National Repository of Grey Literature 74 records found  1 - 10nextend  jump to record: Search took 0.01 seconds. 
Determination of bisphenols in selected beverages by high-performance liquid chromatography
Marvan, Jiří ; Sobotníková, Jana (advisor) ; Olšovská, Jana (referee)
Bisphenols are chemical compounds with a wide range of uses in the chemical industry. They are used in the production of plastic materials as softeners for polymer materials or epoxy resins, as monomers in the synthesis of polycarbonates, or for the elimination of hydrochloric acid in the production of polyvinyl chloride. This thesis deals with the development, validation, and optimization of an analytical method for the determination of selected bisphenols, specifically bisphenol A, bisphenol B, bisphenol F, bisphenol A diglycidyl ether and bisphenol F diglycidyl ether (BPA, BPB, BPF, BADGE, BFDGE), and their metabolites using the high performance liquid chromatography with mass spectrometry, HPLC/MS, and the application of the method to real samples in selected canned beer samples. The following conditions were optimized for chromatographic separation. The Sigma-Aldrich discovery C18 column (150×2,1 mm, 5µm) was chosen. The mobile phase consisted of a mixture of mobile solvent A, which contained 0,05% ammonium hydroxide, and mobile solvent B, which contained of methanol. The flow rate of the mobile phase was 0,240 ml/min. The total analysis time was 22 minutes, using a 5 μl injection of the sample solution with gradient elution. Next, a partial validation of the method was performed, evaluating...
The use of high-performance separation techniques for monitoring the bioaccumulation of selected micropollutants in plants of model root treatment plants
Modroczká, Karin ; Sobotníková, Jana (advisor) ; Coufal, Pavel (referee)
This bachelor's thesis deals with the determination of ibuprofen in model root refineries from Phalaris arundinacea extracts. The goal was to find out if the plant is able to accumulate ibuprofen from the aqueous solution which was added to the plant. A HPLC method with UV/VIS detection was also optimized to determine the ibuprofen content. A C18 column (4.6 mm × 150 mm × 3.5 µm) was used to analyse the samples. An isocratic program was used, in which the mobile phase consisted of methanol and an aqueous acetic acid solution of pH = 3,27. As part of the validation of the method, the repeatability, robustness, and yield (which was 99,04 %) of the method were verified. Furthermore, the linearity of the method, which was from 0,01 mg ml-1 to 2,0 mg ml-1 , the limit of detection (LOD = 0,049 mg ml-1 ) and the limit of quantification (LOQ = 0,16 mg ml-1 ) were determined. After the validation of the method, we can claim that the method is accurate, because the values of the relative standard deviations did not exceed 2 %. Infrared spectroscopy was used to verify the purity of ibuprofen batches. Last but not least, it was proven that Phalaris arundinacea has the ability to accumulate ibuprofen from an aqueous solution. Keywords: HPLC, ibuprofen, Phalaris arundinacea, root wastewater treatment plant,...
The usage of the "Ethanol as internal standard" method for the SPME-GC/FID analysis of volatile compounds in alcoholic products
Zavoralová, Lucie ; Korban, Anton (advisor) ; Sobotníková, Jana (referee)
This bachelor thesis dealt with the optimization of a method for the determination of 10 volatile compounds occurring as minor components in alcoholic products. The quantification was performed by the internal standard method, comparing the results using 1-pentanol and ethanol as classical and proposed internal standards, respectively. In the case of ethanol usage, better repeatability and accuracy of the results were expected as this method does not require any sample pre-treatment. The optimized measurement method was monitored for both internal standards, while following these parameters - repeatability, recovery, linearity and limits of detection and quantification. It was found out that, as expected, the method of the proposed ethanol internal standard gives more accurate results for the analysis of real alcoholic beverage samples. However, it did not outperform the classical internal standard method in all parameters. That one gave better results for repeatability and linearity for the set of calibration solutions measured, despite the fact that each sample had to be pre-treated. It was also found that samples with a high ethanol or other volatile content were not suitable for SPME analysis, because the fibre then loses its ability to sorb these substances in the same proportions and...
Determination of essential oils in hops and beer by GC-MS method
Přikryl, Jaroslav ; Sobotníková, Jana (advisor) ; Nesvadba, Vladimír (referee)
The submitted master's thesis aims to the analysis of hop essential oils using gas chromatography separation and subsequent determination using a pair of mass and flame ionization detectors. In the first part, the thesis focuses on the theoretical approach to the issue of hop essential oils and the technical functionality of the device for the detection and quantitative determination of essential oils. Subsequently, in the second part, work describes the development, optimization and validation of the newly developed method for the extraction and determination of hop essential oil.
Extension of artificial intelligence DeepReI and its application in practice
Hurychová, Nikola ; Sobotníková, Jana (advisor) ; Křížek, Tomáš (referee)
Diploma thesis deals with expanding the artificial intelligence DeepReI with the prediction of retention indices of substances in gas chromatography for standard non-polar and polar stationary phases. The theoretical part describes artificial intelligence, convolutional neural networks, and the principles of neural network learning. There is also a brief overview of the applications of neural networks in analytical chemistry. In the experimental part, the original DeepReI model was extended to predict the retention indices of substances for standard non-polar and polar stationary phases. Furthermore, more accurate predictions of retention indices were achieved for semi-standard non-polar stationary phases compared to existing models. The applicability of the model for substance identification was verified through non-targeted analysis of non-alcoholic beers using gas chromatography with mass detection.
