Liquid chromatography/atmospheric pressure chemical ionization tandem massspectrometry enantiomeric separation of dl-threo-methylphenidate, (Ritalin(R)) using a macrocyclic antibiotic as the chiral selector

Vancomycin, a macrocyclic antibiotic, is an amphoteric glycopeptide produce d by Streptomyces orientalis which has proven to be a viable chiral selecto r for high performance liquid chromatograph (HPLC) (D. W. Armstrong, Y. Tan g, S. Chen, Y. Zhou, C. Bagwill and J-R. Chen, Anal. Chem. (1994; 66: 1473) . While it is related to other glycopeptide antibiotics, vancomycin has a n umber of unique structural features, including 18 stereogenic centers, five aromatic rings, and two side chains one of which is a carbohydrate dimer, Therefore, a vancomycin-based stationary phase appears to be multimodal in that it can be utilized in both normal-phase and reversed-phase liquid chro matography. Consequently, the enantiomeric separation may be operative via several mechanisms, including pi-pi complexation, dipole stacking, inclusio n, hydrogen bonding, or combinations of these interactions. LC/MS/MS is a p owerful tool for quantitative analysis when evaluated on the basis of speed , specificity, reliability and sensitivity. For these reasons, the present paper explored the feasibility of bonded macrocyclic glycopeptide phases fo r chiral LC/MS/MS quantitative analysis. Methylphenidate was used as a mode l compound. A rapid chiral bioanalytical method (<7.5 min) for the determin ation of the enantiomers of methylphenidate was developed A lower limit of quantification (LLOQ) of 87 pg/mL was attained for the human plasma assay. This is to our knowledge the first example of enantioselective reversed-pha se LC/MS/MS for methylphenidate. The chiral column was relatively cost effe ctive and exhibited, excellent performance with no separation deterioration observed after similar to 2500 injections. Copyright (C) 1999 John Whey & Sons, Ltd.