EPR and Optical Absorption Studies of VO2+ Doped Trisodium Citrate Dihydrate Single Crystals
The electron paramagnetic resonance of VO2+ doped trisodium citrate dihydrate (Na3C6H5O7·2H2O) single crystals and powder has been examined at room temperature. The angular variation of the EPR spectra has shown that two different VO2+ complexes are located in different chemical environments, each environment containing two magnetically inequivalent VO2+ sites in distinct orientations occupying substitutional positions in the lattice and showing a very large angular dependence. The crystalline field around the VO2+ ion is nearly axial. The optical absorption spectrum shows three bands, centered at 24631, 16892, and 12195 cm−1. The spin Hamiltonian parameters and the molecular orbital coefficients are calculated from the EPR and optical data, and result are discussed. Keywords EPR; Trisodium Citrate; Absorption the Spectrum; Vanadyl Ion
Evaluation of EPR parameters for compressed and elongated local structures of VO2+ and Cu2+ spin probes in BaO-TeO2-B2O3 glasses
Abstract EPR parameters and the local configurations of the transition metal (TM) ions VO2+ and Cu2+ in BaO-TeO2-B2O3 glasses were experimentally evaluated and also theoretically verified. From the recorded X-band EPR spectra the spin-Hamiltonian parameters (SHP) were determined. The optical spectra of vanadium doped glass samples revealed a single absorption band at 596 nm which was assigned to 2B2g → 2B1g transition, whereas copper doped glasses revealed two absorption bands around 818 and 602 nm which were assigned to 2B1g → 2B2g and 2B1g → 2E2g transitions respectively. Theoretical studies were accomplished on the EPR and optical factors from perturbation theory. It was observed from both the experimental and theoretical SHP values of vanadium containing glasses that the VO2+ ions are in tetragonally compressed octahedral sites with dxy (2B2g) ground state, while the copper containing glasses found to be in tetragonally elongated octahedral sites with d x 2 − y 2 (2B1g) as the ground state. It is found that the magnitude of the relative tetragonal compression ratio ( φ ) of vanadium ion is less than the relative tetragonal elongation ratio ( τ ) of copper ion. The nature of the bonding between TM ions (i.e. vanadium and copper) and their ligands was assessed. Theoretical and experimental EPR parameters are in great concurrence with each other.
Pharmacokinetics of Mivacurium Isomers and Their Metabolites in Healthy Volunteers after Intravenous Bolus Administration
Background Previous studies report the pharmacokinetics of mivacurium isomers after an infusion using venous blood sampling. Although the extent of the mivacurium arterial‐venous gradient is not known, the sampling site is likely to influence mivacurium pharmacokinetic parameters because the drug is rapidly metabolized as it traverses the circulation. The objectives of this study were (1) to determine the pharmacokinetics of mivacurium isomers in healthy persons after intravenous bolus administration using intensive arterial blood sampling, and (2) to characterize the formation and elimination of mivacurium metabolites in human plasma. Methods Eight persons classified as American Society of Anesthesiologists physical status 1 or 2 who were scheduled to undergo elective surgery under balanced anesthesia received 0.15 mg/kg mivacurium chloride as an intravenous bolus. Arterial blood samples were collected every 10 s during the first 2 min and at frequent intervals for 4 h thereafter. Plasma concentrations of mivacurium isomers and their metabolites were determined by two stereoselective high‐performance liquid chromatographic methods coupled with fluorometric detection and noncompartmental pharmacokinetic parameters. Results Mean elimination half‐lives of the trans‐trans, cis‐trans, and cis‐cis isomers were 2.4, 2, and 28.5 min, respectively, with corresponding mean plasma clearances of 29.2, 45.7, and 6.7 ml [center dot] min‐1 [center dot] kg‐1. The volumes of distribution at steady state of the trans‐trans, cis‐trans, and cis‐cis isomers were 0.047, 0.054, and 0.189 l/kg, respectively. Plasma concentrations of monoester and alcohol metabolites peaked 25 s (median) after mivacurium injection, with half‐lives in the range of 90 min, except for the cis alcohol metabolite, which was only negligibly and transiently formed. Conclusions Substantial hydrolysis of mivacurium isomers by cholinesterases was confirmed by the rapid appearance of mivacurium metabolites in plasma. The intensive arterial sampling proved to be critical for the trans‐trans and cis‐trans isomers because the area under the curve between 0 and 2 min accounted for 75% and 86% of the total, respectively.