Absorption and Excretion of Drugs. XVII. Determination of Tetracycline in Urine. (Faculty of Pharmacy, Kyoto University*2) A method for determining urinary concentration of tetracycline was devised by the combination of Permutit column with p-nitrobenzenediazonium chloride reagent. The sample urine is passed through a column of Permutit acidified with hydrochloric acid to adsorb tetracycline on Permutit, this is desorbed with sodium hydroxide solution, and the effluent solution is neutralized.

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... he neutralized solution is colored with p-nitrobenzenediazonium chloride reagent and the amount of tetracycline in the sample urine is determined. Amount of tetracycline excreted into urine was determined by this method after administration of various kinds of tetracycline preparation and it was found that 30-40% is excreted into urine 24 hours after administration. At the same time, biological half-life period of tetracycline was examined and was found to be about eight hours.