PubMed · 13547280
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E GUENSBERGER, J GROSS, J MASARIK. 1958. [Directed electroshock therapy].. https://pubmed.ncbi.nlm.nih.gov/13547280/
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An amphiphilic barbituric acid derivative was found to form stable monolayers showing a clear phase transition at the air/water interface. It is interesting to find that the deposited Langmuir-Blodgett (LB) films of the compound showed circular dichroism (CD) although the molecule itself was achiral. AFM measurements on the transferred one-layer LB film revealed that spiral nanoarchitectures were formed. It was further found that the supramolecular chirality of the LB films was related to symmetry breaking at the interface. Hydrogen bonding and the pi-pi stacking between the neighboring molecules resulted in chiral fibers which formed the spiral structures. To the best of our knowledge, this is the first report on the chirality of the molecular assemblies and spiral nanostructures formed through the air/water interface by achiral molecules.
The retention time of 22 barbituric acid derivatives was measured on a narrow-bore porous graphitized carbon (PGC) column using water-dioxane mixtures as mobile phases. The capacity factor (k), theoretical plate number (N), and asymmetry factor (AF) were calculated for each solute in each mobile phase. The relationships between chromatographic characteristics and physicochemical parameters of solutes were elucidated by stepwise regression analysis (SRA). SRA indicated that the binding of barbiturates to the PGC surface is of mixed character electrostatic and apolar interactive forces are equally involved. Sterical correspondence between the surface of the stationary phase and the solutes also exert a significant influence on the retention behavior.
A capillary electrochromatographic method was developed for the separation of barbiturates. The separation was optimized in a 75 microm ID capillary, packed with 3-(1,8-naphthalimido)propyl-modified silyl silica gel (NAIP), studying the effect of buffer pH, buffer concentration, and mobile phase composition. Using an applied voltage of 20 kV and the short-end injection method (9 cm capillary effective length), the mobile phase of 1.0 mM citrate buffer (pH 5.0) containing 40% methanol provided the baseline separation of barbital, phenobarbital, secobarbital, and thiopental (internal standard) in less than 4.5 min. The method was successfully applied to the analysis of barbiturates in human serum. Under the optimal conditions, good repeatability and linearity were obtained in the range of 2.90-43.29 microg/mL for barbital, phenobarbital, and secobarbital.