Determination of volatile and non-volatile nitrite products in sausages
Hlávka, Jan ; Sobotníková, Jana (advisor) ; Čabala, Radomír (referee)
This diploma thesis deals with the determination of nitrite products in sausages using gas chromatography. In the first part of this thesis, an extraction method was developed for the determination of 4-cyanophenol and N-nitrosoproline in samples of sausage products using gas chromatography with tandem mass spectroscopy. A 1% formic acid solution in acetonitrile was used to extract the analytes from the sausage samples. Due to the lower volatility of the analytes, derivatisation with N,O-bis(trimethylsilyl)trifluoroacetamide was necessary before each analysis. Using this method, an indicative determination of the concentrations of 4-cyanophenol and N-nitrosoproline in selected sausage samples was carried out. The standard addition method was used for the quantification of these analytes because of the strong matrix effect. For the selected types of sausage, it was observed whether or not the concentrations of the analytes differed in products with different meat contents. At the end of this diploma thesis, a validation of a method for the determination of volatile N-nitrosamines in sausage products by gas chromatography with chemiluminescence detection was performed. The analytes were N-nitrosodimethylamine, N-nitrosodiethylamine, N-nitrosodibutylamine, N-nitroso-piperidine, N-nitrosopyrrolidine...
Development and optimization of HPLC method for determination of peroxide impurities in pharmaceutical excipients
Hrubcová, Kateřina ; Křížek, Tomáš (advisor) ; Sobotníková, Jana (referee)
The chemical stability of drugs can be affected by impurities that occur in commonly used excipients. Hydroperoxides are common trace impurities, especially in polymeric excipients, which can cause oxidative degradation of drugs. Several methods for the quantification of trace levels of hydroperoxides (hydrogen peroxide and organic hydroperoxides) are described in the literature. However, there are few studies dealing with the quantification of trace levels (ppm) of hydroperoxides in drug excipients. The goal of this thesis was the development and optimization of an HPLC method with UV detection for the determination of hydroperoxides in drug excipients, based on methods already described in the literature. The developed HPLC method is based on the determination of triphenylphosphine oxide as a product of the rapid and quantitative reaction of triphenylphosphine with hydroperoxides. Method development also included optimization of sample preparation prior to HPLC analysis. During the experimental work, the influence of individual experimental parameters and sample preparation conditions on the determination of hydroperoxides was determined. The optimized HPLC method used a Kinetex F5 column (100 × 4,6 mm, 2,6 µm) and a mixture of water and acetonitrile as the mobile phase with gradient elution. As...
The fate of phosphorus in root wastewater treatment plants
Veselá, Klára ; Sobotníková, Jana (advisor) ; Nováková, Eliška (referee)
This bachelor's thesis deals with the determination of phosphorus in constructed wetlands. Phosphorus in wastewater must be eliminated effectively because there is a government regulation that permits maximal permissible concentration of phosphorus on the exit of wastewater treatment plants. Increased concentration in water leads to eutrophication, which causes the death of aquatic animals and plants. The aim of this bachelor's thesis is the validation of an easy and functional method for the determination of phosphorus in the water matrix. This method uses a complex with malachite green. The next aim was the determination of phosphate in the samples from model constructed wetlands. It's possible to make conclusions about the efficiency of model constructed wetlands out of this. For the determination UV-VIS spectrophotometry was used. The measured absorbance was recalculated to a concentration of phosphorus and after that to the concentration of phosphate. During the validation calibration, accuracy measurement, repeatability measurement, and measurement of absorbance dependence on time were performed. Sensitivity (by comparing the malachite green method with the normed method using phosphomolybdate blue), linearity, trueness, robustness, the limit of detection, and the limit of quantification were...
Determination of calcium in food supplements
Hubčuková, Karmelita ; Hraníček, Jakub (advisor) ; Sobotníková, Jana (referee)
Tato bakalářská práce byla zaměřena na stanovení vápníku ve vybraných potravinových doplňcích s využitím plamenové atomové absorpční spektrometrie. Nejdříve byla prováděna optimalizace podmínek s využitím plamene acetylen-vzduch a následně s využitím plamene acetylen-oxid dusný. Optimalizovanými parametry byla výška paprsku nad hranou hořáku, horizontální poloha hořáku, šířka absorpčního prostředí, průtoková rychlost acetylenu a oxidu dusného. Byla sestrojena kalibrační závislost stanovení vápenatých iontů a odpovídající meze detekce a stanovitelnosti. Následně byly vybrané vzorky potravinových doplňků několika způsoby převedeny do roztoku. Vyzkoušeno bylo rozpouštění v deionizované vodě, rozpouštění v koncentrované kyselině dusičné a rozklad pomocí mikrovlnného tlakového zařízení. Experimentálně bylo stanoveno množství vápníku v potravinových doplňcích, které bylo porovnáváno s údaji uvedenými od výrobce. Správnost měření byla ověřena analýzou referenčního materiálu.

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