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Analytica Chimica Acta (v.762, #)
A tutorial on the application of ion-selective electrode potentiometry: An analytical method with unique qualities, unexplored opportunities and potential pitfalls; Tutorial by Ernő Lindner; Bradford D. Pendley (pp. 1-13).
Display Omitted► Electrochemical cells for potentiometric measurement. ► Characterization of potentiometric electrodes. ► Measurement of ion activities and concentrations with potentiometric electrodes. ► Analysis of real samples: The role of the selectivity coefficient. ► Methods to evaluate the agreement between two methods.Ion-selective potentiometry enjoys practical utility as a simple analytical technique to measure ionic constituents in complex samples. Advances in the field have improved the selectivity and decreased the detection limit of ion-selective electrodes (ISEs) by orders of magnitude such that trace analysis in micro and nanomolar concentrations is now possible with potentiometric sensors. This tutorial reviews the fundamental principles of ion-selective potentiometry, describes the practical considerations involved in the use of these sensors to measure real samples, and discusses the statistical evaluation of experimental results compared with alternative analytical techniques.
Keywords: Ion-selective electrodes; Application of potentiometry; Sources of errors; Method comparison
A review on determination of steroids in biological samples exploiting nanobio-electroanalytical methods by Saurabh K. Yadav; Pranjal Chandra; Rajendra N. Goyal; Yoon-Bo Shim (pp. 14-24).
Display Omitted► Review article on steroids determination from 2009 to present. ► Nanomaterial, molecular imprinting polymer modified and immunosensors are discussed. ► Detection limit is similar to chromatographic techniques for many steroids. ► Future prospects using nanoconducting polymer modified sensor and microchips suggested.The applications of nanomaterial modified sensors, molecularly imprinting polymer based, aptamer based, and immunosensors have been described in the determination of steroids using electroanalytical techniques. After a brief description of the steroids and assays in biological fluids, the principles of electrochemical detection with the advantages and the limitations of the various sensors are presented. The nanomaterial modified sensors catalyze the oxidation/reduction of steroids and are suitable for sensing them in environmental samples and biological fluids. The determination of steroids based on their reduction has been found more useful in comparison to oxidation as the common metabolites present in the biological fluids do not undergo reduction in the usual potential window and hence, do not interfere in the determination. The sensors based on immunosensors and aptamers were found more sensitive and selective for steroid determination. Conducting polymer modified bio-sensors and microchip devices are suggested as possible future prospects for the ultra sensitive and simultaneous determination of steroids and their metabolites in various samples.
Keywords: Steroids; Doping; Carbon nanotubes; Immunosensors; Electrochemical sensors
Application of Multivariate Curve Resolution Alternating Least Squares (MCR-ALS) to remote sensing hyperspectral imaging by Xin Zhang; Romà Tauler (pp. 25-38).
This article summarizes the use of the MCR-ALS method as a powerful tool for the resolution of hyperspectral images on their constituents. Non-negativity, spectral normalization and local rank constraints are used to get physical meaningful resolution results and decrease rotation ambiguities. MCR-BANDS method is used to evaluate the presence and extend of rotational ambiguities.Display Omitted► MCR-ALS is successfully applied to remote sensing hyperspectral images. ► Pure spectra and relative concentrations of image constituents were obtained. ► MCA-ALS results are favorably compared to results obtained by MVSA and VCA methods. ► Physical constraints were implemented to decrease the rotational ambiguities. ► MCR-BANDS is used to evaluate the presence and extent of rotational ambiguities.The application of the MCR-ALS method is demonstrated on two simulated remote sensing spectroscopic images and on one experimental reference remote sensing spectroscopic image obtained by the Airborn Visible/Infrared Imaging Spectrometer (AVIRIS). By application of MCR-ALS, the spectra signatures of the pure constituents present in the image and their concentration distribution at a pixel level are estimated. Results obtained by MCR-ALS are compared to those obtained by other methods frequently used in the remote sensing spectroscopic imaging field like VCA and MVSA. In the case of the analysis of the experimental data set, the resolved pure spectra signatures were compared to reference spectra from USGS library for their identification. In all cases, results were also evaluated for the presence of rotational ambiguities using the MCR-BANDS method. The obtained results confirmed that the MCR-ALS method can be successfully used for remote sensing hyperspectral image resolution purposes. However, the amount of rotation ambiguity still present in the solutions obtained by this and other resolution methods (like VCA or MVSA) can still be large and it should be evaluated with care, trying to reduce its effects by selecting the more appropriate constraints. Only in this way it is possible to increase the reliability of the solutions provided by these methods and decrease the uncertainties associated to their use.
