A method is described for the determination of erythromycin estolate by liquid chromatography. A C18 reversed-phase column (25 x 0.46 cm i.d.) was used with acetonitrile-tetrabutylammonium sulphate (pH 6.5, 0.2 M)-phosphate buffer (pH 6.5, 0.2 M)-water [x:5:5:(90-x), v/v/v/v] as mobile phase. The proportion of acetonitrile (x) has to be adapted to the type of stationary phase used. For RSil C18 LL 42.5% (v/v) was used. The column was heated at 35 degrees C, the flow rate was 1.5 ml min-1 and UV detection was performed at 215 nm. The main component, erythromycin A propionate, was separated from all other components which were present in commercial samples. The impurities most frequently observed were the propionate ester of erythromycin C and the amide N-propionyl-N-demethyl-erythromycin A. Erythromycin A was shown to be present in specialties.

Acetonitriles↗

PubMedDate not supplied

Liquid chromatographic study of the stability of 5-halogeno-2'-deoxyuridines.

The stability of a series of 5-halogeno-2'-deoxyuridines was investigated using liquid chromatography as the analytical technique. Characteristics and profiles of the acidic, neutral and alkaline degradation are described, together with Arrhenius relationships and activation parameters for weakly acidic media.

Bromodeoxyuridine↗

PubMedDate not supplied

Investigation of the kinetics of degradation of hexopyranosylated cytosine nucleosides using liquid chromatography.

Liquid chromatography was used to follow the degradation of hexopyranosylated cytosine nucleosides in buffers of acid, neutral and alkaline pH and of constant ionic strength. The compounds were found to degrade by hydrolysis to cytosine and/or by deamination to the corresponding uracil nucleosides. Degradation in acid is influenced by the number of sugar hydroxyl groups, presence of sugar double bonds and the type of anomer. Stability of some of the compounds was compared with that of related thymine nucleosides. Temperature studies support a unimolecular mechanism of hydrolysis at pH 1.22.

Buffers↗

PubMedDate not supplied

Comparison of bovine platelet and teat alpha 2-adrenoceptor characteristics by [3H]rauwolscine binding.

Alpha 2-adrenoceptors on platelet membranes, isolated from "slaughterhouse cows," were characterized by [3H]-rauwolscine binding. There were 30 +/- 3 [3H]rauwolscine sites per platelet, corresponding to 194 +/- 18 fmol/mg protein. These had an equilibrium dissociation constant (KD) of 5.25 +/- 0.56 nM, a Hill coefficient of 1.00 +/- 0.01 (n = 9), and were competed for by adrenergic compounds stereoselectively. The rank order of catecholamines coincided with that expected for alpha 2-adrenoceptors. Ki-values for inhibition of specific [3H]rauwolscine binding by 7 agonists and 6 antagonists were in the same range as previously observed in teat tissue. It is therefore concluded that quite similar [3H]rauwolscine binding sites were identified and characterized in both bovine teats and platelets. Direct comparison of binding characteristics between alpha 2-adrenoceptors from teat tissue and platelets of the same "primiparous cows," revealed no difference in binding affinity, although a significant higher platelet receptor number was noted in the platelets (platelets: 353 fmol/mg protein; teat tissue: 91 fmol/mg protein; n = 10).

Animals↗

PubMedDate not supplied

Determination by high performance liquid chromatography of the stability of alcoholic solutions for topical use containing tetracycline and 4-epitetracycline.

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Administration, Topical↗

PubMedDate not supplied

[Study of the stability in methanolic solution of tetracycline hydrochloride and some analogues (author's transl)].

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Drug Stability↗

PubMedDate not supplied

[3H]CGP-12177 binding to beta-adrenoceptors of intact bovine mononuclear leukocytes.

Saturation and inhibition binding studies, using [3H]CGP-12177 as radioligand, reveal the presence of a single class of beta-adrenoceptors on intact bovine mononuclear leukocytes. Receptor binding is inhibited by beta-adrenergic agonists with a rank order of potency (-)-isoproterenol > (-)-epinephrine > (-)-norepinephrine, indicating that the receptors are of the beta 2-subtype. By Scatchard analysis, the mean receptor density was 707 +/- 168 receptors/cell and the dissociation constant was 0.89 +/- 0.47 nM. Specific binding was very high and amounted to 80-90%. It is concluded that [3H]CGP-12177 is a promising compound for the reliable determination of the binding characteristics of bovine mononuclear leukocytes.

Adenylyl Cyclases↗