How to Test for Purine

Two types of nitrogenous bases help to comprise DNA, purines and pyrimidines. The purines in the human body are adenine and guanine. They can undergo metabolism to produce hypoxanthine and xanthine. Guanine results in xanthine, while adenine is degraded to hypoxanthine. Scientists looking for the presence of a purine must run a test. Purines have to be tested indirectly by assaying for their derivatives, xanthine and hypoxanthine. Not until the early 20th century was a test available for purines, when a German medical doctor, Albrecht Kossel, devised a test, later named after him, that would detect purines. There are two other tests that scientists can use to detect the presence of purines, the Hoppe-Seyler test and Weidel's test.

Things You'll Need

• Bunsen burner
• Alcohol
• Ether
• Water
• Flask

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Instructions

• 1

  Use Kossel's test to find hypoxanthine, which is a precursor to xanthine but also a purine derivative. Treat the solution to be tested with a mixture of hydrochloric acid and zinc. Add the strong base sodium hydroxide in excess. If the solution turns a ruby red color, hypoxanthine is present.

• 2

  Employ the Hoppe-Seyler test, devised by Felix Hoppe-Seyler. Concentrate urine and extract the residue for testing with a strong alcohol. Evaporate the mixture and precipitate the substance with a basic lead acetate and ammonia. Wash the precipitate and treat with boiling alcohol. Evaporate, then wash with pure alcohol and filter with ether. This process will crystallize the urine for xanthine detection. Add this substance to lime and chlorine. If a dark green ring forms, the substance has xanthine.

• 3

  Use the test developed by Hugo Weidel, which also looks for xanthine. Bathe the substance in chlorine water with a small amount of nitric acid. Evaporate the substance in a water bath. Expose to ammonia gas. If the substance turns a pink or purple color, xanthine is present.