The synthesis of internal standards for the quantitative determination of sphingolipids by tandem mass spectrometry

Novel internal standards have been synthesised for the quantitative determination by tandem mass spectrometry (MS/MS) of the sphingolipids that accumulate in lysosomal storage diseases. The [ d 4 ]C16‐ and [ d 47 ]C24‐isoforms of galactosylceramide (CMH), lactosylceramide (CDH), globotriaosylceramide (CTH), cerebroside sulphate, sphingomyelin and G M1 ‐, G M2 ‐ and G M3 ‐gangliosides were synthesised by the reaction of their lyso ‐forms with the acid chlorides of hexadecanoic 5,5,6,6‐ d 4 acid ([ d 4 ]‐palmitic acid) and tetracosanoic‐ d 47 acid ([ d 47 ]‐lignoceric acid), respectively. The acid chlorides were formed using oxalyl chloride. The structures of the internal standards were confirmed by MS/MS. The fragmentation pattern of each novel compound was similar to that of the corresponding natural form of the sphingolipid, making it a good internal standard for the quantitative determination of the natural sphingolipid by ESI‐MS/MS. Characteristic product ions were identified for each compound. Copyright © 2005 John Wiley & Sons, Ltd.