Analyst, December 1996, Vol. 121 1793 0.140 r 0.125 d E - 0.120 -. 0.115 0.1 10 0.105 ' I L I I I -1.3 -1.2 -1.1 -1.0 -0.9 -0.8 EIV Fig. 8 Batch injection analysis of insulin at MTFE on a glassy carbon substrate (diameter 5 mm). [Insulin]: 5.0, 10.0, 50.0 and 100.0 pmol 1-I; peak height increases with increasing concentration. Injections of 100 pl of solution. Other experimental conditions as in Fig. 3. batch injection analysis can be employed for the determination of zinc in small sample volumes. This technique is very promising for application to the determination of zinc arising from the zinc-insulin complex released into the extracellular fluid during exocytosis from pancreatic @-cells. References Hedeskov, C. J., Physiot. Rev., 1980, 60, 442. Orci, L., Vasssali, J. D., and Perrelet, A., Sci.Am., 1988, 260, 85. Efendic, S., Khan, A., and Ostenson, C. G., Diahete Metah., 1994,20, 81. Derewenda, U., Dercwenda, Z. S., Dodson, G. G., and Hubbard, R. E., in Insulin, ed. Cuatrecasas, P., and Jacobs, S., Springer, Berlin, 1990, ch. 2. Howell S. I., and Tyhurst, M., in The Secretory Process, ed. Poisener, A. M., and Trifarii, J. M., Elsevier, Amsterdam, 1982, vol. 1, ch. 4. 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 2s 26 Blundell, T., Dodson, G., Hodgkin, D., and Mercola, D., in Advances in Protein Chemistry, ed. Anfinsen, C. B., Jr., Edsall, J. T., and Richards, F. M., Academic Press, New York, 1972, pp. 279402. Ferrer, R., Soria, B., Dawson, C. M., Atwater, I., and Rojas, E., Am. J . Physiol., 1984, 246, C520. Perez-Armendariz, E., Atwater, I., and Rojas, E., Biophys.J., 1985, 48, 741. Hales C. N., and Randle, P. J., Biochem. J., 1963, 88, 137. Kekow, J., Ulrichs, K., Muller-Ruchholtz, W., and Gross, W. L., Diabetes, 1988, 37, 321. Millar, J., Slamford, J. A., Kruk, Z. L., and Wightman, R. M., Eur. J . Pharm., 1985,109, 341. Leszczyszyn, D. J., Jankowski, J. A., Viveros, 0. H., Diliberto, E. J., Near J. A., and Wightman, R. M., J . Neurochem., 1991, 56, 1855. 0' Neill, R. D., Analyst, 1994, 119, 767. Huang, L., Shen, H., Atkinson, M. A., and Kennedy, R. T., Proc. Natl. Acad. Sci. USA, 1995,92,9608. Stankovich, M. T., and Bard, A. J., J . Electroanal. Chem., 1977,85, 173. Trijueque, J., Sanz, C., Monlebn, C., and Vicente, F., J . Electroanal. Chem., 1988, 251, 173. Trijueque, J., and Vicente, F., An.Quim., 1990, 86, 538. Trijueque, J . , Vicente, F., Martinez, F., and Vera, J., Port. Electrochim. Acta, 199 1, 9, 399. Honeychurch, M. J., and Ridd, M. J., Electroanalysis, 1996, 8, 49. Wojciechowyki, M., and Balcerzak, J., Anal. Chem., 1990, 62, 1325. Brett, C. M. A., Oliveira Brett, A. M., and Mitoseriu, L. C., Anal. Chem., 1994,66, 3145. Brett, C. M. A., Oliveira Brett, A. M., and Mitoseriu, L. C., Electroanalysis, 1995, 7, 225. Brett, C. M. A., Oliveira Brett, A. M., and Tugulea, L., Anal. Chim. Acta, 1996, 322, 151. Cox, J. A., and Gray, T. J., Anal. Chenz., 1989, 61, 2462. Stamford, J. A., Palij, P., Davidson, C., Jorm, C. M., and Phillips, P. E. M., in Neuromethods, ed. Boulton, A,, Baker, G., and Adams, R. N., Humana Press, Clifton, NJ, 1995, 27, pp. 81-1 16. Blundell, T., Dodson, G., Hodgkin, D., and Mercola, D., in Advances in Protein Chemistry, ed. Anfinsen, C. B., Jr., Edsall, J. T., and Richards, F. M., Academic Press, New York, 1972, p. 325. Paper 6103650C Received May 28, 1996 Accepted July 25, 1996