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T Hobo

Publications and source records attributed to T Hobo.

25 records · Page 2Linked to original sources
PubMed1995

Extraction of water-soluble vitamins from pharmaceutical preparations using AOT (sodium di-2-ethylhexyl sulfosuccinate)/pentane reversed micelles.

Reversed micelles can be used to concentrate water-soluble materials in the water pool. In this study, the extraction of water-soluble vitamins into reversed micelles was attempted, and a flow system was used to determine the time-course of the vitamin extraction. The efficiency of extraction was strongly affected by the extraction temperature and the concentration of reversed micelles, and the selectivity depended on the size of micelles. Water-soluble vitamins could be efficiently and rapidly extracted. The selective extraction of a model mixture of vitamins from pharmaceutical preparations was also attempted. Moreover, the usefulness of the proposed method for the determination of vitamins in various commercial tablets was also demonstrated. Using of this method, the surfactant remains mixed with the extracted compounds, and so we attempted to remove the surfactant from the extract by supercritical fluid extraction. Supercritical carbon dioxide containing 7.5% ethanol as entrainer was found to be the most efficient solvent for removing residual surfactant from the extract.

Ascorbic Acid↗
PubMed1991

Cobalt(II)-catalyzed chemiluminescence in a dioctadecyldimethylammonium chloride bilayer membranous medium for the flow injection determination of phenylpyruvic acid.

A novel chemiluminescence system is described for the flow injection determination of phenylpyruvic acid (PPA). The presence of both ordered surfactant molecular assemblies and a metal ion catalyst in the system is essential for the phosphorescence of benzaldehyde (emitter) produced by the aerobic oxidation of PPA in alkaline solution. Dioctadecyldimethylammonium chloride bilayer aggregates and cobalt (II) allows PPA to be selectively determined down to 1 X 10(-7) M. The linearity is 2 orders of magnitude with a relative standard deviation 3.1% (n = 10) for 1 X 10(-6) M PPA. Of 28 other species (1 X 10(-3) M) tested, only 4-hydroxymanderic acid, 4-hydroxyphenylpyruvic acid, 2,5-dihydroxyphenylacetic acid, and 4-hydroxy-3-methoxyphenylpyruvic acid provided signals 2-13 times more intense than that for 1 X 10(-6) M PPA. PPA present at 10(-3) - 10(-2) M levels in urine from patients with phenylketonuria can be determined with no special sample pretreatment by using this CL procedure. The mechanistic study of the present luminescent reaction are also undertaken in detail. The bilayer aggregates were found to contribute favorably both to the production of key intermediates and to the efficient phosphorescence emission.

Adult↗
PubMedDate not supplied

Temperature effect on chiral recognition of some amino acids with molecularly imprinted polymer filled capillary electrochromatography.

L-Aromatic amino acid imprinted polymers were prepared using azobisnitriles as either photoinitiators or thermal initiators at temperature ranging from 4 to 60 degrees C. Methacrylic acid (MAA) was used as functional monomer and ethylene glycol dimethacrylate (EDMA) was used as cross-linker. The result polymers were ground and sieved to particles < or = 10 microns, filled into the capillary columns and used for enantiomeric separations in capillary electrochromatographic (CEC) mode. The polymer particles < or = 25 were packed into high performance liquid chromatographic (HPLC) columns and used for enantioseparations in the HPLC mode. The mobility and chiral separation of some amino acids were studied on CEC and HPLC columns at different temperature. The relationships of separation factor and column temperatures and demonstrated in linear between logarithm of the separation factor (in alpha) and the inverse of absolute temperature (1/T). Some thermodynamic parameters, such as the apparent change of enthalpy (delta H zero) and the apparent change of entropy (delta S zero), were obtained using van't Hoff plots. The information obtained from the thermodynamic study is discussed in developing strategies for chiral recognitions of amino acids by molecular imprinting technique.

Amino Acids↗