start-ver=1.4
cd-journal=joma
no-vol=620
cd-vols=
no-issue=1-2
article-no=
start-page=50
end-page=54
dt-received=
dt-revised=
dt-accepted=
dt-pub-year=2008
dt-pub=20080714
dt-online=
en-article=
kn-article=
en-subject=
kn-subject=
en-title=
kn-title=A caffeine-sensitive membrane electrode: Previous misleading report and present approach
en-subtitle=
kn-subtitle=
en-abstract=
kn-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.
en-copyright=
kn-copyright=

en-aut-name=KatsuTakashi
en-aut-sei=Katsu
en-aut-mei=Takashi
kn-aut-name=
kn-aut-sei=
kn-aut-mei=
aut-affil-num=1
ORCID=

en-aut-name=TsunamotoYumi
en-aut-sei=Tsunamoto
en-aut-mei=Yumi
kn-aut-name=
kn-aut-sei=
kn-aut-mei=
aut-affil-num=2
ORCID=

en-aut-name=HaniokaNobumitsu
en-aut-sei=Hanioka
en-aut-mei=Nobumitsu
kn-aut-name=
kn-aut-sei=
kn-aut-mei=
aut-affil-num=3
ORCID=

en-aut-name=KomagoeKeiko
en-aut-sei=Komagoe
en-aut-mei=Keiko
kn-aut-name=
kn-aut-sei=
kn-aut-mei=
aut-affil-num=4
ORCID=

en-aut-name=MasudaKazufumi
en-aut-sei=Masuda
en-aut-mei=Kazufumi
kn-aut-name=
kn-aut-sei=
kn-aut-mei=
aut-affil-num=5
ORCID=

en-aut-name=NarimatsuShizuo
en-aut-sei=Narimatsu
en-aut-mei=Shizuo
kn-aut-name=
kn-aut-sei=
kn-aut-mei=
aut-affil-num=6
ORCID=

affil-num=1
en-affil=
kn-affil=Graduate School of Medicine, Dentistry and Pharmaceutical Sciences, Okayama University

affil-num=2
en-affil=
kn-affil=Graduate School of Medicine, Dentistry and Pharmaceutical Sciences, Okayama University

affil-num=3
en-affil=
kn-affil=Graduate School of Medicine, Dentistry and Pharmaceutical Sciences, Okayama University

affil-num=4
en-affil=
kn-affil=Graduate School of Medicine, Dentistry and Pharmaceutical Sciences, Okayama University

affil-num=5
en-affil=
kn-affil=Graduate School of Medicine, Dentistry and Pharmaceutical Sciences, Okayama University

affil-num=6
en-affil=
kn-affil=Graduate School of Medicine, Dentistry and Pharmaceutical Sciences, Okayama University
en-keyword=ion-selective electrode
kn-keyword=ion-selective electrode
en-keyword=caffeinium ion
kn-keyword=caffeinium ion
en-keyword=solvent mediator
kn-keyword=solvent mediator
en-keyword=2-fluoro-2 '-nitrodiphenyl ether
kn-keyword=2-fluoro-2 '-nitrodiphenyl ether
en-keyword=caffeine determination
kn-keyword=caffeine determination
END