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Publications in this journal

• Speciation of challenging elements in food by atomic spectrometry.

  Authors: Lena Ruzik

  Talanta. 93:18-31.

  The review addresses trends in speciation analysis of challenging - rather rarely examined despite their importance for human health - elements in foodstuffs with special attention prior to sampleThe review addresses trends in speciation analysis of challenging - rather rarely examined despite their importance for human health - elements in foodstuffs with special attention prior to sample preparation. Elements of interest are cobalt, iodine, manganese, iron, zinc, copper and molybdenum belong to the group of elements still appealed for searching their speciation despite extremely small contents in foodstuffs. Advantages and weaknesses of recommended procedures are overviewed and discussed, highlighting state-of-the-art speciation methodologies developed so far in the field.

• Highly sensitive glucose biosensor based on the effective immobilization of glucose oxidase/carbon-nanotube and gold nanoparticle in nafion film and peroxyoxalate chemiluminescence reaction of a new fluorophore.

  Authors: Kiomars Zargoosh, Mohammad Javad Chaichi, Mojtaba Shamsipur, Saman Hossienkhani, Sakineh Asghari, Mohammad Qandalee

  Talanta. 93:37-43.

  A novel glucose biosensor based on the chemiluminescence (CL) detection of enzymatically generated H(2)O(2) was constructed by the effective immobilization of glucose oxidase (GOD)/carbon-nanotubesA novel glucose biosensor based on the chemiluminescence (CL) detection of enzymatically generated H(2)O(2) was constructed by the effective immobilization of glucose oxidase (GOD)/carbon-nanotubes (CNTs)/gold nanoparticles (GNPs) in nafion film on graphite support. The influences of various experimental parameters such as solution pH, the action time of the enzyme, interferents and the concentration of CL reagents were investigated. Carbon nanotubes and gold nanoparticles offer excellent catalytic activity toward hydrogen peroxide generation in enzymatic reaction between glucose oxidase and glucose, which would enable sensitive determination of glucose. Under the optimum condition, the linear response range of glucose was found to be 2.25×10(-6) to 1.75×10(-4)molL(-1), and the detection limit (defined as the concentration that could be detected at the signal-to-noise ratio of 3) was 1.00×10(-6)molL(-1). The CL biosensor exhibited good storage stability, i.e., 80% of its initial response was retained after 10 days storage at pH 7.0. The present CL biosensor has been used to determine the glucose concentrations in real serum and urine samples with satisfactory results.

• A test strip platform based on DNA-functionalized gold nanoparticles for on-site detection of mercury (II) ions.

  Authors: Zhiyong Guo, Jing Duan, Fei Yang, Min Li, Tingting Hao, Sui Wang, Danyi Wei

  Talanta. 93:49-54.

  A test strip, based on DNA-functionalized gold nanoparticles for Hg(2+) detection, has been developed, optimized and validated. The developed colorimetric mercury sensor system exhibited a highlyA test strip, based on DNA-functionalized gold nanoparticles for Hg(2+) detection, has been developed, optimized and validated. The developed colorimetric mercury sensor system exhibited a highly sensitive and selective response to mercury. The measurement principle is based on thymineHg(2+)thymine (THg(2+)T) coordination chemistry and streptavidin-biotin interaction. A biotin-labeled and thiolated DNA was immobilized on the gold nanoparticles (AuNPs) surface through a self-assembling method. Another thymine-rich DNA, which was introduced to form DNA duplexes on the AuNPs surface with thymineHg(2+)thymine (THg(2+)T) coordination in the presence of Hg(2+), was immobilized on the nitrocellulose membrane as the test zone. When Hg(2+) ions were introduced into this system, they induced the two strands of DNA to intertwist by forming THg(2+)T bonds resulting in a red line at the test zone. The biotin-labeled and thiolated DNA-functionalized AuNPs could be captured by streptavidin which was immobilized on the nitrocellulose membrane as the control zone. Under optimized conditions, the detection limit for Hg(2+) was 3nM, which is lower than the 10nM, maximum contaminant limit defined by the US Environmental Protection Agency (EPA) for drinking water. A parallel analysis of Hg(2+) in pool water samples using cold vapor atomic absorption spectrometry showed comparable results to those obtained from the strip test. Therefore, the results obtained in this study could be used as basic research for the development of Hg(2+) detection, and the method developed could be a potential on-site screening tool for the rapid detection of Hg(2+) in different water samples without special instrumentation. All experimental variables that influence the test strip response were optimized and reported.

• Development of a fast capillary electrophoresis method for determination of carbohydrates in honey samples.

  Authors: Viviane Maria Rizelio, Laura Tenfen, Roberta da Silveira, Luciano Valdemiro Gonzaga, Ana Carolina Oliveira Costa, Roseane Fett

  Talanta. 93:62-6.

