Quantification of salsolinol enantiomers by stable isotope dilution liquid chromatography with tandem mass spectrometric detection

Salsolinol, 1‐methyl‐6,7‐dihydroxy‐2,3,4,5‐tetrahydroisoquinoline (SAL), is a precursor of a Parkinsonian neurotoxin, N‐methysalsolinol (N‐methyl‐SAL). Previous studies have shown that individual enantiomers of N‐methyl‐SAL possess distinct neurotoxicological properties. In this work, a chiral high‐performance liquid chromatography (HPLC) method with electrospray ionization tandem mass spectrometric (ESI‐MS/MS) detection was developed for the quantification of ( R/S )‐SAL enantiomers. Enantioseparation was achieved on a β ‐cyclodextrin‐bonded silica gel column, and the resolved enantiomers were detected by ESI‐MS/MS operated in positive ion mode. The ESI collision‐induced dissociation (CID) mass spectrum of SAL was studied together with that of its deuterium‐labeled analog (i.e. salsolinol‐ α , α , α ,1‐d 4 , SAL‐d 4 ) so that the fragmentation pathways could be elucidated. Further, using SAL‐d 4 as internal standard in HPLC/MS/MS analysis of SAL improved significantly assay accuracy and reliability. Determination of ( R / S )‐SAL enantiomers present in food samples such as dried banana chips was demonstrated. Copyright © 2008 John Wiley & Sons, Ltd.