Ionophore antibiotics are used to cure and prevent coccidiosis by chicken especially in broiler farming. The residues are found not only in food products (chicken and eggs) but also in the environment (manure, soil or water). In this work the ionophores monensin (MON), salinomycin (SAL), maduramicin (MAD) and lasalocid (LAS) are investigated aiming to study their transformation products (TPs) through biotransformation processes. Biotransformation can be divided into two phases, phase I: oxidation, reduction or hydrolysis and Phase II: conjugation reactions. It is necessary to further examine the biotransformation pathways to determine TPs to be able to detect residues more specifically in different matrices. The technique of electrochemistry (EC) offers the opportunity to simulate biotransformation processes and to generate TPs for further analysis. The combination of EC with liquid chromatography and mass spectrometry (EC-LC-MS) provide a fast and simple tool to separate and determine the EC-generated TPs. The electrochemical flow through cell is coupled to the (LC)-MS system, allowing the reaction mixture to be separated by a RP-18 column and then analyzed in the MS. The oxidation products are generated at different potentials between 0.0 – 2.5 V vs. Pd/H2 using glassy carbon or boron doped diamond as working electrode materials . The results show a broad spectrum of different TPs depending on used solvents and working electrode materials. Among the generated TPs already known as well as unknown TPs of the drugs can be found. Further investigations on structure elucidation of unkown TPs are planned.
Lisa Kotthoff studied chemistry at University of Technology Braunschweig and University of Potsdam. Now she is PhD-student at Federal Institute for Materials Research and Testing in the division of Organic Trace and Food Analysis.
Both prokaryotic and eukaryotic cells contain molecular chaperones: a large group of proteins that assist other proteins in their folding. Molecular chaperones play important roles under normal conditions as well as in stress response and in disease development. Tight interaction with denatured proteins is a general property of molecular chaperones, and so, affinity chromatography on a base of denatured proteins is a perspective method for chaperone analysis. We have made affinity sorbents on a base of Sepharose and a small target protein (e.g. lysozyme) covalently attached to it. The experiments were carried out in the conditions which are native for chaperones and denaturing for the target protein. Cell lysates of bacteria (Escherichia coli, Thermus thermophilus, and Yersinia pseudotuberculosis), archaea (Halorubrum lacusprofundi) as well as lysate of rat liver mitochondria (in normal conditions and after oxidative stress) and human blood serum were analyzed. It is shown that Hsp60 chaperonins were the main proteins that bind to the affinity sorbent (except for the case of blood serum where albumin was the main bound protein). It is demonstrated that, apart from Hsp60, other proteins with a molecular weight of about 100, 50, 40, and 20 kDa are able to interact with denatured lysozyme. We are able to evaluate the quantity of bound proteins and to detect stress changes in protein content. So, this approach can be useful for studying various issues connected with changes in chaperone content. This work was supported by the Russian Science Foundation Grant 14-24-00157.
Natalia Y. Marchenko has completed her PhD from Kharkiv National University (Ukraine) and Institute of Protein Research (Russia). Her research is focused on protein-protein interactions, specifically on studying chaperone-protein interaction in various conditions using different physical and chemical methods, in particular, affinity chromatography. She has published more than 10 papers in peer-reviewed journals.
The efficiency of the sensor in immunoassay is vastly depends on the characteristics of the bioreceptor layer. Oriented chemical immobilization of the recognition element allows achieving not only a strong fixation, but also a significant increase in the sensitivity and accuracy of the immunoassay. The aim of the work was to design an immunosensor for the detection of measles virus antibodies applying electrographing technology. The use of diazonium salts as an electrographing linker allows to fix linker on the surface of the transducer via the diazo group, and to fix receptor element via the functional group. The antigen on the surface of the transducer (glassy carbon electrode) was immobilized by cross-linking the amino groups of the antigen with electrochemically reduced nitro groups of paranitrobenzodiazonium chloride electrografted at a potential of -0.4 V. The immunoassay consisted of incubating the antigen-modified transducer in a measles virus antibodies containing solution and registration of voltammograms in the mediator system - 5 mM solution of [Fe(CN)6]3-/[Fe(CN)6]4- in phosphate buffer sollution (Fig. 1). The concentration of antibodies was determined by decreasing the peak current of the mediator system with comparison to the unmodified electrode (ΔI). Figure 1 - Scheme of immunoassay The influence of the transducer incubation time in the antigen solution and the time of immunoreaction on the analytic parameters of the sensor was studied. Calibration curve is ΔI=32.4 · lg СAB + 112.38.
Alisa N. Kozitsina has completed her PhD from Ural State University named after A.M. Gorkiy (Yekaterinburg, Russia). She is a head of chair of analytical chemistry Institute of Chemical Engineering of the Ural Federal University named after the first President of Russia B.N.Yeltsin. She has published more than 30 papers in reputed journals.