  In this study, the determination of fructose, glucose and sucrose by capillary electrophoresis (CE) was investigated. The tendency of the analyte to undergo electromigration dispersion and the bufferIn this study, the determination of fructose, glucose and sucrose by capillary electrophoresis (CE) was investigated. The tendency of the analyte to undergo electromigration dispersion and the buffer capacity were evaluated using the Peakmaster(®) software and considered in the optimization of the background electrolyte, which was composed of 20mmolL(-1) sorbic acid, 0.2mmolL(-1) CTAB and 40mmolL(-1) NaOH at pH 12.2. Under optimal CE conditions, the separation of the substances investigated was achieved in less than 2min. The detection limits for the three analytes were in the range of 0.022 and 0.029gL(-1) and precision measurements within 0.62-4.69% were achieved. The proposed methodology was applied in the quantitative analysis by direct injection of in honey samples to determine the main sugars presents. The samples were previously dissolved in deionized water and filtered with no other sample treatment. The mean values for fructose, glucose and sucrose were in the ranges of 33.65-45.46g 100g(-1), 24.63-35.06g 100g(-1) and <0.22-1.32g 100g(-1), respectively. The good analytical performance of the method makes it suitable for implementation in food laboratories for the routine analysis of honey samples.

• Artificial neural networks combined with experimental design: A "soft" approach for chemical kinetics.

  Authors: Filippo Amato, José Luis González-Hernández, Josef Havel

  Talanta. 93:72-8.

  The possibilities of artificial neural networks (ANNs) "soft" computing to evaluate chemical kinetic data have been studied. In the first stage, a set of "standard" kinetic curves with knownThe possibilities of artificial neural networks (ANNs) "soft" computing to evaluate chemical kinetic data have been studied. In the first stage, a set of "standard" kinetic curves with known parameters (rate constants and/or concentrations of the reactants), which is some kind of "normalized maps", is prepared. The database should be built according to a suitable experimental design (ED). In the second stage, such data set is then used for ANNs "learning". Afterwards, in the second stage, experimental data are evaluated and parameters of "other" kinetic curves are computed without solving anymore the system of differential equations. The combined ED-ANNs approach has been applied to solve several kinetic systems. It was also demonstrated that using ANNs, the optimization of complex chemical systems can be achieved even not knowing or determining the values of the rate constants. Moreover, the solution of differential equations is here not necessary, as well. Using ED the number of experiments can be reduced substantially. Methodology of ED-ANNs applied to multicomponent analysis shows advantages over classical methods while the knowledge of kinetic reactions is not needed. ANNs computation in kinetics is robust as shown evaluating the effect of experimental errors and it is of general applicability.

• Reverse flow injection analysis method for catalytic spectrophotometric determination of iron in estuarine and coastal waters: A comparison with normal flow injection analysis.

  Authors: Yongming Huang, Dongxing Yuan, Minhan Dai, Yaoxing Liu

  Talanta. 93:86-93.

  A method for determining iron in seawater had been developed by coupling reverse flow injection analysis (rFIA) and catalytic spectrophotometric detection with N,N-dimethyl-p-phenylenediamineA method for determining iron in seawater had been developed by coupling reverse flow injection analysis (rFIA) and catalytic spectrophotometric detection with N,N-dimethyl-p-phenylenediamine dihydrochloride (DPD). With a seawater sample or a standard solution as the carrier, the mixture of DPD and buffer was injected into the carrier stream quantitatively and discretely. After mixing with H(2)O(2), the DPD was oxidized to form two pink semiquinone derivatives that were monitored at 514nm wavelength with a reference at 700nm. The method detection limit was 0.40nmolL(-1), lower than half of that of normal flow injection analysis (nFIA) method. The sample throughput was 10h(-1) with triplicate determination, compared with 4h(-1) for nFIA-DPD method. The analysis results of the certified seawaters CASS-4 (12.33±0.18nmolL(-1)) and NASS-5 (3.47±0.23nmolL(-1)) well agreed with the certified values (12.77±1.04 and 3.71±0.63nmolL(-1), respectively). The typical precision of the method for a 2.97nmolL(-1) iron sample was 4.49% (n=8). Interferences from copper and salinity were investigated. An instrument was assembled based on the proposed method and applied successfully to analyze total dissolvable iron (TDFe) in surface seawater samples collected from the Pearl River Estuary, the results of which revealed non-conservative behavior of TDFe during the estuarine mixing. Results for these samples with both rFIA-DPD and nFIA-DPD methods showed good agreement with each other. The proposed method was superior to the currently used nFIA-DPD method, particularly when it is adapted for field and in situ deployment, due to its lower reagent consumption, higher sample throughput and keeping the manifold tubing clean.

• Evaluation of new mixed-mode UHPLC stationary phases and the importance of stationary phase choice when using low ionic-strength mobile phase additives.

  Authors: Lucie Nováková, Hana Vlčková, Solich Petr

  Talanta. 93:99-105.

