bluuebunny/crossref_metadata_2025 huggingface dataset:
Estimation of a Brillouin power spectrum distribution based on an iterative weighted least mean square method
Authors: Yamada Takayuki , Naruse Hiroshi
Published: September 2003

A fiberoptic strain sensor is being developed that exploits the fact that the difference between the central frequency of Brillouin scattering, which is a type of back scattering that occurs in optical fibers, and the incident light frequency depends on the strain of the optical fiber. The measurement of the central frequency of the Brillouin scattering requires an estimation of the power spectrum distribution of the Brillouin scattering. An improvement in distribution estimation accuracy can potentially improve both the accuracy of central frequency measurements and the precision of strain measurements. Focusing on the problem of the power spectrum distribution of the Brillouin scattering, this paper proposes a weighted repetition least mean square algorithm. The paper also examines the stability of the proposed repetition algorithm and demonstrates the effectiveness of the proposed approach through simulations. © 2003 Wiley Periodicals, Inc. Electron Comm Jpn Pt 1, 87(1): 72–80, 2004; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/ecja.1183
Modeling of CNR characteristics under bandwidth limitation on transmission systems employing optical super wide‐band FM technique
Authors: Fuse Masaru , Kudo Yoshiharu , Ishii Yoshikazu , Nojima Kazuhiro , Morikura Susumu
Published: September 2003

With regards to an optical transmission system employing the optical super wide‐band FM technique, which realizes multichannel video distribution on existing optical access networks, this paper examines the bandwidth limitation on the wide‐band FM signal as a factor of CNR degradation theoretically and experimentally. The required bandwidth for an FM signal has been estimated by the Komai‐Carson law, but there have been few studies of the quantitative relationship between that bandwidth and the amount of CNR degradation. To analyze such CNR degradation, we proposed a model for bandwidth limitation on the wide‐band FM signal with the “equivalent noise pulse.” The CNR theory on our proposed model can explain the actual CNR characteristics with bandwidth limitation. The results show that the bandwidth required is more than four times the standard deviation of the FM spectrum in order to maintain the CNR degradation of less than 1 dB. © 2003 Wiley Periodicals, Inc. Electron Comm Jpn Pt 1, 87(1): 81–89, 2004; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/ecja.1184
Approximate derivation of average bit error rate in DS‐CDMA systems in a frequency‐selective Rayleigh fading environment
Authors: Sasamori Fumihito , Maehara Fumiaki , Takahata Fumio
Published: September 2003

The transmission quality of mobile radio communications is strongly affected by fading with rapid fluctuations in the envelope and phase of the received signal, in addition to the effect of thermal noise. This paper considers a multiple access system (DS‐CDMA system) using the spread spectrum technique with direct spread, and presents a method of deriving the approximate average bit error rate in a frequency‐selective fading environment (the n‐ray Rayleigh fading model), with the maximum Doppler frequency, the delay time of the delayed wave, and the number of stations simultaneously utilizing the channel as parameters. The two‐wave model and the IMT2000 model are considered as examples, and the validity of the proposed method is demonstrated by the fact that the results obtained by the approximate formula agree well with the simulation results even if the parameters are varied. © 2003 Wiley Periodicals, Inc. Electron Comm Jpn Pt 1, 87(1): 90–100, 2004; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/ecja.1185
A modified xylenol orange method to evaluate formation of lipid hydroperoxides during storage and processing of small pelagic fish
Authors: Eymard Sylvie , Genot Claude
Published: September 2003

