HPLC, TLC, and first-derivative spectrophotometry stability-indicating methods for the determination of tropisetron in the presence of its acid degradates

Three stability-indicating assay methods were developed for the determination of tropisetron in a pharmaceutical dosage form in the presence of its degradation products. The proposed techniques are HPLC, TLC, and first-derivative spectrophotometry (1D). Acid degradation was carried out, and the degradation products were separated by TLC and identified by IR, NMR, and MS techniques. The HPLC method was based on determination of tropisetron in the presence of its acid-induced degradation product on an RP Nucleosil C18 column using methanol-water-acetonitrile-trimethylamine (65 + 20 + 15 + 0.2, v/v/v/v) mobile phase and UV detection at 285 nm. The TLC method was based on the separation of tropisetron and its acid-induced degradation products, followed by densitometric measurement of the intact spot at 285 nm. The separation was carried out on silica gel 60 F254 aluminum sheets using methanol-glacial acetic acid (22 + 3, v/v) mobile phase. The 1D method was based on the measurement of first-derivative amplitudes of tropisetron in H2O at the zero-crossing point of its acid-induced degradation product at 271.9 nm. Linearity, accuracy, and precision were found to be acceptable over concentration ranges of 40-240 microg/mL, 1-10 microg/spot, and 6-36 micro/mL for the HPLC, TLC, and 1D methods, respectively. The suggested methods were successfully applied for the determination of the drug in bulk powder, laboratory-prepared mixtures, and a commercial sample.     

Complex formation reactions of palladium(II)-1,3-diaminopropane with various biologically relevant ligands. Kinetics of hydrolysis of glycine methyl ester through complex formation

The interaction of [Pd(DAP)(H₂O)₂]²⁺ (DAP = 1,3-diaminopropane) with some selected bio-relevant ligands, containing different functional groups, were investigated. The ligands used are dicarboxylic acids, amino acids, peptides and DNA constituents. Stoichiometry and stability constants of the complexes formed are reported at 25°C and 0.1 M ionic strength. The results show the formation of 1:1 complexes with amino acids and dicarboxylic acids. The effect of chelate ring size of the dicarboxylic acid complexes on their stability constants is examined. Peptides form both 1:1 complexes and the corresponding deprotonated amide species. DNA constituents form 1:1 and 1:2 complexes. The effect of dioxane on the acid dissociation constants of CBDCA and the formation constant of its complex with Pd(DAP)²⁺ was reported. The kinetics of hydrolysis of glycine methyl ester bound to [Pd(DAP)(H₂O)₂]²⁺ was studied at 25°C and 0.1M ionic strength.      

碳电极上电沉积的Ni-MgO纳米复合物催化甲醇和乙醇电氧化反应

在细小MgO增强颗粒的存在下,采用电沉积法在碳阳极上经瓦特镍制得Ni–MgO纳米复合物,考察了它在碱性介质中电催化氧化甲醇和乙醇反应性能,并与碳涂覆的纯Ni催化剂(Ni/C)性能进行了比较。运用能量散射谱、X射线衍射和扫描电镜分别表征了沉积的纳米复合物的化学组成、相结构和表面形貌,并采用循环伏安法(CV)、计时电流法和电化学阻抗谱(EIS)等电化学技术考察了所制电催化剂阳极的催化活性。结果表明, Ni/C催化剂在电氧化反应中表现出很低的催化活性和稳定性,而MgO的引入显著增加了Ni催化剂在醇氧化反应中的催化活性和抗中毒性能。 EIS和CV结果证实Ni–MgO/C纳米复合物电极具有比Ni/C更低的电荷转移阻力和更高的抗中毒性能。     

Nano emulsion binders for paper coating synthesis and application

The key objectives of coating papers and paperboards are to improve their aesthetic appearance and printability. Coatings offer smoothness, gloss, brightness, and opacity to the base papers and provide them with enhanced printability, which requires resistance to ink splitting forces, smoothness, ink holdout and gloss, etc. Styrene acrylate latexes were synthesized, via emulsion polymerization, and were formulated as coats for white and brown recycled papers. Both processes were characterized specifically for offset printing. The prepared latexes showed enhanced solid content, viscosity, zeta potential and appropriate glass transition temperature for paper coating formulation. The porosity, gloss and Cobb60 values of coated papers increased with the increased addition of nano-emulsion modified latexes. The formulations afforded high printability (print gloss and print density) with local ground calcium carbonate compared with that of the imported pigment (kaolin). Furthermore, the synthesized binder had higher water resistance than the commercial one; which can tightly be correlated with print quality, printability and productivity and most significantly, permits usage of low viscous ink. Coated recycled brown base gave promising results with respect to print quality although offset printing was utilized. The novelty of this work was not only in employing the local alternative binder and local pigment but also in achieving compatibility with environmental regulations since oil-based inks and recycled papers were also used.     