  In this study, the selectivity, retention properties, peak shape and loading capacity for bases were practically evaluated using two UHPLC mixed-mode hybrid CSH stationary phases modified by C18 orIn this study, the selectivity, retention properties, peak shape and loading capacity for bases were practically evaluated using two UHPLC mixed-mode hybrid CSH stationary phases modified by C18 or Phenyl group. The data were compared with the data obtained on other UHPLC hybrid stationary phases (BEH C18, BEH C8, BEH Phenyl and BEH Shield RP18) at both basic and acidic conditions using conventional HPLC buffers (50mM ammonium formate/acetate) as well as low ionic-strength additives such as, e.g. 0.1-0.01% formic/acetic acid and 1mM solution of ammonium formate/acetate, which are widely used in LC-MS applications. Ten pharmaceutically important compounds encompassing acids, bases and neutral were included into the study. Due to properties of CSH sorbent (which possess positively charged surface besides RP group), much improved peak shapes and weaker retention was obtained for bases even at very low concentration of acidic additives. Such conditions are ideally suited for LC-MS analysis of bases, where typical RP chromatographic separation (retention and good selectivity at basic pH) and LS-MS conditions (efficient ionization at acidic pH) are not in agreement. On the other hand, acids were more strongly retained and for some compounds the peak shape was influenced negatively due to ion-exchange mechanism. Further, the behavior of acidic, basic and neutral solutes is discussed using various additives at both basic and acidic pH for all above stated columns. The robustness of retention times after pH change from basic to acidic was also evaluated. The new CSH stationary phases represent an interesting selectivity tool preferably for separation of basic compounds.

• Simplified and miniaturized procedure based on ultrasound-assisted cytosol preparation for the determination of Cd and Cu bound to metallothioneins in mussel tissue by ICP-MS.

  Authors: Isela Lavilla, Marta Costas, Sandra Gil, Sandra Corderí, Goretti Sánchez, Carlos Bendicho

  Talanta. 93:111-6.

  A simplified and miniaturized procedure for the determination of Cd and Cu bound to metallothioneins (MTs) by ICP-MS in mussel tissue has been developed. Cytosol preparation was based on the indirectA simplified and miniaturized procedure for the determination of Cd and Cu bound to metallothioneins (MTs) by ICP-MS in mussel tissue has been developed. Cytosol preparation was based on the indirect sonication of slurries containing the lyophilized sample dispersed in 1mL of extractant by means of a sonoreactor Cup-Horn. Rabbit liver MTs (Apo-MT-I, Apo-MT-II and Cd(7)-MT-II) and a conventional cytosol preparation procedure were used for validation purposes. The usual heating step and additional centrifugations of the conventional procedure for cytosol preparation can be omitted when using ultrasound treatment. The possible effect of denaturation on MTs and its effect on the metal bound to MTs were evaluated. Variables influencing the ultrasound-assisted cytosol preparation procedure were carefully optimized for simultaneous determination of both metals. Chromatographic conditions to separate the MT fraction from other proteins present in cytosols were also studied. Six samples can be processed within 3min of sonication. An acid ultrasound-assisted extraction procedure with diluted acid was also proposed for determining total Cd and Cu. Finally, Cd and Cu bound to MTs as well as total Cd and Cu were determined in mussels from Pontevedra and Ares-Betanzos coastal inlets (Galicia, Spain).

• Polymer modified glassy carbon electrode for the electrochemical determination of caffeine in coffee.

  Authors: Meareg Amare, Shimelis Admassie

  Talanta. 93:122-8.

  4-Amino-3-hydroxynaphthalene sulfonic acid (AHNSA) was electropolymerized on a glassy carbon electrode. The deposited film showed electrocatalytic activity towards the oxidation of caffeine. The4-Amino-3-hydroxynaphthalene sulfonic acid (AHNSA) was electropolymerized on a glassy carbon electrode. The deposited film showed electrocatalytic activity towards the oxidation of caffeine. The polymer-modified electrode showed high sensitivity, selectivity and stability in the determination of caffeine in coffee. The peak current increased linearly with the concentration of caffeine in the range of 6×10(-8) to 4×10(-5)molL(-1), with a detection limit of 1.37×10(-7)molL(-1) (LoD=3δ/slope). Analysis of caffeine in coffee was affected neither by sample matrices nor by structurally similar compounds. Recoveries ranging between 93.75±2.32 and 100.75±3.32 were achieved from coffee extracts indicating the applicability of the developed method for real sample analyses.

• A rapid method for the determination of honey diastase activity.

  Authors: Nikola Sakač, Milan Sak-Bosnar

  Talanta. 93:135-8.

  A new rapid method for the determination of honey diastase activity using direct potentiometric principles has been proposed. A platinum redox sensor has been used to quantify the amount of freeA new rapid method for the determination of honey diastase activity using direct potentiometric principles has been proposed. A platinum redox sensor has been used to quantify the amount of free triiodide released from a starch triiodide complex after starch hydrolysis by honey diastase. The method was tested on honey samples with varying diastase activities. The first 5min of data for each sample were used for linear regression analysis in order to calculate diastase activity. The new method was compared with classical Schade and commercial Phadebas procedures. The results showed good correlations with both methods and offered a simple method for unit conversion to DN units for diastase activity, making the method suitable for routine analysis.