Keywords: Multivariate Curve Resolution; Remote sensing hyperspectral imaging; MCR-ALS; MVSA; VCA; Endmember
Voltammetry coupled to mass spectrometry in the presence of isotope18O labeled water for the prediction of oxidative transformation pathways of activated aromatic ethers: Acebutolol by Ugo Bussy; Illa Tea; Véronique Ferchaud-Roucher; Michel Krempf; Virginie Silvestre; Nicolas Galland; Denis Jacquemin; Moa Andresen-Bergström; Ulrik Jurva; Mohammed Boujtita (pp. 39-46).
.Display Omitted► Voltammetry coupled to mass spectrometry method as a useful tool for on-line predictions of electrochemical transformations. ► Evidence of the O-dealkoxylation reaction pathway of acebutolol in the presence of labeled water. ► New approach for on line EC-MS applications.The coupling between an electrochemical cell (EC) and a mass spectrometer (MS) is a useful screening tool (EC-MS) to study the oxidative transformation pathways of various electroactive species. For that purpose, we showed that the EC-MS method, carried out in the presence and absence of isotope18O labeled water leads not only to a fast identification of oxidation products but also leads to a fast elucidation of the mechanism pathway reaction. We examined herein the case of the electrochemical hydrolysis of activated aromatic ether. Acebutolol (β-blockers) was selected herein as model of activated aromatic ether, and its electrochemical oxidation was examined in both the presence and absence of isotope18O labeled water. To elucidate electrochemical hydrolysis pathway reaction: O-dealkylation or O-dealkoxylation, our approach was used to prove its applicability. The electrochemical oxidation mechanism was then elucidated showing an O-dealkoxylation reaction. In addition, density functional theory (DFT) calculations fully support the experimental conclusions.
Keywords: EC-MS; Mass-voltammetry; Acebutolol; O-Dealkylation; Prediction of oxidative metabolism
Electrocatalytic assay of mercury(II) ions using a bifunctional oligonucleotide signal probe by Ziping Zhang; Jungang Yin; Zhaoyang Wu; Ruqin Yu (pp. 47-53).
The G-quadruplex–hemin (G4–hemin) complex exhibited good electrocatalytic activity toward the reduction of hydrogen peroxide when it was immobilized on a gold electrode through T–Hg2+–T interaction mediated surface hybridization reaction, which enabled the design of a bifunctional oligonucleotide signal probe for label-free, electrocatalytic assay of Hg2+.Display Omitted► A bifunctional oligonucleotide was designed for Hg2+ electrochemical sensing. ► Electrocatalytic property of G4–hemin was investigated using cyclic voltammetry. ► Electrocatalytic reduction of H2O2 by G4–hemin provided amplified signal for Hg2+. ► A simple and effective electrochemical Hg2+ biosensor was successfully developed.Engineered nucleic acid probes containing recognition and signaling functions find growing interest in biosensor design. In this paper, we developed a novel electrochemical biosensor for sensitive and selective detecting of Hg2+ based on a bifunctional oligonucleotide signal probe combining a mercury-specific sequence and a G-quadruplex (G4) sequence. For constructing the electrochemical Hg2+ biosensor, a thiolated, mercury-specific oligonucleotide capture probe was first immobilized on gold electrode surface. In the presence of Hg2+, a bifunctional oligonucleotide signal probe was hybridized with the immobilized capture probe through thymine–mercury(II)–thymine interaction-mediated surface hybridization. The further interaction between G4 sequence of the signal probe and hemin generated a G4–hemin complex, which catalyzed the electrochemical reduction of hydrogen peroxide, producing amplified readout signals for Hg2+ interaction events. This electrochemical Hg2+ biosensor was highly sensitive and selective to Hg2+ in the concentration of 1.0nM to 1μM with a detection limit of 0.5nM. The new design of bifunctional oligonucleotide signal probes also provides a potential alternative for developing simple and effective electrochemical biosensors capable of detecting other metal ions specific to natural or artificial bases.
