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Application of Diffusive Gradients in Thin Films Technique in Food and Environmental Analysis
Reichstädter, Marek ; Čáslavský, Josef (referee) ; Urík,, Martin (referee) ; Diviš, Pavel (advisor)
Tato dizertační práce zkoumá vývoj techniky difúzního gradientu v tenkém filmu (DGT) pro stanovení rtuti (Hg) a dalších stopových kovů a dále rozšířené možnosti použití této techniky. Technika DGT je v této práci vyvinuta pro stanovení Hg a dalších stopových prvků v různých kapalných médiích. Dvě rozdílná sorpční média specifická pro rtuť byla testována pro použití v technice DGT – Purolite S924 a cysteinem modifikovaná aminopropyl silika (CAPS). Purolite S924 je komerčně dostupný chelatační iontoměnič, CAPS byla připravena v laboratorních podmínkách imobilizací cysteinu na 3-aminopropyl funkcionalizovanou siliku pomocí glutaraladehydu. Obě testovaná sorpční média ukázala slibný aplikační potenciál pro užití v technice DGT díky funkčnosti v roztocích o širokém rozsahu pH i iontové síly. Funkčnost DGT s novými sorpčními médii byla porovnána s technikami DGT s běžně používanými sorbenty Chelex-100 a 3-merkaptopropylfunkcionalizovanou silikou. Hlavní výhodou sorpčních médií Purolite S924 a CAPS je schopnost současného stanovení Hg a dalších stopových kovů (Cd, Pb, Co, Ni, Cu). Vzhledem k odlišným požadavkům na sorpční média používaná v technice DGT nebylo dosud současné kvantitativní stanovení Hg a dalších stopových kovů možné. Doposud byly zapotřebí dvě samostatné techniky DGT – jedna pro Hg a druhá pro další stopové kovy, což zvyšuje množství vzorků pro analýzu a množství použitého spotřebního materiálu. Technika DGT s CAPS byla použita pro stanovení koncentrací kovů v námořních přístavech v Oostende a Zeebrugge na belgickém pobřeží Severního moře. Přestože byla technika DGT původně představena pro použití v analytické chemii životního prostředí, byla v této práci zkoumáno i použití této techniky v analýze potravin. V prostředí rybí omáčky byla ověřena funkčnost techniky DGT a stanoveny difúzní koeficienty Hg a dalších stopových prvků. Technika DGT byla následně použita pro stanovení koncentrace rtuti a dalších stopových kovů v různých komerčně dostupných vzorcích rybí omáčky. Výsledky nově navrhnutého analytického postupu s použitím techniky DGT byly porovnány s výsledky přímé analýzy atomovou absorpční spektroskopií s termální dekompozicí a amalgamací zlatem (TD-AAS) a po mikrovlnném rozkladu vzorků omáčky také s výsledky sektorové hmotnostní spektrometrie s indukčně vázanou plazmou (SF-ICP-MS). Díky předkoncentrační schopnosti techniky DGT byly dosaženy nižší detekční limity ve srovnání s TD-AAS nebo SF-ICP-MS. Technika DGT díky schopnosti oddělení analytů z komplexní matrice rybí omáčky rovněž snížila opotřebení a koroze kovových částí použitých instrumentálních technik.
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Effect of roasting on the sensory profile of coffee
Šajdlerová, Kristýna ; Vítová, Eva (referee) ; Diviš, Pavel (advisor)
This bachelor thesis deals with the effect of roasting on the content of carbohydrates and aromatic compounds in coffee. It also studies changes in coffee acidity based on different level of roasting. In the practical part there was measured pH, it was conducted setting of glucose, fructose and sucrose content by liquid chromatography, analysis of aromatic compounds using gas chromatography and also sensoric analysis of 17 types of coffee. Each one was roasted using two different temperatures (210 °C and 240 °C). Based on the statistical processing of basic chemical analysis and sensory analysis, significant differences were found between determined parametres of coffee samples roasted at 210 ° C and 240 ° C. Processing of results of sensory and chemical analysis of coffee samples did not manage to differentiate coffee samples from each other based on their geographic origin. At a lower level of coffee roasting there was found weak, but statistically significant correlation between the results of the sensory analysis and the content of aromatic compounds, while for the higher degree of coffee roasting no correlation was found.