• Rapid sample preparation procedure for determination of retinol and α-tocopherol in human breast milk.

  Authors: Markéta Kašparová, Jiří Plíšek, Dagmar Solichová, Lenka Krčmová, Barbora Kučerová, Miloslav Hronek, Petr Solich

  Talanta. 93:147-52.

  The liposoluble vitamins (retinol and α-tocopherol) concentration in human breast milk is of a cardinal knowledge especially for nutrition of prematurely born. It enables the feeding optimization ofThe liposoluble vitamins (retinol and α-tocopherol) concentration in human breast milk is of a cardinal knowledge especially for nutrition of prematurely born. It enables the feeding optimization of these important micronutrients for preterm infants. The novel rapid liquid-liquid extraction procedure for human breast milk investigation was developed and validated according to FDA guidelines. The recovery of retinol was 82-90% measured at three concentration levels 1.0, 2.5 and 5.0μmol/L, for α-tocopherol 92-109% at concentration levels 2.5, 5.0 and 10.0μmol/L. The repeatability of extraction procedure expressed as relative standard deviation was 3.26% for retinol and 4.79% for α-tocopherol. Developed extraction procedure was applied on 120 human breast milk samples. The separation of vitamins was completed using advantages of a monolithic column which accomplished demands of acceleration made by modern bio-analytical HPLC methodology. The analytes of interest were detected by diode-array detector at wavelengths 325nm for retinol and 290nm for α-tocopherol.

• Amino acid side chain-like surface modification on magnetic nanoparticles for highly efficient separation of mixed proteins.

  Authors: Soo Youn Lee, Chi Young Ahn, Jiho Lee, Jeong Ho Chang

  Talanta. 93:160-5.

  This work reports on the realization of specific functionalized silica-coated magnetic nanoparticles (Si-MNPs) for effective protein separation through surface modification with various amino acidThis work reports on the realization of specific functionalized silica-coated magnetic nanoparticles (Si-MNPs) for effective protein separation through surface modification with various amino acid side chain-like functional groups such as thiol (SH), disulfide (SS), carbon chain (C(n)), carboxyl (COOH), amine (NH(2)), and aldehyde (CHO). This study also suggests an improved and convenient method for the synthesis of functionalized Si-MNPs by hydrolysis condensation with silan-coupling agents. The protein adsorption effects in a coexistent mixed state are explored using various proteins, which have different isoelectric point (pI) values and molecular weights, in order to elucidate the binding performance of different proteins one solution. The adsorption efficiency of bovine serum albumin (BSA; 66kDa; pI=4.65) and lysozyme (LYZ; 14.3kDa; pI=11) is 70-100% with various amino acid side chain-like functional groups. However, the adsorption efficiency of a mixed protein solution of BSA and LYZ was different. Although the relatively bulky BSA molecule displayed 50% and 20% adsorption corresponding to pH 4.65, and pH 11, respectively, the smaller LYZ provided almost 100% adsorption at both pH 4.65 and pH 11.

• Preparation of molecular imprinted polymers using bi-functional monomer and bi-crosslinker for solid-phase extraction of rutin.

  Authors: Huan Zeng, Yuzhi Wang, Xiaojie Liu, Jinhuan Kong, Chan Nie

  Talanta. 93:172-81.

  Molecular imprinted polymers (MIPs) were prepared using rutin as the template, different reagents as the functional monomer and different reagents as the cross-linker by solution polymerization.Molecular imprinted polymers (MIPs) were prepared using rutin as the template, different reagents as the functional monomer and different reagents as the cross-linker by solution polymerization. Several parameters that would influence the performance of MIPs were investigated including the type of functional monomer (single or double) and cross-linker (single or double), and the molar ratio of the template, the functional monomer and the cross-linker. The optimum synthesis conditions of MIPs were found to be bi-monomers (acrylamide-co-2-vinyl pyridine, 3:1) and bi-crosslinker (ethylene glycol dimethacrylate-co-divinylbenzene, 3:1). The ratio of the template, the functional monomer and the cross-linker was found to be 1:6:20. MIPs synthesized under these conditions were filled into the cartridges as the adsorbents of solid-phase extraction (SPE). A competition test was conducted to authenticate the selectivity and the specificity of molecularly imprinted solid-phase extraction (MISPE) for rutin using the mixture solution of standard rutin and its structural analogs including quercetin, naringenin and kaempferol. Compared with purchased SPE including C(18), silica and PCX, MISPE showed better selectivity and enrichment property for rutin in the extracted solutions of Chinese medicinal plants than any others. The mean recoveries were 85.93% (RSD: 3.04%, n=3) for Saururus chinensis (Lour.) Bail and 88.61% (RSD: 3.36%, n=3) for Flos Sophorae, respectively, which indicated that the optimized rutin-MIPs possess the value of practical application.

