Selective LC Determination of Cabergoline in the Bulk Drug and in Tablets: In Vitro Dissolution Studies

Cabergoline (CAB) is an ergot alkaloid derivative with dopamine agonist activity. A novel, simple, and rapid stability-indicating high-performance liquid chromatographic (HPLC) method for assay of CAB in tablets has been developed and validated. Chromatography was performed on a 4.6 mm i.d. × 250 mm, 5 μm particle, cyano column with acetonitrile–10 mM phosphoric acid, 35:65 (v/v), containing 0.04% triethylamine, as mobile phase, at a flow rate of 1.0 mL min^?1, and UV detection at 280 nm. Response was a linear function of concentration in the range 0.1–4 μg mL^?1 (r ² = 0.9999). The recovery of the method was good (99.45%) and RSD values for intra-day and inter-day precision were 0.24–0.88% and 0.66–1.19%, respectively. The method can be used for quality-control assay of CAB in tablets, for stability studies, and for in vitro dissolution studies.     

The Effect of a Cationic Polyelectrolyte on the Forces between Two Cellulose Surfaces and between One Cellulose and One Mineral Surface

The effect of a cationic polyelectrolyte, PCMA, on the forces between two cellulose surfaces and between one cellulose surface and one mica surface has been studied using the interferometric surface force apparatus (SFA). The cellulose surfaces were prepared by Langmuir-Blodgett deposition of trimethylsilyl cellulose onto hydrophobized mica. Prior to measurements the surfaces were desilylated to obtain pure cellulose. Introduction of a cationic polyelectrolyte into the solution drastically changed the interactions between the cellulose layers. It was found that the cationic polyelectrolyte does adsorb onto the cellulose surface, although the adsorbed amount is low. The adsorbed layer is very thin, as expected at a low electrolyte concentration. Before the adsorption has reached equilibrium, when only some polyelectrolyte had adsorbed, the adhesion between the surfaces was high, and it was noted that the cellulose layer was damaged on separation. After a longer adsorption time an electrostatic repulsion and no adhesion were observed between the polyelectrolyte-coated cellulose surfaces. An electrostatic repulsion was observed between cellulose and mica. When cationic polyelectrolyte was introduced to the system it overcompensated the charges on both surfaces, and the range and magnitude of the double-layer force was higher than without polyelectrolyte. The relevance of the results to flocculation mechanism and efficiency in cellulose systems is discussed. Copyright 2000 Academic Press.     

Reaktionen mit phosphororganischen Verbindungen, 49. Synthese und 1H-NMR-Spektren von (3-Acylbicyclo[2.2.1]hept-5-en-2-yl)phosphonsäureestern

Reactions with Organophosphorus Compounds, 49. Synthesis and ¹H NMR Spectra of (3-Acylbicyclo[2.2.1]hept-5-en-2-yl)phosphonates Reaction of the (E)-(β-acylvinyl)phosphonates 1 with cyclopentadiene yields the isomeric norbornylphosphonates 2 (endo-acyl, exo-P) and 3 (exo-acyl, endo-P) in a 7:3 ratio. With 1,3-cyclohexadiene the corresponding bicyclooctenyl derivatives 7 and 8 are obtained from 1a . The (Z)-phosphinylacrylate 4 gives with cyclopentadiene the isomers 5 (exo-CO₂Me, exo-P) and 6 (endo-CO₂Me, endo-P) in nearly equal amounts. The configuration of the cycloadducts has been proved by ¹H NMR spectroscopy.     

A generalization of the Rouse-Zimm model

The idea of consistently averaging the hydrodynamic interaction and its various consequences for Hookean dumbbells are reviewed. For long chains this idea can be used to generalize the Rouse-Zimm model for polymer solutions. Unlike the usual Rouse-Zimm model, the new model for steady shear flow predicts a nonzero second normal stress coefficient and shear rate dependent material functions. In the limit of long chains, the viscosity and the normal stress coefficients are universal functions of the reduced shear rate.This paper was presented at the Frühjahrstagung des Fachausschusses Polymerphysik der Deutschen Physikalischen Gesellschaft at Kaiserslautern (West Germany), March 12–14, 1986.     

Electron propagator calculations of molecular electron affinities

An approximate electron propagator method for predictive calculations of molecular electron affinities is proposed. The self-energy accounts for relaxation effects to all orders Additional correlation effects are treated using a diagonal approximation with shifted denominators. Applications to CN, NH₂, and PH₂ are reported.     

Preparation and characterization of Co(II), Ni(II) and Cu(II) complexes of a ligand containing 1,3,4-thiadiazole groups

(1R,2R)-1,2-bis-(5-amino-1,3,4-thiadiazole-2-yl)ethane-1,2-diol (L) has been prepared by the reaction of thiosemicarbazide with (2R,3R)-(+)-tartaric acid (I) and phosphorous oxychloride, and its complexes with Co(II), Ni(II) and Cu(II) have been obtained. The structures of the ligand and its complexes have been established by i. r., ¹H- and ¹³C-n.m.r. spectra, u.v.–vis–nir spectroscopy, elemental analyses, T.g.-D.t.a. and magnetic susceptibility measurements.     

Thermally induced sign change of Soret coefficient for dilute and semidilute solutions of poly(N-isopropylacrylamide) in ethanol

We studied the thermal diffusion behavior of poly(N-isopropylacrylamide) (PNiPAM) in ethanol in a temperature range from T = 14.0 degrees C to T = 40.0 degrees C by means of thermal diffusion forced Rayleigh scattering. The obtained Soret coefficient S(T) of PNiPAM was positive for lower temperatures (T < 34 degrees C), while S(T) showed a negative value for higher temperatures (T > 34 degrees C). This means PNiPAM molecules move to the cold side for temperatures T < 34 degrees C, whereas they move to the warm side for T > 34 degrees C. This is the first nonaqueous polymeric system for which a sign change with temperature has been observed. We performed static and dynamic light scattering experiments in the same temperature range. The second virial coefficient determined from dilute solutions by static light scattering (SLS) was positive in the comparable temperature range. The results of SLS for the semidilute solution showed a strong repulsion among PNiPAM chains which was enhanced by increasing temperature. These results imply that the observed thermally induced sign change of S(T) does not depend on the intermolecular interactions among PNiPAM chains.     

Vertical distribution of the natural and artificial radionuclides in various soil profiles to investigate soil erosion

Vertical distributions of ¹³⁷Cs and ²¹⁰Pb in soil profiles were examined to study their availability in soil erosion at Gökova region where there exists intensive agricultural activities on sloppy fields. Since the mobility of these radionuclides depend on soil characteristics, soil samples were analyzed also for their physical and chemical properties. From ¹³⁷Cs inventories measured, erosion rates for cultivated and disturbed (no cultivation) soils were calculated to range from 79.1 to 6.5 t^.ha^-1.y^-1 and from 79.9 to 3.5 t^.ha^-1.y^-1, respectively. The ²¹⁰Pb technique is found to be not suitable for erosion determination for this area, presumably due to the coal-fired power plants operating in the region.     

Computation of Rotation Matrices Making Lined‐Up to the Local Cartesian Coordinates

Rotation matrices were expressed in terms of Gaunt coefficients and complex spherical harmonics. The rotation matrices were calculated using two different ways. In the first, Gaunt coefficients and normalized complex spherical harmonics were directly calculated using binomial coefficients; in the second, Gaunt coefficients and complex spherical harmonics were recursively calculated. The methods were compared with respect to accuracy and computation time (CPU) for low and very high quantum numbers.