The oxygen active forms in the human body are associated with the processes of free radicals generation, which in excess can lead to many diseases. Inhibitors of radical reactions are antioxidants, which are able to interact with them to form inactive products. Therefore, special attention is paid to the development of methods for studying the total antiradical capacity (TAC) of various compounds. The direct methods for studying TAC are informative, but the complexity of the methodology and equipment, the inability to study colored samples, limits the possibility of applying these methods to a number of objects. Therefore, there is a need to develop a simpler, more rapid and universal method. The potentiometric method of determinationTAC using the 2,2'-azobis(2-amidinopropane)dihydrochloride (AAPH) as a source of peroxyl radicals was first proposed in the work1. New assay is based on a regular change of the redox potential of the systam in the radicals generation reaction and their inhibition by antioxidants. TAC was evaluated as a product of the peroxyl radicals generation rate by the induction period. The induction period is the time of complete consumption of the antioxidant in the reaction mixture. Potentiometric methods were used to study the TAC of model antioxidants. The reliability of the results obtained is confirmed by the known spectrophotometric method using the stable DPPH radical. The developed new potentiometric method is informative, expressive and promising for analysis of food, biological objects and objects of pharmacy. 1. Patent RUS 2618426. A.V. Ivanova, E.L. Gerasimova, E.R. Gazizullina, A.I. Matern. Publication date 03.05.2017.
Alla Ivanova has completed her PhD from Ural State University of Economics(Yekaterinburg, Russia).She is associate professor of the Department of Analytical Chemistry, Institute of Chemical Engineering of the Ural Federal University named after the first President of Russia B.N.Yeltsin. She has published more than 25 papers in reputed journals.
Biosensors using horseradish peroxidase (HRP) as a biorecognition element are very common for the determination of hydrogen peroxide, alcohol, dopamine, aminophenol and glucose. Unfortunately, use of HRP is known for variety of disadvantages such as chemical and thermal instability and loss of enzymatic activity during immobilization.The determination of pseudo-peroxidase activity of iron oxide magnetic particles (IOMPs) replacing enzymes in biosensor construction was an aim of this study. Spectrophotometry, square wave voltammetry and cyclic voltammetry were used for the assay of peroxidase-like activity. Hydrogen peroxide, common substrate of HRP, was used as substrate for IOMPs during all measurements and three-electrode screen printed electrodes with carbon working electrode were used for electrochemical measurement. According to the results,significant pseudo-peroxidase activity of IOMPs was proved,Michaelis-Menten constant was determined to be in range from 156.6. to 199.1 mmol/l and limit of detection was set to be in range from 0.36 to 13.1 mmol/l according used method. Also comparison of non-catalyzed reaction and reaction catalyzed by IOMPs was performed and significant increase of signal using catalyzed reaction was observed. It appears the IOMPs can provide suitable replacement of HRP in both optical and electrochemical biosensor´s construction and future practical adaptation in portable analytical devices is very perspective.
Lipasesare enzymes cleaving ester bonds in molecules such as lipids. Lipases are used as biorecognition elements of biosensors in analytical chemistry, mainly in pharmaceutical, healthcare, environmental etc. industry. Standard method for determination of lipase activity is based on cleaving ester bonds in lipase buffer containing Tween. Our intention was to find more sensitive substrate with faster response. Our method is based on cleaving of Indoxyl-acetate by porcine lipase to indoxyl and acetate, after connection of enol and keto form of indoxyl, blue indigo color arises. Coloration of solution is measurable by spectrophotometry at 620 nm wavelength. Calibration curve has Michaelis-Menten-likebehavior and Michaelis-Menten constant was set to be 8.62 mmol/l. Correlation coefficient equal to 0.999 and limit of detection was defined to be equal to 0.12 mmol/l. Our method is more accurate andshows better sensitivity. If we compare data of our method and standard assay, method with Indoxyl-acetatereach higher absorbance during less time. Novel substrate for lipase - Indoxyl acetate was found.
This work describes different effective microfluidic-chip devices used as miniaturized sample preparation technique. The most critical stage of the analytical process is the preparation of the sample requiring different stages prior to analysis, long extraction times, large volumes of reagents, etc., with the objective of obtaining a good clean-up its final analysis The devices presented allow to work in different configurations depending on the nature of the analyte to be extracted: either by liquid phase microextraction or by electromembranes. Two pumps are used to introduce the sample and the acceptor phase into the microfluidic device. The microfluidic device is fabricated using two patterned plates of poly(methyl methacrylate), which are symmetrical. The channels are separated by a polypropylene membrane. The geometry of the devices is critical for its optimization. The length, the width and the depth changes depending on whether liquid phase microextraction or electromembrane extraction is used as technique. An optimal design of these devices provide high selectivity, clean-up, reduce sample volume and low consumption of reagents and significantly reduce time of analysis. Additionally, the microchip-devices are reusable (allow membrane exchange) and each membrane is stable during more than ten consecutive microextractions
Dr. María Ramos Payán has completed herPhDfrom University of Seville, Spainand postdoctoral studies from University of Copenhagen (Denmark), University of North Carolina (USA) and Microelectronic National Center of Barcelona (Spain). She is leader of the microfluidic research line. She has published more than 30 papers in reputed journals and has been serving as an editorial board member of repute.