• LabVIEW control software for scanning micro-beam X-ray fluorescence spectrometer.

  Authors: Pawel Wrobel, Mateusz Czyzycki, Leszek Furman, Krzysztof Kolasinski, Marek Lankosz, Alina Mrenca, Lucyna Samek, Dariusz Wegrzynek

  Talanta. 93:186-92.

  Confocal micro-beam X-ray fluorescence microscope was constructed. The system was assembled from commercially available components - a low power X-ray tube source, polycapillary X-ray optics andConfocal micro-beam X-ray fluorescence microscope was constructed. The system was assembled from commercially available components - a low power X-ray tube source, polycapillary X-ray optics and silicon drift detector - controlled by an in-house developed LabVIEW software. A video camera coupled to optical microscope was utilized to display the area excited by X-ray beam. The camera image calibration and scan area definition software were also based entirely on LabVIEW code. Presently, the main area of application of the newly constructed spectrometer is 2-dimensional mapping of element distribution in environmental, biological and geological samples with micrometer spatial resolution. The hardware and the developed software can already handle volumetric 3-D confocal scans. In this work, a front panel graphical user interface as well as communication protocols between hardware components were described. Two applications of the spectrometer, to homogeneity testing of titanium layers and to imaging of various types of grains in air particulate matter collected on membrane filters, were presented.

• The potential of ion mobility spectrometry (IMS) for detection of 2,4,6-trichloroanisole (2,4,6-TCA) in wine.

  Authors: Zeev Karpas, Ana V Guamán, Daniel Calvo, Antonio Pardo, Santiago Marco

  Talanta. 93:200-5.

  The off-flavor of "tainted wine" is attributed mainly to the presence of 2,4,6-trichloroanisole (2,4,6-TCA) in the wine. In the present study the atmospheric pressure gas-phase ion chemistry,The off-flavor of "tainted wine" is attributed mainly to the presence of 2,4,6-trichloroanisole (2,4,6-TCA) in the wine. In the present study the atmospheric pressure gas-phase ion chemistry, pertaining to ion mobility spectrometry, of 2,4,6-trichloroanisole was investigated. In positive ion mode the dominant species is a monomer ion with a lower intensity dimer species with reduced mobility values (K(0)) of 1.58 and 1.20cm(2)V(-1)s(-1), respectively. In negative mode the ion with K(0)=1.64cm(2)V(-1)s(-1) is ascribed to a trichlorophenoxide species while the ions with K(0)=1.48 and 1.13cm(2)V(-1)s(-1) are attributed to chloride attachment adducts of a TCA monomer and dimer, respectively. The limit of detection of the system for 2,4,6-TCA dissolved in dichloromethane deposited on a filter paper was 2.1μg and 1.7ppm in the gas phase. In ethanol and in wine the limit of detection is higher implying that pre-concentration and pre-separation are required before IMS can be used to monitor the level of TCA in wine.

• Relation factor: A new strategy for quality control in the determination of pesticides in environmental aqueous matrices.

  Authors: Rivelino M Cavalcante, Danielle M Lima, Gabrielle M Fernandes, Wersângela C Duaví

  Talanta. 93:212-8.

  The effects promoted by environmental aqueous matrices on pesticide determinations have been assessed, and for the first time, a simple, low-cost and efficient strategy for the correction ofThe effects promoted by environmental aqueous matrices on pesticide determinations have been assessed, and for the first time, a simple, low-cost and efficient strategy for the correction of analytical results has been determined. This method can be useful as a parameter of quality control in a quality assurance programs. Evaluation of the matrix effect showed that environmental aqueous matrices, e.g., estuarine water, promote a distinctive and significant effect on the determination of pesticides. The picloram, atrazine and methyl parathion pesticides suffered the smallest effects promoted by the estuarine matrix, whereas chlorpyrifos and cypermethrin suffer a significant effect. For picloram, the matrix effect was a function of its physiochemical properties. However, for atrazine, methyl parathion, chlorpyrifos and cypermethrin, the matrix effect was promoted by environmental matrix components. As strategy for analytical quality control, it has been determined that there are relation factors (RFs) between pesticides and the selected surrogates standards. These RFs are not altered by the complexities and compositions of simple and complex aqueous matrices. Predetermined RFs was applied to the picloram, atrazine and methyl parathion assessment in a real sample from the estuary of the Jaguaribe River, and the results showed that when no quality control was applied, the concentration levels would be underestimated, leading to incorrect results and inaccurate conclusions.

• Determination of carboxylic acids in water by gas chromatography-mass spectrometry after continuous extraction and derivatisation.

  Authors: Beatriz Jurado-Sánchez, Evaristo Ballesteros, Mercedes Gallego

  Talanta. 93:224-32.

