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  • Author or Editor: H. Mager x
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Abstract  

The principles of selective separations by recrystallization are explained and formulae for the calculation of decontamination factors are presented. Experiments with strontium sulfate and radioactive strontium ions demonstrate the validity of the theoretical considerations. Similar or higher decontamination factors are found than those calculated for a uniform distribution of the radioactive strontium ions between crystals and solution. The high values are explained by assuming a recrystallization mechanism which consists of dissolution and redeposition of crystal layers. The half-times of recrystallization increase sharply with Sr2+ or SO 4 2− concentration in the solution. In nitric acid solutions as well as in mixtures containing nitrates and nitric acid the solubility of strontium sulfate is rather high, accordingly the decontamination factors are low under these conditions and furthermore the recrystallization half-times are long.

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A new rapid, simple, economical, and environment-friendly reversed- phase high-performance thin-layer chromatography (RPHPTLC) method has been established for the simultaneous determination of glycyrrhizin and glabridin in Glycyrrhiza glabra roots, rhizomes and selected herbal formulations. The method was carried out using RP-18 silica gel 60 F254S HPTLC glass plates and methanol–water (7:3 v/v) as the mobile phase. The developed plates were scanned and quantified densitometrically at 256 and 233 nm for glycyrrhizin and glabridin, respectively. Glycyrrhizin and glabridin peaks from G. glabra roots and rhizomes and herbal formulations were identified by comparing their single spots at R F = 0.63 ± 0.02 and R F = 0.28 ± 0.01, respectively. Linear regression analysis revealed a good linear relationship between the peak areas and the amounts of glycyrrhizin and glabridin in the ranges of 1000–7000 and 100–700 ng band−1, respectively. The method was validated, in accordance with the International Conference on Harmonization (ICH) guidelines for precision, accuracy, and robustness. The proposed method will be useful to determine the therapeutic doses of glycyrrhizin and glabridin in herbal formulations as well as in bulk drug.

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Summary

We have recently reported on the effect of the environmental conditions on the quantity of diosgenin. Attempts for the simultaneous quantification of trigonelline and diosgenin using normal-phase silica gel plates were not successful. A high-performance thin-layer chromatography (HPTLC) method was developed using glass-backed plates coated with RP-18 silica gel 60 F254S and acetonitrile-water (7.5:2.5, V/V) as the mobile phase. Trigonelline and diosgenin peaks were well separated with R F values 0.29 ± 0.02 and 0.17 ± 0.01, respectively. The TLC plates were directly scanned at 267 nm for trigonelline and at 430 nm after derivatization with vanillin-sulfuric acid for diosgenin. Linear regression analysis revealed a good linear relationship between the peak area and the amounts of trigonelline and diosgenin in the range of 200–1400 and 50–300 ng per band, respectively. The method was validated in accordance with the International Conference on Harmonization (ICH) guidelines for precision, accuracy, and robustness.

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