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Titolo:
Influence of natural, electrically neutral lipids on the potentiometric responses of cation-selective polymeric membrane electrodes
Autore:
Buhlmann, P; Hayakawa, M; Ohshiro, T; Amemiya, S; Umezawa, Y;
Indirizzi:
Univ Tokyo, Sch Sci, Dept Chem, Bunkyo Ku, Tokyo 1130033, Japan Univ Tokyo Tokyo Japan 1130033 ept Chem, Bunkyo Ku, Tokyo 1130033, Japan
Titolo Testata:
ANALYTICAL CHEMISTRY
fascicolo: 14, volume: 73, anno: 2001,
pagine: 3199 - 3205
SICI:
0003-2700(20010715)73:14<3199:IONENL>2.0.ZU;2-8
Fonte:
ISI
Lingua:
ENG
Soggetto:
QUATERNARY AMMONIUM-SALTS; NONIONIC SURFACTANTS; LIQUID MEMBRANES; BULK OPTODES; ION SENSORS; COMPLEXATION; CREATININE; IONOPHORES; PHENOLS; LIPOPHILICITY;
Tipo documento:
Article
Natura:
Periodico
Settore Disciplinare:
Life Sciences
Physical, Chemical & Earth Sciences
Citazioni:
51
Recensione:
Indirizzi per estratti:
Indirizzo: Buhlmann, P Univ Minnesota, Dept Chem, 207 Pleasant St SE, Minneapolis, MN55455 USA Univ Minnesota 207 Pleasant St SE Minneapolis MN USA 55455 USA
Citazione:
P. Buhlmann et al., "Influence of natural, electrically neutral lipids on the potentiometric responses of cation-selective polymeric membrane electrodes", ANALYT CHEM, 73(14), 2001, pp. 3199-3205

Abstract

Ionophore-free ion exchanger electrodes were found to exhibit quite a highselectivity for the creatininium ion; however, measurements in diluted urine samples revealed large emf drifts. Potentiometric, chromatographic, NMR,and mass spectrometric evidence did not reveal any major cationic interfering agents, and anionic interfering agents cannot trivially explain the consistently positive emf drifts; Ultrafiltration of urine samples showed thatthe interfering agents have molecular weights below 1000 u, The drifts areapparently caused by electrically neutral lipophilic compounds of low molecular weight that are easily extracted into organic phases. Follow-up experiments showed that p-cresol and cholesterol cause no significant emf responses but that coproporphyrin, phosphatidylserine, taurocholic acid, cholic acid, phosphatidylethanolamine, and octanoic acid cause positive emf drifts of the type that was observed with the urine samples. The extent of the responses and the response time depend not only on the specific compound but also on the cation in the sample solution. These results suggest that the emf drifts are due to extraction of such natural lipids into the organic membrane phase where they interact in an ionophore-like fashion with the analyte and interfering ions. Changes in the potentiometric selectivities after contact with natural lipids support this interpretation. The same effect of natural lipids is also expected for ionophore-based electrodes. Indeed, exposure of a valinomycin-based electrode to a methylene chloride extract of urine resulted in a significant reduction of the Na+ discrimination, increasing log K-K,Na(pot) from -3.9 to -3.1.

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Documento generato il 07/04/20 alle ore 22:47:44