Terbium Sensitized Luminescence for the Determination of Ketoprofen in Pharmaceutical Formulations

This paper explores an ultra-sensitive luminescence method for the determination of Ketoprofen (KP) in pharmaceutical formulations. The technique is indirect and exploits the luminescence enhancement of terbium (Tb³⁺) by complexation with KP (Tb³⁺–KP), which was monitored at respective excitation and emission wavelengths of λ _ex = 258 nm and λ _em = 549 nm. The effect of varying the Tb³⁺ concentration and using multiple solvents was examined to determine optimal experimental conditions. Maximum sensitization was accomplished in the presence of methanol where the most favourable condition for the formation of the complex was recorded at a level of 1.0 × 10⁻⁵ M of Tb³⁺. Under these optimum experimental conditions, linear calibration curve was obtained in the range of 2.8 × 10⁻⁷–3.1 × 10⁻⁶ M with a detection limit of 8.7 × 10⁻⁸ M. The technique was validated with ‘working’ reference standards and produced relative standard deviations < 2% indicating that the reproducibility was highly acceptable. The proposed method was successfully applied to assays of KP in pharmaceutical formulations with average recoveries of 92–98%. The results were found to be in good agreement with those obtained by HPLC. The method is highly suited for general applications of this nature.     

Study of the 133Ba nucleus with the ( \vec d , p) reaction

Excited states in ¹³³Ba were studied with the ¹³²Ba ( $ \vec d $ , p) ¹³³Ba reaction at 24.0MeV, with a polarized deuteron beam using the Munich magnetic spectrograph Q3D. Many unambiguous spin-parity assignments were made up to an excitation energy of 2.2MeV, which allow a detailed comparison with different theoretical calculations, such as the interacting boson-fermion model and the shell model.     

Terbium sensitized luminescence for the determination of fexofenadine in pharmaceutical formulations

A sensitive and specific luminescence method for the determination of Fexofenadine (FEX), in pharmaceutical formulations is reported. The method is based on the sensitization of terbium (Tb³⁺) by complex formation with FEX. The luminescence signal for Tb–FEX complex is greatly enhanced by the addition of triethylamine (ET₃N) and zinc nitrate in methanol solution. Monitoring of the signal is accomplished when the instrument is in the phosphorescence mode with the excitation and emission wavelengths set at λ_ex = 220 nm and λ_em = 550 nm respectively. Optimum conditions for the formation of the complex in methanol were 2.25 × 10^?6 M of Tb³⁺, 5.00 × 10^?6 M of Et₃N and Zn²⁺ which allows for the determination of 10–800 ppb of FEX in the batch mode with a detection limit of 0.3 ppb. The proposed method was successfully applied for the determination of FEX in pharmaceutical formulations.     

Initial Carbon–Carbon Bond Formation during the Early Stages of the Methanol‐to‐Olefin Process Proven by Zeolite‐Trapped Acetate and Methyl Acetate

Methanol‐to‐olefin (MTO) catalysis is a very active field of research because there is a wide variety of sometimes conflicting mechanistic proposals. An example is the ongoing discussion on the initial C?C bond formation from methanol during the induction period of the MTO process. By employing a combination of solid‐state NMR spectroscopy with UV/Vis diffuse reflectance spectroscopy and mass spectrometry on an active H‐SAPO‐34 catalyst, we provide spectroscopic evidence for the formation of surface acetate and methyl acetate, as well as dimethoxymethane during the MTO process. As a consequence, new insights in the formation of the first C?C bond are provided, suggesting a direct mechanism may be operative, at least in the early stages of the MTO reaction.     

Existence of Solutions for Nonlinear Implicit Differential Equations: An Equilibrium Problem Approach

In this article, we study the existence of solutions for nonlinear implicit differential equations associated to a time-dependent pseudomonotone (respectively, quasimonotone) operator by using a new approach based on the theory of equilibrium \hboxproblems. More precisely, we first establish some existence results of solutions for mixed equilibrium problems where the \hboxbifunctions are, respectively, maximal monotone and \hboxpseudomonotone (quasimonotone) in the topological sense. Then, we write the nonlinear implicit differential equations in the form of a mixed equilibrium problem. By using the existence results for mixed equilibrium problems, we establish the existence of solutions of nonlinear implicit differential equations. This new approach provides some new and nice results which improve and unify most of the recent results obtained in this direction.     

Flow injection method for the assay of the anti-arrhythmic procainamide HCl in drug formulations utilizing statistical optimization techniques

A flow injection spectrophotometric method for the determination of procainamide HCl was explored. The method was based on the oxidation of procainamide HCl with cerium(IV) in sulphuric acid media and subsequent monitoring of the absorbance of the oxidized form of the drug at 480 nm. A sample rate of 250 samples per hour was attained. The procedure was optimized by the Factorial Design at two upper and lower levels of the five parameters sample loop size, flow rate, coil length, sulphuric acid and cerium(IV) concentrations. The latter three indicated high interactions and revealed significance to peak height value therefore optimized by the Super Modified Simplex programme. The optimized FI system with a linear calibration range of 100-600 ppm was found to be adequate and suitable for determination of procainamide HCl in proprietary drugs. A high degree of accuracy of the results was demonstrated by a statistical comparison with those obtained by the British Pharmacopoeia method of the same batch of drugs.     

Latent reactive groups unveiled through equilibrium dynamics and exemplified in crosslinking during film formation from aqueous polymer colloids

The concept of using equilibrium dynamics to provide for both protection and unveiling of latent functional groups at appropriate times in aqueous polymer colloid coatings designed for crosslinking only during film formation is introduced; the new functional monomer, 4-hydroxyethylsulfonylstyrene (HESS), readily undergoes emulsion copolymerization with acrylates to form stable latexes, followed by crosslinking by loss of water during film formation.     

A sequential injection method for the determination of piroxicam in pharmaceutical formulations using europium sensitized fluorescence

A simple, selective and sensitive luminescence method for the assay of piroxicam (PX) in pharmaceutical formulation is developed. The method is based on the luminescence sensitization of europium (Eu³⁺) by complexation with PX. The signal for PX–EU is monitored at λ_ex=358 nm and λ_em=615 nm. Optimum conditions for the formation of the complex in methanol were 0.01 M TRIS buffer and 0.2 mM of Eu³⁺ which allows the determination of 100–2000 ppb of pX in batch method and 100–1000 ppb with limit of detection (LOD) = 23.0 ppb using sequential injection analysis (SIA). The relative standard deviations of the method range between 2 and 3% indicating excellent reproducibility of the method. The proposed method was successfully applied for he assay of PX in pharmaceutical formulations (Feldene capsules and tablets). Average recoveries of 101.0±0.3 and 98.8±2.7% were obtained for capsules in methanol using batch and sequential injection (SI) methods, respectively.