title: Determination of free-form amphetamine in rat brain by ion-pair liquid chromatography-electrospray mass spectrometry with in vivo microdialysis.
abstract: An ion-pair liquid chromatography-electrospray mass spectrometry (LC-ESI-MS) method with in vivo microdialysis for the determination of free-form amphetamine in rat brain has been developed. A microdialysis probe was surgically implanted into the striatum of the rat and artificial cerebrospinal fluid (aCSF) was used as the perfusion medium. Samples were collected and then analyzed off-line by LC-ESI-MS. A reversed phase C18 column was employed for LC separation. Trifluoroacetic acid (TFA) was added in the mobile phase (acetonitrile-water, 10:90, v/v) as an ion-pair reagent. The ion-pair process disguises the protonated amphetamine cations from the ESI-MS electric field as neutral molecules. Post-column addition of volatile organic acid was utilized to minimize TFA signal suppression effect on ESI-MS detection. More than six-fold enhancement of ESI-MS response was achieved by the post-column addition of propionic acid. Good linearity (0.01-1.00 microg/ml, r2 = 0.99) and detection limit (0.002 microg/ml) were determined. Good precision and accuracy were obtained. The applicability of this newly developed method was demonstrated by continuous monitoring of amphetamine concentrations in rat brain after a single 3.0 mg/kg i.p. administration.
authors.affiliation: Department of Chemistry, Soochow University, P.O. Box 86-72, Taipei 111, Taiwan. msfuh@mail.scu.edu.tw
authors.forename: Ming-Ren
authors.initials: MR
authors.lastname: Fuh
authors.forename: Chiuan-Hung
authors.initials: CH
authors.lastname: Haung
authors.forename: Shiang-Ling
authors.initials: SL
authors.lastname: Lin
authors.forename: Wynn H T
authors.initials: WH
authors.lastname: Pan
mesh_terms: D000661:Amphetamine / Q000032:analysis* / Q000134:cerebrospinal fluid / Q000493:pharmacokinetics; D000818:Animals; D001921:Brain / Q000378:metabolism*; D000697:Central Nervous System Stimulants / Q000032:analysis* / Q000134:cerebrospinal fluid / Q000493:pharmacokinetics; D002852:Chromatography, Ion Exchange; D008297:Male; D017551:Microdialysis; D051381:Rats; D017207:Rats, Sprague-Dawley; D012015:Reference Standards; D015203:Reproducibility of Results; D012996:Solutions; D021241:Spectrometry, Mass, Electrospray Ionization
chemical_list: D000697:Central Nervous System Stimulants; D012996:Solutions; D000661:Amphetamine