Determination of amphetamine in rat brain by in vivo microdialysis and ion‐pairing liquid chromatography with electrospray tandem mass spectrometry

Abstract

An ion-pairing liquid chromatography/electrospray tandem mass spectrometry (LC/ES-MS/MS) method with in vivo microdialysis for the determination of 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/ES-MS/MS. A reversed-phase C18 column was employed for LC separation and MS/MS was utilized for detection. Trifluoroacetic acid (TFA) was added to the mobile phase (acetonitrile/water) as an ion-pairing reagent. Detection was by ES-MS/MS directly, and no post-column addition of organic modifier was needed. Dual linear ranges were determined from 0.1-0.5 microg/mL and 0.005-0.1 microg/mL, respectively. The detection limit, based on a signal-to-noise ratio of 3, was 0.001 microg/mL (5 nM). Good precision and accuracy were obtained. The applicability of this newly developed method was demonstrated by continuous monitoring of amphetamine concentrations in rat brain. Amphetamine reached a maximum concentration of 0.086 +/- 0.017 microg/mL over 20-40 min after a single 3.0 mg/kg intraperitoneal administration.

Simple means to alleviate sensitivity loss by trifluoroacetic acid (TFA) mobile phases in the hydrophilic interaction chromatography–electrospray tandem mass spectrometric (HILIC–ESI/MS/MS) bioanalysis of basic compounds

“…It not only controls the pH of the mobile phases, but also acts as an ion-pair agent to improve peak shapes of basic compounds on silica-based columns. TFA is volatile and therefore can be used in LC-MS, and it has been used in the LC-MS analyses of peptides [4] as well as small molecules [5]. Our research group has also been using bare silica column operated under hydrophilic interaction chromatography (HILIC) mode with TFA-containing mobile phases for the LC-MS analyses of small molecules in biological matrices [6][7][8][9][10][11].…”

Towards Practical Endoscopic Mass Spectrometry

“…18) Nowadays, it is relatively convenient to couple the microdialysis probe to an ESI source. [19][20][21] For a solid or biological surface, extraction of analytes can be performed by the following methods.…”

LC-MS Development Strategies for Quantitative Bioanalysis

“…Ion-pair reversed-phase chromatography using perfluorinated carboxylic acids, such as trifluoroacetic acid (TFA), pentafluoropropanoic acid (PFPA) and heptafluorobutanoic acid (HFBA), in the mobile phase has been found to be a viable alternative to straight reversed-phase chromatography for the quantitation of basic polar analytes by positive ion ESI [143][144][145][146][147][148][149]. The advantages of this technique include the elimination of peak tailing and the increase of the retention.…”