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At least 127 records · Page 7Linked to original sources
PubMed1998

[Determination of enantiomeric purity by simultaneous dual circular dichroism and ultraviolet spectrophotometry].

A method is described for the determination of enantiomeric composition. The ellipticity and absorbances of the sample are measured simultaneously by CD and UV spectroscopies, and the resulting G value is determined. G is an intensive physico-chemical parameter, a close derivative of anisotropy factor. Its magnitude is identical with opposite sign for enantiomers. The experimental G value is concentration-independent, as long as both absorption and ellipticity are linear functions of concentration. The analytical procedure introduced here is simple, rapid, and inexpensive, even though it includes calibration with standards of established enantiomeric composition. Provided the sample contains some UV-active contaminant(s), the method can be used after achiral chromatographic purification. By virtue, the method lacks several sources of error, arising normally from concentration inaccuracies. Applicability of the principles is tested by the example of phenylglycine and mandelic acid. Advantages of the method allowed the determination of phenylglycine enantiomer purity with an accuracy of 0.1%.

Calibration↗
PubMed1988

Membrane-buffer partition coefficients of tetracaine for liquid-crystal and solid-gel membranes estimated by direct ultraviolet spectrophotometry.

The membrane-buffer partition coefficient of tetracaine was measured by direct ultraviolet spectrophotometry in dimyristoylphosphatidylcholine unilamellar liposomes at temperatures above and below the main phase transition. The partition coefficients of uncharged tetracaine to solid-gel (18 degrees C) and liquid-crystal (30 degrees C) membranes were 6.9 x 10(4) and 1.2 x 10(5), respectively. Despite the general assumption that local anesthetic binding to the solid membrane is negligible, this study showed that the solid membrane binding amounts to 57.5% of the liquid membrane binding. Binding of the charged form to the liquid or solid membrane was not detectable under the present experimental condition of 0.03 mM tetracaine bulk concentration. The present method measures metachromasia of local anesthetics when bound to lipid membranes. Its advantage is that the separation of the vesicles from the solution is not required. A linearized equation is presented that estimates the partition coefficient or binding constant graphically from a linear plot of the absorbance data. The method is applicable for estimation of drug partition when a measurable spectral change occurs due to complex formation.

Buffers↗
PubMed2002

[Simultaneous determination of four components in the compound child phenobarbital tablet using ultraviolet spectrophotometry].

OBJECTIVE: To establish a method to determine four components in the child phenobarbital tablet. METHODS: Ultraviolet spectrophotometry was used to determine four components without separation. RESULTS: The contents of aspirin, phenacetin, caffeine and phenobarbital could be measured simultaneously. The average recoveries of four components in simulated samples and the compound child phenobarbital tablet samples were 99.0%, 98.9%, 99.8%, and 101%, respectively, and relative standard deviations of those were 2.0%, 2.0%, 2.9%, and 2.2%, respectively. CONCLUSION: The method is simple, fast, reliable, and can be used to monitor the quality of compound drugs.

Aspirin↗
PubMed2001

[Study of direct determining animal and plant oil in sewage by ultraviolet spectrophotometry method].

In this paper, the trace oil in sewage have been emulsified with S-T emulsifier and determined by ultraviolet spectrophotometry. Under normal temperature, the oil even dispersed in sewage with S-T emulsifier. It is stable and direct determined without separation. The oil is from sewage. The linear range is 0-92 micrograms.mL-1, and rate of recovery is 89%-129%. The method is quick and simple.

Animals↗
PubMed1985

[Ultraviolet spectrophotometry of the cerebrospinal fluid in the differential diagnosis of strokes].

The authors describe the possibility of using the results of ultraviolet spectrophotometry of the cerebrospinal fluid (CSF) for the differential diagnosis of ischemic, hemorrhagic and mixed cerebral strokes. It was found that repeated examinations may be of a definite prognostic value. A correlational analysis showed that the greatest effect on the optical density of the CSF in cases of hemorrhagic strokes is exercised by protein and bilirubin and in cases of ischemic strokes by protein and aspartate aminotransferase (AST).

Adult↗