Mostrando recursos 1 - 20 de 3.699

  1. Determination of temperature effecton the measurements of pKa of some weak acids and weak bases using capillary zone electrophoresis

    Gravador, Rufielyn Sungcaya
    This study was done to determine the pKa values of a number of weak acidic and basic compounds at different temperatures and to be able to identify the effects of temperature variations in the measured pKa using capillary zone electrophoresis. The method employed was adopted from Fuguet et al [12] in which internal standard is used. Running buffers of different pH were prepared. The maximum voltage was chosen based from Ohm’s law to reduce the Joule heating effects. Considering the linearity in the relationship between voltage and current to be with an r2≥0.999, the maximum voltage was found to be...

  2. Speciation of chromium in Algeciras bay

    Assefa, Anteneh Taye
    Algeciras Bay is exposed to contamination from chromium because of the industrial activities carring out around the water, i.e Steel Industry and two Petrol Refineries can be mentioned. More over there are several activities which are being carried out including big ports, fishing and recreational activities. Most of the other trace metals in the water have been studied. Considering the environmental and health effects of this metal, study of its level and speciacion in the bay is necessary for wellbeing of all which are directly or indirectly dependent on this water. Unfiltered samples were used for total chromium determination and filtered samples were used for the other...

  3. Multi-class, multi residue method for determination of penicillins, cephalosporins and quinolones in cow milk and validation in accordance with Commission Decision 2002/657/E C

    Amatya, Rameshwari
    The method was developed to determine simultaneously 19 drugs of three classes (seven Penicillins and Cephalosporins, and five Quinolones) regulated by European legislation 2377/90/EC in cow milk using LC-MS/MS. To make the sample preparation as simple as possible deproteinization step using organic solvent was eliminated. SPE clean up and concentration was done using OASIS HLB cartridge. The separation of 19 antibiotics was achieved in 11 minutes using C8 column with gradient elution. MS data was acquired on MRM mode with two transitions for each compound. Validation procedure was conducted based on European directive 2002/657/EC. 89% of drugs presented recoveries higher than 65 % with exception of AMOX (57%) and...

  4. Determination of cyclophosphamide in human urine by HPLC coupled to tandem mass spectrometry

    Marahatta, Anu
    Biological samples urine are much more complex due to presence of proteins, salts, acids, bases and various organic compounds with similar chemistry to analytes of interest. As a result, the extraction methods for biological samples have been difficult. The main task was to remove maximum interfering substance from urine matrix and conversion of analytes into a more suitable form for injection. Therefore, optimization of SPE method was done by changing different parameter such as different type and amount of sorbent, composition and volume of elution, washing solvent. The use of 24 well SPE plate for matrix purification significantly allows the use of small urine and solvent volumes,...

  5. Process monitoring of continuous flow organic syntheses by means of inline fiber optical Raman spectroscopy

    Rehman, Muhammad Saif Ur
    The objective of the current study was to investigate the feasibility of the inline optical fiber Raman spectroscopy as a tool for the process monitoring of the continuous flow organic syntheses. The synthesis of 2-bromo-3,4,5-trimethoxytoluene (product) was studied as a model reaction under a set of different conditions. The reaction was carried out under the batch as well as in the multi jet oscillating disc (MJOD) milli reactor. The reaction was varied by doubling the concentration of the substrate; 3,4,5-trimethoxytoluene (0.15M, 0.3M and 0.6M) whereas the concentration of the solvent (acetic anhydride) was kept constant. The Raman instrument was adjusted to record five spectra per minute. The...

  6. Quality system design and implementation in proficiency test provider laboratory based in an international norm

    Pereira, Glauce Guimarães
    Proficiency testing is defined as the use of interlaboratory comparisons to determine the performance of individual laboratories for specific tests or measurements and to monitor laboratories‘ continuing performance. The number of PTs is increasing in the last years because the result of this exercise is useful not just for costumers, but also for other interested parties, such as regulators, laboratory accreditation bodies and other organizations who specify requirements for laboratories. Hence, it is very important to organize PT with criteria, focus and quality. The objective of this work was design of a quality system in Mat Control Laboratory of the University of...

