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ID 33027
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Author
Tsunamoto, Yumi
Komagoe, Keiko
Masuda, Kazufumi
Abstract
Although a previous study [S.S.M. Hassan, M.A. Ahmed, M.M. Saoudi, Anal. Chem. 57 (1985) 1126] had shown that a caffeine-sensitive electrode made with picrylsulfonate and 1-octanol as a cation-exchanger and a solvent mediator, respectively, had a wide working pH range (5.5-9.5) and exhibited a Nernstian response, we could not find such response in this electrode. The present result was reasonable, because the pK, value of caffeinium ion was reported to be around 0.7 and the neutral form of caffeine was predominant in the pH range examined. Thus, we reinvestigated the response characteristics of a caffeine electrode, taking into consideration the pKa value, and constructed a new electrode with a combination of the lipophilic cation-exchanger, tetrakis[3,5-bis(2-methoxyhexafluoro-2-propyl)phenyl]borate (HFPB), and the solvent mediator with high degree of dielectric constant, 2-fluoro-2'-nitrodiphenyl ether (FNDPE). This electrode showed a pH-dependent response to caffeinium ion and gave a detection limit of 50 mu M with a slope of 55 mV per concentration decade at pH 2. The use of other solvent mediators was less effective than that of FNDPE. The electrode was applied for the determination of caffeine in some central stimulants.
Keywords
ion-selective electrode
caffeinium ion
solvent mediator
2-fluoro-2 '-nitrodiphenyl ether
caffeine determination
Note
Published with permission from the copyright holder.
This is published in Analytica Chimica Acta, 2008 Vol.620 Issue.1-2 pp.50-54
Publisher URL: http://dx.doi.org/10.1016/j.aca.2008.05.027
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(C)2008 by Elsevier B.V.
Published Date
2008-07-14
Publication Title
Analytica Chimica Acta
Volume
volume620
Issue
issue1-2
Publisher
Elsevier Science B.V.
Start Page
50
End Page
54
ISSN
0003-2670
NCID
AA00524834
Content Type
Journal Article
language
英語
Copyright Holders
Elsevier Science B.V.
File Version
author
Refereed
True
DOI
Web of Science KeyUT
Submission Path
analytical_chemistry/39