Showing papers in "Analytical Letters in 2007"
TL;DR: Carbon and its derivatives, as the high performance material, occupy a special place in electrochemistry due to its "in many ways, extreme properties" as mentioned in this paper, and the possibilities of carbon-based electrodes in electroanalytical investigation in pharmaceutical dosage forms and biological samples using modern electrochemical techniques.
Abstract: Carbon and its derivatives, as the high performance material, occupy a special place in electrochemistry due to its ‐in many ways‐ extreme properties. Recent trends and advances in the electrochemistry of carbon‐based electrodes are reviewed. The varieties of carbon‐based electrodes, their basic physicochemical properties and some characteristics are surveyed. Special attention is paid to the possibilities of carbon‐based electrodes in electroanalytical investigation in pharmaceutical dosage forms and biological samples using modern electrochemical techniques. This review includes a summary of the rules that must be considered for drug analysis from its dosage forms and biological samples using carbon‐based electrodes. The present review is the first comprehensive report on the heterogeneous and homogeneous carbon electrodes, and an addition to many excellent reviews on carbon electrodes in the literature. This review summarizes some of the recent developments and applications of carbon‐based ele...
158 citations
TL;DR: In this article, a review describes some new approaches of biomolecule immobilization and transduction of biological processes in the field of biosensors based on electrogenerated polymers.
Abstract: This review describes some new approaches of biomolecule immobilization and transduction of biological processes in the field of biosensors based on electrogenerated polymers. These recent advances were classified according to the nature of the conventional immobilization procedure involved, namely adsorption onto electropolymerized films, entrapment during the electropolymerization process, covalent binding on electrogenerated polymers, and anchoring by affinity interactions between biomolecules and polymers.
86 citations
TL;DR: In this article, a review of biosensors based on nanostructured material is presented, focusing on alignment, uniform dispersion, selective growth, and diameter control parameters that are critical to the successful integration of nanostructure into sensors and devices.
Abstract: Nanostructures such as nanotubes (NTs), nanowires (NWs), and nanoparticles present new opportunities as sensing platforms for biological and environmental applications. Having micrometer‐scale lengths and nanometer‐scale diameters, NTs and NWs can be manipulated with current microfabrication, as well as self‐assembly techniques to fabricate nanoscale devices and sensors. Alignment, uniform dispersion, selective growth, and diameter control are parameters that are critical to the successful integration of nanostructures into sensors and devices. Overcoming these challenges should lead to sensors with better selectivity, sensitivity, and longer operational lifetime. This review discusses biosensors based on nanostructured material.
84 citations
TL;DR: The optical properties of quantum dots have made them attractive materials in diverse fields of application as discussed by the authors, such as sensing, diagnosis, imaging, and optical tracking, and the mechanisms behind these various responses are not yet all fully understood.
Abstract: The optical properties of quantum dots (QDs) have made them attractive materials in diverse fields of application. Since water‐soluble derivatives were obtained, quantum dots have attracted intensive research interest in sensing, diagnosis, imaging, and optical tracking. The analytes that have been targeted span ions, small chemical molecules, proteins, nucleic acids, and cells. The fluorescence of functionalized QDs can be quenched, enhanced, or even ‘switch’ on and off in different cases. However, the mechanisms behind these various responses are not yet all fully understood. This review gives an overview of the emerging use of QDs in analysis. Typical examples, in particular in relation to the discussion on mechanisms are highlighted.
66 citations
TL;DR: In this article, some heavy metal uptake in mushroom species, their metal content in soil substrate, and the relation in between metal concentration in mushroom and soil were investigated, which indicated that in general, heavy metal contents in all mushroom species were lower than the underlying soil substrates except for some mushroom species.
Abstract: In this study some heavy metal uptake in mushroom species, their metal content in soil substrate and the relation in between metal concentration in mushroom and soil were investigated. Mushroom species and soil in which mushroom species were grown were collected from Tokat region of Turkey. Six different mushroom species and their underlying soil (0–10 cm layer) samples were analyzed for some heavy metals (Cu, Pb, Fe, Zn, Cd, Mn, Ni, Cr and Co). The analysis was performed with an atomic absorption spectrometer. The results indicate that in general, heavy metal contents in all mushroom species were lower than the underlying soil substrates except for some mushroom species. The results obtained from the analyses of mushroom and underlying soil samples were evaluated using linear correlation analysis and concentration factors to identify the metal accumulation of mushrooms.
