Application of extraction disks in dissolution tests of clenbuterol and levothyroxine tablets by capillary electrophoresis

Sample preparation procedures using octadecyl (C₁₈) extraction disks were developed to obtain accurate and reproducible results for determinations of clenbuterol (20 μg per dose) and levothyroxine (100 μg per dose) in dissolution media of solid oral dosage forms. Preconcentration of samples allowed final concentrations of 1.1 μg/ml of clenbuterol and 4.0 μg/ml of levothyroxine to be reached prior to CE analysis. The results obtained by CE were in good agreement with those of HPLC. The precision of the migration time, peak area, peak height and accuracy were determined in both intea-day (n = 6) and inter-day (n =18) assays. Linearity was demonstrated over the ranges 0.5–80.0 μg/ml of clenbuterol and 1.0–30.0 μg/ml of levothyroxine. The mean recoveries were higher than 94.0%, ranging from 50 to 125% levels with respect to dose potencies. The proposed methodology may be generally applied to determine drugs at ng/ml concentrations.     

High-performance liquid chromatographic analysis of bile acids in hamster bile

A high-performance liquid chromatographic procedure has been developed for the determination of pentamidine concentrations in serum samples. A microbore, reversed-phase column was used with a mobile phase consisting of methanol and water with sodium heptanesulfonate and triethylamine as modifiers. Pentamidine could be extracted from serum only by the addition of an ion-pairing agent, di(2-ethylhexyl) phosphoric acid, to the chloroform used for extraction. The method can be used to reliably detect levels as low as 5 ng/ml. The pentamidine concentration in the serum of eleven patients 24 h after their tenth daily dose of pentamidine averaged 60 +/- 34 ng/ml.     

Built to order: molecular tinkertoys from the [Re(6)(mu(3)-Se)(8)](2+) clusters

Ligand substitution of [Re(6)(mu(3)-Se)(8)(PEt(3))(5)(CH(3)CN)](SbF(6))(2) (1) with pyridyl-based ligands, 2,4,6-tri-4-pyridyl-1,3,5-triazine (L1) and 5,10,15,20-tetra(4-pyridyl)-21H,23H-porphine (L2), produced respectively the star-shaped tricluster (T1) and tetracluster (T2) arrays, wherein three (T1) and four (T2) units of the [Re(6)(mu(3)-Se)(8)](2+) core-containing clusters are interconnected by the corresponding bridging ligands. These novel supramolecular assemblies were characterized by a combination of NMR ((1)H and (31)P) spectroscopy, ESI-MS, and microanalysis. The molecular and solid-state structures of T1 have also been established by single-crystal X-ray diffraction.     

Work function and negative electron affinity of ultrathin barium fluoride films

Thin films of barium fluorides with different thicknesses were deposited on GaAs substrate by electron beam evaporation. The aim of the work was to identify the best growth conditions for the production of coatings with a low work function suitable for the anode of hybrid thermionic-photovoltaic (TIPV) devices. The chemical composition and work function φ of the films with different thicknesses were investigated by X-ray photoelectron spectroscopy (XPS) and ultraviolet photoelectron spectroscopy (UPS). The lowest value of φ = 2.1 eV was obtained for the film with a thickness of ~2 nm. In the valence band spectra of the films at low kinetic energy, near the cutoff, a characteristic peak of negative electron affinity was present. This effect contributed to a further reduction of the film's work function.     

Ultramicro test for sulphur in organic material

Summary An ultramicro capillary method for the detection of sulphur in organic compounds is proposed. The sample is heated with a copper oxide-boron trioxide mixture, the sulphur trioxide evolved is reduced to sulphur dioxide by mercury and the gas is then detected by thep-rosaniline/formaldehyde reagent. Sensitivity ranges between 20 to 40 ng of sulphur. Sample taken should be 100 to 1000 ng. The test is unaffected by phosphorus, arsenic, and halogen derivatives, and by nitro and nitroso groups.

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Zusammenfassung Ein Ultramikroverfahren zum Nachweis von Schwefel in organischen Substanzen wird vorgeschlagen. Die Probe wird in einer Kapillare mit einer Mischung aus Kupferoxid und Bortrioxid erhitzt, das freigesetzte Schwefeltrioxid mit Quecksilber zu Dioxid reduziert und dieses mit p-Rosanilin und Formaldehyd nachgewiesen. Die Nachweisgrenze liegt bei 20 bis 40 ng Schwefel. Etwa 100 bis 1000 ng Probe werden angewendet. Der Nachweis wird von Phosphor, Arsen und Halogenen nicht gestört, auch nicht von Nitro- oder Nitrosogruppen.

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Résumé On propose une méthode ultramicro pour la recherche du soufre dans les composés organiques. On chauffe l'échantillon avec un mélange oxyde de cuivre-anhydride borique, l'anhydride sulfurique qui se dégage est réduit en anhydride sulfureux par le mercure et le gaz est alors décelé par le réactifp-rosaniline formaldéhyde. La sensibilité se situe entre 20 et 40 ng de soufre. La prise d'essai doit être de 100 à 1000 ng. Le phosphore, l'arsenic et les dérivés halogènés ne gênent pas la recherche, ni les groupes nitro et nitroso.

     

The strong perfect graph conjecture holds for diamonded odd cycle-free graphs

In this paper, we show that the strong perfect graph conjecture holds for a new class of graphs which we call diamonded odd cycle-free graphs. The class of diamonded odd cycle-free graphs contains the classes of threshold graphs and K₄\e-free graphs.     

Investigation of volatile acids on the ultramicro scale

Summary A capillary procedure is described for testing nanogram amounts of anions that evolve weak volatile acids which also show oxidizing properties. Two sensitive reagents, phenolphthalein-indigo carmine and alizarin yellow R are used for this purpose. The method is simple and reliable. A capillary diffusion method for the detection of azide is also proposed. Some applications of the method are reported.

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Zusammenfassung Zum Nachweis von Nanogrammengen schwacher, flüchtiger Säuren mit oxydierender Wirkung bzw. ihrer Anionen wurden Kapillarreaktionen angegeben. Phenolphthalein-Indigokarmin und Alizaringelb R sind hierfür geeignete empfindliche Reagenzien. Für den Nachweis von Azid wird eine Kapillardiffusionsmethode vorgeschlagen. Einige Anwendungsbeispiele wurden angeführt.

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Presented at the 6th International Symposium on Microchemical Techniques, September 7–11, 1970, Graz, Austria.