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The possibility of using a short 20x4 mm chromatographic column with a heterosurface sorbent for direct determination of theophylline and caffeine in blood plasma and a 120x4 mm column for determination of tetracycline antibiotics in cow’s milk was studied. Complete separation of tetracycline peaks was not achieved. Determination of caffeine and theophylline was performed successfully in plasma filtrates without long and time-consuming stages of preliminary preparation of the sample without protein deposition. Before backwashing, unfiltered blood plasma can be injected in an amount equivalent to 50 mg of dry matter. Retention characteristics of caffeine and theophylline are practically stable: the retention factor of theophylline for k = 4,0 + 0,1 for caffeine k = 8,5 + 0,4 eluent in composition of 0.02 M sodium hydrogen phosphate (pH = 6,0) – acetonitrile (90:10).

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The suitability of the process of obtaining sodium hypochlorite by electrolytic chlorination of sodium chloride solution for the purposes in a chemical laboratory is shown. The process was carried out in a 1 l non-flowing cell with four bipolar titanium electrodes 6x10 cm with oxide-ruthenium anodes. The distance between the electrodes is 1 mm, the temperature of the initial solution is 7-8ºC. The concentration of sodium chloride 25 g/l is convenient for acquaintance with the basic electrochemical laws of the process since the dependence of the concentration of “active chlorine” on the electrolysis time is linear up to 9 g/l at a current density of 0.1 A / cm2. The study of the effect of side processes on the output of the target product is carried out at a current density of 0.125 and 0.15 A/cm2 (the dependence is nonlinear). The dependence at a concentration of 35 g/l, 0.1 A/cm2 is similar to the dependence at 25 g/l and 0.125 A/cm2. To determine the concentration of “active chlorine” the aliquot was taken from the reaction mixture at equal intervals, diluted by 25 times. The solution was acidified and titrated with methyl orange.