59 citations
TL;DR: In this article, a modified carbon paste electrode with chitosan was used for the determination of Hg(II) ions in water using anodic stripping voltammetry.
Abstract: This paper describes the preparation and electrochemical application of a modified carbon paste electrode with chitosan for the determination of Hg(II) ions in water using anodic stripping voltammetry. Experimental parameters, including the pH of the supporting electrolyte, time and potential of accumulation and scan rate were investigated. The best voltammetric response was observed for a paste composition of 60% (m/m) of graphite powder, 20% (m/m) of chitosan and 20% (m/m) of mineral oil, with 0.1 mol/l NaNO3 solution at pH 6.3 as supporting electrolyte, a preconcentration potential of −0.2 V, preconcentration time of 270 s and a scan rate of 25 mV/s. Under these optimal experimental conditions, the voltammetric signals were linearly dependent on the Hg(II) concentration in the range of 9.99×10−7 to 3.85×10−5 mol/l with a detection limit of 6.28×10−7 mol/l. Three “spiked” samples of water were evaluated using the proposed sensor, and results agreed with those obtained by a reference method at ...
54 citations
TL;DR: In this paper, a mini-review discusses the analytical technique of gas chromatography-mass spectrometry (GC•MS), specifically basic principles and instrumentations. The applications of GC•MS to a number of studies for determining organic compounds from around the world are presented and highlight its universal use and acceptance.
Abstract: This mini‐review discusses the analytical technique of gas chromatography‐mass spectrometry (GC‐MS), specifically basic principles and instrumentations. The applications of GC‐MS to a number of studies for determining organic compounds from around the world are presented and highlight its universal use and acceptance. Selected applications show that GC‐MS is an integral and complimentary part of many field studies involving organic compound detection and determination.
53 citations
TL;DR: In this article, a simple HPLC method with UV detection for the identification of the acetylcholinesterase reactivator -HI•6 is described, and two salts of HI•6 (dichloride and dimethanesulfonate) are tested.
Abstract: Description of the simple HPLC method with UV detection for the identification of the acetylcholinesterase reactivator–HI‐6 is described. Two salts of HI‐6 (dichloride and dimethanesulfonate) were tested. Using this method 0.5 µM LOD was determined. Our method could be used in future as standard method for the evaluation of HI‐6 stability and purity.
50 citations
TL;DR: A general view of the electroanalytical applications of metal-salen complexes is discussed in this article, where a brief history of the synthesis and reactivity of metal−salen complex is presented.
Abstract: A general view of the electroanalytical applications of metal‐salen complexes is discussed in this review. The family of Schiff bases derived from ethylenediamine and ortho‐phenolic aldehydes (N,N′‐ethylenebis(salicylideneiminato)—salen) and their complexes of various transition metals, such as Al, Ce, Co, Cu, Cr, Fe, Ga, Hg, Mn, Mo, Ni, and V have been used in many fields of chemical research for a wide range of applications such as catalysts for the oxygenation of organic molecules, epoxidation of alkenes, oxidation of hydrocarbons and many other catalyzed reactions; as electrocatalyst for novel sensors development; and mimicking the catalytic functions of enzymes. A brief history of the synthesis and reactivity of metal‐salen complexes will be presented. The potentialities and possibilities of metal‐Salen complexes modified electrodes in the development of electrochemical sensors as well as other types of sensors, their construction and methods of fabrication, and the potential application of ...
49 citations
TL;DR: The application of QD fluorophores facilitates multiplex assays and therefore can contribute to enhanced throughput in biomonitoring.
Abstract: The application of quantum dots (QDs) as labels in immunoassay microarrays for the multiplex detection of 3-phenoxybenzoic acid (PBA) and atrazine-mercapturate (AM) has been demonstrated. PBA and AM are biomarkers of exposure to the pyrethroid insecticides and to the herbicide atrazine, respectively. Microarrays were fabricated by microcontact printing of the coating antigens in line patterns onto glass substrates. Competitive immunoassays were successfully performed using QDs (QD560 and QD620) as reporters. The multiplexed immunoassays were characterized by fluorescence microscopy and SEM. The application of QD fluorophores facilitates multiplex assays and therefore can contribute to enhanced throughput in biomonitoring.
