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Results for “aqueous media”

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At least 19 recordsLinked to original sources

PubMed1977

Degradation of carmustine in aqueous media.

The degradation rate of carmustine was investigated in buffered aqueous media at several pH values. The buffering agents studied were those with potential use in parenteral formulations of this drug: acetate, citrate, and phosphate. The apparent first-order degradation rate constants were calculated using a linear regression procedure. A pH range over which minimum degradation occurred was ascertained. General acid and specific base catalysis was demonstrated for the degradation of carmustine. From the data at 5, 22, and 37 degrees, the apparent activation energies for carmustine degradation in buffered aqueous media were computed and were strongly pH dependent.

Buffers↗

PubMed1976

Micellar solubilization of fatty acids in aqueous media containing bile salts and phospholipids.

1. The solubility of fatty acids in aqueous media containing bile salts alone and in admixture with either lecithin (phosphatidylcholine) or phosphatidylethanolamine was determined. 2. Over the pH range 2-0-7-4, the order of fatty acid solubility in aqueous solutions containing bile salts was linoleic greater than oleic greater than elaidic greater than palmitic greater than stearic. The solubility of each fatty acid increased as the pH of the miceus solutions of bile salts greatly increased the solubility of palmitic acid and stearic acid. 4. In the presence of bile salts and lecithin, the solubility of oleic acid and elaidic acid decreased with increasing pH of the micellar solution, indicating a competitive effect between the fatty acid anions and lecithin. The solubility of linoleic acid increased linearly with lecithin concentration. 5. Phosphatidylethanolamine as an additive to bile salts increased the solubility of both saturated and unsaturated fatty acids in the pH range 2-3-7-4. The effectiveness of phosphatidylethanolamine as an amphiphile was similar to that of lecithin, although at pH 3.0 fatty acid solubility was greater in the presence of phosphatidylethanolamine. 6. The significance of these findings is discussed in relation to the intestinal absorption of fatty acids in sheep.

Animals↗

PubMed1978

Tritium release from Ti-T layers in air, in aqueous media and in animal experiments.

In connection with Ti-T incorporation hazard to which operators of neutron generators are exposed the release of tritium from Ti-T preparations of different ages was studied in experiments carried out in air, in aqueous media and in living animals. Samples were prepared with activities from 10 to 30 mCi and the effect of storage on the tritium release rate was also observed. In 250 days a fraction of 10(-3) of the tritium activity was absorbed by aqueous liquids. In air the release varied from 10(-6) to 10(-7) per hour. The Ti-T samples of different ages, introduced surgically into the abdominal cavity of rats, showed the tritium release rate to decrease with time. The tritium activity observable in the circulation was 5 to 6 orders of magnitude smaller compared with the introduced value. The observations permit the inference that in the case of Ti-T incorporation only a minor fraction of the tritium burden can be assessed from the activity measured in the urine.

Air Pollutants, Radioactive↗

PubMedDate not supplied

Reduction in dentin wear resistance by irradiation and effects of storage in aqueous media.

Electromechanical dentin abrasion measurements showed that the irradiation treatment applied before radiotracer dentin abrasion measurements reduced the wear resistance of dentin. This caused changes in the measured relative abrasitivities of dentifrices. Effects of storage in aqueous media were also investigated.

Dentifrices↗

PubMed1978

Physicochemical properties of glycyrrhizic acid in aqueous media II: Effect on flocculation-deflocculation behavior of suspensions of sulfathiazole and graphite.

The flocculation-deflocculation behavior of sulfathiazole and graphite in aqueous solutions of glycyrrhizic acid was studied by measuring the sedimentation volume and turbidity of supernates. The dispersing effect of glycyrrhizic acid on suspension of sulfathiazole showed a maximum in the pH 3-4 region, the same pH region where the zeta-potential of sulfathiazole particles showed a negative maximum. The results were explained by the variation of degrees of ionization of glycyrrhizic acid and sulfathiazole with pH. With graphite suspensions, the pH region where the dispersing effect of glycyrrhizic acid showed a maximum shifted to a higher pH compared with sulfathiazole. This result can be attributed to the fact that graphite is a nonpolar substance so the surface properties are not affected by a pH change. Hence, the adsorption of glycyrrhizic acid occurs even in a fairly high pH range.

Adsorption↗

PubMed1977

Degradation kinetics of a substituted carbinolamine in aqueous media.

The apparent first-order breakdown of the medicinally active agent 3-(p-chlorophenyl)-2-ethyl-2,3,5,6-tetrahydroimidazo[2,1-b]thiazol-3-ol was studied in aqueous solutions where dehydration gave the unsaturated compound 3-(p-chlorophenyl)-5,6-dihydro-2-ethylimidazo[2,1-b]thiazole. This thiazole was the primary solvolytic product produced in approximately quantitative yields for the temperature range studied and ostensibly underwent no further reaction in acidic media even on prolonged heating. Investigations were carried out at various pH values in standard buffers at constant ionic strength. The ionization constants of the compounds are reported as well as the apparent activation energies for the degradation in acid and acetate buffers. The influence of ionic strength on the velocity constant was determined.

Buffers↗

PubMed1976

Magnetic circular dichroism of heme-isocyanide complex in aqueous media.

The nature of the ethyl isocyanide complexes of ferri- and ferro-heme was investigated in terms of the magnetic circular dichroism (MCD) spectroscopy. The complex formation of heme with ethyl isocyanide was critically dependent on the solvent system, thus, on structures of heme before addition of the ligand. The MCD spectra of the heme ethyl isocyanide complexes revealed that: (1) The addition of ethyl isocyanide to both ferri- and ferro-heme in an aqueous solution gave respective high-spin heme complexes with no more than one ethyl isocyanide molecule per one heme. (2) The ferro-heme with ethyl isocyanide in an aqueous ethanol solution formed a typical monomeric low spin ferro-hemochrome with two ligands (ethyl isocyanide) on both sides of the heme plane. (3) In the presence of excess ethyl isocyanide in an aqueous ethanol solution the ferri-heme gave an MCD spectrum similar to that for the monomeric low spin ferro-hemochrone. Therefore, ethyl isocyanide was believed to reduce the ferri-heme in an aqueous ethanol solution. (4) The ferro-heme ethyl isocyanide complex in an aqueous solution offered a Faraday B term around 450 nm instead of an apparent Faraday A term observed for the ethyl isocyanide complex of the cytochrome P-450. These results are not consistent with the view that the ferro-heme ethyl isocyanide complex in an aqueous solution can be a heme chromophore model for the cytochrome P-450 ethyl isocyanide complex.

Binding Sites↗

PubMed1978