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Abstract  

Differential thermal analysis (DTA) was the first thermal analysis technique used to qualitatively characterize natural clays and respective curves has been used since more than 60 years as their ‘fingerprint’. With the development of microprocessed equipments in the last decades, derivative thermogravimetric (DTG) curves also may be used for this purpose in some cases, which also may allow a quantitative characterization of clay components. TG and DTG curves are more indicated than DTA or DSC curves to identify and to better analyze the several decomposition steps of natural or synthetic organoclays. These questions are discussed in applications developed to characterize Brazilian kaolinitic clays, bentonites and organophilic clays.

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Chemometric assessment of thermal oxidation of some edible oils

Effect of hot plate heating and microwave heating on physicochemical properties

Journal of Thermal Analysis and Calorimetry
Authors: M. Khan, Anila Sarwar, and M. Wahab

Abstract  

The effect of microwave heating was studied in six varieties of edible oil. Variations in physicochemical properties were observed and compared with the data obtained by hot plate heating. Fourier-transform infrared spectra of the oils showed substantial variations after both types of heating in the region of hydrogen’s stretching (C–H) vibration, region of double bond’s stretching (C=O), and fingerprint region. The visible spectra of mustard and olive oil showed the reduction in carotenoid, flavonoid, and chlorophyll pigments after heating. The oil samples were discriminated as saturated, monounsaturated, and polyunsaturated fats using chemometric techniques on physical and spectroscopic measurements.

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Abstract  

A set of 35 uranium ore and 10 yellow cake samples, collected worldwide from different mines and production sites, were analyzed for their impurity spectrum by ICP-MS. Pattern recognition techniques such as cluster analysis were applied to the data set in order to characterize samples with relation to their geographical origin. The results obtained show a clear relationship between samples taken from the same geological origin and constitute a satisfactory fingerprint for establishing the origin of the material. In addition to the impurity data, data on the isotopic composition of radiogenic lead is used to resolve ambiguity when impurity cluster analysis fails to deliver unambiguous origin data.

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Abstract  

Obsidian samples from the Tokaj Mountains (Hungary) and from the neighbouring Zemplin Hills (Slovakia) were analysed by instrumental and epithermal neutron activation analysis for obtaining a “fingerprint” for discrimination of potential natural sources of raw material that would permit tracing the origin of archaeological obsidian artefacts. These techniques fully discriminate the Zemplin Hills sources (Carpathian I, eastern Slovakia) and the Tokaj Mountain sources (Carpathian II, north-eastern Hungary) as well as these Central European sources from those already studied of the Mediterranean basin and adjacent regions.

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Abstract  

INAA results obtained on 11 vegetal samples proposed as European reference standards, in nutritional, agricultural and analytical studies are reported. A comparison is also reported with the data obtained by 38 European laboratories, by using spectrochemical methods (ICP atomic absorption, X-ray fluorescence, etc.). The usefulness of Instrumental Neutron Activation Analysis (INAA) is stressed, particularly when more usual methods are not sensitive enough for microelements that are important markers of toxic and pollutant substances. To this class belong lanthanides and other rare elements (Sc, Cs, Rb), which can be used both as fingerprint of soil provenance and for evaluating the homogeneity of the sample.

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Summary  

The crude methanolic extracts of a single bean from samples of organic, natural or genetically modified (GM) soybeans [Glycine max. (Merrill) L.] were analyzed by direct infusion electrospray ionization mass spectrometry (ESI-MS). These extracts, containing the most polar natural products of soybeans (free aglycones, monoglucosides, diglucosides and esters including isoflavones and flavones) provide characteristic fingerprinting mass spectra owing to different proportions or sets of components. Spectra distinctiveness is confirmed by chemometric multivariate analysis of the ESI-MS data, which place the three-types of beans into well-defined groups. When ESI-MS is applied, these polar components constitute therefore unique chemotaxonomic markers able to provide fast soybean typification.