Lipid oxidation causes deterioration of the quality of fatty fish during processing and storage. Its development should be evaluated by measurement of several oxidation products, among them the hydroperoxides. However, most of the methods for determining hydroperoxides already in use failed when tested on fatty fish. The objective of this study was to adapt the ferrous ion xylenol orange assay (FOX) for easy and sensitive measurement of hydroperoxides in fatty fish such as small pelagics during their storage and processing. The proposed procedure is based on the assay developed by Hermes‐Lima et al. that consists of a colourimetric assay performed directly on the methanol extract from minced fish. The reactant was replaced by Wolff's reagent (FOX2 reagent) to improve the solubility of the extract and to simplify the procedure. It was shown that absorbance should be measured at 560 nm instead of 580 nm. The method is valid between 0.3 and 0.6 absorbance units. The modified method is easy, sensitive and allowed differentiation between fresh horse mackerel samples and those stored for 12 h at 17 °C on the basis of their hydroperoxide levels.
The influence of variety and harvest time on the bitterness and phenolic compounds of olive oil
Authors: Škevin Dubravka , Rade Desanka , Štrucelj Dubravka , Mokrovšak Željko , Neđeral Sandra , Benčić Đani
Published: September 2003

The influence of harvest time on the intensity of bitterness and the level of phenol compounds in olive oil from the region of western Istria, obtained from 2 local (Bianchera and Busa) and one introduced, Italian variety (Leccino) was studied. Olive fruits were harvested at 3 different harvesting periods, during 4 successive crops seasons. Immediately after harvesting, the fruits were processed under the same conditions in a pilot plant. Basic quality parameters, the content of total polyphenols, o‐diphenols and the intensity of bitterness were determined in oil samples. Samples of oil obtained from the Bianchera and Busa varieties were additionally tested for stability at elevated temperature (98 °C) and under the influence of UV‐light.

The results elaborated statistically showed the level of phenol compounds and the intensity of bitterness to be significantly influenced by both the harvest time and olive variety, with the influence of harvest time being more pronounced. The applied tests for accelerated deterioration of oil indicated a more rapid increase in the peroxide value in oil samples of both varieties exposed to UV‐light than in those exposed to elevated temperature. Both tests showed better stability of the oil obtained from the Bianchera variety.
1H nuclear magnetic resonance as a fast tool for determining the composition of acyl chains in acylglycerol mixtures
Authors: Guillén María D. , Ruiz Ainhoa
Published: September 2003

Several samples containing different proportions of standard compounds such as tristearin, triolein, trilinolein, and trilinolenin, covering a broad range of compositions, some similar to those of edible oils, were prepared by weight. The 1H nuclear magnetic resonance (NMR) spectra of these samples were recorded and their signals were assigned. It was shown that concentrations of linolenic acyl groups close to 0.4% or higher can be detected by this technique. The area of 5 discrete proton signals of the spectrum was determined. Considering the ratio between this area and the concentration of the corresponding types of hydrogen atoms in the sample, equations calculating the proportions of the acyl groups were deduced. The high level of agreement between data coming from 1H NMR spectra and data obtained by weight shows the usefulness of this methodology. In addition, it has the advantage that it is very fast and simple in comparison with the classical methods, and does not require a chemical modification of the sample. For this reason, the described method constitutes a valuable alternative for the determination of the proportions of different acyl groups in acylglycerol mixtures, such as, for example, oils and fats.
In vivo antioxidant effect of aqueous and etheric coriander (Coriandrum sativum L.) extracts
Authors: de Almeida Melo Enayde , Bion Francisca Martins , Filho Jorge Mancini , Guerra Nonete Barbosa
Published: September 2003

Research has shown that aqueous and etheric coriander extracts, composed of phenolics and carotenoids, exhibit a considerable antioxidant action. Considering the importance of natural antioxidants in the reduction of free radicals and oxidised compounds, coriander extracts obtained through sequential extraction, were administered by gavage to Wistar rats during 30 and 60 d consecutively. At the end of each experimental period, the animals were sacrificed to obtain the blood and the liver. The effect of extracts on plasma and liver lipid peroxidation was assessed by evaluation of thiobarbituric reactive substances. Initially, the aqueous extract demonstrated a superior antioxidant activity in plasma but this was replaced by the etheric extract by the end of the experiment. Of the 2 extracts, in the etheric exerted a superior antioxidant activity in both liver and plasma. The effectiveness of the extracts appears to be related to the biological material that is used (liver or plasma), furthermore to the duration of administration and the type of extract.
Unique block molecules based on glycerol skeleton as C‐3 building blocks for liquid crystals formation by self‐assembly and their future potential for the “nano‐chemistry”
Authors: Urata Kouichi
Published: September 2003