43 citations
TL;DR: A noninvasive bioelectrical impedance assay referred to as electric cell–substrate impedance sensing (ECIS) was applied in order to monitor the apoptosis‐induced changes in human colon cancer HT‐29 cell shape in an integral and quantitative fashion with a time resolution on the order of minutes.
Abstract: Physiological cell death occurs primarily through an evolutionarily conserved form of cell suicide termed apoptosis, which may be triggered by cytokines, depletion of growth factors, or certain chemicals. It is morphologically characterized by severe alterations in cell shape like cell shrinkage and disintegration of cell–cell contacts. Aspirin and other nonsteroidal anti‐inflammatory drugs (NSAIDs) inhibit proliferation of human colon cancer cells in vitro. We applied a noninvasive bioelectrical impedance assay referred to as electric cell–substrate impedance sensing (ECIS) in order to monitor the apoptosis‐induced changes in human colon cancer HT‐29 cell shape in an integral and quantitative fashion with a time resolution on the order of minutes. In whole‐cell biosensors the cells are grown directly on the surface of small gold‐film electrodes. From readings of the electrical impedance of the cell‐covered electrode, we deduced alterations of aspirin on HT‐29 cells in cell–cell and cell–substrat...
TL;DR: In this paper, an original highly selective and sensitive PVC membrane sensor, working as a Fe(III) ion selective electrode and using 4.5% AMMTO as an ionophore, has been developed.
Abstract: An original highly selective and sensitive PVC membrane sensor, working as a Fe(III) ion selective electrode and using 4‐amino‐6‐methyl‐3‐methylmercapto‐1,2,4‐triazin‐5‐one (AMMTO) as an ionophore, has been developed. This cetain sensor demonstrated the following performance; a linear dynamic range between 1.0×10−6 and 1.0×10−1 M with a near Nernstian slope of 19.4±0.5 mV per decade; a detection limit of 6.8×10−7 M; characteristically, the best performance was obtained with a membrane composition of 30% poly(vinyl chloride), 65.5% nitrophenyl octyl ether, 2% sodium tetraphenyl borate and 2.5% AMMTO. Furthermore, the potentiometric response of the developed electrode is independent of the solution pH in the range of 2.2–4.8. The sensor possesses the advantages of short conditioning time, fast response time (<15 s) and, especially, great selectivity towards transition and heavy metal ions and some mono, di‐ and trivalent cations. The electrode can be used for at least 9 weeks without any considerab...
TL;DR: In this paper, a matrix-assisted laser desorption ionization/time-of-flight mass spectrometry (M+H)+ ionization was used for ammelide and ammeline under positive ion conditions with sinapinic acid as the matrix.
Abstract: Melamine, cyanuric acid, two compounds connected to tainted pet food, and related analogs have been analyzed using matrix‐assisted laser desorption ionization/time‐of‐flight mass spectrometry. (M+H)+ ions were observed for ammelide and ammeline under positive ion conditions with sinapinic acid as the matrix. With alpha‐cyano‐4‐hydroxy‐cinnamic acid as the matrix, a matrix‐melamine complex was observed; however, no complex was observed with sinapinic acid as the matrix. (M−H)− was observed for cyanuric acid with sinapinic acid as the matrix.
TL;DR: A piezoelectric immunosensor based on a competitive format was developed for determination of ochratoxin A (OTA) concentration as mentioned in this paper, which exhibited a working range of 50-1000 ng/mL and a detection limit of 16.1 ǫ n/mL.
Abstract: A piezoelectric immunosensor based on a competitive format was developed for determination of ochratoxin A (OTA) concentration. Surface modifications via two self‐assembled monolayers (SAMs) were investigated respectively and a better result was obtained with the SAM of 16‐mercaptohexadecanoic acid (16‐MHDA). The quartz crystal microbalance (QCM)‐based immunosensor was fabricated by immobilizing anti‐OTA antibodies onto the surface of the 16‐MHDA‐modified electrode, and allowing competition between free OTA and that conjugated with BSA to occur. The assay exhibited a working range of 50–1000 ng/mL and a detection limit of 16.1 ng/mL. Studies of interference and matrix effects were performed to evaluate the feasibility of the developed immunosensor for the direct analysis of OTA in real samples. Recoveries were conducted at 50, 200, and 1000 ng/g and were determined to be in the range of 142%–76%. The OTA assay is specific. No cross‐reactivates were observed with citrinin.
