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Monitoring of threo ‐methylphenidate enantiomers in oral fluid by capillary electrophoresis with head‐column field‐amplified sample injection
Author(s) -
Theurillat Regula,
Thormann Wolfgang
Publication year - 2014
Publication title -
electrophoresis
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.666
H-Index - 158
eISSN - 1522-2683
pISSN - 0173-0835
DOI - 10.1002/elps.201300325
Subject(s) - enantiomer , chromatography , chemistry , methylphenidate , analyte , stereoselectivity , capillary electrophoresis , racemic mixture , cyclodextrin , attention deficit hyperactivity disorder , stereochemistry , medicine , organic chemistry , psychiatry , catalysis
Threo ‐methylphenidate is a chiral psychostimulant drug widely prescribed to treat attention‐deficit hyperactivity disorder in children and adolescents. An enantioselective CE ‐based assay with head‐column field‐amplified sample stacking for analysis of threo ‐methylphenidate enantiomers in liquid/liquid extracts of oral fluid is described. Analytes are electrokinetically injected across a short water plug placed at the capillary inlet and become stacked at the interface between plug and buffer. Enantiomeric separation occurs within a few minutes in a pH 3.0 phosphate/triethanolamine buffer containing 20 mg/mL (2‐hydroxypropyl)‐β‐CD as chiral selector. The assay with six point multilevel internal calibration provides a linear response for each enantiomer in the 10–200 ng/mL concentration range, is simple, inexpensive, and reproducible, and has an LOQ of 5 ng/mL. It was applied to oral fluid patient samples that were collected up to 12 h after intake of an immediate release tablet and two different extended release formulations with racemic methylphenidate. Drug profiles could thereby be assessed in a stereoselective way. Almost no levorotary threo ‐methylphenidate enantiomer was detected after intake of the two extended release formulations, whereas this enantiomer was detected during the first 2.5 h after intake of the immediate release preparation. The noninvasive collection of oral fluid is an attractive alternative to plasma for the monitoring of methylphenidate exposure in the pediatric community.