Studies on design of liquid crystalline block molecules with non‐conventional mesophase morphoplogies have been proposed by Tschierske and co‐workers. These block molecules have a rigid core, a lateral substituent, and an alkyl chain segmenting blocks from each other. Related to this, diglyceryl alkyl ethers found by us have glycerol as a rigid core, a lateral substituent, and an alkyl chain similar to the Tschierske design. These two cases are compared with each other with regard to the relationship between the molecular structure and the liquid crystalline morphologies and other properties. Recently, new soft materials suitable for liquid crystals exhibiting self‐assembly of phase‐segregated structures have been designed. Typical examples of such “block” molecules containing glycerol having a C‐3 building block include: (i) undecyl‐glycerylether‐ modified siloxane derivatives with a siloxane segment as the rigid core and alkyl chains with 2, 3‐dihydroxypropoxy group as a hydrophilic group at a lateral or terminal position of the siloxane segment; (ii) novel hyper branched dendrimers forming the basis of polyglycerol nanocapsules with a core‐shell molecular architecture; (iii) carbon nanotubes based on cyclodextrins (CDs); (iv) polymerizable amphiphilic diacetylene‐containing phospholipids suitable for construction of functional nanocomposites. This is done by self‐assembly and polymerization of diacetylene creating a “block molecular structure” with a polyacetylene chain as a rigid core segment, the lipid headgroups as the hydrophilic segment, and terminal flexible alkyl chains. On the basis of these results, future potential of block molecules as a soft building material for liquid crystalline structures was discussed.
Oxidative flavour deterioration of fish oil enriched milk
Authors: Let Mette B. , Jacobsen Charlotte , Frankel Edwin N. , Meyer Anne S.
Published: September 2003

The oxidative deterioration of milk emulsions supplemented with 1.5 wt‐% fish oil was investigated by sensory evaluation and by determining the peroxide value and volatile oxidation products after cold storage. Two types of milk emulsions were produced, one with a highly unsaturated tuna oil (38 wt‐% of n‐3 fatty acids) and one with cod liver oil (26 wt‐% of n‐3 fatty acids). The effect of added calcium disodium ethylenediaminetetraacetate (EDTA) on oxidation was also investigated. Emulsions based on cod liver oil with a slightly elevated peroxide value (1.5 meq/kg) oxidised significantly faster than the tuna oil emulsions, having a lower initial peroxide value (0.1 meq/kg). In the tuna oil emulsions the fishy off‐flavour could not be detected throughout the storage period. Addition of 5—50 ppm EDTA significantly reduced the development of volatile oxidation products in the cod liver oil emulsions, indicating that metal chelation with EDTA could inhibit the decomposition of lipid hydroperoxides in these emulsions. This study showed that an oxidatively stable milk emulsion containing highly polyunsaturated tuna fish oil could be prepared without significant fishy off‐flavour development upon storage, provided that the initial peroxide value was sufficiently low.
Determination and certification of the relative mass fractions of triglycerides and cholesterol in pure and adulterated butter oil
Authors: Zeleny Reinhard , Schimmel Heinz
Published: September 2003

Pure butter oil and adulterated butter oil (5% coconut oil added) were certified for the relative mass fractions of triglycerides C24‐C54 and cholesterol by employing a reference method defined in EC‐regulation 454/95 based on gas chromatographic separation of the triglycerides on packed or capillary columns. Four data sets each of packed‐column and capillary‐column methods were accepted and utilised to establish the certified values. Technical evaluation of the data revealed that calibration is a critical issue in terms of composition of the calibrant and possible precipitation. Recalculations of submitted data were carried out, which mainly involved linear interpolation to calculate the response factors of components not present in the calibrant. This procedure decreased the overall variation of results. Data derived from capillary‐column methods differing in column length, diameter, coating, and temperature program were found to be comparable to those obtained by the more uniform packed‐column methods as regards precision, repeatability, and obtained S‐values. The presented results shall provide a basis to further refine the existing reference method.
On‐line LC‐NMR‐MS characterization of sesame oil extracts and assessment of their antioxidant activity
Authors: Dachtler Markus , van de Put Frans H. M. , v. Stijn Frans , Beindorff Christiaan M. , Fritsche Jan
Published: September 2003