TL;DR: In this article, a new sorbent was characterized using a variety of physical chemistry techniques including, high resolution solid state 13C and 29Si CP/MAS NMR, X-ray photoelectron spectroscopy (XPS), thermal analysis (TGA and DTA), elemental analysis, and BET surface analysis as well as infrared spectroglobalization (FTIR).
Abstract: Silica gel was modified by thiosalicylic acid via homogeneous routes to obtain immobilized silica gel sorbent (TSA‐immobilized silica gel). This new sorbent was characterized using variety of physical chemistry techniques including, high resolution solid state 13C and 29Si CP/MAS NMR, X‐ray photoelectron spectroscopy (XPS), thermal analysis (TGA and DTA), elemental analysis, and BET surface analysis as well as infrared spectroscopy (FTIR). New support was used for the selective extraction and concentration of lead ions by silica gel modified with thiosalicylic acid, as a highly selective and stable reagent, from aquatic samples and its determination with FAAS. Lead ions can be desorbed with 4 mol dm−3 HNO3. The sorption capacity for lead ions are found in the range of 64.40 to 69.90 µmol g−1 of chelating matrix. Tolerance limits for electrolytes and some trace metals in the sorption of lead is reported. Preconcentration factor was found as 150 for Pb(II). The lead in drinking water, mineral water...
TL;DR: In this paper, the ultrafine and highly dispersed platinum nanoparticles (average size 3 nm) were used for the construction of a glucose biosensor in a simple method and an excellent response to glucose has been obtained with a high sensitivity (137.7 mu A mM(-1) cm(-2)) and fast response time (5 s).
Abstract: In the present paper the ultrafine and highly dispersed platinum nanoparticles ( average size 3 nm) were used for the construction of a glucose biosensor in a simple method. An excellent response to glucose has been obtained with a high sensitivity (137.7 mu A mM(-1) cm(-2)) and fast response time (5 s). The biosensor showed a detection limit of 5 mM (at the ratio of signal to noise, S/ N = 3) and a linear range form 0.2 to 3.2 mM with a correlation coefficient r = 0.999. The apparent Michaelis - Menten constant (k(m)) and the maximum current were estimated to be 9.36 and 1.507 mA mM(-1) cm(-2), respectively. In addition, effects of pH value, applied potential and the interferents on the amperometric response of the sensor were investigated and discussed.
TL;DR: A surface plasmon resonance (SPR) •immunosensor based on nano-size gold hollow ball (GHB) with dendritic surface has been developed for detection of Ochratoxin A (OTA) as discussed by the authors.
Abstract: A surface plasmon resonance (SPR)‐immunosensor based on nano‐size gold hollow ball (GHB) with dendritic surface has been developed for detection of Ochratoxin A (OTA). A thionine thin film was initially electropolymerized onto the SPR‐probe surface, and then anti‐OTA monoclonal antibody (anti‐OTA) was immobilized onto the SPR‐probe surface by means of GHB conjugation. The binding of target molecules onto the immobilized antibodies causes an increase in the resonant angle of the sensor chip, and the resonant angle shift was proportional to the OTA concentration in the range of 0.05–7.5 ng/ml with a detection limit of 0.01 ng/ml at a signal/noise ration of 3. A glycine‐HCl solution (pH 2.8) was used to release antigen‐antibody complexes from the biorecognition surface. Good reusability was exhibited. Moreover, spiking various levels of OTA into three milk samples was assayed using the proposed immunoassay. Analytical results show the precision of the developed immunoassay is acceptable. Compared wi...
TL;DR: In this paper, the mechanism of the electrochemical oxidation of Coumaric acid on a glassy carbon electrode was investigated using cyclic, differential pulse, and square wave voltammetry at different pHs.
Abstract: The mechanism of the electrochemical oxidation of p‐coumaric acid on a glassy carbon electrode was investigated using cyclic, differential pulse, and square wave voltammetry at different pHs. The oxidation of p‐coumaric acid is irreversible over the whole pH range. After successive scans, the p‐coumaric acid oxidation product deposits on the electrode surface, forming a polymeric film that undergoes reversible oxidation at a lower potential than p‐coumaric acid. This polymeric film increases in thickness with the number of scans, covering the electrode surface, and impeding the diffusion of the p‐coumaric acid and its oxidation on the electrode. The oxidation of p‐coumaric acid is pH dependent up until values close to the pKa. For pHs higher than pKa, the p‐coumaric acid oxidation process is pH independent. An electroanalytical determination procedure of p‐coumaric in pH 8.7 0.2 M ammonium buffer was developed, and a detection limit, LOD=83 nM, and the limit of quantification, LOQ=250 nM, were ob...
