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Janja Turšic, Boštjan Podkrajšek, Boris Pihlar, Štefica Cerjan–Stefanovic, Milko Novic
PROFICIENCY TESTS AND LABORATORY REFERENCE MATERIALS IN ION CHROMATOGRAPHY

International Schools of Ion Chromatography are well-accepted annual meetings among users of ion chromatography in Slovenia and Croatia. Special attention is also given to some features of metrology e.g. tracebility and uncertainty. Within schools, proficiency tests are organized, with the aim of checking the performance of participating laboratories as well as of testing different analytical approaches suitable for certain types of samples. The procedure for preparation of a laboratory reference solution (Cl- and Br-) using primary techniques with direct traceability to SI units is also shown.

Jiri Haze, Michal Skocdopole, Jan Krejci, Radimir Vrba, Lukas Fujcik, Dagmar Krejcova, Zuzana Grosmanova
ARTIFICIAL SYNAPSIS – THE DETECTOR OF PESTICIDE TOXICITY

Fast detection of organophosphorous pesticide toxicity in field conditions has not been fully solved yet. The new tool for field measurement of organophosporous pesticides toxicity is described. The detection is based on the inhibition of acetylcholinesterase. The enzyme acetylcholinesterase is immobilized on a miniature electrochemical detector, which is made by Thick Film Technology (TFT). The dimensions of TFT electrochemical sensor are 7,35 x 25,4 mm. The detector is placed in a narrow gap in which the analyzed sample and acetylthiocholine flow. This arrangement simulates the removal of acetylcholin from synaptic gap. It creates the simple model of synapsis - the Artificial Synapsis (AS).
The AS detects the integral sample toxicity. It enables organophosporous pesticides traces to be detected in washout from leaves as well as their direct measurement in rivers, ponds, vaste waters and drinking water sources. The preconcentration of the sample is possible. The detection limit varies in wide range depending on the toxicity of pesticide.
Structure and function of AS is described. Limit of detection (LOD) was found for pesticide Syntostigmin 10-10 mol.

Jiri Haze, Michal Skocdopole, Jan Krejci, Radimir Vrba, Lukas Fujcik, Dagmar Krejcova, Milan Kraus
PORTABLE DEVICE FOR PESTICIDE TOXICITY ANALYSIS FOR MEASUREMENT IN FIELD CONDITIONS

The new portable microfluidic device for field measurement is presented. It consists of two loop pumps. The first loop asssures the mixing of solution. The 95% of solution circulates through the first loop. The second loop consists of capillary which creates the hydrodynamic resistance and the chamber with biosensor. The Artificial Synapsis (AS) is integrated in the chamber, which detects the integral organophosphorous pesticide toxicity. The 5% of solution circulates through AS. Both parts are integrated in a compact device with size of 200 x 100 x 100 mm.
The signal from biosensor is evaluated by Bioanalyzer electronic unit. It is destinated for detection of traces of pesticides in washout from leaves for direct measurment in rivers, ponds, vaste waters and drinking water sources. The electronic unit contains the unique software for data aquisition and biosensor signal analysis. The whole device consists of two basic units and several accessories. The article describes structure and function of this device.

Adamek Martin, Prasek Jan, Krejci Jan, Fujcik Lukas
GRAPHITE PASTES IN THICK FILM SENSORS AREA

Miniature electrochemical sensors can be produced by thick film technology (TFT). The optimal properties of thick film electrode materials are main problems of sensors design. The optimisation of graphite pastes properties for TFT chemical sensor is discussed. The commercial TFT graphite pastes, which are used for common application, are cheap and easily producible, but they are not efficient for electrochemical measurement. These pastes have insufficient sensitivity and they have other bad properties. Graphite pastes, which were designed for special chemical analysis, are technically known, but these pastes are not workable by screen-printing. The first step in rheological properties addition to graphite electrochemical pastes is the goal of this work. This will ensure the pastes printability that will enable the reproducible mass production.
The graphite powder with paraffin wax mixture is the basic component of common chemical graphite pastes. There were examined different properties of these pastes in dependence on graphite powder and binding material content in this work. Finally there are described some measurement with commercial and specially prepared TFT graphite electrodes. All measurements were done using a standard electrochemical couple of potassium ferrocyanideferricyanide.

