A spectrophotometric procedure has been developed for the determination of microquantities of sphingolipids. The assay system involved includes the methanolysis of the fatty acid moiety of the sphingolipid with boron trifluoride in methanol to yield a long chain base containing a free amino group. The long chain amine, sphingosine, is then extracted into an organic phase and reacted with aqueous trinitrobenzene sulfonic acid to yield a product with an absorption maximum at 340 mμ. Lipid peroxidation products and silicic acid do not seriously interfere in the 340 region. A wide variety of pure sphingolipids yielded equivalent optical densities per mole of sphingolipid. Sphingolipids assayed included cerebroside, cerebroside sulfate, ganglioside and sphingomyelin.

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