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Published:
Journal of Analytical Toxicology,
ISSN 0146-4760,
Volume 24,
Number 8, November/December,
pp. 718-725
Automated In-Tube Solid-Phase
Microextraction Coupled with Liquid Chromatography–Electrospray Ionization
Mass Spectrometry for the Determination of Selected Benzodiazepines
Haodan
Yuan, Zoltan Mester, Heather Lord, and Janusz Pawliszyn*
Department of Chemistry, University of Waterloo, Waterloo, Ontario, N2L 3G1, Canada
A
simple, rapid, and sensitive method, which allowed us to simultaneously determine
seven benzodiazepines (diazepam, nordiazepam, temazepam, oxazepam, 7-aminoflunitrazepam,
N-desmethylflunitrazepam, and clonazepam) in buffer solution and in urine and
serum samples, was investigated by automated in-tube solid-phase microextraction
(SPME) coupled with liquid chromatography–electrospray ionization mass
spectrometry (LC–ESI-MS). In-tube SPME, in which the analytes were extracted
from the sample directly into an open tubular capillary column by repeated draw/eject
cycles of sample solution, is an extraction technique for organic compounds
in aqueous samples. The separation of benzodiazepines was carried out under
ion-suppressed reversed-phase conditions by using methanol/50mM ammonium acetate
in water (60:40) as a mobile phase with a Supelco LC-18 column. The optimal
extraction condition was 10 draw/eject cycles of 30 mL of sample in 100mM Tris-HCl
(pH 8.5) at a flow rate of 0.3 mL/min using a piece of 60-cm length Supelco-Q
plot capillary column as the extraction capillary. The quantitative study was
explored by operating in selected-ion monitoring (SIM) mode. The calibration
curves were linear in the range from 0.5 ng/mL or 2 ng/mL to 500 ng/mL. The
detection limits were from 0.02 ng/mL to 2 ng/mL. At the optimized capillary
and fragmentor voltages, the characteristic ions for each compound clearly showed
up in the spectra and it is possible to use the LC–MS to identify these
compounds. The method was applied to the analysis of biological samples without
interfering peaks. However, the recoveries for some of the compounds in serum
samples need to be further improved. Reproduction
of editorial content of this journal is prohibited without publisher’s
permission.
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