Ondrej Sajdl, Radimir Vrba, Jan Krejci, Lukas Fujcik
MS EXCEL AND STANDARDIZATION OF MEASUREMENT RESULT EVALUATION OF BIOSENSOR INPUT CONTROL

Nearly in every practical part of some scientific project solution we meet demand to discover or verify a function of a developed device (instrument, sensor, etc.) This process (a measurement) is usually executed repeatedly and usually by various people. A practice shows that if we don’t unify the evaluation result, especially if we have greater number of measurements (hundreds or more), it can cause its ambiguity and thereby to its depreciation. To prevent this depreciation, it is necessary jointly to interpret and to evaluate attained results – to standardize. Analysis and practical solution exploiting Microsoft Excel is presented in this paper.

Lukas Fujcik, Radimir Vrba, Jan Krejci, Michal Skocdopole, Ondrej Sajdl, Jiri Haze
INPUT CONTROL OF SENSOR PARAMETERS AND REPRODUCIBILITY OF SENSOR MEASUREMENT

Fast detection of pesticide toxicity in the field conditions is very important in many aspects (longtime influence of low concentrations on man´s health, pesticide storage, price of one test etc.). The pesticide concentration measurements are performed on a biosensor with acetylcholinesterase (AChE). The AChE is a very sensitive compound. The measurement uses principle of an artificial synapse (AS) and inhibition of an enzyme Acetylcholinesterase (AChE). The AS is a very effective detector of the pesticide toxicity. Therefore properties of the sensor have to be measured without AChE at first. This process is called input control of the sensor. The reproducibility of electrochemical detector is studied first using hydrogen peroxide and second ferri-ferrokyanide redox couple. The parameters of electrochemical detector itself were evaluated statistically.

Gregorio Andria, Giuseppe Cavone, Vincenzo Di Lecce, Anna M. L. Lanzolla
MATHEMATIC MODEL FOR MEASUREMENT AND CHARACTERIZATION OF AIR POLLUTION IN AREAS WITH HIGH ROAD-TRAFFIC LEVELS

The paper deals with measurement and behaviour characterization of the main substances influencing air pollution in an urban area with high road traffic level. To this aim, the correlation existing between some pollutants is identified and a mathematic model able to forecast and describe the time varying behaviour of contaminating substances is implemented. Finally, some information about reliability degree of estimate is provided.

Dubravka Doležal, Tatjana Tomic
VALIDATION PROCEDURES FOR DETERMINATION OF TOTAL ORGANIC CARBON IN WATER

The determination of total organic carbon (TOC) content in water is useful as a measure of pollution. It is an analytical process which is validated and it demonstrates that it is suitable for its intended purpose. Several validation parameters are done to conduct validation procedures.

Francesco Adamo, Gregorio Andria, Filippo Attivissimo, Nicola Giaquinto
A STUDY OF THE MOISTURE EFFECTS ON THE ACOUSTIC WAVES

This paper focuses on the study of a mathematical model to measure the moisture content of agricultural soils. After the proposal and analysis of a measurement method based on the propagation of elastic waves in a granular unconsolidated medium, a mathematical relationship between the propagation velocity of an acoustic wave and the moisture content of the soil is obtained. The authors carefully study and verify the conditions that guarantee the applicability of the model; the analysis shows that a right choice of the frequency of the transmitted signal allows the applicability of the model to a wide range of agricultural soils.

Zeyi Zhou, Yadong Yu
STUDY OF COMPUTER CONTROL DYNAMIC VOLUMETRIC METHODS AND PREPARATION OF WATER CALLIBRATION GASES

A new type apparatus of dynamic volumetric calibration system was designed and made in correspond with ISO 6145. The main parameters of dynamic volumetric method can be monitored recorded and calculated by a personal computer. The calibration gases of water in nitrogen with ranges of 10-7~10-6 mol/mol were prepared in the form of diffusion tubes by dynamic volumetric method. Test in comparison with a standard dew point apparatus expressed that the water diffusion tubes are reliable and accurate, and the uncertainties of the calibration gases of water in nitrogen are in the ranges of 3%~4%.

Page 888 of 936 Results 8871 - 8880 of 9356