Development and validation of stability-indicating HPLC method for the simultaneous determination of paracetamol, tizanidine, and diclofenac in pharmaceuticals and human serum

A method is described for the simultaneous determination of paracetamol, tizanidine, and diclofenac in mixtures. The method was based on HPLC separation of the three drugs followed by UV detection at 254 nm. The separation was carried out on a Hypersil ODS, C18 (250 x 4.6 mm id, 10 microm particle size) column using the mobile phase aqueous 0.2% ammonium carbonate-methanol (60 + 40, v/v) at a flow rate of 1 mL/min. The linear regression analysis data were used for the regression curve in the range of 170-10 000 ng/mL for paracetamol, 120-10 000 ng/mL for tizanidine, and 20-10 000 ng/mL for diclofenac. No chromatographic interference from tablet excipients was found. In order to check the selectivity of the proposed method, degradation studies were carried out using hydrolysis (acid, basic, and neutral), thermolysis, and oxidation. The developed method, after being validated in terms of precision, robustness, recovery, LOD, and LOQ, was successively applied to the analysis of pharmaceutical formulations and human serum.     

Role of added counterions in the micellar growth of bisquaternary ammonium halide surfactant (14-s-14): 1H NMR and viscometric studies

The change in the morphology of a series of dicationic gemini surfactants C(14)H(29)(CH(3))(2)N(+)-(CH(2))(s)-N(+)(CH(3))(2)C(14)H(29), 2Br(-) (14-s-14; s=4-6) on their interaction with inorganic (KBr, KNO(3), KSCN) and organic salts (NaBenz, NaSal) have been thoroughly investigated by means of (1)H NMR spectral analysis and the results are well supported by viscosity measurements. The presence of salt counterions results in structural transition (spherical to nonspherical) of gemini micelles in aqueous solution. With an increase in salt concentration all the three gemini surfactants showed changes in their aggregate morphology. This change is dependent on the nature and size of the added counterion. The effect of inorganic counterions on the micellar growth is observed to follow the Hofmeister series (Br(-) < NO(3)(-) < SCN(-)). The roles of organic counterions are discussed on the basis of probable solubilization sites of the substrate molecule in the gemini micelles, showing more growth in case of Sal(-) than Benz(-). The results are confirmed in terms of the obtained values of chemical shift (δ), line width at half height (lw), and relative viscosity (η(r)). Also, the growth of micelles was most pronounced for the gemini surfactant with the shortest spacer (s=4). This was attributed to the unique molecular structure of gemini surfactant micelles having flexible polymethylene spacer chain linking the twin polar headgroups.     

Gliding motion of bacteria on power‐law slime

The present investigation deals with an undulating surface model for the motility of bacteria gliding on a layer of non‐Newtonian slime. The slime being the viscoelastic material is considered as a power‐law fluid. A hydrodynamical model of motility involving an undulating cell surface which transmits stresses through a layer of exuded slime to the substratum is examined. The non‐linear differential equation resulting from the balance of momentum and mass is solved numerically by a finite difference method with an iteration technique. The manner in which the various exponent values of the power‐law flow affect the structure of the boundary layer is delineated. A comparison is made of the power‐law fluid with the Newtonian fluid. For the power‐law fluid with respect to different power‐law exponent values, shear‐thinning and shear‐thickening effects can be observed, respectively. Copyright © 2004 John Wiley & Sons, Ltd.     

Two New Insecticidal Amide Dimers from Fruits of Piper nigrum Linn.

The methanolic extract of dried ground seeds of Piper nigrum Linn . afforded fourteen compounds, of which thirteen were amides, including two new isomeric insecticidal amides, pipsaeedine ( 1 ) and pipbinine ( 2 ), along with eleven known amides and piptaline; (this is the first report of isolation of these compounds from this plant). The structures of 1 and 2 have been elucidated as (E,E)‐1‐[(E)‐5‐(7‐{6‐[5‐(piperidin‐1‐yl)‐5‐oxopent‐3‐enyl]‐1,3‐benzodioxol‐4‐yl}‐1,3‐benzodioxol‐5‐yl)‐1‐oxopenta‐2,4‐dienyl]piperidine and (E,E)‐1‐[(E)‐5‐(4‐{6‐[5(piperidin‐1‐yl)‐5‐oxopent‐3‐enyl]‐1,3‐benzodioxol‐4‐yl}‐1,3‐benzodioxol‐5‐yl)‐1‐oxopenta‐2,4‐dienyl]piperidine, respectively, through extensive 1D‐ and 2D‐NMR spectral studies, while the known constituents have been identified through comparison of their spectral data with those reported in the literature. Compounds 1 and 2 exhibited toxicities of 45.0 and 40.0 ppm, respectively, against fourth instar larvae of Aedes aegypti Liston.     