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Analysis of milk by ICP-OES technique
Kaňová, Veronika ; Hrstka, Miroslav (referee) ; Diviš, Pavel (advisor)
The theoretical part of the thesis deals with the chemical composition of cow’s milk, with the description of chosen methods of sample pretreatment and with the description of the used technique ICP-OES. The practical part is aimed at individual preparations of samples and at analysis of chosen chemical elements (Ca, Na, K, Mg a P). Milk is a really complicated polydisperse system. The preparation of samples with milk is very important step before the measurement itself. In the thesis a comparison of four selected methods of sample preparation was made: bare dilution, dilution with addition of Triton X 100, wet ashing and sonication. Selected elements were analysed with the help of ICP-OES. Final concentrations were compared with CRM of dried milk. Data showed that the most accurate are methods of preparation of diluted sample and wet ashing. Four different types of milk were analysed with the help of those two selected methods. The diluted samples showed a bigger anomaly of measuring than the mineralization of wet ashing which came to the loss of analyte because of fat elements contained in milk.
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Determination of steviol glycosides in beverages
Porubčanová, Vladimíra ; Diviš, Pavel (referee) ; Vespalcová, Milena (advisor)
This diploma thesis deals with sweet substances from Stevia rebaudiana and with their determination in beverages. The ambition was to adjust the separation method for major steviol glycosides (stevioside and rebaudioside A) by HPLC so as to be fast and effective enough, too. In experimental part was successfully developed the separatin method, so it is possible to determine the steviol glycosides and conservation substances, specifically benzoic and sorbic acid (eventually their sodium or potassium salts). At first, for analysis was used monolithic column, on which stevioside and rebaudioside A weren´t separated. Other analyses were performed on column Ascentis express C18 (150 x 4.6; 2.7 µm). The most suitable separation method was performed by mobile phase made up with 29:71 v/v mixture of acetonitrile and acetate buffer (with pH 4.2). The flow rate was 0.28 ml/min and the column temperature was kept constant at 50 °C. The analysis of steviol glycosides and conservation substances with these condition was verified on the samples of real beverages.
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Study of the migration of selected metals from beverages packaging
Šťávová, Elena ; Vespalcová, Milena (referee) ; Diviš, Pavel (advisor)
This master’s thesis follows on bachelor’s thesis and deals with study of migration of aluminium and tin from metal containers. Manufactory of metal containers, corrosion of cans, chemical behaviour of aluminium and tin in food, its effects on health and possibilities of the determination in food and characterization of inductively coupled plasma optical emission spectrometry (ICP-OES) are described in theoretical part. In experimental part 30 different beverages in cans and glass and 6 tomato purees purchased at common stores were analysed. Measured concentrations of aluminium in beverages from cans and from glass containers were compared. It was found that beverages from cans didn’t contain higher concentrations of aluminium than beverages from glass containers. This could be caused by the fact that the aluminium is very stable metal, it has high corrosive endurance and therefore is very suitable for food packaging. Measured concentrations of tin in tomato purees were compared with the maximum permissible level of tin in canned food determined by European legislation. None of them exceed the 200 mg/kg level. All of the measured concentrations were very low, because all of the cans contained protective layer of lacquer, which gives protection against corrosion and also effectively protects from releasing of tin into the can content.
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Determination of iodine in food
Malčíková, Hana ; Reichstädter, Marek (referee) ; Diviš, Pavel (advisor)
The bachelor thesis deals with the optimization of ICP-OES method to determination of iodine in mineral waters. At first, the Theoretic part characterize the iodine in general, next it concerns with it as the essential/biogenic element, which is necessary for the proper functioning of the human organism, with its occurrence in food and with its industrial utilization. In next chapters the thesis is describing analytical methods of iodine determination specifically ion chromatography and inductively coupled plasma optical emission spectrometry. The principle and instrumentation description of both methods are found. The Experimental part is focused on optimization of ICP-OES methods, device setup for IC, on preparation of samples of mineral waters and the samples analysis using both methods. The results of the Experimental part show a content of iodine in mineral waters accessible in the Czech Republic and the Slovak Republic.
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Possibilities of determining the origin of the wine from the element composition
Škařupa, Přemysl ; Gregor,, Tomáš (referee) ; Diviš, Pavel (advisor)
The aim of this diploma thesis was to evaluate the possibility of determining the origin of the wine on the basis of elemental composition. For this purpose an analysis of major and minor elements was accomplished in selected varieties of wines. In total, 48 parameters for six wine subregions in Bohemia and Moravia was determined and used. The sum of 35 parameters represented the concentration of selected elements and other 13 parameters were created from the measured values. The concentration of elements was determined by inductively coupled plasma mass spectrometry (ICP-MS). For the purpose of classification of samples into groups multivariate statistical methods were used. The measured data set was firstly separated using analysis of variance (ANOVA) and discriminant analysis (DA). It has been proved that the selected variables influence the distribution of wines into categories according to their geographic location. Canonical discriminant analysis, principal component analysis (PCA) and cluster analysis has been used for graphical projection. Simultaneously the model based on our analysis was created to enable classify an unknown sample of wine according to the origin.
