Abstract
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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