A simplified preparation of cardiolipin, with note on purification of lecithin for serologic use.

Since the original report of the isolation of cardiolipin (I), the usefulness of this substance in serodiagnostic tests for syphilis has been demonstrated (2-5). In this laboratory an antigen consisting of a mixture of cardiolipin, lecithin, and cholesterol (4) is now in routine use in complement fixation tests for evidence of syphilis (6). It was therefore important to devise more efficient and economical procedures for the preparation of cardiolipin. Some improvements over the original method have already been reported (7, 8). It has now proved possible to improve the preparation still further. The fundamental procedures are the same as those previously employed, but some steps which at first. appeared necessary have been omitted, others have been simplified, and the yield has been increased by establishing the necessary conditions for complete recovery of cardiolipin from the barium salts. The simplified procedure is presented in this paper by describing the details of a typical preparation. The method depends on the fact that cardiolipin is an acid and readily forms stable salts: the barium, sodium, and cadmium salts are those used for purification. These salts are rather easily converted one to another and the accompanying impurities may be removed in successive steps by taking advantage of the differing solubilities of the several salts in various combinations of solvents. Since purified lecithin is also required in the mixtures used as antigens, some notes on the application of the previously described method for the purification of lecithin (9) are also included.