Keywords: Mercury; Oligonucleotide probe; Electrocatalytic amplification; Electrochemical biosensor
Homogeneous liquid–liquid microextraction via flotation assistance for rapid and efficient determination of polycyclic aromatic hydrocarbons in water samples by Majid Haji Hosseini; Mohammad Rezaee; Saeid Akbarian; Farhang Mizani; Mohammad Reza Pourjavid; Masoud Arabieh (pp. 54-60).
Display Omitted► Homogeneous liquid–liquid microextraction via flotation assistance was developed based on applying low density organic solvents. ► In this research, a special extraction cell was designed to facilitate collection of the low-density solvent extraction. ► In this work, air flotation was used to break up the organic-in water emulsion and to finish the extraction process.In this work, a rapid, simple and efficient homogeneous liquid–liquid microextraction via flotation assistance (HLLME-FA) method was developed based on applying low density organic solvents without no centrifugation. For the first time, a special extraction cell was designed to facilitate collection of the low-density solvent extraction in the determination of four polycyclic aromatic hydrocarbons (PAHs) in water samples followed by gas chromatography-flame ionization detector (GC-FID). The effect of different variables on the extraction efficiency was studied simultaneously using experimental design. The variables of interest in the HLLME-FA were selected as extraction and homogeneous solvent volumes, ionic strength and extraction time. Response surface methodology (RSM) was applied to investigate the optimum conditions of all the variables. Using optimized variables in the extraction process, for all target PAHs, the detection limits, the precisions and the linearity of the method were found in the range of 14–41μgL−1, 3.7–10.3% (RSD, n=3) and 50–1000μgL−1, respectively. The proposed method has been successfully applied to the analysis of four target PAHs in the water samples, and satisfactory results were obtained.
Keywords: Homogeneous liquid–liquid microextraction-flotation assistance; Polycyclic aromatic hydrocarbons; Gas chromatography; Water samples
A novel digestion method based on a choline chloride–oxalic acid deep eutectic solvent for determining Cu, Fe, and Zn in fish samples by Emadaldin Habibi; Kamal Ghanemi; Mehdi Fallah-Mehrjardi; Ali Dadolahi-Sohrab (pp. 61-67).
.Display Omitted► A novel digestion method: lack of concentrated acids or oxidizing reagents. ► First report of using choline chloride–oxalic acid (ChCl–Ox) for digestion. ► Complete dissolution of biological samples in ChCl–Ox for solubilization metals. ► Extraction recoveries greater than 95%: validated by the fish protein CRM. ► Successfully applied in different fish tissues (Muscle, Liver, and Gills).A novel and efficient digestion method based on choline chloride–oxalic acid (ChCl–Ox) deep eutectic solvent (DES) was developed for flame atomic absorption spectrometry (FAAS) determination of Cu, Zn, and Fe in biological fish samples. Key parameters that influence analyte recovery were investigated and optimized, using the fish protein certified reference material (CRM, DORM-3) throughout the procedure. In this method, 100mg of the sample was dissolved in ChCl–Ox (1:2, molar ratio) at 100°C for 45min. Then, 5.0mL HNO3 (1.0M) was added. After centrifugation, the supernatant solution was filtered, diluted to a known volume, and analyzed by FAAS. Under optimized conditions, an excellent agreement between the obtained results and the certified values was observed, using Student's t-test ( P=0.05); the extraction recovery of the all elements was greater than 95.3%. The proposed method was successfully applied to the determination of analytes in different tissues (muscle, liver, and gills) having a broad concentration range in a marine fish sample. The reproducibility of the method was validated by analyzing all samples by our method in a different laboratory, using inductively coupled plasma optical emission spectrometry (ICP-OES). For comparison, a conventional acid digestion (CAD) method was also used for the determination of analytes in all studied samples. The simplicity of the proposed experimental procedure, high extraction efficiency, short analysis time, lack of concentrated acids and oxidizing agents, and the use of safe and inexpensive components demonstrate the high potential of ChCl–Ox (1:2) for routine trace metal analysis in biological samples.
