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ANALYTICAL CHEMISTRY, VOL. 57, NO. 1, JANUARY 1985
the potassium ion case. It can be seen that the electrode has good (ca. 9OX) selectivity for Ba2+over K+ and that the response to the latter is distinctly sub-Nernstian (41.2 mV/ decade). Qualitatively similar results are obtained for Na+ and Mg2+,but these ions give a poorly reproducible and very slow response (>30 min) in acetonitrile. It is possible that such ions, by virtue of small size, could interact with the crown carrier in other than 1:l stoichiometry. The crown-polymer conjugate-based electrodes could be used for at least 20 days with no loss of response or selectivity when stored in the 0.01 M Et4NC1O4-acetonitri1e solvent between measurements. In view of these findings, it appears that these electrodes could be useful for Ba2+activity measurements in acetonitrile and, perhaps, other aprotic organic solvents. Registry No. Ba, 7440-39-3.
I
,d 0'
LITERATURE CITED Flgure 3. Calibration curves of cis-crown-polymer based electrodes in acetonitrile at 25 'C: curve 1, theoretical slope for univalent cation; curve 2, experimental response curve for K+; curve 3, experimental
response curve for Ba2+;curve 4, theoretical slope for divalent cation.
Nernstian with an experimental slope of 28.2 mV/activity decade. Base-line potentials (E,,f)were reestablished within 10 minutes when the electrodes are reimmersed in the 0.01 M Et4NC104-acetonitrile medium. In contrast, the electrode coated with poly(acry1amide) polymer alone yielded a very sluggish response to Ba2+with response times in excess of 30 min. This confirms our feeling that the presence of the carrier in the membrane serves to stabilize the electrode potential and to improve the reproducibility and dynamic behavior. We also investigated the selectivity of the crown-polymer conjugate electrodes for Ba2+with respect to other cations in acetonitrile. Representative results are shown in Figure 3 for
(1) Pungor, E.; T&h, K. "The Chemistry of Non-aqueous Solvents"; Lagowski, J. J. Ed.; Academic Press: New York, 1978; Val. VA, Chapter 4. (2) . . Izutsu, K.: Nakamura. T. Bunseki 1981, 502-504; Chem. Abstr. 1981, 9 5 , 1612792. (3) Kakabadse, G. J. Ion-Selective Electrode Revlews 1981, 3, 127-187. (4) Pungor, E.: T&h, K.; Klatsminyi, P. G.; Izutsu, K. Pure Appl. Chem. 1983. 55, 2029-2065. (5) Heerman, L. F.; Rechnltz, G. A. Anal. Chem. 1972, 4 4 , 1655-1658. (6) Coetzee, J. F.; Istone, W. K. Anal. Chem. 1980, 52, 53-59. (7) Izutsu, K.: Nakamura, T.; Iwata, K. Anal. Chim. Acta 1980, 117, 329-335. (8) Nakamura, T.; Yumoto, Y.; Izutsu, K. Bull. Chem. SOC. Jpn. 1982, 55, 1850-1853. (9) Cox, Brian Geoffrey; Waghorne, W. Earle; Pigott, Charles K. J. Chem. SOC.,Faraday Trans. 11879, 7 5 , 227-235. (10) Nakamura, T.; Morozumi, S.; Izutsu, K. Chem. Lett. 1982, 1317; Chem. Abstr. 1982, 9 7 , 2 2 9 2 3 2 ~ . (1 1) Feigenbaum, W. W.; Michael, R. H. J. Polym. Sd., Polym. Chem. Ed. 1971, 9 , 817-820. (12) Baumlnger, S.; Wilcheck, M. Methods Enzymol. 1980, 7 0 , 151-156.
RECEIVED for review July 26, 1984. Accepted Septbmber 27, 1984. This work was supported by NSF Grant CHE-8318192.
CORRECTION Comparison of Phase-Resolved and Steady-State Fluorimetric Multicomponent Determinations Using Wavelength Selection Linda B. McGown and Frank V. Bright (Anal. Chem. 1984, 56, 2195-2199). On page 2196, under Data Collection, the first sentence should read All fluorescence measurements (steady-state and phase-resolved) were made with an SLM 4800s spectrofluorometer (SLM Instruments, Inc.) with a 450-W xenon arc lamp source and photomultiplier tube (Hamamatsu R928) detection.
