LC–MS/MS Determination of Catecholamines in Urine Using FMOC-Cl Derivatization on Solid-Phase Extraction Cartridge

A method for the determination of catecholamine derivatives in human urine is proposed that includes the derivatization of target compounds on a solid-phase extraction cartridge and determination of the analytes by a UHPLC method with tandem mass-spectrometric detection. 9-Fluorenyl-methoxycarbonyl chloride was used as the derivatization agent. The limits of detection for the analytes were 2.5 ng mL^?1 for 9-fluorenyl-methoxycarbonyl-adrenaline, 5 ng mL^?1 for 9-fluorenyl-methoxycarbonyl-octopamine, and 25 ng mL^?1 for 9-fluorenyl-methoxycarbonyl-dopamine. The proposed procedure was tested on real samples obtained from volunteers.     

Numerical Determination of the Relaxation Parameters of NMR in Complex Heterogeneous Systems

The methods of mathematical processing of the envelopes of spin-echo signals have been considered within the framework of the multiphase relaxation theory. A mathematical model for separation of multiexponential relaxation curves into individual exponential components of spin-spin relaxation times T _2i and amplitudes I _i is described. The multiphase nature of the relaxation of protons in complex heterogeneous systems has been revealed, and the relaxation characteristics of individual components — spin-spin relaxation times and amplitudes — have been determined.     

High-frequency electron paramagnetic resonance investigation of Mn3+ centers in SrTiO3

A high-frequency (49 and 70 GHz) electron paramagnetic resonance (EPR) study is reported on SrTiO₃ single crystals doped with 0.5-at% of manganese. EPR spectra originating from the S=2 ground state of Mn³⁺ ions are shown to belong to the different types of Jahn–Teller centers that arise as a result of varied ordering of the oxygen vacancies due to the reducing process. The present results indicate the strong covalent reduction of the density of unpaired spins (Fermi term) at the manganese nucleus for the various types of centers.     

The silafulvene: a potentially stable compound containing a double carbonsilicon bond

Two conformations of dimethylsilafulvene are calculated via a CNDO/2 procedure. One of them is planar while in the other the CH₃SiCH₃ plane is perpendicular to the cyclopentadienyl ring plane. The conformation energies differ by 19.8 kcal/mol.     

Application of Ranging Analysis to the Quality Assessment of Wines on a Nominal Scale

This work is dedicated to wine quality assessment methods as a problem of considerable current interest. Well-known approaches to wine quality assessment are considered based on the concentrations of volatile substances in wines and on the results of their taste tests. Comparative analysis was carried out for the evaluation of wines on a nominal scale of quality (high, medium, low, and adulterated) by means of discriminant analysis. It was found that the classification of wines based on quality with the use of discriminant analysis as a ranging analysis method with consideration for the concentrations of volatile substances, which are responsible for their organoleptic properties, is highly competitive with their expert (tasting) evaluation. A mathematical model was constructed for the classification of wines into the above categories, and a program module was developed for the automation of calculations.     

Determination of some cathinones,tropane alkaloids,and “pharmaceutical narcotics” in urine

A procedure is proposed for determining some narcotic and psychoactive substances (cathinones, tropane alkaloids, derivatives of ?-aminobutyric acid) in urine, including sample preparation and the determination of analytes by HPLC coupled with electrospray ionization tandem mass spectrometry. Sample preparation involved acid hydrolysis or the dilution of the sample. The lower limit of quantification is 200 pg/mL; the limit of detection is 100 pg/mL; and the calibration curves are linear in the range 0.2–50 ng/mL. The procedure was tested on real samples provided by the Toxicological Department of the Krasnodar Regional Narcological Dispensary. The high sensitivity of the analytical system ensures its use for the determination of narcotic preparations within a certain time after their intake, which may be of particular importance for forensic examinations.     

Selective separation of methanol-water mixture using functionalized boron nitride nanosheet membrane: a computer simulation study

Structural Chemistry - The separation of alcohol-water mixture from each other is one of the significant subjects for scientists in the pharmacy and engineering fields owing to economic savings. In...