Keywords: Deep eutectic solvent; Choline chloride–oxalic acid (ChCl–Ox); Fish tissues; Metal; Digestion; Flame atomic absorption spectrometry (FAAS)
The direct determination of double bond positions in lipid mixtures by liquid chromatography/in-line ozonolysis/mass spectrometry by Chenxing Sun; Yuan-Yuan Zhao; Jonathan M. Curtis (pp. 68-75).
Display Omitted► An ozonolysis reactor was coupled in-line with mass spectrometry (O3-MS). ► Double bond positions in FAME were determined unambiguously without standards. ► LC directly connected to O3-MS allowed double bond localization in lipid mixtures. ► LC/O3-MS applied to bovine fat demonstrated practical use in lipid analysis.The direct determination of double bond positions in unsaturated lipids using in-line ozonolysis-mass spectrometry (O3-MS) is described. In this experiment, ozone penetrates through the semi-permeable Teflon AF-2400 tubing containing a flow of a solution of fatty acid methyl esters (FAME). Unsaturated FAME are thus oxidized by the ozone and cleaved at the double bond positions. The ozonolysis products then flow directly into the atmospheric pressure photoionization (APPI) source of a mass spectrometer for analysis. Aldehyde products retaining the methyl ester group are indicative of the double bond positions in unsaturated FAME. For the first time, O3-MS is able to couple directly to high performance liquid chromatography (HPLC), making the double bond localization in lipid mixtures possible. The application of LC/O3-MS has been demonstrated for a fat sample from bovine adipose tissue. A total of 9 unsaturated FAME including 6 positional isomers were identified unambiguously, without comparison to standards. The in-line ozonolysis reaction apparatus is applicable to most mass spectrometers without instrumental modification; it is also directly compatible with various LC columns. The LC/O3-MS method described here is thus a practical, versatile and easy to use new approach to the direct determination of double bond positions in lipids, even in complex mixtures.
Keywords: Double bond location; Lipids; Ozonolysis; Mass spectrometry; Liquid chromatography; Fatty acid methyl ester
A novel dual-function molecularly imprinted polymer on CdTe/ZnS quantum dots for highly selective and sensitive determination of ractopamine by Huilin Liu; Dongrui Liu; Guozhen Fang; Fangfang Liu; Cuicui Liu; Yukun Yang; Shuo Wang (pp. 76-82).
Display Omitted► We have developed a novel dual-function MIP-coated QDs material. ► The MIP-coated QDs combine the advantage of molecular imprinting and QDs. ► We used MIP-coated QDs as fluorescence sensing material for recognize RAC. ► We used QDs@MIP as sorbent to combine SPE with HPLC for the determination.A novel dual-function material was synthesized by anchoring a molecularly imprinted polymer (MIP) layer on CdTe/ZnS quantum dots (QDs) using a sol–gel with surface imprinting. The material exhibited highly selective and sensitive determination of ractopamine (RAC) through spectrofluorometry and solid-phase extraction (SPE) coupled with high performance liquid chromatography (HPLC). A series of adsorption experiments revealed that the material showed high selectivity, good adsorption capacity and a fast mass transfer rate. Fluorescence from the MIP-coated QDs was more strongly quenched by RAC than that of the non-imprinted polymer, which indicated that the MIP-coated QDs acted as a fluorescence sensing material could recognize RAC. In addition, the MIP-coated QDs as a sorbent was also shown to be promising for SPE coupled with HPLC for the determination of trace RAC in feeding stuffs and pork samples. Under optimal conditions, the spectrofluorometry and SPE-HPLC methods using the MIP-coated QDs had linear ranges of 5.00×10−10–3.55×10−7 and 1.50×10−10–8.90×10−8molL−1, respectively, with limits of detection of 1.47×10−10 and 8.30×10−11molL−1, the relative standard deviations for six repeat experiments of RAC (2.90×10−9molL−1) were below 2.83% and 7.11%.