  This paper describes a new approach for the determination of monocarboxylic, dicarboxylic and tricarboxylic acids (35 compounds) in water. The analytes, in acid medium (pH ∼1.3), were sorbed on anThis paper describes a new approach for the determination of monocarboxylic, dicarboxylic and tricarboxylic acids (35 compounds) in water. The analytes, in acid medium (pH ∼1.3), were sorbed on an 80mg LiChrolut EN-Supelclean ENVI-18 (1:1) column and subsequently eluted with methanol. After evaporation of the extract to ∼10μL, the analytes were spiked with 60μL of the derivatising reagent and derivatised in a household microwave oven for 3min. Among the reagents tested (BF(3)/1-butanol; acetyl chloride/1-butanol; isobutyl chloroformate/1-butanol; trimethylphenylammonium hydroxide, N,O-bis-(trimethylsilyl)acetamide, N,O-bis-(trimethylsilyl)trifluoroacetamide and trimethylchlorosilane), the best results in terms of reaction yield and stability of the derivatives were obtained with the mixture of 1% trimethylchlorosilane in N,O-bis-(trimethylsilyl)trifluoroacetamide. Microwave assisted derivatisation was used as an alternative heating approach for the rapid silylation of carboxylic acids. The proposed method proved to be a suitable analytical procedure for several types of carboxylic acids in water, with limits of detection within the range 0.6-15ngL(-1), precision values from 4.0 to 6.0% (as within-day relative standard deviation) and recoveries from 93 to 101% for all the target analytes.

• Characterization of interactions between organotin compounds and human serum albumin by capillary electrophoresis coupled with inductively coupled plasma mass spectrometry.

  Authors: Jing Sun, Bin He, Qian Liu, Ting Ruan, Guibin Jiang

  Talanta. 93:239-44.

  Thermodynamic data such as the binding constants are vital parameters describing interactions between exotic trace compounds and biomolecules in biochemical property modeling. In this study, theThermodynamic data such as the binding constants are vital parameters describing interactions between exotic trace compounds and biomolecules in biochemical property modeling. In this study, the stability constants of organometallic compound and protein complexes were studied by using capillary electrophoresis coupled with inductively coupled plasma mass spectrometry (CE-ICP-MS), considering its low detection limits and low sample demand. Four organotin compounds (trimethyltin (TMT), tripropyltin (TPrT), tributyltin (TBT), triphenyltin (TPhT)) and human serum albumin (HSA) were used as model organometallic compounds and protein, respectively. Affinity capillary electrophoresis (ACE) and nonequilibrium capillary electrophoresis assays of equilibrium mixtures (NECEEM) were performed and compared by using ICP-MS as the detector to determine the binding constants of organotin compounds and HSA in 1:1 molar ratio assumption. Constant measurements of the two methods were both simple, however, ACE assays were more accurate and more appropriate for the constant determination of the organotin-HSA complexes, considering the errors of the NECEEM method. A good precision of the binding constants (logK(b)) using the ACE method was proved by different mathematical calculations, and the values were 6.13±0.51 (TMT), 5.72±0.38 (TPrT), 5.68±0.34 (TBT), 6.05±0.38 (TPhT) respectively for each of the organotin-HSA complexes, showing non-covalent interaction between organotin compounds and HSA. Meanwhile, this study also confirms the suitability of CE-ICP-MS method for further studies on organometallic complexation.

• Gas-phase fragmentation of host-guest complexes between β-cyclodextrin and small molecules.

  Authors: Xiaoxiao Ma, Zhenwei Wei, Xingchuang Xiong, You Jiang, Junwei He, Sichun Zhang, Xiang Fang, Xinrong Zhang

  Talanta. 93:252-6.

  Noncovalent interactions are ubiquitous in molecular interaction and supramolecular self-assembly. As a model system, host-guest complexes between β-cyclodextrin (β-CD) and small molecules have beenNoncovalent interactions are ubiquitous in molecular interaction and supramolecular self-assembly. As a model system, host-guest complexes between β-cyclodextrin (β-CD) and small molecules have been extensively studied and widely used in a variety of application fields including drug transportation and fluorescence enhancement. However, details on how guest molecules interact with the β-CD hosts to demonstrate the observed effects still remain to be further studied. In this work, we report the study of gas-phase fragmentation of host-guest complexes formed between β-CD and small guest molecules by using collision induced dissociation (CID). The CID mass spectra of the complexes changed dramatically as the collision energy was increased. Fragmentation patterns of β-CD complexed with different small molecules were analyzed and the differences in the presence/absence of fragment ions from the β-CD were attributed to varied proton affinity of the small molecules. Furthermore, the CE(50) values fitted from the fragmentation curves were used in the qualitative evaluation of interactions in noncovalent host-guest systems.

• Probing cysteine self-assembled monolayers over gold nanoparticles - Towards selective electrochemical sensors.

  Authors: Ahmed Galal, Nada F Atta, Ekram H El-Ads

  Talanta. 93:264-73.

