Anal. Chem. 1984,56, 1135-1137
Registry No. Cadmium, 7440-43-9;mercury, 7439-97-6;carbon, 7440-44-0.
LITERATURE CITED (1) Nielsen, E.; Wium-Anderson, W. Mar. Blol. (Berlin) 1970, 6, 93. (2) Black, J. Ph.D. Dissertation, The University of Michigan, Ann Arbor, MI, 1974. (3) Anderson, D. M.; Morel, F. M. Limnol. Oceanogr. 1978, 23,283. (4) Gachter, R. K.: Lum-Shue-Chan; Chou, Y. K. Schweiz. Z. Hydro/. 1973, 35, 252. (5) Ailen, H. E.; Hall, R. H.; Brisbin, T. D. Environ. Sci. Techno/. 1980, 14, 441. (6) Sunda, W.; Guiiiard, R. R. J . Mar. Res. 1978, 3 4 , 511. (7) Andrew, R. W.; Beisinger, K. E.; Glass, G. E. Wafer Res. 1977, 1 1 , 309. (8) Brezonic, P. L.; Brauner, P. A.; Stumm, W. Wafer Res. 1978, 10, 805. (9) Batley, 0. E.;Florence, T. M. J . Electroanal. Chem. 1978, 72, 121. (10) Jacobsen, E.; Lindseth, H. Anal. Chim. Acta 1977, 72, 123. (11) Buffle, J.; Cominoll, A,; Greter, F. L.; Haerdl, W. 4th International SAC Conference Proc. Anal. Div. Chem. SOC. 1978, Vol. 15. (12) Benes, P.; Steinnes, E. Water Res. 1974, 6,947. (13) Bersier, P.; Bersier, J.; Hugli, F. Helv. Chim. Acta 1980, 43, 478. (14) Berge, H.; Kunkel, S. Anal. Chlm. Acta 1971, 54, 221. (15) Bowers, R . C.; Wilson, A. M. J . Am. Chem. SOC. 1958, 80, 2968. (16) Schimpff, W. K. Ph.D. Dissertation, The Universlty of Mlchlgan, Ann Arbor, M I , 1971. (17) Pungor, E.; Feher, 2s.J . Nectroanal. Chem. 1977, 75, 241. (18) Chien. Y. W.; Oisen, C . L.; Sokoioski, T. 0. J . Pharm Scl. 1973, 62, 435.
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(19) Gough, D. A.; Leypoldt, J. K. Anal. Chern. 1979, 51,439. (20) Stewart, E. E. M.S. Thesis, West Virginia University, Morgantown, WV, 1983. (21) Freese, J. W. M.S. Thesis, West Virginla University, Morgantown, WV, 1981. (22) Dube, G. B. Ph.D. Dissertation, The Pennsylvania State University, State College, PA, 1979. (23) Florence, T. M. J . Elecfroanal. Chem. 1970, 27, 273. (24) Zirlno, A.; Heaiy, M. L. Environ. Scl. Techno/. 1972, 6 , 243. (25) Dryssen, D.; Lumme, P. Acta Chem. Scand. 1982, 16, 1785. (26) Biedermann, 0.; Ciavatta, L. Acta Chem. Scand. 1982, 16, 2221. (27) Schonberger, E. A.; Pickering, W. F. Talanta 1980, 27, 11. (28) Sinko, I . ; Dolezal, J. J . Electroanal. Chem. 1970, 25, 299. (29) Lewin, V. H.; Rowell, M. J. Effluenf Wafer Treat. J . 1973, 13, 273.
RECEIVED for review September 12,1983. Accepted February 1, 1984. Although the information described in this article has been funded partially by the US.Environmental Protection Agency under assistance agreement R810540-01-0to R.B.S.,it has not been subjected to the Agency’s required peer and administrative review and therefore does not necessarily reflect the views of the Agency and no official endorsement should be inferred. Acknowledgment is also made to the donors of the Petroleum Research Fund, administered by the American Chemical Society, for partial support of this research.
Voltammetric pH Measurements with Surface-Modified Electrodes and a Voltammetric Internal Reference Israel Rubinstein Department of Plastics Research, Weizmann Institute of Science, Rehouot 76100, Israel
It Is demonstrated that by comblnlng surface-modified electrodes with voitammetrlc technlques, it Is possible to construct pH probes conslstlng exclusively of metal wlre electrodes, which are natural candidates for mlnlaturlzatlon. Changes In the pH translate to shlfts in voltammetric peak potentials. Two modes of operation are presented, one that employs a pH-sensitive reference electrode and another that employs a pH-dependent electroactlve specles confined to the worklng electrode. In the latter mode, a second, pH-independent electroactlve species Is also bound to the working electrode, to provide a voltammetric-type reference potential.
Numerous methods have been suggested and used to date for pH measurement, mostly potentiometric (1,2).Of these, the pH-sensitive glass electrode has by far been the most widely used, due to its high selectivity, reliability, wide pH range, and convenience of use. Other types of pH electrodes, e.g., the antimony-antimonous oxide (1,3,4) or other innovative metal oxide electrodes ( 5 , 6 ) ,have also been studied. The need to miniaturize pH probes has been recognized for some time, primarily for biological applications and also in corrosion studies (7,8). p H electrodes for either extra- or intracellular measurements were constructed and tested, both in vitro and in vivo (9-16). Here, again, glass pH microelectrodes are much preferred over any other type. Innovative single-barreled or double-barreled glass electrodes with tip diameter as small as