Nonlinear Interaction of S-Polarized Incident Radiation and Surface Waves in Magnetoactive Plasma

The effect of an external magnetic field on the nonlinear interaction of S-polarized electromagnetic radiation incident on a S-polarized surface wave in a plasma layer was studied analytically. We have calculated the amplitudes of generated waves at combination frequencies. The generated waves are of P-polarization and can be either electromagnetic or surface waves, depending on the signal of the value=\documentclass{article}\pagestyle{empty}\begin{document}$ ^{\chi '^2 = \frac{{k'^2 }}{{\varepsilon '}} - \frac{{\omega '^2 }}{{c^2 }} + k'\frac{\partial }{{\partial x}}\frac{{\varepsilon '_2 }}{{\varepsilon '\varepsilon '_1 }}} $\end{document}.     

Synthesis and Thermodynamic Investigation of 4-Amino-6-Hydroxy-2-Mercapto Pyrimidine (AHMP) Complexes with Some Selected Divalent Metal(II) Ions

The synthesis and characterization of zinc(II), cadmium(II), lead(II), mercury(II) and phenylmercury(II) complexes of 4-amino-6-hydroxy-2-mercapto pyrimidine (AHMP) are reported. The stoichiometry of the complexes was found to be 1:2 except for the phenylmercury(II) complex where the ratio is 1:1. Characterization of these complexes was carried out by means of elemental analyses, IR and ¹H NMR measurements. In these complexes the ligand is bonded to the metal through its sulfur atom. The potentiometric results showed the formation of 1:1 and 1:2 complexes and the corresponding stability constants were determined for both Zn(II) and Cd(II) ions. The high insolubility of mercury(II), phenylmercury(II) and lead(II) complexes prevented the determination of their stability constants. The concentration distribution of the complexes in solution was evaluated. The effect of temperature on the dissociation constant of AHMP and the formation constants of both the Zn-AHMP and Cd-AHMP complexes were studied and the thermodynamic parameters were calculated.     

Mixed-Ligand Complexes of 2-(Aminomethyl)benzimidazole Palladium(II) with Various Biologically Relevant Ligands

cis-Dichloro(2-(aminomethyl)benzimidazole)palladium(II), [Pd(AMBI)Cl₂], was synthesized and characterized. The stoichiometry and stability constants of the complexes formed between [Pd(AMBI)(H₂O)₂]²⁺ with various biologically relevant ligands containing different functional groups are investigated. The ligands used are dicarboxylic acids, amino acids, peptides and DNA constitutents. The results show the formation of 1:1 complexes with amino acids and dicarboxylic acids. The effect of the chelate ring size of the dicarboxylic acid complexes on their stability constants is examined. Peptides form both 1:1 complexes and the corresponding deprotonated amide species. Structural effects of the peptide on the amide deprotonation are investigated. DNA pyrimidinic constituents such as uracil, uridine, thymidine and thymine form 1:1 and 1:2 complexes, whereas purinic constituents such as inosine 5′-monophosphate (5′-IMP) and guanosine 5′-monophosphate (5′-GMP) form only 1:1 complexes. The concentration distribution of the complexes in solution was evaluated. The effect of increasing chloride ion concentration on the formation constant of CBDCA with Pd(AMBI)²⁺ was reported.     

Mixed ligand complexes of Cu(II)-2-(2-pyridyl)-benzimidazole and aliphatic or aromatic dicarboxylic acids: Synthesis, characterization and biological activity

The synthesis and structural characterization of mixed ligand complexes derived from 2-(2-pyridyl)-benzimidazole (PBI) (1ry ligand) and aliphatic or aromatic dicarboxylic acids (2ry ligand) are reported. Cu(II) complexes were characterized on the bases of their elemental analyses, IR, ESR and thermal analyses. The elemental analysis indicated the formation of mixed ligand complexes in a mole ratio 1:1:1 (Cu:L(1):L(2)), L(1)=PBI and L(2)=oxalic acid, phthalic acid or malonic acid. IR spectra showed that PBI acts as a neutral bidentate coordinated to the Cu(II) via the pyridyl and imidazolyl nitrogen atoms. The dicarboxylic acids are bidentate with monodentate carboxylate groups. Thermal decomposition study of complexes was monitored by thermogravimetric (TG) and derivative thermogravimetric (DTG) analysis in N(2) atmosphere. The decomposition course and steps were analysed and the activation parameters of the nonisothermal decomposition were calculated from the TG curves and discussed. The isolated metal chelates were screened for their antimicrobial activities and the results are reported, discussed and compared with some known antibiotics.