Modification of Working Electrode Surface with Carbon Nanotubes as an Electrochemical Sensor for Estimation of Melting Points of DNA

Screen-printed with three electrode system was used in this study. A working electrode has been printed from carbon nanotubes based paste on silver layer modified with nano-patterned structures for the first case. In the second case, vertically aligned carbonnanotubes were grown on the Au working electrode. The process of the nanotubes growing was tested to create homogenous and high density carbon nanotubes layer directly on the thick-film silver layer. Based on the characterization of electrodes, we used Au based for detection of nucleic acids. Moreover, we were able to estimated melting points of DNA. © 2009

Lactoferrin isolation using monolithic column coupled with spectrometric or micro-amperometric detector

Lactoferrin is a multifunctional protein with antimicrobial activity and others to health beneficial properties. The main aim of this work was to propose easy to use technique for lactoferrin isolation from cow colostrum samples. Primarily we utilized sodium dodecyl sulphate - polyacrylamide gel electrophoresis for isolation of lactoferrin from the real samples. Moreover we tested automated microfluidic Experion electrophoresis system to isolate lactoferrin from the collostrum sample. The well developed signal of lactoferrin was determined with detection limit ( 3 S/N) of 20 ng/ml. In spite of the fact that Experion is faster than SDS-PAGE both separation techniques cannot be used in routine analysis. Therefore we have tested third separation technique, ion exchange chromatography, using monolithic column coupled with UV-VIS detector (LC-UV-VIS). We optimized wave length ( 280 nm), ionic strength of the elution solution (1.5 M NaCl) and flow rate of the retention and elution solutions (0.25 ml/min and 0.75 ml/min. respectively). Under the optimal conditions the detection limit was estimated as 0.1 mu g/ml of lactoferrin measured. Using LC-UV-VIS we determined that lactoferrin concentration varied from 0.5 g/l to 1.1 g/l in cow colostrums collected in the certain time interval up to 72 hours after birth. Further we focused on miniaturization of detection device. We tested amperometric detection at carbon electrode. The results encouraged us to attempt to miniaturise whole detection system and to test it on analysis of real samples of human faeces, because lactoferrin level in faeces is closely associated with the inflammations of intestine mucous membrane. For the purpose of miniaturization we employed the technology of printed electrodes. The detection limit of lactoferrin was estimated as 10 mu g/ml measured by the screen-printed electrodes fabricated by us. The fabricated electrodes were compared with commercially available ones. It follows from the obtained results that the responses measured by commercial electrodes are app. ten times higher compared with those measured by the electrodes fabricated by us. This phenomenon relates with smaller working electrode surface area of the electrodes fabricated by us ( about 50%) compared to the commercial ones. The screen-printed electrodes fabricated by us were utilized for determination of lactoferrin faeces. Regarding to fact that sample of faeces was obtained from young and healthy man the amount of lactoferrin in sample was under the limit of detection of this method

Flow injection analysis coupled with carbon electrodes as the tool for analysis of naphthoquinones with respect to their content and functions in biological samples

Naphthoquinones are one of the groups of secondary metabolites widespread in nature, where they mostly appear as chromatic pigments. They embody broad-range of biological actions from phytotoxic to fungicidal. An anticancer effect of naphthoquinones stimulates an interest in determination and characterization of single derivatives of 1,2- and 1,4-quinones in biological samples. The main aim of this work was to suggest a technique suitable to determine lawsone, juglone and/or plumbagin in biological samples and to study of their influence on BY-2 tobacco cells. The BY-2 tobacco cells were cultivated in the presence of the naphthoquinones of interest ( 500 mu g.l(-1)) for 24 h and then the morphological changes were observed. We found out that naphthoquinones triggered the programmed cell death at BY-2 cells, which can be confirmed by the apoptotic bodies in nucleus. After that we suggested and optimized different electrochemical techniques such differential pulse voltammetry ( DPV) coupled with hanging mercury drop ( HMDE) and carbon paste electrode, micro flow device coupled with carbon screen printed electrodes and flow injection analysis coupled with Coulochem III detector to determine them. The detection limits of naphthoquinones of interest were expressed as 3S/N and varied from units to hundreds of ng per millilitres according to methods used. Moreover, we utilized DPV coupled with HMDE and micro flow device to determine content of juglone in leaves Persian walnut ( Juglans regia). We determined that the leaves contained juglone tenths of g per 100 g of fresh weight. The results obtained show the convincing possibilities of using of these methods in analysis of plant secondary metabolites

Proportional counter measurement system

The thesis deals with gas-filled proportional counters intended for the detection of presence of ionising radiation and its properties. Proportional counters make it possible to find out about the type and energy of ionising particles. The thesis analyses the theory regarding the character of ionising radiation and its detection, describes the measuring apparatus used and the possibilities of verification of counters function. It also deals with the character of signals from the detectors and its imitation. It documents the measurements carried out with various sources of ionising radiation and interpretation of the acquired data, suggests and describes possible improvements of the measuring apparatus

Laboratory electronic load 400 W

Tato práce se zabývá konstrukcí laboratorní elektronické zátěže, jejíž využití spočívá ve zkoušení různých zdrojů elektrické energie, například elektronických napájecích zdrojů nebo akumulátorů. Práce uvádí možná zapojení takové zátěže, zmiňuje továrně vyráběná zařízení, popisuje postup při návrhu zařízení, výběr součástek, provádění simulací pro ověření funkce navržených obvodů a mechanickou konstrukci.This thesis deals with the construction of a laboratory electronic load purpose of which is to test various sources of electric energy, for instance electronic power supplies or accumulators. The thesis states possible designs of electronic circuits forming such an electronic load, it mentions factory manufactured devices, it describes the way of designing parts of the device, choice of components, conduction of circuit simulations for function verification of designed circuits and mechanical construction.

