Anal. Chem. 1987, 5 9 , 1078-1081
1078
a T
A
0
& C
3nA
D
E
F
Figure 6. Standard addition determination of Cu (8-s preconcentration) in reference material NBS 1643b: (A) sample solution; (B) 0.35 pM Cu added; (C) 0.98 pM Cu added: (D)1.78 WMCu added: (E) 2.66 W M Cu added: (F) 3 . 6 7 pM Cu added.
because the CME responds only to Cu(I), hydroxylamine M) was also added at the same time that sulfate (2.0 x the pH adjustment was made. Consequently, the analysis performed consisted of the determination of total dissolved Cu. Two quantitation approaches were employed: calibration curve and standard addition. The results are summarized in Table I. Both approaches gave excellent agreement with the reference Cu value. The precision of the standard addition determination (see Figure 6) was considerably improved over that obtained by comparison with calibration standards prepared by spiking deionized waterlacetate buffer solutions. In all determinations, no voltammetric waves other than those assigned to Cu redox processes were observed following preconcentration. Ag, present at a level of 9.8 (&0.8)ppb, did
not have a sufficiently high concentration to produce a direct or indirect interference.
LITERATURE CITED Flato, J. B. Anal. Chem. 1972, 44(11). 75A-87A. Cheek, G. T.: Nelson, R. F. Anal. Lett. 1978, 17, 393-402. Cox, J. A.; MaJda,M. Anal. Chem. 1980, 52,861-864. Price, J. F.; Baldwin, R. P. Anal. Chem. 1980, 52, 1940-1944. Lubert, K. H.; Schnurrbusch, M.: Thomas, A. Anal. Chim. Acta 1982, 144, 123-136. Izutsu, K.; Nakamura, T.; Takizawa, R.; Hanawa, H. Anal. Chim. Acta 1983, 149. 147-155. Cox, J. A.: Kulesza, P. J. Anal. Chim. Acta 1983, 754, 71-78. Wang, J.; Greene, B.; Morgan, C. Anal. Chim. Acta 1984, 158, 15-22. Guadalupe, A. R.; Abruna, H. D. Anal. Chem. 1985, 57, 142-149. Wier, L. M.; Guadalupe, A. R.; Abruna, H. D. Anal. Chem. 1985, 5 7 , 2009-201 1. Kalcher, K. Anal. Chim. Acta 1985, 177, 175-182. O'Rlordan, D. M. T.; Wallace, G. G. Anal. Chem. 1986, 58, 128-131. Gehron, M. J.; Brajter-Toth, A. Anal. Chem. 1988, 58, 1488-1492. Baldwin, R. P.; Christensen, J. K.; Kryger, L. Anal. Chem. 1988, 5 8 , 1790-1798. Burger, K. Chelates in Analyfical Chemlstfy; Flaschka, H. A,, Barnard, A. J., Jr., Eds.; Marcel Dekker: New York, 1969; Vol. 2, pp 179-212. Smith, G. F.; McCurdy, W. H., Jr. Anal. Chem. 1952, 24, 371-373. Luke, C. L.; Campbell, M. E. Anal. Chem. 1953, 25, 1588-1593. Irving, H.; Mellor, D. H. J . Chem. SOC. 1962, 5237-5245. Schilt, A. A.; McBride, L. The Copper Reagents: Cuproine, Neocuproine, Bathocuproine, 2nd ed.; G. F. Smith Chemical: Columbus, OH, 1972. Monien, H.; Gerlach, U.; Jacob, P. Fresenius' 2.Anal. Chem. 1981, 306, 136-143. Martell, A. E.; Smith, R. M. Critical Stabillty Constants; Plenum: New York, 1974; Vol. 2, p 260.
RECEIVED for review October 21, 1986. Accepted January 12, 1987. This work was supported by the NATO Scientific Affairs Division Grant 85/0679 and by the College of Arts and Sciences of the University of Louisville.
Performance Characteristics and Regeneration of a Tetraphenylboron(I I I) Selective Electrode Adel F. Shoukry, Sayed S. Badawy,* and Yousry M. Issa Department of Chemistry, Faculty of Science, University of Cairo, Giza, Egypt
A tetraphenylboron (1PB)lon-selective poly( vinyl chloride)membrane electrode based on an ion pair complex of TPBwith hexadecyipyridinium cation (HDP') was prepared with dloctyi phthalate as a plasticizer. Effects of changing the Ion palr percent in the membrane and pH of the test solution on the electrode potential were studied. It was found that soaklng the electrode in HDP solution gives better response characterlstlcsthan those obtained from electrodes soaking in TPB solution. A method for regeneratlon of the exhausted electrode was proposed. The electrode was hlghly selective for TPB with respect to some amlno acids and organic and inorganic anions. TPB was determined successfully by POtentlometrlc titratlon with standard HDP solution when using the investigated electrode as the sensor.
Recently, the use of tetraphenylborates is a growing concern in many fields. They have been used in biological studies (1-4), in construction of solar batteries (5), and in nuclear waste treatment (6-8). In the analytical chemistry field, sodium tetraphenylborate (NaTPB) has been used in titri-
metric determination of some pharmaceutical compounds (9-11). The most important use of tetraphenylborate in this field is its incorporation in construction of a considerable number of plastic membrane ion-selective electrodes used for detection of high molecular weight organic cations (12-19). The only determination method of tetraphenylboron (TPB) ion using a membrane electrode based on hexadecyl trimethyldodecyl sulfate was tried by Fogg et al. (20). A slight response with opposite slope to that expected for an anion electrode was obtained. Because of the importance of this material and the lack of literature on a rapid and simple method for its determination, we found it worthy to investigate the response characteristics of a T P B ion-selective membrane electrode based on the hexadecylpyridinium (HDP)-TPB ion pair. Generally, the most serious drawback of all the previously reported poly(viny1 chloride) (PVC)-membrane ion-selective electrodes is their limited lifetime. No method to reactivate the electrode has been reported until now. The present paper includes a treatment of this problem and a method is given for the regeneration of the exhausted PVC-membrane electrode.
0003-2700/87/0359-1078$01.50/00 1987 American Chemical Society
ANALYTICAL CHEMISTRY, VOL. 59, NO. 8, APRIL 15, 1987
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Table I. Effect of Soaking on the Performance Characteristics of TPB Electrodes (at 20 " C ) time of soaking
slope, mV/decade
soaking in NaTPB intercept, mV
response time, s
slope, mV/decade
soaking in HDPBr intercept, mV
response time, s
Electrode A 5 min l h 2h 4h 6h 8h 24 h 72 h
47.8 48.0 49.5 47.9 47.6 46.7 28.0 23.0
-50.5 -63.0 -74.0 -83.7 -89.0 -116.0
15 10