  Cysteine forms self-assembled monolayers over gold nanoparticles. Based on this knowledge, a novel electrochemical sensor (Au-Au(nano)-Cys-SDS) has been constructed by the formation of self-assemblyCysteine forms self-assembled monolayers over gold nanoparticles. Based on this knowledge, a novel electrochemical sensor (Au-Au(nano)-Cys-SDS) has been constructed by the formation of self-assembly monolayer (SAM) of cysteine on gold-nanoparticles modified gold electrode (Au-Au(nano)-Cys) to be utilized for determination of dopamine in the presence of sodium dodecyl sulfate (SDS). Electrochemical investigation and characterization of the modified electrode sensor was achieved using cyclic voltammetry, electrochemical impedance spectroscopy, scanning electron, and atomic force microscopies. Au-Au(nano)-Cys electrode in the presence of SDS gave comparable high current response to that of the gold nanoparticles modified gold electrode (Au-Au(nano)). The Au-Au(nano)-Cys-SDS electrode current signal was remarkably stable via repeated cycles and long term stability due to the strong AuS bond. Very small peak separation, almost zero or 15mV peak separation was also obtained by repeated cycles indicating unusual high reversibility. The oxidation peak current was determined to be linearly dependent on the dopamine concentration. A resulting calibration curve using square wave voltammetry (SWV) was obtained over concentration range of 30-100μmolL(-1) and 120-320μmolL(-1) with correlation coefficients of 0.996 and 0.994 and a limit of detection of 16 and 57nmolL(-1), respectively. Using differential pulse voltammetry (DPV), a highly selective and simultaneous determination of tertiary mixture of ascorbic acid AA, dopamine, and acetaminophen APAP was explored at this modified electrode. It has been demonstrated that Au-Au(nano)-Cys-SDS electrode can be used as a sensor with excellent reproducibility, sensitivity, and long term stability.

• A simple approach for retention prediction in the pH-gradient reversed-phase liquid chromatography.

  Authors: A Pappa-Louisi, Ch Zisi

  Talanta. 93:279-84.

  A simple approach for retention modeling of solutes under pH-gradient conditions at various organic contents in the mobile phase is proposed. This approach is based on a retention model arising fromA simple approach for retention modeling of solutes under pH-gradient conditions at various organic contents in the mobile phase is proposed. This approach is based on a retention model arising from the evaluation of the retention data of a set of 17 OPA derivatives of amino acids obtained in two series of 22 pH-gradient runs performed between a given initial and final pH value (between 2.8 and 10.7 or 3.2 and 9.0) with different gradient duration and with different organic modifier content in the eluent. The derived model is a fifth-parameter equation easily manageable through a linear least-squares fitting. It requires only 6 initial pH-gradient experiments, allows a very satisfactory prediction for various pH-changes of the same kind with those used in the fitting procedure and seems to be very promising in separation optimization under pH-gradient conditions. The pH-gradient method appears to be especially suitable and effective for separation of amino acid derivatives whereas the application of pH-gradients from 3.2 to 9.0 proved to be beneficial.

• Improved liquid-chromatography tandem mass spectrometry method for the determination of the bioactive dipeptides, carnosine and anserine: Application to analysis in chicken broth.

  Authors: Alba Macià, Maria-José Motilva, Maria-Paz Romero, Agustín Labrador, Alba Domínguez, Lluís Peiro

  Talanta. 93:293-300.

  An improved method, based on ultra-performance liquid chromatography (UPLC) coupled to tandem mass spectrometry (MS/MS), has been developed to determine the bioactive dipeptides carnosine (CAR) andAn improved method, based on ultra-performance liquid chromatography (UPLC) coupled to tandem mass spectrometry (MS/MS), has been developed to determine the bioactive dipeptides carnosine (CAR) and anserine (ANS) in chicken broth. These analytes are hydrophilic (polar) and in order to improve their retention, the chromatographic mode used was hydrophilic interaction chromatography (HILIC) (1.7μm particle size). In order to remove the salt before the chromatographic analysis of the chicken broth (0.8%, w/w), an exhaustive sample pre-treatment strategy was necessary since the salt is not volatilized and could block the ionization source and lead to signal suppression. The chicken broth was firstly centrifuged to remove the fat and chicken proteins, and then was pretreated by off-line solid-phase extraction (SPE), using traditional cartridges, or off-line μElution plate (μSPE), using microplates, and the results were compared. Due to the high polar character of the dipeptides studied and the sample matrix, these compounds were not retained in the sorbent hydrophilic-lipophilic balanced (HLB) and were eluted in the load step, whereas the salt was retained in the sorbent. This fact was observed by the addition of silver nitrate in the chicken broth extract, where before the SPE or μSPE a white precipitate (silver chloride) was formed and after the SPE or μSPE this precipitate was not observed. By using these sample pre-treatment strategies, the extraction recoveries were higher than 80%, and the matrix effect was lower than 12%. Once the improved method was developed, the quality parameters of the method were studied. The LODs and LOQs of the CAR and ANS were lower than 6 and 1.8μg/l, respectively. Then, the method was applied to analyse a commercial chicken broth. This improved method allowed determining CAR and ANS between 6 and 10mg dipeptide/l chicken broth in 10min (sample pre-treatment and chromatographic analysis). Therefore, the proposed improved method is concluded to be rapid, sensitive and selective for the determination of polar compounds by MS in samples that contain salt.