TL;DR: In this article, the authors developed a miniaturized optical ratiometric ethanol sensor to be used for in situ measurements, which is based on the fluorescent dye Nile Blue Chloride.
Abstract: The need for low‐cost, robust alcohol sensors has increased with the renewed interest in alternative fuels as well as high‐throughput screening of biological processes involving the production of ethanol. The goal of this research was to develop a miniaturized optical ratiometric ethanol sensor to be used for in situ measurements. The sensor is based on the fluorescent dye Nile Blue Chloride. When in solution, the dye exhibits a single fluorescence peak. However, a dual emission peak is observed upon physical immobilization of the dye in the hydrogel poly(ethylene glycol) dimethacrylate. The dual emission allows for ratiometric measurements, thus circumventing drawbacks associated with fluorescence intensity measurements such as signal variations due to dye bleaching, source intensity fluctuations, etc. In developing this sensor we investigated ethanol sensitivity; alcohol selectivity; response time; and cross‐sensitivity with pH, polarity, and ionic strength. We found that the sensor is sensitiv...
TL;DR: In this article, the authors used a gradient elution to identify nine biologically active phenolic constituents: catechin; epicatechin; trans− and cis−reserve. But, their method was not suitable for the analysis of red wine.
Abstract: Ten samples of commercially Italian red wines were analyzed in order to determine the phenolic content. Variations in wine types are largely due to differences in concentration and composition of these compounds. Polyphenolic compounds are a large and complex group of substances which constitute one of the most important quality parameters of wine. These constituents of red wine contribute to organoleptic characteristics and to antioxidant and anti‐inflammatory properties. Moderate wine consumption is associated with several beneficial physiological effects, which include anticancer activities, inhibition of platelet aggregation, and inhibition of LDL oxidation which constitutes the initial stage of the pathogenesis of arteriosclerosis. For the analysis, reversed‐phase high performance liquid chromatography (HPLC) method coupled with UV‐Vis detection was used. The method uses a gradient elution to identify nine biologically active phenolic constituents: catechin; epicatechin; trans‐ and cis‐resve...
TL;DR: In this paper, an adsorptive cathodic stripping voltammetric method using a hanging mercury drop electrode (HMDE) was described in order to determine the ultra trace of lead ions with carbidopa in different real samples.
Abstract: In the present work, an adsorptive cathodic stripping voltammetric method using a hanging mercury drop electrode (HMDE) was described in order to determine the ultra trace of lead ions with carbidopa in different real samples. The method is based on accumulation of lead metal ion on mercury electrode using carbidopa as a suitable complexing agent. The potential was scanned to the negative direction and the differential pulse stripping voltammograms were recorded. The instrumental and chemical parameters were optimized. The optimized conditions were obtained in pH of 8.4, carbidopa amount of 1.0×10−6 M, accumulation potential of 0. 0 V, accumulation time of 100 s, scan rate of 100 mV/s and pulse height of 50 mV. The relationship between the peak current versus concentration was linear over the range of 2.4×10−10–4.8×10−7 M. The limits of detection were 5.8×10−11 M and the relative standard deviation at 4.8×10−10, 2.1×10−8, and 2.4×10−7 M of lead ion were obtained 3.2, 2.9, and 2.7%, respectively (...
TL;DR: In this paper, the fast Fourier transform continuous cyclic voltammetry (FFCV) was applied for the very fast monitoring of thiamine in its pharmaceutical formulations, which is very simple, precise, accurate, time-saving and economical compared to all previous reported methods.
Abstract: In this work, a highly sensitive method for the fast monitoring of thiamine hydrocholoride in flow‐injection systems has been developed. The fast Fourier transform continuous cyclic voltammetry (FFCV) in flowing solution as a detection system was applied for the very fast monitoring of thiamine in its pharmaceutical formulations. This technique is very simple, precise, accurate, time‐saving and economical, compared to all previous reported methods. The effects of various parameters on the sensitivity of the detection system were considered. The best condition was obtained within the pH value of 2, and scan rate value of 25 V s−1, accumulation potential of −400 mV, and accumulation time of 0.6 s. The proposed method has some advantages over other reported methods such as, there is no need for the removal of oxygen from the test solution, has a sub‐nanomolar detection limit, and finally the method is fast enough for the determination of any such compound, in a wide variety of chromatographic method...
