Determination of Vardenafil in Pure and Dosage Forms by Spectrophotometry

Journal of Applied Spectroscopy - Three simple, sensitive, precise, and rapid spectrophotometric methods are developed and optimized for the assay of vardenafil in pharmaceutical formulations. The...     

Polymerization of butadiene on nanoparticles’ surfaces and formation of metal/polymer nanocomposites

In this paper, we demonstrate that laser vaporization of metals in the presence of a small concentration of butadiene vapor leads to the polymerization of butadiene and incorporation of the metal nanoparticles within the polymer matrix. The metal nanocomposites are characterized by electron microscopy, X-ray diffraction and EDX. The results from high pressure mass spectrometry indicate that multiple additions of butadiene molecules on the metal cations Fe⁺, Ni⁺ and Pt⁺, generated by laser vaporization, take place at room temperature thus providing an efficient means of initiating further polymerization reactions. The Pt⁺ reactions show extensive fragmentations and elimination steps generating hydrocarbon ions. The laser vaporization/polymerization method provides the ability to encapsulate several different metals or metal oxides which undoubtedly will play a significant role in tuning the various properties of the polymer composites.     

1-Benzopyran-4(4H)-ones as novel activated alkenes in the Baylis-Hillman reaction: a simple and facile synthesis of indolizine-fused-chromones

1-Benzopyran-4(4H)-one derivatives have been successfully employed as novel activated alkenes in the Baylis-Hillman coupling with heteroaromatic-aldehydes, nitrobenzaldehydes and isatin-derivatives and the corresponding adducts, derived from pyridine-2-carboxaldehyde, have been transformed into a novel indolizine-fused-chromone framework.     

Sensitive and selective spectrophotometric methods for the determination of pheniramine maleate in bulk drug and in its formulations using sodium hypochlorite

Two simple, selective and sensitive spectrophotometric methods are described for the determination of pheniramine maleate (PAM) in pure and dosage forms. The method is based on the reaction of PAM with hypochlorite in the presence of Kolthoff buffer (phosphate-borate) of pH 7.0 to form the chloro derivative of PAM, destruction of the excess hypochlorite by nitrite ion (the chloro derivative of drug is unaffected under the optimized conditions) followed by the oxidation of iodide with the chloro derivative of PAM to iodine (I ₃ ^? which is either measured directly at 355 (method A) or reacted with starch to form a blue chromogen measurable at 590 nm (method B). The optimum conditions that affect the reaction were ascertained, and under these conditions linear relationship was obtained in the concentration ranges of 2–50 and 1–25 μg/mL PAM in methods A and B, respectively. The calculated molar absorptivity values are 7.26 × 10³ and 1.28 × 10⁴ L/(mol cm) for method A and method B, respectively. Sandell’s sensitivity values, limits of detection (LOD) and quantification (LOQ) are calculated as per ICH guidelines. The proposed methods were applied successfully to the determination of PAM in tablets and injection with good accuracy and precision and without interferences from common additives. The results obtained by the proposed methods were compared favourably with those of the reference method. The accuracy and reliability of the proposed methods were further checked by recovery studies via standard addition procedure.     

Iodometric determination of milligram and microgram amounts of levocetirizine in pharmaceuticals

Four simple, selective and sensitive methods are described for the determination of levocetirizine dihydrochloride (LCT) in bulk drug and in tablets. The methods exploit the well-known analytical reaction between iodide and iodate in the presence of acid solution. Iodide present is oxidized by iodate in an amount equivalent to the HCl present in LCT to iodine and the liberated iodine is determined by four different procedures which inturn quantify LCT at varying detection range and sensitiveness. Two direct titrimetric procedures involve titration of iodine by thiosulphate either towards starch end point (method A) or potentiometrically (method B). Both the methods have a reaction stiochiometry of 1: 1 (LCT: liberated iodine) and have quantification ranges of 2–20 mg LCT for method A and method B. The liberated iodine is also measured spectrophotometrically at 350 nm (method C) or the iodine-starch complex measured at 570 nm (method D). In both the methods, the absorbance is found to be linearly dependent on the concentration of iodine which in turn is related to LCT concentration. The calibration curves are linear over 5–40 and 1.25–12.5 mg mL^?1 LCT for method C and method D, respectively. The calculated molar absorptivity and Sandel sensitivity values are 1.0 × 10⁴ L mol^?1 cm^?1 and 0.0435 mg cm^?2, respectively for method C, and their respective values for method D are 2.9 × 10⁴ L mol^?1 cm^?1 and 0.0156 mg cm^?2. The intra-day and inter-day accuracy and precision studies were carried according to the ICH guidelines. The method was successfully applied to the analysis of two brands of tablets LCT. The accuracy was also checked by placebo blank and synthetic mixture analyses besides recovery study via standard addition procedure.     

Simple and one-pot synthesis of tri and tetracyclic frameworks containing [1,8]naphthyridin-2-one moiety from the Baylis-Hillman adducts

A facile synthesis of tri and tetracyclic frameworks containing [1,8]naphthyridin-2-one skeleton from the Baylis-Hillman alcohols via the Johnson-Claisen rearrangement, followed by the treatment with Fe/AcOH in simple one-pot multi-step process is described.