Keywords: Quantum dots; Molecularly imprinted polymer; Sensing material; Solid-phase extraction; High performance liquid chromatography; Ractopamine
Copper nanoclusters as peroxidase mimetics and their applications to H2O2 and glucose detection by Lianzhe Hu; Yali Yuan; Ling Zhang; Jianming Zhao; Saadat Majeed; Guobao Xu (pp. 83-86).
Display Omitted► Copper nanoclusters exhibit peroxidase-like activity for the first time. ► They can catalyze the oxidation of TMB by H2O2 to produce a blue color reaction. ► They have high stability and activity under harsh conditions. ► Copper nanocluster-based colorimetric assays for H2O2 and glucose were developed.Copper nanoclusters (Cu NCs) are found to possess intrinsic peroxidase-like activity for the first time. Similar to nature peroxidase, they can catalyze the oxidation of 3,3′,5,5′-tetramethylbenzidine by H2O2 to produce a nice blue color reaction. Compared with horseradish peroxidase, Cu NCs exhibits higher activity near neutral pH, which is beneficial for biological applications. The increase in absorbance caused by the Cu NCs catalytic reaction allows the detection of H2O2 in the range of 10μM to 1mM with a detection limit of 10μM. A colorimetric method for glucose detection was also developed by combining the Cu NCs catalytic reaction and the enzymatic oxidation of glucose with glucose oxidase. Taking into account the advantages of ultra-small size, good stability, and high biocompatibility in aqueous solutions, Cu NCs are expected to have potential applications in biotechnology and clinical diagnosis as enzymatic mimics.
Keywords: Enzyme mimics; Nanoclusters; Biosensors; Copper; Peroxidase
Localized surface plasmon resonance sensor for simultaneous kinetic determination of peroxyacetic acid and hydrogen peroxide by Javad Tashkhourian; Mohammad Reza Hormozi-Nezhad; Javad Khodaveisi; Razieh Dashti (pp. 87-93).
.Display Omitted► A sensor for determination of peroxyacetic acid and hydrogen peroxide is introduced. ► Sol–gel silica thin film containing Ag-NPs was synthesized as a sensor membrane. ► Change in the localized surface plasmon resonance intensity of Ag-NPs was observed. ► The analytical performance of this sensor has been evaluated in disinfectant solutions.A new sensor for simultaneous determination of peroxyacetic acid and hydrogen peroxide using silver nanoparticles (Ag-NPs) as a chromogenic reagent is introduced. The silver nanoparticles have the catalytic ability for the decomposition of peroxyacetic acid and hydrogen peroxide; then the decomposition of them induces the degradation of silver nanoparticles. Hence, a remarkable change in the localized surface plasmon resonance absorbance strength could be observed. Spectra-kinetic approach and artificial neural network was applied for the simultaneous determination of peroxyacetic acid and hydrogen peroxide. Linear calibration graphs were obtained in the concentration range of (8.20×10−5 to 2.00×10−3molL−1) for peroxyacetic acid and (2.00×10−5 to 4.80×10−3molL−1) for hydrogen peroxide. The analytical performance of this sensor has been evaluated for the detection of simultaneous determination of peroxyacetic acid and hydrogen peroxide in real samples.
Keywords: Kinetic methods; Peroxyacetic acid; Hydrogen peroxide; Surface plasmon resonance; Silver nanoparticles; Artificial neural network