TL;DR: In this article, the authors highlight two aspects of ionic liquids that to date have either no or limited studies: (1) exploitation of unique features of ionics to develop novel spectroscopic methods and (2) development of novel Spectroscopic Methods, for the sensitive and accurate determination of thermal physical properties.
Abstract: In this mini-review we highlight two aspects of ionic liquids that to date have either no or limited studies. They are (1) exploitation of unique features of ionic liquids to develop novel spectroscopic methods and (2) development of novel spectroscopic methods, for the sensitive and accurate determination of thermal physical properties of ionic liquids. In the first category, we will describe several novel methods which were developed utilizing unique properties of ionic liquids for measurements which are not possible otherwise. They include the sensitive and accurate method to determine enantiomeric compositions of a variety of pharmaceutical products with different size, shape, and functional groups. This method is based on the use of a chiral IL which serves both as a solvent and also as a chiral selector. Ionic liquids have also been successfully used to substantially enhance the sensitivity of thermal lens measurements. In the second category, we will describe recent development in which transient grating technique and thermal lens technique have been successfully used for the sensitive, accurate, nondestructive determination of thermal physical prop- erties of ILs.
TL;DR: In this paper, a method for the determination of piroxicam in flow-injection systems has been developed, which is very simple, precise, accurate, time saving, and economical compared to all of the previously reported methods.
Abstract: In this work a novel method for the determination of piroxicam in flow‐injection systems has been developed. A system using fast Fourier transform continuous cyclic voltammetry (FFTCV), at a gold microelectrode in flowing solution, was used for determining piroxicam in its pharmaceutical formulations. The developed technique is very simple, precise, accurate, time saving, and economical, compared to all of the previously reported methods. The effects of various parameters on the sensitivity of the method were investigated. The best performance was obtained with a pH value of 2, scan rate value of 40 V/s, accumulation potential of (400) mV, and accumulation time of 0.4 s. The proposed method has some advantages over other reported methods, such as, no need for the removal of oxygen from the test solution, a picomolar detection limit, and finally that the method is fast enough for the determination of any such compound, in a wide variety of chromatographic methods. To obtain a sensitive determinati...
TL;DR: The proposed DPP method was applied to commercial tablets and average percentage recovery was in agreement with that obtained by spectrophotometric comparison method, and was extended to the in vitro determination of moxifloxacin in spiked human serum and urine.
Abstract: A simple, fast, sensitive and fully validated differential pulse polarographic (DPP) method for the determination of trace amounts of moxifloxacin in pharmaceutics, serum and urine is reported. Moxifloxacin exhibited irreversible cathodic peak over the pH 5.00–11.00 in Britton–Robinson (B–R) buffer. At pH 10.00 (the analytical pH), a well‐defined peak at −1.61 V versus saturated calomel electrode was obtained. The current has been characterized as being diffusion‐controlled process. The diffusion current constant (id) was 1.48±0.12 and the current–concentration plot was rectilinear over the range from 5×10−7 to 1×10−4 M with correlation coefficient (n=10) of 0.995. The proposed method was applied to commercial tablets and average percentage recovery was in agreement with that obtained by spectrophotometric comparison method. The method was extended to the in vitro determination of moxifloxacin in spiked human serum and urine.
TL;DR: In this paper, a reproducible solid phase microextraction (SPME) coating was prepared on the surface of silanized silica fibers by molecularly imprinted polymerization using prometryn as template molecule.
Abstract: A novel reproducible solid‐phase microextraction (SPME) coating was prepared on the surface of silanized silica fibers by molecularly imprinted polymerization using prometryn as template molecule. The structure and extraction performance of molecularly imprinted polymer (MIP) coating was studied with the scanning electron microscope and high performance liquid chromatography (HPLC). Specific selectivity was found with the prometryn MIP‐coated fiber to prometry and its structural analogues such as atrazine, simetryn, terbutylazin, ametryn, propazine and terbutryn. In contrast, these triazines could not be selectively extracted by the non‐imprinted polymer fiber or commercial polydimethylsiloxane (PDMS), polydimethylsiloxane/divinylbenzene (PDMS/DVB), polyacrylate (PA) fibers.
