A gadolinium-based magnetic ionic liquid for supramolecular dispersive liquid–liquid microextraction followed by HPLC/UV for the determination of favipiravir in human plasma

Favipiravir is a potential antiviral medication that has been recently licensed for Covid-19 treatment. In this work, a gadolinium-based magnetic ionic liquid was prepared and used as an extractant in dispersive liquid–liquid microextraction (DLLME) of favipiravir in human plasma. The high enriching ability of DLLME allowed the determination of favipiravir in real samples using HPLC/UV with sufficient sensitivity. The effects of several variables on extraction efficiency were investigated, including type of extractant, amount of extractant, type of disperser and disperser volume. The maximum enrichment was attained using 50 mg of the Gd-magnetic ionic liquid (MIL) and 150 μl of tetrahydrofuran. The Gd-based MIL could form a supramolecular assembly in the presence of tetrahydrofuran, which enhanced the extraction efficiency of favipiravir. The developed method was validated according to US Food and Drug Administration bioanalytical method validation guidelines. The coefficient of determination was 0.9999, for a linear concentration range of 25 to 1.0 × 10⁵ ng/ml. The percentage recovery (accuracy) varied from 99.83 to 104.2%, with RSD values (precision) ranging from 4.07 to 11.84%. The total extraction time was about 12 min and the HPLC analysis time was 5 min. The method was simple, selective and sensitive for the determination of favipiravir in real human plasma.     

Dinuclear gold (I)-di-N-heterocyclic carbene complexes: syntheses,structure, density functional theory calculation and photoluminescence study

The synthesis and characterizations for a series of dinuclear gold (I)-di-NHC complexes, 1–8 through the trans-metalation method of their respective silver (I)-di-NHC complexes, i–viii are reported (where NHC = N-heterocyclic carbene). The successful complexation of a series of unusual non-symmetrical and symmetrical di-NHC ligands, 3,3'-(ethane-1,2-diyl)-1-alkylbenzimidazolium-1'-butylbenzimidazolium (with alkyl = methyl, ethyl, propyl, butyl, pentyl, hexyl, heptyl, benzyl) with the gold (I) ions are suggested by elemental analysis, Fourier transform-infrared, ¹H- and ¹³C-NMR data. The ¹³C-NMR spectra of 1–8 show a singlet sharp peak in the range of 190.00–192.00 ppm, indicating the presence of a carbene carbon that bonded to the gold (I) ion. From single crystal X-ray diffraction data, the structure of complex 6 with the formula of [di-NHC-Au (I)]₂·2PF₆ is obtained [where NHC = 3,3'-(ethane-1,2-diyl)-1-hexylbenzimidazolium-1'-butylbenzimidazolium]. The photophysical study in solid state of 6 displays an intense photoluminescence with a strong emission maxima, λ_em = 480 nm, upon excitation at 340 nm at room temperature. Interestingly, the emission maximum at 77 K shows a structural character with a strong peak at 410 nm, a medium at 433 nm and a weak at 387 nm, accompanied by a tail band to about 500 nm.     

Search for supersymmetric particles in light gravitino scenarios and sleptons NLSP

A search for sleptons, neutralinos, charginos, sgoldstinos and heavy stable charged sleptons in the context of scenarios where the lightest supersymmetric particle is the gravitino, is presented. Data collected during 2000 with the DELPHI detector at centre-of-mass energies from 204 to 208 GeV were analysed and combined with all the data collected from 1995 to 1999 at lower energies. No evidence for the production of sleptons, neutralinos and charginos has been found, therefore new limits on the mass of these supersymmetric particles and on the model parameter space are set. The search for heavy stable charged sleptons also updates the stable sleptons mass limit. The absence of evidence for sgoldstino production allows limits to be set on its mass and on the scale of supersymmetry breaking. Received: 6 November 2002 / Published online: 14 February 2003     

Organophosphorus chemistry,XII. Reaction of furil with alkyl phosphites and ylide-phosphoranes