Sesame lignans were isolated by solvent extraction and subsequently purified by solvent crystallization from crude, unroasted sesame oil, and a sesame oil deodorizer distillate. In addition, an aliquot of the purified sesame oil extract was treated with camphorsulfonic acid to obtain a sesaminol‐enriched extract. The sesame lignan composition of the extracts was characterized by on‐line liquid chromatography nuclear magnetic resonance spectroscopy mass spectrometry coupling (LC‐NMR‐MS). The effect of the sesame oil extracts as well as pure sesame lignans and γ‐tocopherol on the oxidative stability of sunflower oil (lignan‐free) was studied by the Rancimat assay. The Rancimat assay revealed the following oxidative stability order: sesame oil extract < sesame oil deodorizer distillate < sunflower oil (no added sesame oil extracts) < sesamol < sesaminol‐enriched sesame oil extract. In addition, the radical‐scavenging capacity of these extracts was assessed by the Trolox® equivalent antioxidant capacity (TEAC) assay. The TEAC assay revealed a slightly different AOX activity order: sesamin < sesame oil extract < sesaminol‐enriched sesame oil extract < sesamol. In conclusion, the sesaminol‐enriched extract revealed strong antioxidant activity and is therefore suitable to increase the oxidative stability of edible oils high in polyunsaturated fatty acids.
3, 4‐Dihydroxymandelic acid amides of alkylamines as antioxidants for lipids
Authors: Ley Jakob P. , Bertram Heinz‐Jürgen
Published: September 2003

The antioxidative and radical scavenging activity of the 3, 4‐dihydroxymandelic acid (DHMA) amides of hexylamine, 2‐ethylhexylamine, octylamine, and cyclohexylamine was determined by several physicochemical test systems. The amides were synthesized by protecting group‐free coupling of in situ prepared N‐hydroxysuccinimidylester of DHMA and the amines. The radical scavenging activity was determined using the DPPH (2, 2‐diphenyl‐1‐picrylhydrazyl) method and by quenching superoxide anions generated using a horse radish peroxidase/H2O2 system. In the DPPH assay, all amides show higher radical scavenging activity (EC50 0.09‐0.12 mol/molDPPH) compared to the standard antioxidants ascorbic acid (EC50 0.27 mol/molDPPH) and tocopherol (EC50 0.25 mol/molDPPH). The amides are also more potent superoxide radical scavengers (IC50 < 600 nm) than standard ascorbic acid (IC50 700 nm). Activity against lipid peroxidation was determined by accelerated autoxidation of highly unsaturated oils and squalene using the Rancimat. Again, the antioxidative potentials of the DHMA amides against lipid oxidation as determined by the Rancimat, are at least equal or higher compared to the standard lipid antioxidants tocopherol, BHT, BHA, and ascorbylpalmitate (concentration in soybean oil 0.05%, all other oils 0.025%, squalene 0.005%). In squalene, an equi‐amount mixture of DHMA octylamide and α‐tocopherol shows a synergistic effect. Last but not least, the amides are able to protect an emulsion of linoleic acid/β‐carotene against oxidation initiated by N, N‐azodiisobutyramidine dihydrochloride (IC50 0.19‐0.77 mmol/l, ascorbic acid > 0.9, tocopherol 0.08). The DHMA octylamide in combination with ascorbic acid shows a synergistic antioxidative effect in the emulsion model. In conclusion, the new alkylamides of DHMA are easy to synthesize, potent radical scavengers and protect lipids, in particular the highly unsaturated, both in bulk and in emulsions against autoxidation.
Numeric Simulation of Ion‐Site Association Effects in Ion‐Selective Electrode Response
Authors: Mikhelson Konstantin N.
Published: September 2003