  7. Speciation of mercury in environmental samples

    Ruiz , Wilder Leonardo Gamboa
    Mercury is one of the most toxic elements impacting on human and ecosystem health and therefore is one of the most studied environmental pollutants. All mercury species are toxic, with organic mercury compounds generally being more toxic than inorganic species. For this reason, the assessment of mercury distribution in environmental samples is a key task in analytical chemistry. Reverse phase chromatography (RPC) coupled to a UV post-column oxidation system and vapor generation atomic fluorescence spectrometry was optimised for the speciation and determination of inorganic and organic mercury (methylmercury and ethylmercury) in the form of APDC complexes. The mercury-APDC complexes were separated on a reverse phase column and oxidized on-line...

  8. Development and application of quality standard procedures ((operation,, verification and maintenance)) for an LC--MS system

    Daniel, Christy Sarmiento
    In this work, the standard procedures required for the operation, verification and maintenance of a liquid chromatography coupled to mass spectrometry system have been developed. These procedures have been designed and prepared with the aim to establish a quality control system to ensure the proper functioning of each component of the instrumentation, the LC and the MS, and to verify the performance of the LC-MS coupling. For this purpose, standard procedures were elaborated and proved in the normal routine laboratory work to evaluate their real applicability. Moreover, the verification of the performance of the LC-MS system was carried out experimentally...

  9. Application of bismuth modified disposable screen printed carbon electrode for metal- plant thiols complexation studies

    Feyssa, Belachew Tolla
    The application of Bismuth modified cheap and disposable screen printed carbon electrode (BiSPCE) for voltammetric studies of metal–thiol rich peptides complexation was evaluated considering systems consisting of cadmium as a metal and GSH and PC2 as thiol peptides. Comparison of the performance of BiSPCE with the commonly used glassy carbon electrode (BiFE) was made. The information obtained about the complexation sequence using the former electrode was quite consistent with previous studies made on GSH and Cd systems using the conventional mercury electrodes due to the absence of signal splitting, the good sensitivity and the wider linearity range. In contrast with the conventional mercury electrodes, the anodic signals associated...

  10. Enrofloxacin in soils: determination of sorption parameters by liquid chromatography

    Medeiros, Joana Pinto Magalhães de
    There are several parameters influencing the sorption of analytes to soils. In this Master project, the sorption behavior of enrofloxacin (ENR) was characterized in six soils of basic pH and different properties, through the study of sorption isotherms. The Freundlich model fitted all the data, while the Langmuir equation was adjusted only to the soils showing an L-type isotherm. The values of experimental distribution coefficients (Kd) obtained for ENR ranged from 0.69 to 2.04 L/g, in agreement with the ones found in the literature. Principal component analysis was performed in the set of soils, and the properties that appeared to have a greater influence in ENR sorption...

  11. Optimization of an SPE clean-up approach for the analysis of sulfonamides in animal feed

    Kumar, Praveen Kumar
    In this work, clean up strategy is optimized for an analytical method based on liquid chromatography with UV detection for determination of eight sulfonamides (sulfachloropyridazine, sulfadiazine, sulfadimidine, sulfadoxine, sulfamethoxypyridazine, sulfaquinoxaline, sulfamethoxazole and sulfadimethoxine) in pig feed. Solid Phase Extraction is used for clean up and the performance of different sorbents - C 18, Oasis HLB, Plexa and Plexa PCX is assessed by their clean up efficiency and recovery of analytes. Oasis HLB and Plexa PCX sorbents provide better clean up and recovery values than C18 and Plexa. A spiked feed of 2 mg/kg is used to assess mean recoveries and precision in terms of repeatability, r and...

  12. Evaluation of extraction methods for recovery of fatty acids from marine products

    Xiao, Liping
    The extraction efficiency of Soxhlet, acid hydrolysis and Bligh and Dyer were evaluated by using direct methylation on extracts and residues for calculating the mass balance of fatty acids for eight marine powders (fishmeals, krillmeals, cod filet, salmon filet and herring roe). The results show that Soxhlet gave lowest extracted fatty acid content, especially for the samples which contain a high amount of phospholipid. Acid hydrolysis and Bligh and Dyer extract gave comparable extracted fatty acid contents with direct methylation. The mass balance of fatty acids in extract and residue is close to 100% for the three extraction methods which indicate that fatty acid was not lost during the...

