PubMed Health⌕ Search

Biomedical subjects

H Bethke

Publications and source records attributed to H Bethke.

7 recordsLinked to original sources
PubMed1978

Dihydroergotoxine: separation and determination of four components by high-performance liquid chromatography.

The evaluation of a new high-performance liquid chromatographic method is described. It permits the separation and determination of the four components of dihydroergotoxine (dihydroergocristine, dihydroergocornine, dihydro-alpha-ergocryptine, and dihydro-beta-ergocryptine) in a single step. On reversed-phase microparticles, complete baseline separation is possible with different mobile phases containing about 10(-2) M base. The analysis of dihydroergotoxine mesylate drug substance or its dosage forms can be carried out in about 15 min. No reference substance is required for the determination of the proportions of the components. This method is simple and exhibits high accuracy, reproducibility, and selectivity. It permits the analytical control of dosage forms containing dihydroergotoxine mesylate to ensure that they comply with the specifications for the drug substance used in clinical and pharmacological studies.

Chemical Phenomena↗
PubMed1976

Determination of the content and purity of ergotamine preparations by means of high-pressure liquid chromatography.

A reversed-phase system of high-pressure liquid chromatography with solvent gradient is described for testing the purity of ergotamine as an active substance and for checking its concentration in pharmaceutical preparations. Because of its good resolution, this system can be used not only for the selective assay of ergotamine but also for the identification and quantitative determination, in the same chromatogram, of seven known isomerization and hydrolysis breakdown products. Simultaneous detection at two different UV wavelengths also makes it possible to measure further breakdown products formed by addition at the 9,10 double bond (lumi-compounds). The advantages of the system lie in the determination of all of the products within ca. 20 min, direct injection of low-dosage injection solutions and sensitive detection of polar breakdown products. The system is reproducible with regard to retention times and quantitative determination. It is suitable as a quality-control method for the routine determination of the content and purity of ergotamine preparations.

Chromatography, High Pressure Liquid↗
PubMed1976

Fluorescence densitometric method for the determination of gluconic and lactobionic acids ("sugar acids") in pharmaceutical preparations.

An in situ fluorimetric method has been developed for the quantitation of gluconic and lactobionic acids and their salts in tablet formulations. The method is based on glycol cleavage with lead tetraacetate followed by treatment with dichlorofluorescein. Calcium gluconate and lactobionate were determined in Calcium-Sandoz and Ca-C 1000 Sandoz effervescent tablets. The reproducibility corresponded to relative standard deviations between 0.7 and 3.5% (usually below 2%). Detection limits of 0.2 mug per spot can be obtained. Interfering compounds such as citric acid, sugars and ascorbic acid can be separated from the "sugar acids". The linearity of the calibration graphs between 0.5 and 5 mug per spot is satisfactory (r = 0.994-0.999). The method is simple and could be applied to the routine analysis of suitable pharmaceutical formulations. Other compounds with glycol structures should also be adaptable to this technique.

Chromatography, Thin Layer↗