Kinetic spectrophotometric determination of certain cephalosporins using oxidized quercetin reagent

A simple, precise and accurate kinetic spectrophotometric method for determination of cefoperazone sodium, cefazolin sodium and ceftriaxone sodium in bulk and in pharmaceutical formulations has been developed. The method is based upon a kinetic investigation of the reaction of the drug with oxidized quercetin reagent at room temperature for a fixed time of 30 min. The decrease in absorbance after the addition of the drug was measured at 510 nm. The absorbance concentration plot was rectilinear over the range 80–400 μg mL⁻¹ for all studied drugs. The concentration of the studied drugs was calculated using the corresponding calibration equation for the fixed time method. The determination of the studied drugs by initial rate, variable time and rate-constant methods was feasible with the calibration equations obtained but the fixed time method has been found to be more applicable. The analytical performance of the method, in terms of accuracy and precision, was statistically validated; the results were satisfactory. The method has been successfully applied to the determination of the studied drugs in commercial pharmaceutical formulations. Statistical comparison of the results with a well established reported method showed excellent agreement and proved that there is no significant difference in the accuracy and precision.     

A new alkaloid and a new diterpene from Cleome paradoxa B.Br. (Cleomaceae)

A new alkaloid, paradoxonine, and its enol tautomer, paradoxenoline, in addition to a new cembranoid diterpene, paradoxenoic acid, were isolated from the chloroformic fraction of the methanolic extract of Cleome paradoxa B.Br. The structures of the isolated compounds were established based on their spectral data, including MS, (1)HNMR, (13)CNMR, COSY, HMBC and HMQC. This is the first report on the isolation of alkaloids from the family Cleomaceae.     

Selection of surfactants for cell lysis in chemical cytometry to study protein-DNA interactions

Protein-DNA interactions play a defining role in many cellular processes. Studying such interactions at the single-cell level is important and challenging. Here we make the first step toward achieving this goal with chemical cytometry. Chemical cytometry utilizes capillary separation for detailed chemical analyses of single cells. The cell is injected into a capillary, lysed, and its components are analyzed by CE or capillary chromatography with highly sensitive detection. In order to apply chemical cytometry to studies of protein-DNA interactions, cell lysis must not destroy protein-DNA complexes. Surfactants represent the most practical means of cell lysis inside the capillary. This work aimed at finding surfactants and lysis conditions that do not destroy protein-DNA complexes. We studied three groups of surfactants--ionic, zwitterionic, and nonionic--with respect to their ability to lyse the cell membrane without significantly influencing the stability of protein-DNA complexes. Nonequilibrium CE of equilibrium mixtures with surfactants in the equilibrium mixtures and in the run buffer was used to measure the equilibrium constant, K(d), and rate constant, k(off), of protein-DNA complex dissociation. We found that nonionic surfactants worked best: they lyse the plasma membrane without significantly influencing K(d), k(off), or the EOF. This work creates the foundation for studies of protein-DNA interactions in single cells by chemical cytometry.     

Synthesis and characterization of copper(I) halide/pseudohalide adducts of 2-benzoylpyridine and x-ray crystal structure of [di-μ-iodo-bis(N,O-2-benzoylpyridine)dicopper(I)]

Dark-brown copper(I) complexes of the type CuXL, for X = Cl, Br, I, SCN and N₃, and orange-yellow complexes of the type (CuX)₂L, for X = Cl or Br, where L = 2-benzoylpyridine, have been prepared and characterized. All complexes exhibit strong CT bands in the visible region and gave non-conducting solutions in acetone and nitrobenzene. The IR spectral data suggest that 2-benzoylpyridine acts as a monodentate ligand in the orange-yellow complexes and as a bidentate chelating ligand in the brown complexes, whereas bridging halides and pseudohalides exist in both types. The structure of the 1 : 1 black iodide complex, as determined by X-ray crystallography, features a discrete, centrosymmetric [CuI(2-benzoylpyridine)]₂ molecule with a short CuCu distance of 2.587(1) Å. Each copper atom in the dimeric molecule is tetrahedrally coordinated by two μ-iodine atoms and the carbonyl oxygen and nitrogen atoms of the chelating 2-benzoylpyridine ligand. The orange-yellow complexes display visible emission when excited in the UV region, whereas the brown complexes do not.     

Ligandless temperature-controlled ionic liquid-phase microextraction of lead(II) ion prior to its determination by FAAS

We describe the application of temperature-controlled ionic liquid based microextraction (TC-IL-ME) of lead(II) ion. The method does not require the use of an organic solvent or a ligand. Rather, the IL is directly added to the aqueous sample containing Pb(II) in a centrifuge tube, and the mixture is heated to 80 °C for 4 min. After cooling at 0 °C, the solution turns cludy due to the formation of fine droplets of the IL containing Pb(II). The IL is separated by centrifugation, acidified, and directly submitted to FAAS by microinjection. The effects of pH value, volume of IL, extraction time, temperature, sample volume and matrix were optimized to result in a preconcentration factor of 30, a detection limit of 5.8 μg L^?1, and a limit of quantification of 19.3 μg L^?1. The method was validated by analyzing a certified reference material (NCSZC81002B; hair). A recovery test performed with spiked samples gave values between 102 % and 105 %. The method was also used to determine Pb(II) in hair samples.

