[Sisomicin. The mechanism of admixture inactivation and formation]. / Sizmotisin. K. voprosu o mekhanizme inaktivatsii i obrazovaniia primesei.

Inactivation of sisomicin in aqueous solutions was studied under various conditions. At pH 4-10 and a temperature of 60 degrees C the inactivation rate constant was equal to (5-10) X 10(-5) hour-1 and remained stable. At lower pH values the inactivation rate constant increased: 5.5 10(-3) (60 degrees C) at pH 0.5. The activation energy of the inactivation reaction was 27 (pH 0.5) and 32 (pH 4.0) kcal/mol. The study on the behaviour of sisomicin in solutions with different pH values under the environmental conditions and in the atmosphere of nitrogen showed that at low pH values the inactivation was mainly determined by hydrolysis of the glycoside bond. Formation of coloured compounds did not include the oxidation reaction. At pH about 7.0 oxidation of the antibiotic or of the products of its degradation with respect to the double bond played a significant role in the inactivation and formation of the coloured substances.

[Determination of the sulfate ion content in antibiotic sulfate salts by a complexometric titration method]. / Opredelenie soderzhaniia sul'fat-ionov v sernokislykh soliakh antibiotikov metodom kompleksometricheskogo titrovaniia.

A possibility of assaying antibiotic sulfates, such as gentamicin, kanamycin, monomycin, neomycin, ristomycin, streptomycin, florimycin and polymyxin M sulfates for sulfate ions by titration with barium chloride in the presence of chlorphosphonaso-III, a metal indicator immediately in the salt solutions or after elimination of the cation by means of ion exchange (sulfocation exchange resins in H+-form) was tested. The procedure was shown to be adequate to the classical weight method.

[Cephalosporin C stability in aqueous solutions]. / Ustoichivost' tsefalosporina C v vodnykh rastvorakh.

Stability of cephalosporin C in aqueous solutions at various temperatures was studied. The kinetic parameters of the inactivation process providing estimation of the inactivation rate constant of cephalosporin C at pH 0-12.5 and various temperatures were evaluated. It was found that the zinc ions had no specific effect on the inactivation rate.

[Gentamicin stability and a method for its quantititive determination]. / Ustoichivost' gentamitsina i metod ego kolichestvennogo opredeleniia

Stability of gentamycin in solutions at various pH levels was studied. It was shown that in acid media inactivation proceeded according to the equation of the 1st order reaction. Dependence of the inactivation rate constant on the temperature corresponded to Arrenium equation. A polarimetric procedure for determination of gentamycin providing the assay of the antibiotic levels at various purification stages biginning from the eluates after the ion-exchange columns is described. The results obtained with the above procedure were shown to correlate satisfactorily with those of the microbiological analysis.