Wyniki wyszukiwania - BazTech

1

A comparative study of the molecular lipophilicity indices of vitamins A and E, and of some precursors of vitamin A, estimated by HPLC and by different computation methods

Briciu R. D., Kot-Wasik A., Namieśnik J., Sârbu C.

Acta Chromatographica

|

2009

|

Vol. 21, no. 2

237--250

EN

Lipophilicity indices for vitamins A and E, and for some precursors of vitamin A, have been determined for the first time by reversed-phase high-performance liquid chromatography (RPHPLC) on C 18 and C 8 columns. For each column the mobile phases were methanol-water mixtures with methanol in volume proportions from 86 to 90% ( υ/υ ) in 1% steps. The regression correlation coefficients obtained for both stationary phases were excellent (usually >0.999). To compare the experimental lipophilicity estimated for the compounds by use of log k′ w , S , φ 0 , the means of k′ and log k′ , and the scores of k′ and log k′ corresponding to the first principal component, and log P values calculated by use of different computer software a correlation matrix was constructed. Better correlations were obtained in both cases between the mean of k′ and the mean of log k′ , and scores corresponding to the first principal component obtained by applying principal-components analysis to the matrix of retention factors and computed log P values. The best correlations were found between the mean of k′ and scores corresponding to the first principal component determined on C 8 and most of the computed log P values.

2

Fuzzy soft modeling of environmental data. A study of the imp act of a phosphatic fertilizer plant on the adjacent environment in Gdańsk

Sârbu C., Szczepaniak K., Astel A., Biziuk M.

Chemia i Inżynieria Ekologiczna

|

2005

|

Vol. 12, nr 5-6

587-601

EN

Cluster analysis is a large field, both within fuzzy sets and beyond it. Many algorithms have been developed to obtain bard clusters from a given data set. Among those, the c-means algorithms are probably the most widely used. Hard c-means execute a sharp classification, in which each object is either assigned to a class or not. The membership to a class of objects therefore amounts to either 1 or 0. The application of fuzzy sets in a classification function causes this class membership to become a relative one and consequently an object can belong to several classes at the same time but with different degrees. The c-means algorithms are prototype-based procedures, which minimize the total of the distances between the prototypes and the objects by the construction of a target function. Fuzzy generalized n-means is easy and well improved tool, which have been applied in many fields of chemistry. In this paper, different fuzzy classification algorithms of the 35 grass and soil samples based on the 37 chemical element concentrations have been allowing an objective interpretation of their similarities and differences, respectively. Much more, the results ob13ined can be very useful in their reclassification. The new fuzzy approach namely, fuzzy cross-classification algorithm, (FHCsC) allows the qualitative and quantitative identification of the characteristics (chemical elements) responsible for the observed similarities and dissimilarities between grass and soil samples. In addition, the fuzzy hierarchical characteristics clustering (FHiCC) and fuzzy horizon13l characteristics clustering (FHoCC) procedures revealed a high similarity between some chemical elements concentrations in grass and soil samples.

PL

Analiza podobieństwa obejmuje nie tylko zastosowanie logiki rozmytej, ale również wiele innych podejść matematycznych. Opracowano wiele algorytmów, których celem jest wyodrębnienie wyraźnych skupień (hard clusters) z danego zbioru danych. Prawdopodobnie najczęściej stosowanymi algorytmami są tzw. algorytmy c-średnie (c-means algorithms). Twarde c-średnie (hard c-means) służy do ostrej klasyfikacji, podczas której obiekt jest przypisany do danej klasy lub do niej nie należy. W takim przypadku przynależność obiektu do klasy wynosi 1 lub O. Zastosowanie układów rozmytych lfuzzy sets) w obliczaniu funkcji klasyfikującej powoduje, że dany obiekt może należeć do kilku klas równocześnie, ale w różnym stopniu przynależności. Algorytmy c-średnie są procedurami określanymi jako procedury prototyp-zależne (prototype-based procedures), które minimalizują odległości między prototypami a obiektami dzięki odpowiedniej formie funkcji docelowej. Algorytm rozmytych uoglnionych n-średnich (fuzzy generalized n-means) jest łatwym i dobrze opracowanym narzędziem, które wykorzystuje się w wielu dziedzinach chemii. W niniejszym opracowaniu różne algorytmy klasyfikacji rozmytej zostały zastosowane do wyników oznaczeń 37 stężeń pierwiastków w 35 próbkach trawy i gleby, co pozwoliło obiektywnie zinterpretować podobieństwa i różnice między danymi. Nowe podejście algorytm rozmytej klasyfikacji krzyżowej (fuzzy cross-classijication algorithm, FHCsC) pozwala jakościowo i ilościowo zidentyfikować zmienne (pierwiastki chemiczne) odpowiedzialne za obserwowane podobieństwa i różnice między próbkami trawy i gleby. Dodatkowo procedury: rozmyta hierarchiczna analiza wiązkowa (fuzzy hierarchical characteristics clustering, FHiCC) i rozmyta pozioma analiza wiązkowa (fuzzy horizontal characteristics clustering, FHoCC) wykazały znaczne podobieństwo między stężeniami pewnych pierwiastków w próbkach trawy i gleby.

3

Thin-layer chromatographic estimation of the lipophilicity of some metallic complexes of diclofenac with potential anti-inflammatory activity

Sârbu C., Demertzis M. A., Kovala-Demertzi D.

Acta Chromatographica

|

2000

|

No. 10

222-230

EN

The relative lipophilicity of seven complexes of diclofenac sodium {[2-[(2,6-dichlorophenyl)amino]phenyl]acetate}, NaL, with Cu2+, Co2+, Ni2+, Mn2+, Fe3+, Fe2+ and Pd2+, with potential anti-inflammatory properties, have been determined by reversed-phase thin-layer chromatography on C18 and CN plates with water–methanol mixtures as mobile phases. The RF values of the compounds increased linearly with increasing concentra-tion of methanol in the mobile phase. Generally, the presence of a cation increases the lipophilicity, expressed as the intercept (RM0), in the same manner. This means that the lipophilic behavior of metallic complexes depends primarily on the structure of ligand, although a more lipophilic effect was observed for Fe2+, Ni2+ and Fe3+ on C18 plates and for Cu2+ and, again, Fe2+ and Pd2+ on CN plates.