title: Enantioselective analysis of ritalinic acids in biological samples by using a protein-based chiral stationary phase.
abstract: OBJECTIVE
  This study was to develop and validate a new chiral HPLC-UV method for the quantitative analysis of enantiomeric ritalinic acid (RA) in human plasma.
  
  
  METHODS
  An alpha1-acid glycoprotein column was used with the mobile phase containing 0.4% acetic acid and 0.1% dimethyloctylamine, pH 3.4. The detection of enantiomeric RAs was at 220 nm.
  
  
  RESULTS
  A baseline separation for d- and l-RA was achieved by a separation factor of 2.08. Methylphenidate, the precursor of RA, was eluted with the front solvent, and thus does not interfere in the analysis of RA in our method. The assay was successfully applied for the in vitro analysis of enantiomeric ritalinic acids produced by human and dog plasma and dog liver.
  
  
  CONCLUSIONS
  Data demonstrated that the esterase(s) in human plasma metabolize d-methylphenidate faster than its l-isomer. The yielded intrinsic clearances (Clint) are 1.02 and 2.17 microl/min/mg protein, respectively, for d and l-methylphenidate.
authors.affiliation: School of Life Science and Technology, Beijing Institute of Technology, No. 5, Zhongguancun St., South Beijing, 100081, China. zhangjh@bit.edu.cn
authors.forename: Jianhua
authors.initials: J
authors.lastname: Zhang
authors.forename: Yulin
authors.initials: Y
authors.lastname: Deng
authors.forename: Jim
authors.initials: J
authors.lastname: Fang
authors.forename: Gordon
authors.initials: G
authors.lastname: McKay
mesh_terms: D000818:Animals; D002021:Buffers; D043182:Carboxylesterase / Q000737:chemistry; D002384:Catalysis; D002851:Chromatography, High Pressure Liquid / Q000379:methods; D004285:Dogs; D006801:Humans; D006868:Hydrolysis; D008774:Methylphenidate / Q000031:analogs & derivatives* / Q000032:analysis* / Q000097:blood / Q000737:chemistry*; D010949:Plasma / Q000737:chemistry; D011506:Proteins / Q000032:analysis / Q000737:chemistry; D012996:Solutions; D013237:Stereoisomerism
chemical_list: D002021:Buffers; D011506:Proteins; D012996:Solutions; D008774:Methylphenidate; D043182:Carboxylesterase; C009189:ritalinic acid