Development of an electrospray ionization mass spectrometric method for the quantification of theophylline in horse serum

Abstract

A rapid and selective method has been developed for the determination of theophylline in horse serum by LC-ESI/MS/MS. The analytical method includes a protein precipitation extraction for sample preparation, liquid chromatography separation technique and ionspray tandem mass spectrometry. The drug was extracted from serum using a protein precipitation with acetonitrile and the supernatants were analyzed using an LC-ESI/MS/MS instrument. The chromatography was performed using a 50 x 2.1 mm C(8) analytical column and an isocratic mobile phase composes of 60:40 acetonitrile-0.5% formic acid in water with a flow rate fixed at 350 microL/min. A linear (weighted 1/concentration) relationship was used to perform the calibration over an analytical range of 0.1-20 ppm. The intra-batch precision and accuracy at LLOQ, medium and high concentration were 11.7, 6.9 and 5.4% and 95.8, 107.8 and 95.8%, respectively, and the inter-batch precision and accuracy at LLOQ, medium and high concentration were 10.4, 7.9 and 7.3% and 97.3, 105.2 and 95.9%, respectively. This LC-ESI/MS/MS method for the determination of theophylline in horse serum has been proved to within generally accepted criteria used for bioanalytical assay and was used successfully during clinical investigation.

Collision‐induced dissociation studies of caffeine in positive electrospray ionisation mass spectrometry using six deuterated isotopomers and one N1‐ethylated homologue

“…Figure shows a typical ESI mass spectrum of caffeine 1 which was obtained at a cone voltage of 80 V. The fragmentation pattern is consistent with that of earlier published spectral data . Considerations about the formation, the composition, and the chemical structures of the obtained fragments are the subject of the following discussion ( vide infra ).…”

“…In the literature, the formation of this fragment is explained by a retro‐Diels‐Alder reaction and the resulting molecule is consequently presented as an open‐chain structure . Taking into account the calculated empirical formula C 6 H 7 N 3 O (Table ) and the calculated number of ‘double‐bond equivalents’ a cyclic β‐lactam structure for fragment c seems to be feasible . Except for fragment b all fragments observed directly or indirectly arise from fragment c .…”

“…From a retrospective point of view the identification of metabolites originating from the synthetic xanthine CPFPX should theoretically have been possible with the knowledge extracted from existing publications which deal with various MS‐fragmentation mechanisms of caffeine . However, the published experiments were performed either by using advanced spectrometers in combination with additional ionisation modes like collision‐activated dissociation (CAD) or by a priori using different ionisation methods like electron ionisation (EI).…”

METABOLISM OF THE A1 ADENOSINE RECEPTOR POSITRON EMISSION TOMOGRAPHY LIGAND [18F]8-CYCLOPENTYL-3-(3-FLUOROPROPYL)-1-PROPYLXANTHINE ([18F]CPFPX) IN RODENTS AND HUMANS

“…It is conspicuous that all but one hydroxylated derivative, P2, of m/z 339, had fragments of m/z 321, corresponding to a desaturated species formed by the loss of a molecule of water. The fragmentation reactions mainly reflect eliminations of HF and H 2 O, C-N bond cleavage, and ring closures according to those proposed for theophylline (Beaudry et al, 2005). Assuming that the fragmentation of in vitro formed metabolites follows the same dmd.aspetjournals.org main pathway as that for CPFPX, it is reasonable to suppose that P1, P2, and P7 are hydroxylated and P3 oxidized at the cyclopentyl moiety, P4 and P5 are hydroxylated at the N1-propyl chain, and P6 is difunctionalized at the cyclopentyl ring.…”

Prepeak of trolox caused by theophylline and its application to the determination of theophylline in rat plasma

“…A number of analytical separation methods have been employed to determine theophylline in plasma such as: gas chromatography with mass spectrometry (GC/MS) [22], high-performance liquid chromatography with ultraviolet detection (HPLC-UV) [23][24][25][26][27], MS (LC/MS) [28][29][30], and electrochemical detection (HPLC-ECD) [31][32][33][34], capillary electrophoresis [35], and immunoassay [36][37][38][39][40]. Although HPLC represents a common and powerful technique for the analysis of biological samples, all the methods, except for HPLC-UV, are not always useful for pharmacokinetics.…”