An approach to biologically important S‐heterocycles,dithiocarbamyls, and their relevant phosphono derivatives

The feasibility of insertions of carbanions between two sulfur atoms has been reported when 5‐(4‐chlorophenyl)‐4‐cyano‐1,2‐dithiol‐3‐thione ( 1 ) and tetramethylthiuram disulfide ( 17 ) were allowed to react with unsaturated 2a,b and active phosphonium salts 11a,b . The reactions afforded, mainly, 1,3‐dithiols 4a,b and 14a,b together with substituted thiophenes 10a,b and 16a,b . Reactions of 1 and 17 with α‐alkylthiomethyl phosphonates 24a,b afforded the phosphonates 25a,b and 26a,b , respectively.     

Determination of amlodipine besylate by adsorptive square-wave anodic stripping voltammetry on glassy carbon electrode in tablets and biological fluids

The adsorptive and electrochemical behavior of amlodipine besylate on a glassy carbon electrode were explored in Britton-Robinson buffer solution by using cyclic and square-wave voltammetry. Cyclic voltammetric studies indicated the oxidation of amlodipine besylate at the electrode surface through a single two-electron irreversible step and fundamentally controlled by adsorption. The solution conditions and instrumental parameters were optimized for the determination of the authentic drug by adsorptive square-wave stripping voltammetry. Amlodipine besylate gave a sensitive adsorptive oxidation peak at 0.510 V (versus Ag/AgCl). The oxidation peak was used to determine amlodipine besylate in range 4.0×10⁻⁸ to 2.0×10⁻⁶ with a detection limit of 1.4×10⁻⁸ M. The procedure was successfully applied for the assay of amlodipine besylate in tablets (Norvasc)^®. The percentage recoveries were in agreement with those obtained by the reference method. Applicability to assay the drug in urine and serum samples was illustrated. The mean percentage recoveries were 96.31±1.18 and 96.98±1.17, respectively. The proposd method used for monotoring clinically relevant concntrations of drug in human urine and serum.     

High-performance liquid chromatographic determination of proquazone and its m-hydroxy metabolite in spiked human plasma and urine

A simple and rapid high-performance liquid chromatographic method for the determination of proquazone (PQZ) and its major metabolite, m-hydroxyproquazone, in spiked human plasma and urine was developed. Plasma samples were purified using acetonitrile as a protein precipitant, while urine samples were diluted only with the mobile phase and filtered prior to injection. Samples containing the parent compounds and glafenine (internal standard) were eluted from a reversed-phase C8 column using acetonitrile-0.025 M sodium acetate (60 + 40) adjusted to pH 5 as the mobile phase and detected at 234 nm. Peak area ratios of the analytes versus internal standard were used for calibration. The mean recoveries from plasma and urine samples spiked with PQZ and its m-hydroxy metabolite ranged from 97.87 to 103.88%. The relative standard deviation for the within- and between-day analyses were < 4%. The proposed method was applied for the assay of PQZ in laboratory-made tablets.     

Synthesis of Nano-Cadmium Sulfide by Pulsed Laser Ablation in Liquid Environment

A pulsed laser-assisted in liquid environment method has been developed successfully to synthesize size-tunable (5–12 nm) and different shapes (sphere, rod, rope) of nano II–VI semiconductor (cadmium sulfide). This method can be carried out in two ways; the first one is the top-down technique, which has been discussed in publications in the last few decades, and the other one is the bottom-up technique, which appears for the first time in this paper. X-ray diffraction, ultraviolet-visible spectroscopy, and transmission electron microscopy confirm that the nanoparticles are crystalline. The methods lead to the production of nanomaterials, which are important for photonics and biosensing applications. Both synthesized methods can be applied in all materials because of their ability to ablate almost all kinds of materials due to the ultrahigh energy density and control over the growth process by manipulating the process parameters such as intensity, wavelength, and so on.     

Use of Cerium (IV) in the Spectrophotometric and Spectrofluorimetric Determinations of Penicillins and Cephalosporins in Their Pharmaceutical Preparations

Spectrophotometric and spectrofluorimetric procedures for the quantitative determination of four penicillins [Amoxycillin (AMX), Bacampicillin (BAC), Piperacillin (PPN) and Sultamcillin (SULT)] and ten cephalosporins [Cefadroxil (CDL), Cefamandole nafate (MAN), Cefuroxime axetil or sodium (CFX), Cefaclor (CFCR), Ceftazidime (CZD), Ceftizoxime (CTIZ), Ceftriaxone (CTRX), Cefoperazone (CPZ), Cefixime (CXIM) and Cefpodoxime proxetil (CFPD)] are described. Both methods are based on the acidic oxidation of the antibiotics with cerium (IV) at elevated temperature. The effect of the reagent concentration, volume of the acid,and the heating temperature were studied to optimize the reaction conditions. Each antibiotic was determined by either measuring the absorbance difference at 317 nm or the cerous inherent fluorescence at 256 and 356 nm for excitation and emission wavelengths, respectively. The two procedures have been successfully applied to the assay of these antibiotics in their pharmaceutical dosage forms. The obtained results have been statistically compared with those obtained by the official methods.