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Abstract  

This study discussed the phenomena on thermal polymerization of α-methylstyrene (AMS). A curve scanned by temperature-programmed technique was performed by differential scanning calorimetry (DSC). Heat of polymerization (ΔH) and onset temperature of exothermic (T 0) behavior were determined to be 28010 J g-1 and about 1381C, respectively. A dimer formation mechanism was proposed for initiation of the propagating chain. Spectroscopic identification of dimer structure was conducted by infrared (IR) spectroscopy in the wavenumber from 650 to 1100 cm-1associated with molecular fingerprint characteristics. The mechanism of thermal polymerization on α-methylstyrene proposed in this study was similar to that of styrene suggested by Mayo.

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In traditional Chinese medicine, plants of the genus Peganum have been used to treat cough, hypertension, diabetes, asthma, jaundice, lumbago, and many other ailments. In this study, seeds of the plants of genus Peganum, including P. harmala Linn., P. multisectum (Maxim) Bobr, P. nigellastrum Bunge, and Peganum variety were collected from different provinces in China. A simple, rapid, and effective thin-layer chromatographic (TLC) fingerprint combined with bioautographic technique has been established for the identification of acetylcholinesterase (AChE) inhibitors from these seeds. The methanol extracts of seeds were separated on silica gel plates with ethyl acetate-methanol-ammonia 10:1.5:0.5 (ν/ν) as mobile phase, and then the plates were inspected under UV 366 nm and visualized by spraying with both Dragendorff’s and vanillin-sulfuric acid reagents as well as by bioautographic assay. Moreover, the limits on AChE inhibitive activity of harmine and harmaline were found to be 0.01 μg, in comparison to that of galanthamine of also 0.01 μg. The TLC fingerprints combined with the bioautographic method could distinguish the seeds of the different species of genus Peganum investigated. Moreover, harmine and harmaline displayed similar AChE inhibition compared to galanthamine.

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JPC - Journal of Planar Chromatography - Modern TLC
Authors: Mieczysław Sajewicz, Łukasz Wojtal, Michał Hajnos, Monika Waksmundzka-Hajnos, and Teresa Kowalska

In a previous paper we discussed the possibility of fractionating the essential oils of different sage species by low-temperature preparative layer chromatography (PLC), followed by preparative isolation of the contents of each fraction and further analysis by GC-MS. In that way we attempted to emphasize the practical usefulness of lowtemperature planar chromatography for investigation of volatile compounds. In this study, we explore a possibility of fractionating essential oils contained in the different sage species by low-temperature analytical TLC followed by direct mass spectrometric analysis of the separated fractions. This objective can be achieved by TLC-MS with on-line transfer of the eluted fractions. The densitograms obtained from five different sage species (i.e., S. lavandulifolia, S. staminea, S. hians, S. triloba , and S. nemorosa ) are compared. Each densitogram is accompanied by mass spectra recorded for each peak. Videoscans of the chromatograms are also presented. In this way multiple fingerprints of the analyzed plant material, each comprising a densitogram and a selection of mass spectra, were obtained. Advanced chemometric treatment of these multiple fingerprints can be used to reveal statistically significant differences between the plant species. Analytical and chemotaxonomic advantages and further aspects for this kind of approach are discussed.

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Twenty-seven isolates of Phytophthora infestans collected in Hungary in 2001 were tested for mating type, response to metalaxyl, isozyme geno­type at glucose-6-phosphate isomerase (Gpi) and peptidase A (Pep) loci and nuclear DNA fingerprints with probe RG57. The ratios of the mating types A1 to A2 were 5:6 and 9:7 among isolates from potato and tomato, respectively. Seventeen isolates were sensitive to metalaxyl, 1 isolate responded intermediately and 9 isolates were resistant. No novel combi­nations of isozyme alleles were found; all isolates were Gpi 100/100, and genotypes at the Pep locus were 96/96 (63%), 83/96 (11%) and 100/100 (26%). In contrast, all of the 22 RG57 fingerprints exhibited patterns that have not been reported in Hungary before. On the basis of combined traits, 22 multilocus genotypes, unnoted elsewhere in Europe, were con­struct­ed among the 27 isolates analysed. These results indicate that varia­bi­lity in the Hungarian P. infestans populations is likely due to local events (asexual and sexual interactions) rather than migration from other countries.

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