Synthesis, ion-exchange properties and analytical applications of stannic selenoarsenate: Comparison with other heteropolyacid salts

Summary Stannic selenoarsenate samples have been prepared by adding a mixture which is 0.05 M in sodium arsenate and 0.05 M in sodium selenite to a 0.05 M solution of stannic chloride in different volume ratios at pH 1. Its ion-exchange properties, pH titration curves and X-ray pattern were studied. Adsorption behaviour of 24 metal ions in different solvent systems has been examined. The analytical importance of this material has been demonstrated by achieving the following binary and ternary separations: Hg²⁺-Cd²⁺, Co²⁺-Fe³⁺, Cu²⁺-Fe³⁺, Hg²⁺-Zn²⁺-Al³⁺, Hg²⁺-Cu²⁺-Al³⁺, Hg²⁺-Ni²⁺-Al³⁺, Hg²⁺-Zn²⁺-Fe³⁺ and Hg²⁺-Ni²⁺-Fe³⁺. A comparison of the ion-exchange properties of this material has also been made with some other tin(IV) based ion-exchangers.

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Synthese, Ionenaustauscher-Eigenschaften und analytische Anwendungen von Zinn-Selenoarsenat: Vergleich mit anderen Heteropolysalzen

Zusammenfassung Zinn-Selenoarsenat wurde durch Mischen von 0,05 M Natriumarsenat-, 0,05 M Natriumselenitund 0,05 M Zinn(IV)-Chlorid-Lösungen bei pH 1 in verschiedenen Verhältnissen hergestellt. Die Ionenaustauscher-Eigenschaften, pH-Titrationskurven sowie Röntgendiagramme wurden untersucht und das Adsorptionsverhalten von 24 Metallionen in verschiedenen Lösungsmittelsystemen geprüft. Die analytische Verwertbarkeit wurde an Hand der folgenden Trennungsmöglichkeiten gezeigt: Hg²⁺-Cd²⁺, Co²⁺-Fe³⁺, Cu²⁺-Fe³⁺, Hg²⁺-Zn²⁺-Al³⁺, Hg²⁺-Cu²⁺-Al³⁺, Hg²⁺-Ni²⁺-Al³⁺, Hg²⁺-Zn²⁺-Fe³⁺, Hg²⁺-Ni²⁺-Fe³⁺. Vergleiche mit anderen Ionenaustauschern auf Zinn(IV)-Basis werden ebenfalls beschrieben.

     

Microbial transformation of mestranol by Cunninghamella elegans

The microbial transformation of an oral contraceptive, mestranol (1) by Cunninghamella elegans yielded two hydroxylated metabolites, 6beta-hydroxymestranol (2) and 6beta,12beta-dihydroxymestranol (3). Metabolite 3 was found to be a new compound. These metabolites were structurally characterized on the basis of spectroscopic techniques.     

The determination of technetium-99 in seawater and marine algae

Technetium-99 is preconcentrated from acidified seawater containing a trace of bromine by adsorbing it as the pertechnetate ion on the anion exchanger Duolite A101D. After elution with 4 M nitric acid, it is purified from other radionuclides by scavenging with hydrous iron(III) oxide and extracting from 5 M sodium hydroxide medium into methyl ethyl ketone. The organic phase is then evaporated and technetium is electrodeposited from oxalic acid medium onto a bronze disc and counted with a low background β-counter. Overall recovery is > 90% and the precision is ±0.2 pCi l^-1 at a technetium level of 0.6–1.0 pCi l^-1. Concentrations of the radionuclide in the central Irish Sea were found to lie in the range 0.4–2 pCi l^-1. The same analytical scheme can be used for determining the element in nitric acid digests of marine algae.