Development of a methodology utilizing gas chromatography ion-trap tandem mass spectrometry for the determination of low levels of caffeine in surface marine and freshwater samples |
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Authors: | Sergei S Verenitch Asit Mazumder |
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Institution: | (1) Water and Watershed Research Program, University of Victoria, P.O. Box 3020 STN CSC, Victoria, British Columbia, V8W 3N5, Canada |
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Abstract: | A methodology for monitoring low level of caffeine in aqueous samples via gas chromatography coupled with an ion-trap tandem
mass spectrometry detection system (IT-MS/MS) was developed. Four IT-MS/MS operating parameters, including the collision-induced
dissociation (CID) voltage, the excitation time (ET), the isolation time (IT) and the maximum ionization time (MIT) were optimized
in order to maximize the sensitivity of the IT-MS/MS technique towards the analyte and its isotope-labeled standard. After
optimization, a limit of detection of 500 fg μl−1 with S/N = 3 was achieved. Taking into account blank values and the matrix background, a method detection limit of 1.0–2.0 ng l−1 was derived and applied to all of the samples analyzed in the study. Various mass spectrometric conditions have been applied
to caffeine and its trimethyl-13C-labeled standard to elucidate fragmentation pathways for new and commonly occurring product ions observed in the collision-induced
dissociation (CID) spectra produced by the ion trap. Ion structures and fragmentation pathway mechanisms have been proposed
and compared with previously published data. An isotope dilution method using 13C-labeled caffeine as a surrogate internal standard was employed to determine and correct the recovery of native caffeine
in water samples. The developed methodology has been applied for the determination of caffeine in surface marine and freshwater
samples collected on the west coast of Vancouver Island in British Columbia, Canada. The results obtained for the marine water
samples indicated a wide variation in the level of caffeine, ranging from 4.5 to 149 ng l−1, depending on the location of the sampling site within the inlet. The concentrations of caffeine in samples from lakes associated
with various residential densities ranged from ND to 6.5, 1.8 to 10.4 and 6.1 to 21.7 ng l−1 for low, moderate and high residential densities, respectively. |
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Keywords: | Caffeine Surface water Ion trap GC-MSMS |
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