Effects in ion‐selective electrode response and selectivity, caused by ion‐site association in membranes are studied by means of numeric simulations based on a generalized model, which does not rely on a certain degree of the dissociation of electrolytes in membranes. The variability of the experimental values of the potentiometric selectivity coefficients is considered in view of the association in membranes. The reasons why the “dissociation approach” often fits experimental data are also discussed. A novel version of segmented sandwich membrane method is proposed for direct potentiometric measurements of ion‐site association constants in membranes, and preliminary experimental results are presented.
Highly Selective PVC‐Membrane Electrodes Based on Three Derivatives of (Tetraphenylporphyrinato)Cobalt(III) Acetate for Determination of Trace Amounts of Nitrite Ion
Authors: Shamsipur Mojtaba , Javanbakht Mehran , Hassaninejad Ali Reza , Sharghi Hashem , Ganjali Mohammah Reza , Mousavi Mir Fazlollah
Published: September 2003

Three different para‐substituted derivatives of (tetraphenylporphyrinato) cobalt(III) acetate were examined as suitable ionophores for the preparation of polymeric membrane (PME) and coated graphite (CGE) nitrite‐selective electrodes. The electrodes revealed a Nernstian behavior over very wide NO2− ion concentration ranges (1.0×10−6−1.0×10−1 M for the PME and 5.0×10−8−5.0×10−2 M for the CGE based on the p‐isopropyl derivative) and very low detection limits (8.0×10−7 M for the PME and 2.0×10−8 M for the CGE). The potentiometric response is independent of the pH of solution in the pH range 4.5–7.0. The electrodes manifest advantages of relative long lifetime, fast response and, most important, good selectivities relative to a wide variety of inorganic and organic anions. In fact the selectivity behavior and detection limit of the proposed NO2− ion‐selective electrodes show great improvements compared to the previously reported electrodes for nitrite ion. The proposed PMEs and CGEs can be used for at least 2 and 4 months, respectively, without any divergence in potentials. The electrodes were successfully applied to the determination of nitrite ion in different real samples such as sausage, milk, flour and cheese.
Spectral Imaging and Electrochemical Study on the Response Mechanism of Ionophore‐Based Polymeric Membrane Amperometric pH Sensors
Authors: Long Robert , Bakker Eric
Published: September 2003

The response features of amperometric ionophore‐based chemical sensors were evaluated in regular ion‐selective membranes, poly(vinyl chloride) plasticized with o‐nitrophenyl octyl ether, with a H+‐selective chromoionophore as model ionophore. Direct imaging experiments upon discrete applied voltage pulses revealed that the diffusion coefficients in such membranes are very similar to that found in membranes under zero current conditions, at about 10−8 cm2 s−1. In the potential range that defines the limiting current, it was found by these imaging experiments that the ionophore is saturated at the membrane surface, as expected. The observed concentration profiles could be well described with established diffusion theory. At more extreme potentials, the observed diffusion profiles were different, and could be explained by the extraction of additional, uncomplexed hydrogen ions into the membrane phase. The results were correlated to the amperometric response behavior of the same electrodes. At the limiting current, Cottrell fits were performed, and similar diffusion coefficients were found as in the imaging experiments. The pH‐dependent normal pulse voltammetric responses were analyzed in terms of their half wave potential, and found to show a Nernstian pH response, suggesting that they function in close analogy to their potentiometric counterparts. The breakdown of Nernstian pH response at low pH is explained by extraction of electrolyte into the membrane under these conditions, which renders the interface non‐polarizable and leads to loss of voltammetric features. The results adequately support the previously published response mechanism of such ionophore‐based amperometric sensors, including the origin of the limiting current, the capability of such membranes to be responsive to ion activities, the requirement of applying baseline potentials between pulses, and the reason for the altered selectivity at extreme potentials.
Copper Ion Selective Membrane Electrodes Based on Some Schiff Base Derivatives
Authors: Sadeghi S. , Eslahi M. , Naseri M. A. , Naeimi H. , Sharghi H. , Shameli A.
Published: September 2003

