, and pH. The most striking characteristic of this new surfactant is its high hydrophobicity. It is favorable to interactions with hydrophobic chiral analytes, and thus may provide better chiral recognition for the compounds.