Laboratory electronic load 400 W

This thesis deals with the construction of a laboratory electronic load purpose of which is to test various sources of electric energy, for instance electronic power supplies or accumulators. The thesis states possible designs of electronic circuits forming such an electronic load, it mentions factory manufactured devices, it describes the way of designing parts of the device, choice of components, conduction of circuit simulations for function verification of designed circuits and mechanical construction

High-performance liquid chromatographic method with amperometric detection employing boron-doped diamond electrode for the determination of sildenafil, vardenafil and their main metabolites in plasma

A simple, fast and sensitive HPLC method with electrochemical detection employing boron-doped diamond electrode (BDD) for the determination of sildenafil (Viagra™), vardenafil (Levitra™) and their main metabolites, N-desmethyl sildenafil and N-desethyl vardenafil in human plasma is presented. The assay involved drug extraction by tert-butyl methyl ether and isocratic reversed-phase liquid chromatography with amperometric detection. Complete separation of all analytes was achieved within 12min. The mobile phase consisted of 20mM sodium dihydrogen phosphate with 40mM sodium perchlorate/acetonitrile (70:30, v/v), pH 3.5. The electrode working potential was +1520mV (vs. Pd/H2). Calibration curves were linear over the concentration range of 10-400ngmL-1. Phloretin was used as an internal standard. The limits of detection (LOD) and quantification (LOQ) for the studied analytes were within the range of 2-4ngmL-1 and 7.0-13.4ngmL-1, respectively. The developed method was applied to human plasma samples spiked with analytes at therapeutic concentrations. The study confirms the method's suitability for both pharmacokinetic studies and therapeutic monitoring. © 2011 Elsevier B.V

Determination of Phloridzin and Other Phenolic Compounds in Apple Tree Leaves, Bark, and Buds Using Liquid Chromatography with Multilayered Column Technology and Evaluation of the Total Antioxidant Activity

Apples are known to be a rich source of phenolic compounds, however detailed studies about their content in the individual parts of apple trees are reported rarely. For this purpose, we tested various stationary phases for the determination of phenolic compounds in leaves, bark, and buds. Phloridzin, phloretin, chlorogenic acid, rutin, and quercitrin were analyzed with high performance liquid chromatography coupled with diode array detection. A YMC Triart C18-ExRS 150 × 4.6 mm, 5 µm particle size analytical column with multilayered particle technology was used. The separation was performed with a mobile phase that consisted of acetonitrile and 0.1% phosphoric acid, according to the gradient program, at a flow rate of 1 mL/min for 12.50 min. The concentration of phenolic compounds from 13 cultivars was in the range of 64.89–106.01 mg/g of dry weight (DW) in leaves, 70.81–113.18 mg/g DW in bark, and 100.68–139.61 mg/g DW in buds. Phloridzin was a major compound. The total antioxidant activity was measured using flow analysis and the correlation with the total amount of phenolic compounds was found. This finding can lead to the re-use of apple tree material to isolate substances that can be utilized in the food, pharmaceutical, or cosmetics industries

Hazards of secondary bromadiolone intoxications evaluated using high-performance liquid chromatography with electrochemical detection

This study reported on the possibility of intoxications of non-target wild animals associated with use of bromadiolone as the active component of rodenticides with anticoagulation effects. A laboratory test was done with earthworms were exposed to bromadiolone-containing granules under the conditions specified in the modified OECD 207 guideline. No mortality of earthworms was observed during the fourteen days long exposure. When the earthworms from the above test became a part of the diet of common voles in the following experiment, no mortality of consumers was observed too. However, electrochemical analysis revealed higher levels of bromadiolone in tissues from earthworms as well as common voles compared to control animals. There were determined comparable levels of bromadiolone in the liver tissue of common voles after primary (2.34 +/- 0.10 mu g/g) and secondary (2.20 +/- 0.53 mu g/g) intoxication. Therefore, the risk of secondary intoxication of small mammalian species feeding on bromadiolone-containing earthworms is the same as of primary intoxication through baited granules. Bromadiolone bio- accumulation in the food chain was monitored using the newly developed analytical procedure based on the use of a liquid chromatography coupled with electrochemical detector (HPLC-ED). The HPLC-ED method allowed to determine the levels of bromadiolone in biological samples and is therefore suitable for examining the environmental hazards of this substance

Utilization of high performance liquid chromatography for determination of antioxidant capacity

In this study, we are interested in possibility of determination and expression of biological value of twenty perspective genotypes of apricot (Prunus armeniaca L.). Work was focused on verification and validation of HPLC technique with electrochemical detector (ED) for determination of total antioxidant capacity (TAC), which may represent suitable method for comparison of biological value of fruits.[NAZV 91A032]; [GACR 102/08/1546