Picomole scale stereochemical analysis of sphingosines and dihydrosphingosines. 
We have developed a simple picomole (low nanogram) scale HPLC scheme which can separate all eight isomers of sphingosine and dihydrosphingosine thus leading to the identification of their relative and absolute configurations.  The amino group of the sample is derivatized to its fluorescent N-naphthimide which is analyzed by normal and chiral phase HPLC, coupled with fluorescence peak detection.  If necessary, the results of this HPLC method can be further corroborated by measurements of circular dichroic (CD) spectra of the N-naphthimido-derivatives and/or N,O-chromophoric derivatives.