Food quality requires the control of nutritional value, sensorial properties, authenticity, and safety of food products. Honey is one of the most often food frauding product, with adulteration, dilution, substitution, mislabelling and misrepresentation of source. One of the parameters used for authenticity assessment of honey, in the lights of its production and description, is sugar profile. Honeydew honeys derive from secretions of living parts of plants or excretions of plant-sucking insects on plants. It contains a more complex mixture of sugars with appreciably higher content of reducing disaccharides and higher sugars compared to floral honey. Sugar profile of 64 authentic honeydew honey samples of five botanical origins were determined using high-performance anion exchange chromatography coupled with pulsed amperometric detection. Dionex CarboPac PA100 column allows the separation of fructose, glucose, sucrose, turanose, maltose, melbiose, trehalose, isomaltose, erlose, arabinose, panose, maltotriose, raffinose, and melezitose with minimum sample preparation. The detection method was sensitive enough to allow the determination of lower concentrations of sugars, while also being robust enough to handle higher concentrations of the major components, glucose and fructose. The quantification of a broad range of sugars in honey samples was used for verification of natural origin, as well as assessment of botanical origin of specific species of honeydew honey.
Ms. Vesna Vasić is a PhD student at the University of Belgrade - Faculty of Chemistry, at the Department for Analytical Chemistry. Field of her interest is development of analytical (chromatographic) methods for determination of bioactive compounds in food, and application of statistical (chemometrics) methods in analytical chemistry (mostly pattern recognition, modelling and image analysis).
Chemiresistor gas sensors have been developed extensively for sensing trace concentrations of the vapors of explosive materials. The chemiresistor gas sensors compared to other techniques offer numerous benefits such as high sensitivity, wide linear range of response, and minimum space requirement along with the low-cost devices. 2,4-Dinitrotoluene (DNT) as the most common nitroaromatic explosive has wide range of applications in ammunition. It is mainly released to environment during military activities such as ammunition production and packing. Also, this nitroaromatic is released as a vapor from in the most land mines including anti-personnel and anti-vehicle mines. In this study, an electrochemical sensor based on deposition of polyvinyl alcohol/ polyaniline (PVA/PANI) nanocomposite was designed. The synthesized PVA/PANI nanocomposite were characterized by scanning electron microscopy, FTIR spectroscopy and X-ray diffraction. Results showed that the synthesized PANI nanoparticles have mean particle size of 45 nm with relatively uniform size distribution. The performance of the designed sensor was tested in a static setup used for production of explosive material vapor. The developed sensor was employed for measurement of various concentration of explosives’ vapor (0.1 to 100 ppm) under static air conditions. The fabricated sensor showed good sensitivity toward DNT and had a linear range at the concentration range of 0.5-50 ppm. Also, selectivity tests were carried out in the presence of DNT and vapor of other organic matters and the results indicated that the designed sensor’s possess high sensitivity and selectivity toward DNT.
Catalytic effect of chromium oxide nanoparticles on the thermal behavior and decomposition reaction kinetic of the double base propellant formulation was investigated by various techniques, i.e., simultaneous thermogravimetry-differential thermogravimetry (TG-DTG) and differential scanning calorimetry (DSC). The results showed that chromium oxide nanoparticles significantly change thermal pattern of the studied propellant. the results revealed that addition of chromium oxide nanoparticles caused to shift in the DSC peaks. Moreover, the catalyst decreases activation energy of the decomposition stage of propellant at about 60 kJ/mol. However, the catalyst enhances decomposition temperature of propellant and improves the thermal stability of propellant, make the decomposition easier and more thorough in main reaction zone. Non-isothermal DSC data was used to predict the thermokinetic parameters such as activation energy (Ea), frequency factor (A), the critical ignition temperature of thermal explosion (Tb), the self-accelerating decomposition temperature (TSADT) and thermodynamic parameters of the studied propellant via a well- known integral methods (i.e., Flynn-Wall-Ozawa) and also two differential methods (i.e., Kissinger and Starink) were calculated and compared.
Dr. Pourmortazavi received his PhD in analytical chemistry in 2010. Now, he is Associate Prof. in Malek-e-Ashtar University of Technology. He has published more than 128 papers in reputed journals and has been serving as an editorial board member of repute. His researches focuses on the use of various analytical methods to study the structures of materials and nanomaterials.