Summary The reaction of furil (1) with trialkyl phosphites2 yielded caged phosphorane derivatives of types3a-c. Dry hydrogen chloride gas converted3a-c into the respectivea-hydroxyvinyl-phosphates8a-c which are equally produced by reacting furil with the appropriate dialkyl phosphite7. The reaction of furil with ylide-phosphoranes10 proceeded according to the Wittig reaction mechanism to give the respective ethylenes11a-c. The new compounds have been characterized by their spectroscopic data (IR, PMR,³¹P-NMR, MS) and elementary analyses.Dedicated to Prof. M. Sidky on the occasion of his 60th birthday     

Preparation of cellulose and cellulose derivative azo compounds

Wood pulp and cotton linter are the most common sources of cellulose forindustrial use. Methyl cellulose (MC) and cellulose sulfate (CS) were preparedusing bleached wood pulp and cotton linter. Coloured azo compounds were alsoprepared from coupling cellulose, wood pulp, MC and CS with aromatic diazoniumsalt. The presence of electron-releasing or withdrawing substituents affectedthe electrophilic substitution reaction. The produced azo compounds werecharacterized by FT-IR methodology, as well as mass spectrometry, in which thefunctional groups and the ion fragments of the products were analyzed.     

Covalent modification of calcium hydroxyapatite surface by grafting phenyl phosphonate moieties

The reaction between phenyl phosphonic dichloride (C₆H₅P(O)Cl₂) and synthetic calcium hydroxy- and fluorapatite has been investigated. The presence of mono- or polymeric (C₆H₅PO) fragment bound to hydroxyapatite was evidenced by IR, and solid-state ³¹P NMR spectroscopy. X-ray powder analysis has shown that the apatitic structure remains unchanged during the reaction. In contrast, no reaction was found using fluorapatite. According to the results found for these two different apatites a mechanism was proposed for the formation of covalent P-O-P bonds as the result of a reaction between the C₆H₅P(O)Cl₂ organic reagent and (HPO₄)⁻ and/or OH⁻ ions of the hydroxyapatite.     

Synthesis of new thiazole analogues of pyochelin, a siderophore of Pseudomonas aeruginosa and Burkholderia cepacia. A new conversion of thiazolines into thiazoles

Three pyochelin analogues and their methyl esters all containing a thiazole ring have been synthesised from the same Weinreb amide key intermediate. One of these analogues called HPTT-COOH, a molecule released in the course of pyochelin and yersiniabactin biosynthesis, was efficiently synthesised using a new base induced conversion of the key compound 2′-(2-hydroxyphenyl)-2′-thiazoline-4′-(N-methoxy,N-methyl) carboxamide into 2′-(2-hydroxyphenyl)-2′-thiazole-4′-(N-methoxy,N-methyl) carboxamide.     

An energy-transport model for semiconductors derived from the Boltzmann equation

An energy-transport model is rigorously derived from the Boltzmann transport equation of semiconductors under the hypothesis that the energy gain or loss of the electrons by the phonon collisions is weak. Retaining at leading order electron-electron collisions and elastic collisions (i.e., impurity scattering and the elastic part of phonon collisions), a rigorous diffusion limit of the Boltzmann equation can be carried over, which leads to a set of diffusion equations for the electron density and temperature. The derivation is given in both the degenerate and nondegenerate cases.     

Polarographic behaviour and determination of paracetamol and salicylamide after treatment with nitrous acid

A polarographic procedure is described for the determination of paracetamol (acetaminophen) and salicylamide after treatment with nitrous acid. The different experimental parameters affecting the derivatization process and the polarographic analysis were studied. The derivatization products were found to be reduced at the dropping mercury electrode over the whole pH range in Britton-Robinson buffers. At pH 7.0, well defined diffusion-controlled cathodic waves were produced for both compounds. Plots of limiting current vs. concentration were linear over the ranges 0.05–0.75 and 0.25–1.5mM for paracetamol and salicylamide, respectively, in the d.c. mode, with minimum detectability of 2.5 × 10^–6 and 1.25 × 10^–5 M, respectively. The procedure was applied to the analysis of some pharmaceutical dosage forms and the results were in good agreement with those obtained by official and compendial methods.