TL;DR: In this paper, a highly selective and sensitive lutetium(III) microelectrode was introduced, for the first time, which was used as a membrane-active component to prepare a highly sensitive Lu(III)-selective polymeric membrane micro electrode.
Abstract: In this work, for the first time, we introduce a highly selective and sensitive lutetium(III) micro‐sensor. N‐(2‐furylmethylene) pyridine‐2,6‐diamine (FPD) was used as a membrane‐active component to prepare a highly sensitive Lu(III)‐selective polymeric membrane microelectrode. Theoretical calculations for FPD, lutetium and some other metal ions were carried out and selectivity toward Lu(III) ions was confirmed. The best performance was achieved by a membrane composed of 32% PVC, 60% o‐nitrophenyloctyl ether, 4% potassium tetrakis (p‐chlorophenyl) borate (KTpClPB) and 4% FPD. The electrode exhibits a Nernstian response for Lu(III) ions over a particular concentration range (1.0×l0−11−1.0×10−6 mol l−1) with a slope of 20.5±0.2 mV decade−1. The detection limit is 3.0×10−11 mol l−1 while the sensor presents a response time of <10 s and a useful working pH range of 4.0–10.5. As a matter of fact, the proposed sensor discriminates relatively well for Lu(III) ions in compare to common alkali, alkaline e...
TL;DR: In this paper, direct electrochemistry of alpha-lipoic acid (ALA) was performed at a glassy carbon electrode using cyclic, differential pulse and square wave voltammetry over a wide range of pH.
Abstract: Direct electrochemistry of alpha‐lipoic acid (ALA) was performed at a glassy carbon electrode using cyclic, differential pulse and square wave voltammetry over a wide range of pH. The oxidation of ALA is an irreversible process, pH independent, and involves the charge transfer of one electron. The diffusion coefficient of ALA was calculated from the results obtained at pH 6.9 in 0.1 M phosphate buffer and was shown to be D 0=1.1×10−5 cm2 s−1. The limits of detection (LOD) and quantification (LOQ) calculated from the results obtained at this pH are 1.8 and 6.1 µM, respectively. The lipoic acid content in two dietary supplements samples, a syrup containing ALA and capsules of ALA, has been determined directly at the glassy carbon electrode by differential pulse voltammetry using the standard addition method.
TL;DR: In this paper, a square wave adorptive stripping voltammetry (SWAdSV) and flow-injection analysis with square wave adsorptive-stripping voltammetric detection (FIA•SWAdsV) were developed for the determination of fluoxetine (FXT).
Abstract: Electroanalytical methods based on square‐wave adsorptive‐stripping voltammetry (SWAdSV) and flow‐injection analysis with square‐wave adsorptive‐stripping voltammetric detection (FIA‐SWAdSV) were developed for the determination of fluoxetine (FXT). The methods were based on the reduction of FXT at a mercury drop electrode at −1.2 V versus Ag/AgCl, in a phosphate buffer of pH 12.0, and on the possibility of accumulating the compound at the electrode surface. The SWAdSV method was successfully applied in the quantification of FXT in pharmaceutical products, human serum samples, and in drug dissolution studies. Because the presence of dissolved oxygen did not interfere significantly with the analysis, it was possible to quantify FXT in several pharmaceutical products using FIA‐SWAdSV. This method enables analysis of up to 120 samples per hour at reduced costs.
TL;DR: In this paper, the authors presented methods for detection of aflatoxin B1 and type-A trichothecenes, based on the use of indirect competitive ELISA format coupled with a 96-well screen-printed microplate.
Abstract: In this work are presented methods for detection of aflatoxin B1 and type‐A trichothecenes, based on the use of indirect competitive ELISA format coupled with a 96‐well screen‐printed microplate. Electrochemical immunoassays for AFB1, T‐2, and HT‐2 were performed and the activity of the alkaline phosphatase or horseradish peroxidase labeled enzymes were measured using intermittent pulse amperometry (IPA) as electrochemical technique. Using standard solutions of the target analyte the LOD of the assays were 0.3 and 0.2 ng ml−1 for T‐2 and AFB1 respectively, while the sensitivity was 1.2 ng ml−1 for both. For Aflatoxin B1, a stability study of electrochemical plate was also performed. Moreover, the matrix effect was evaluated using two different extraction treatments from corn.