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Supercritical fluid extraction and negative ion electrospray liquid chromatography tandem mass spectrometry analysis of phenobarbital, butalbital, pentobarbital and thiopental in human serum
Author(s) -
Spell J. Christopher,
Srinivasan Karthik,
Stewart James T.,
Bartlett Michael G.
Publication year - 1998
Publication title -
rapid communications in mass spectrometry
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.528
H-Index - 136
eISSN - 1097-0231
pISSN - 0951-4198
DOI - 10.1002/(sici)1097-0231(19980715)12:13<890::aid-rcm251>3.0.co;2-x
Subject(s) - chemistry , chromatography , mass spectrometry , electrospray , electrospray ionization , selected reaction monitoring , triple quadrupole mass spectrometer , tandem mass spectrometry , analytical chemistry (journal)
Four commonly used barbiturates (phenobarbital, butalbital, pentobarbital and thiopental) were analyzed in human serum using supercritical fluid extraction (SFE) and negative ionization LC/ESI‐MS/MS. Barbital was used as the internal standard. Carbon dioxide SFE was performed at 40 °C and 500 atm, with a total extraction time of 35 min. The analytes were collected off‐line in a liquid trap containing absolute methanol. Samples were then concentrated by vacuum centrifugation. The high performance liquid chromatography separation utilized gradient elution with a total analysis time of 21 min. The precursor and major product ions for the four barbiturates were monitored on a triple quadrupole mass spectrometer with negative ion electrospray ionization (ESI) in the multiple reaction monitoring mode as follows: (1) thiopental ( m/z 241.20 → 58.00), (2) phenobarbital ( m/z 231.10 → 188.0), (3) pentobarbital ( m/z 225.10 → 181.90) and (4) butalbital ( m/z 222.80 → 179.90). In the case of phenobarbital, pentobarbital and butalbital, the most abundant product ion arises from the loss of 43 u (HCNO loss). However, in the case of thiopental, the most abundant product ion was observed at m/z 58.0 (the [M − 183] − ion, or NCS − ). Mechanisms for the formation of the collision induced dissociation reaction products of these barbiturates are proposed. © 1998 John Wiley & Sons, Ltd.