• Isotope dilution direct injection mass spectrometry method for determination of four tyrosine kinase inhibitors in human plasma.

  Authors: K Mičová, D Friedecký, E Faber, T Adam

  Talanta. 93:307-13.

  Therapeutic drug monitoring is recommended for the optimal management of patients with several malignant diseases. The aim of this study was to develop and validate an isotope dilution directTherapeutic drug monitoring is recommended for the optimal management of patients with several malignant diseases. The aim of this study was to develop and validate an isotope dilution direct injection mass spectrometry method for the high throughput determination of tyrosine kinase inhibitors in plasma from leukemic and cancer patients. The plasma for analysis was deproteinated by methanol and the centrifuged supernatant was directly injected to mass spectrometer without separation step. Multiple reaction monitoring modes on a hybrid triple quadrupole - linear ion trap mass spectrometer (5500 QTRAP) were used for the detection and quantification of imatinib, nilotinib, lapatinib, and dasatinib. We developed a fast method with analysis time of 55s and 19s in multiple injection setting. The method was successfully validated and applied to the patient plasma samples. In order to overcome insufficient sensitivity of dasatinib, multiple reaction monitoring cube mode in linear ion trap (MRM(3)) was successfully applied. The limits of quantification were in the range 1.0-5.5ng/ml. Imprecisions were lower than 6.9% and the accuracy of the quality control samples ranged between 99.0 and 107.9%. Isotope dilution direct injection mass spectrometry method allows high-throughput therapeutic drug monitoring of tyrosine kinase inhibitors in plasma. The method offers low-cost analyses as a result of its speed and the exclusion of separation step and can be advantageously used in routine clinical practice. The method can be applied on various drugs and biochemical markers with the use of triple quadrupole instruments.

• Simultaneous electrochemical determination of uric acid, xanthine and hypoxanthine based on poly(l-arginine)/graphene composite film modified electrode.

  Authors: Fengyuan Zhang, Zaihua Wang, Yuzhen Zhang, Zhixiang Zheng, Chunming Wang, Yongling Du, Weichun Ye

  Talanta. 93:320-5.

  Poly(l-arginine)/graphene composite film modified electrode was successfully prepared via a facile one-step electrochemical method and used for simultaneous determination of uric acid (UA), xanthinePoly(l-arginine)/graphene composite film modified electrode was successfully prepared via a facile one-step electrochemical method and used for simultaneous determination of uric acid (UA), xanthine (XA) and hypoxanthine (HX). The electrochemical behaviors of UA, XA and HX at the modified electrode were studied by cyclic voltammetry and differential pulse voltammetry (DPV), and showed that the modified electrode exhibited excellent electrocatalytic activity toward the oxidation of the three compounds. The calibration curves for UA, XA and HX were obtained over the range of 0.10-10.0, 0.10-10.0 and 0.20-20.0μM by DPV, respectively and the detection limits for UA, XA and HX were 0.05, 0.05 and 0.10μM (S/N=3), respectively. With good selectivity and high sensitivity, the modified electrode has been applied to simultaneous determination of UA, XA and HX in human urine with satisfactory result.

• Highly selective and sensitive method for cysteine detection based on fluorescence resonance energy transfer between FAM-tagged ssDNA and graphene oxide.

  Authors: Hongli Liu, Yuhui Wang, Aiguo Shen, Xiaodong Zhou, Jiming Hu

  Talanta. 93:330-5.

  In this work, a new platform for effective sensing cysteine (Cys) was developed based on fluorescence resonance energy transfer (FRET) between FAM-tagged single-stranded DNA (FAM-ssDNA) and grapheneIn this work, a new platform for effective sensing cysteine (Cys) was developed based on fluorescence resonance energy transfer (FRET) between FAM-tagged single-stranded DNA (FAM-ssDNA) and graphene oxide (GO). Due to the noncovalent assembly between FAM-ssDNA and GO, fluorescence quenching of the FAM took place because of FRET. This method relied on the competitive ligation of Ag(+) by Cys and "cytosine-cytosine" (C-C) mismatches in a FAM-labeled DNA strand of the self-hybridizing strand. At first, enough amount of Ag(+) was introduced to bind "C-C" mismatches and form double-stranded DNA (dsDNA), which had weak affinity to GO and kept FAM away from GO surface. However, the presence of Cys removed Ag(+) away from "cytosine-Ag(+)-cytosine" (C-Ag(+)-C) base pairs, leading to the formation of ssDNA again and FRET, and then fluorescence of the FAM-ssDNA was efficiently quenched. The fluorescence intensity decrease was found to be proportional to the increase of concentration of Cys in both aqueous buffer (2-200nM) and human serum (5-200nM), and the sensitivity of the proposed method towards Cys was much higher than that of other reported assays for Cys.

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