  13. Exploring the capabilities of gas chromatography and liquid chromatography single and tandem mass spectrometry for discriminating and characterizing marine oils by using chemometric tools

    Zeng, Yingxu
    Assessing the capabilities of instrumental techniques for discriminating marine oils and studying the positional distribution of fatty acids on the backbone of triacylglycerols (TAG) are of vital importance from commercial, nutritional, biochemical and technological points of view. This represents a great challenge for analysts due to the wide variety of fatty acids and the complexity of naturally occurring TAG species. In this thesis, the potential of gas chromatography (GC) for discriminating full fatty acid methyl ester (FAME) profiles of marine oils (cod liver, salmon, seal and whale oils) is evaluated by means of principal component analysis (PCA). The FAME profiles from...

  14. Interaction of alkylphenols and alkylphenol ethoxylates with sewage sludges and soils

    Milinovic, Jelena
    A common practice for the reuse of sewage sludge from waste water treatment plants (WWTPs) is its application in agricultural soils as fertilizer.

  15. Total analysis and assessement of mobile metal ions in sediments from Algeciras Bay, Spain

    Kosore, Charles Mitto
    Total metal concentrations in surface sediments from seventeen sampling points in Algeciras Bay were determined by total acid decomposition with IR heating technique.

  16. Validation of chromatographic method for the determination of melatonin in wine and grapes using high performance liquid chromatography-fluorescence detection

    Mwaikono, Kilaza Samson
    This master research project reports two validated methods for determination of melatonin in wine using high performance liquid chromatography and fluorescence detector.

  17. Manufacture, characterisation and analytical application of nanomaterials in sensor devices

    Ajaero, Chukwuemeka
    The main objective of this study consisted of developing a new type of amperometric sensors based on depositing gold nanoparticles obtained from two different synthetic routes (thermal and ultrasonic methods) on the surface of a Sonogel Carbon matrix, in order to build electrochemical devices.

  18. Determination of volatile fatty acids in municipal wastewater by gas chromatography-mass spectrometry preceded by headspace- solid phase microextraction with PDMS-CAR fibre

    Pokhrel, Teeka Ram
    An analytical procedure based on headspace – solid phase microextraction (HS-SPME) followed by gas chromatography-mass spectrometry (GC-MS) has been developed for the determination of free volatile fatty acids in municipal wastewater samples. Polydimethylsiloxane-Carboxen (PDMS-CAR) fibre was found to have greater affinity to extract lower chain fatty acids. Extraction and gas chromatographic parameters of importance such as desorption time, sample volume, amount of salt to be added and extraction time have been optimized. Detection limits were in the low to medium mg/L levels. To evaluate the applicability of the developed HS-SPME procedure on real samples, municipal wastewater treatment plant samples were analysed.

  19. Applicability of head space solid phase microextraction (HS-SPME) with polyethylene glycol (PEG) fibre for GC-MS determination of volatile fatty acids in aqueous samples

    Faniband, Moosa Hassan
    A method consisting of head-space solid phase micro extraction (HS-SPME) followed by gas chromatography coupled with mass spectrometry (GC-MS) was developed for determination of volatile fatty acids in wastewater. A new fibre polyethylene glycol (PEG) was evaluated for the sample preparation. This fibre is designed to show high sample capacity, faster mass transfer during extraction, shorter equilibrium times and faster desorption process. The developed method showed good sensitivity with comparable limit of detection (LOD) and limit of quantitation (LOQ) values. The selection of various parameters included extraction time, extraction temperature, sample volume and desorption conditions. The experimental results showed low detection limits ranging between 0.01 mg/L to 0.06 mg/L...

  20. Application of surface plasmon resonance and spectroscopic techniques for characterizing the interaction between human c-KIT G-quadruplex DNA and water soluble porphyrins

    Shenkutie, Sintayehu Manaye
    G-quadruplex DNA structures are hypothesized to be involved in regulation of telomere homeostasis and gene expression.

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