Flow-through Cell Based on an Array of Gold Microelectrodes Obtained From Modified Integrated Circuit Chips

Abstract

The construction of a flow-through cell incorporating an array of gold microelectrodes is described and its application to flow injection analysis with amperometric detection is presented. Simple modification of almost any conventional integrated circuit chip, used as an inexpensive source of pre-assembled gold micro-wires, leads to the rapid and successful preparation of arrays of 8–48 elements. The polymeric encapsulation material from the top face of the chip is removed by abrasion until the gold micro-wires (used to interconnect the silicon circuit to the external contact pins of the chip) are disrupted and their transversal (elliptical) sections become exposed. Once polished, the flat and smooth top surface of the gold microelectrode-array chip (MEAC) is provided with a spacer and fitted under pressure against an acrylic block with the reference and auxiliary electrodes, to form the electrochemical (thin-layer) flow cell, while the contact pins are plugged into a standard IC socket. This design ensures autonomous electric contact with each electrode and allows fast dismantling for polishing or substitution. The performance of flow cells with MEACs was investigated utilizing the technique of reverse pulse amperometry without oxygen removal. A method was established for the determination of the copper concentration in sugar cane spirit, regulated by law for beverages. Samples from industrial producers and small-scale (alembic) brewers were compared. With a 24 MEAC, a detection limit of 30 µg l^-1 of copper (4.7 × 10^-7 mol l^-1 of Cu^II for 100 µl injections) was calculated. Routine operation was established at a frequency of 60–90 determinations per hour. Intercomparison with atomic absorption spectrometric determinations resulted in excellent agreement.

References

1. S. Pons and M. Fleischmann, Anal. Chem., 1987, 59, 1291A.
2. J. Wang, Microelectrodes, VCH, New York, 1984.
3. M. I. Montenegro, M. A. Queiros and J. L. Dascbach, Microelectrodes: Theory and Applications, Kluwer, Dordrecht, 1991.
4. R. M. Wightman, Anal. Chem., 1981, 53, 1125A.
5. A. M. Bond, Analyst, 1994, 119, R1.
6. R. D. O'Neill, Analyst, 1994, 119, 767.
7. R. M. Penner and N. S. Lewis, Chem. Ind. (London), 1991, 788.
8. J. Ruzicka and E. H. Hansen, Flow Injection Analysis, Wiley, New York, 1981.
9. L. Nyholm and G. Wilmark, Anal. Chim. Acta, 1992, 257, 7.
10. P. R. Fielden and T. McCreedy, Anal. Chim. Acta, 1993, 273, 111.
11. W. L. Caudill, J. O. Howell and R. M. Wightman, Anal. Chem., 1982, 54, 2532.
12. J. Wang, A. Brennsteiner, L. Angnes, A. Sylvester, R. R. LaGasse and N. Bitsch, Anal. Chem., 1992, 64, 151.
13. H. P. Wu, Anal. Chem., 1993, 65, 1643.
14. C. Fernandez, A. J. Riviejo and J. M. Pingarron, Anal. Chim. Acta, 1995, 314, 13.
15. P. R. Fielden, T. McCreedy, N. Ruck and D. Vaireanu, Analyst, 1994, 119, 953.
16. M. J. Mc Grath, T. Fang, D. Diamond and M. R. Smyth, Anal. Lett., 1995, 28, 685.
17. B. Ross and K. Cammann, Talanta, 1994, 41, 977.
18. V. B. Nascimento, M. A. Augelli, J. J. Pedrotti, I. G. R. Gutz and L. Angnes, Electroanalysis, 1997, 9, 335.
19. Brasil, leis e decretos, Agriculture Ministry, Brazil, Portaria No. 371, September 18, 1974.
20. B. S. L. Neto, C. W. B. Bezerra, L. R. Polastro, P. Campos, R. F. Nascimento, S. M. B. Furuya and D. W. Franco, Quim. Nova, 1994, 17, 220.
21. J. B. Faria, PhD Thesis, Universidade de São Paulo, 1989.
22. R. Lafon, T. Lafon and P. Couillaud, Le Cognac, Baillière, Paris, 1964, p. 91.
23. P. J. S. Barbeira, L. H. Mazo and N. R. Stradiotto, Analyst, 1995, 120, 1647.
24. J. J. Pedrotti, L. Angnes and I. G. R. Gutz, Electroanalysis, 1996, 8, 673.
25. C. Pasquini and L. C. Faria, J. Autom. Chem., 1991, 13, 143.
26. K. Stulik and V. Pacáková, Electroanalytical Measurements in Flowing Liquids, Ellis Horwood, Chichester, 1987, ch. 3.
27. J. J. Pedrotti, L. Angnes and I. G. R. Gutz, Anal. Chim. Acta, 1994, 298, 393.