A series of Schiff base derivatives were studied to characterize their abilities as a copper ion carrier in PVC membrane electrodes. The electrode based on 2,2′‐[4,4′diphenyl‐methanebis(nitrilomethylidyne)]‐bisphenol exhibits a Nernstian response for copper ions over the activity range 8.0×10−6−1.0×10−1 mol L−1 with detection limit of about μ mol L−1 of copper ion in comparison with two other Schiff bases. The response time, pH effect and other characteristics of the electrodes were studied in a static mode. The effect of the methyl group substitute on Schiff base structure with SO2 bridging group in different positions with respect to OH group was studied. The results show that behavior of the electrodes is not considerably influenced by the position of methyl substitute. The selectivity coefficients were determined with modified fixed interference method (FIM) and matched potential method (MPM). The proposed electrodes comparatively show good selectivity with respect to alkali, alkaline earth and some transition metal ions. The electrodes were used for the determination of copper in black tea, multivitamin and mineral capsule and as an indicator electrode in potentiometric titration of copper ion.
Ion‐Partitioning Bulk Membrane CHEMFET as Highly Sensitive Calcium Probe
Authors: Moschou Elizabeth A. , Chaniotakis Nikolas A.
Published: September 2003

The development of a novel, highly sensitive calcium CHEMFET‐based sensor system is presented. The CHEMFET utilizes a bulk phase ion‐partitioning membrane as the chemical recognition element while the signal transduction is achieved via a pH‐ISFET. The ion‐partitioning membrane is doped with two different ionophores, one selective to calcium, and the other to protons. Calcium ions partitioned into the bulk of the membrane phase will displace protons of equal charge out of the membrane for electroneutrality reasons, and towards the pH‐ISFET's gate, generating the observed signal. It is shown that the increase of the calcium to proton carrier concentration ratio in the membrane phase, the use of a strong calcium ionophore, and a weak proton carrier contribute to the increase of the sensor sensitivity. The performance of the optimized Ca‐CHEMFET is evaluated by the successful determination of the free calcium ion activity in blood serum samples.
Modification of a Thin Gold Film with Boronic Acid Membrane and Its Application to a Saccharide Sensor Based on Surface Plasmon Resonance
Authors: Soh Nobuaki , Sonezaki Makoto , Imato Toshihiko
Published: September 2003

A study of the response behavior of saccharides to surface plasmon resonance (SPR) based sensor, in which a boronic acid membrane‐modified thin gold film was used as a sensor chip is described. The following three procedures were used in the modification of the sensor chip: first, 3‐aminophenylboronic acid (3‐APB) was coupled with 11‐mercaptoundecanoic acid to form a self‐assembled monolayer (SAM) on the gold film of the sensor chip, second, 3‐APB was immobilized on the sensor chip by electrochemical polymerization, and third, the sensor chip was coated with a vinyl polymer by the radical polymerization of vinylphenylboronic acid. SPR responses were measured in a flow system, where the above three types of sensor chip were assembled in the flow cell of the SPR sensor. The SPR responses caused by the interaction between the boronic acid membrane modified on the sensor chip and saccharides were evaluated by measurement of an angle shift of the SPR sensor. A weak response was observed for the SPR sensor using the sensor chip modified with SAM and the electropolymerized membrane, while the sensor chip modified with the vinylboronic acid polymer membrane showed a selective and enhanced response to saccharides. From the SPR response for the latter sensor, the findings indicate that the interaction between the boronic acid membrane on the sensor chip and the saccharides was in the order glucose<mannose<galactose<fructose. Namely, the interaction between the boronic acid and cis‐diol moiety in the saccharides appears to be stronger in the order 2,3‐cis‐diol<3,4‐cis‐diol<1,2‐cis‐diol. The adsorption behavior of sorbose to the sensor chip modified with the boronic acid polymer membrane followed the Freundlich‐type adsorption isotherm. The electrochemical polymerization of 3‐APB on the gold film of the SPR sensor chip was monitored in situ by combining an SPR system with an electrochemical analyzer system.
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

Carbonate 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

Chemically 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

The 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

We 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

The 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

Ion‐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

Different 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

Calix[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

Ion‐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

As 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

A 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

The 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

A 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

The 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

Different 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

The 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

A 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.