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Study of extraction of the biologically active substances from elderberry marc
Lošková, Tereza ; Diviš, Pavel (referee) ; Vespalcová, Milena (advisor)
This bachelor thesis deals with the determining of anthocyanin pigments in the extracts of elderberry marc (Sambucus nigra L.). The theoretical part is divided into four main chapters. In the first chapter there is botanical characteristics of elderberry, its origin and occurrence, chemical composition and the possibilities of usage in a food industry. The second part is devoted to characterization of phenolic compounds in berry fruits. Bigger attention is given to anthocyanin dyes, its occurrence, properties, health and antioxidant effects and the possibilities of usage in food industry. The third chapter is devoted to methods of determination of discussed dyes and phenolic compounds. The fourth chapter deals with the possibilities of disruption of plant cell walls. In the experimental part a series of elderberry marc's extraction was made. The purpose was to optimize the extraction course and to get the highest yield of dyes in an economically and operationally acceptable way. Time dependence of extractions was studied and a kind of extraction solvent and a ratio of its components were optimized. Distilled water or its mixture with ethanol was used as a solvent. During the water extraction the temperatures 25 °C and 50 °C were maintained and with the higher temperature the higher yields were obtained. Apart from this another supporting components as cellulolytic enzyme, ultrasound or shaker were used. The most effective method of extraction proved to be the extraction by the mixture water-ethanol (50:50) in the volume 80 mL. The total anthocyanins yield of this extraction was, expressed as cyanidin-3-glucoside equivalent, 914,4 ± 3,8 mg100 g-1 dry weight after 10 hours and the total phenolics yield was, expressed as gallic acid equivalent, 1957,0 ± 9,9 mg100 g-1 dry weight at the same time. The usage of ultrasound increased the efficiency of the extraction by water at 50 °C by 12 %. On the contrary, the usage of cellulolytic enzyme didn't increase the anthocyanin yield, because the enzyme was inactive.
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Determination of honey authenticity and adulteration by anion exchange chromatography
Ždiniaková, Tereza ; Diviš, Pavel (referee) ; Vespalcová, Milena (advisor)
Cieľom tejto diplomovej práce je stanoviť kvalitu a zloženie medu, taktiež stanoviť jeho botanický pôvod na základe profilu sacharidov v mede. Med je prírodný produkt vysokej kvality a vďaka značnej spotrebe a nemalej trhovej hodnote je tiež terčom na falšovanie. S cieľom identifikovať podvody a cudzorodé látky, pochádzajúce z cukrových sirupov, boli analyzované oligosacharidy a polysacharidy na báze maltodextrínov. Teoretická časť popisuje chemické zloženie medu a hlavné princípy aplikovanej inštrumentálnej techniky. Poskytuje literárny prehľad existujúcich analytických metód na stanovenie sacharidov prítomných v mede a na odhalenie jeho falšovania. Boli definované hlavné body falšovania a autenticity, vrátane legislatívnych aspektov a opisu bežných druhov falšovania. Experimentálna časť obsahuje postupy, ktoré vedú k vývoju a optimalizácii chromatografických podmienok a parametrov elektrochemického detektora na stanovenie sacharidov a maltodextrínov (oligosacharidov a polysacharidov) vo vzorkách medu. Použitá analytická technika bola vysoko účinná aniónovo-výmenná chromatografia (HPAEC) spojená s pulzným amperometrickým detektorom (PAD). Vyvinutá a optimalizovaná chromatografická metóda bola taktiež validovaná z hľadiska linearity, dynamického rozsahu, analytických limitov, presnosti a správnosti. Na záver bola táto vypracovaná metóda úspešne zhodnotená analýzou autentických a falšovaných vzoriek medu rôzneho botanického pôvodu pochádzajúcich z členských štátov EÚ.
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Bioavailability of magnesium and zinc from food supplements
Lindovský, Patrik ; Křikala, Jakub (referee) ; Diviš, Pavel (advisor)
This bachelor's thesis deals with the analysis of dietary supplements containing magnesium and zinc. The analysis examined the content of active substance and solubility in simulated gastric acid. The method used to analyze the active substance content was inductively coupled plasma optical emission spectrometry. This method was also used to determine the degree of solubility of the active substances. A total of thirteen different samples of dietary supplements were examined, all of which contained magnesium as the active ingredient and four of these samples additionally contained zinc. All samples contained the declared amount of magnesium. The zinc amount in food supplements was in accordance with the content stated on the label. In some samples the amount of zinc was determined to be lower, but the deviation from the declared amount did not exceed 14 %. Solubility tests have shown that some products do not contain a suitable type of coating to protect the active substance, which may cause a deterioration in bioavailability.
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