ID | 33027 |
FullText URL | |
Author |
Katsu, Takashi
Tsunamoto, Yumi
Komagoe, Keiko
Masuda, Kazufumi
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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.
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Keywords | ion-selective electrode
caffeinium ion
solvent mediator
2-fluoro-2 '-nitrodiphenyl ether
caffeine determination
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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 Direct access to Thomson Web of Science record (C)2008 by Elsevier B.V. |
Published Date | 2008-07-14
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Publication Title |
Analytica Chimica Acta
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Volume | volume620
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Issue | issue1-2
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Publisher | Elsevier Science B.V.
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Start Page | 50
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End Page | 54
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ISSN | 0003-2670
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NCID | AA00524834
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Content Type |
Journal Article
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language |
English
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Copyright Holders | Elsevier Science B.V.
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File Version | author
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Refereed |
True
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DOI | |
Web of Science KeyUT | |
Submission Path | analytical_chemistry/39
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