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Direct Determination of Endogenous Melatonin in Human Saliva by Column-switching Semi-microcolumn Liquid Chromatography/mass Spectrometry with On-line Analyte Enrichment by Akira Motoyama; Taketoshi Kanda; Ryujiro Namba is a Chemistry article available to read on EtoBox.

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An analytical method that enables direct and sensitive determination of endogenous melatonin (MLT) in human saliva was developed by means of column-switching semi-microcolumn liquid chromatography (i.d.: 1-2 mm)/mass spectrometry (LC/MS). The system allows direct injection analysis of a 400-microL aliquot of saliva with minimal sample pretreatment (internal standard (IS) addition and vortex mixing) and a relatively short run-time (10 min). The system consists of three columns to attain large volume injection and on-line analyte enrichment. A pre-column packed with a silica-based mixed-functional C8 (4.0 mm i.d. x 20 mm) was used for on-line sample cleanup. MLT and an IS, the d7 isomer of MLT (d7-MLT), were heart-cut by valve switching and enriched at the top of the intermediate trapping column packed with a silica-based C18 (4.0 mm i.d. x 10 mm). Subsequently, the analytes were backflushed into a semi-micro C18 silica column (2.0 mm i.d. x 150 mm) for the final separation. MLT and IS were ascertained by positive electrospray ionization and selected ion monitoring (SIM). MLT was monitored based on its fragment ion at m/z 174.1 by in-source collision-induced dissociation (CID). The v

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Author

Akira Motoyama; Taketoshi Kanda; Ryujiro Namba

Publisher

John Wiley and Sons; Wiley (John Wiley & Sons); John Wiley & Sons Inc.; Wiley (ISSN 0951-4198)

Published

2004

Language

EN

Field

Chemistry (Physical Sciences)