Ispitivanje kinetike reakcije natrijum-etilksantogenacetata i alkilamina

In this work kinetics investigation of the reaction between sodium ethyl xantogenacetate (NaEtXAc) and primary as well as secondary alkylamines, for each pair NaEtXAc-amine, was performed. Firstly, in order to determine the wavelength for following the reaction, the influence of the structures of reactants on the absorption was investigated. Absorption of the system was followed at l = 280 nm. The values of rate constants for 16 selected amines, at the different temperatures, were determined. Considering high correlations coefficients, r > 0.988, it was confirmed that investigated reactions are the second-order. On the basis of reaction constants, at the different temperatures, several thermodynamic parameters were calculated such as the energy of activation Ea,, frequency factor A, the entropy of activation DS#2S, Gibbs’s free-energy of activation DG#2S and enthalpy of activation DH#2S. By evaluation of the obtained results some assumptions, that refer to the reaction mechanisms of nucleophilic attack of the amine on the thiocarbonyl carbon, were made. Following the proposed mechanism activated complex, as a critical step, is formed in this reaction.U cilju ispitivanja kinetike reakcije natrijum-etilksantogenacetata (NaEtXAc) sa primarnim i sekundarnim alkilaminima za svaki par NaEtXAc-amin ispitan je prvo uticaj strukture ovih jedinjenja na apsorpciju kako bi se odredila talasna dužina na kojoj će se pratiti reakcija. Praćena je promena apsorpcije sistema na l= 280nm. Određene su konstante brzina reakcija za šesnaest odabranih amina na različitim temperaturama. Na osnovu visokih vrednosti korelacionih koeficijenata r > 0,988, potvrđeno je da ispitivane reakcije slede kinetiku reakcije drugog reda. Na osnovu vrednosti reakcionih konstanti na različitim temperaturama izračunato je nekoliko termodinamičkih parametara ispitivanih reakcija: energija aktivacije Ea, faktor učestanosti A, entropija aktivacije ΔS#25, Gibsova slobodna energija aktivacije ΔG#25 i entalpija aktivacije ΔH#25. Obradom dobijenih rezultata pretpostavljen je reakcioni mehanizam nukleofilnog napada amina na tiokarbonilni ugljenik, pri čemu kao limitirajući korak nastaje aktivirani kompleks

Determination of metal content in some herbal drugs - Empirical and chemometric approach

The concentrations of Cu, Zn, Mn, Fe, K, Ca, Mg, Al, Ba and B in 26 herbal drugs of special importance in phytopharmacywere studied. Flame atomic absorption and emission spectrometry (FAAS, FAES), as well as inductively coupled plasma atomic emission spectrometry (ICP-AES), were applied in this work. The whole procedure, from sample preparation, via dissolution, to measurements, was validated by using CRM (NIST 1573a-tomato leaves), and the obtained recovery values are in the range from 91 to 102%. Drug samples originated from medicinal plants cultivated in Serbia contained Cu (4.47-14.08 mg kg(-1)), Zn (8.4-54.5 mg kg(-1)), Mn (9-155 mg kg(-1)), Fe (47-546 mg kg(-1)), K (0.20-6.24%), Ca (0.18-1.84%), Mg (0.13-1.09%), Al (16-416 mg kg(-1)), Ba (11.70-84.83 mg kg(-1)) and B (5.1-118.7 mg kg(-1)). In order to get a better insight into the elemental patterns, a common chemometric approach to data evaluation was used. Four significant factors identified by principal component analysis (PCA) were attributed partly to the significant influential sources and high mobility of some elements thus referring to potential anthropogenic contamination as well

Evaluation of osteopontin and CA125 in detection of epithelial ovarian carcinoma

The objective of this study was to determine the potential of osteopontin (OPN) and OPN + CA125 (cancer antigen 125) combination in differential diagnosis of the ovarian cancers and non-malignant ovarian disease. Serum and plasma samples were obtained preoperatively from 79 women undergoing surgery for pelvic mass; 48 of them had ovarian carcinoma, and 31 had benign cyst. The samples were analyzed for the levels of OPN and CA 125 (using ELISA and CMIA methods) and then compared with the final pathologic results. The median plasma level of OPN in patients with benign and malignant cysts was 356.33 ng/ml and 865.15 ng/ml, respectively (p lt 0.001). Receiver operating characteristic (ROC) analysis for plasma OPN revealed the area under the curve (AUC) of 0.838. At the predefined specificity of 90%, OPN showed sensitivity of 62.5%, whereas the combination of OPN + CA125 reached 74.9% at the same specificity