Recebido em 16/10/96; aceito em 14/1/97 ULTRAMICROELECTRODES. PART II: CONSTRUCTION AND APPLICATIONS. This work describes the techniques of construction and several applications of ultramicroelectrodes in electrochemistry and electroanalytical chemistry. Disc shaped UME are produced by embedding metal wires on insulating materials such as glass or epoxy resin. In the field of electrochemistry, UME have been applied in studies of the hydrogen evolution reaction and the electrocrystallization of metals. The negligible values of sensibility for ohmic drop and the enhanced mass transport rate by spherical diffusion are the main advantages of UME in these applications. New important conclusions regarding the phenomena under study were drawn from the experimental results. The applications in electroanalytical chemistry involved the determination of contaminants such as heavy metals and nitrites in natural waters and food products. The use of UME requires little sample manipulation and, in general, no need for oxygen removal or the addition of supporting electrolytes.

This work reports the application of carbon-fiber and gold ultramicroelectrodes for the determination of nitrites in different media. The linear-sweep voltammetric response for nitrite oxidation on carbon fiber and gold was investigated in the anodic potential range up to 1.6 V (vs. the saturated calomel electrode). The experiments were performed in sulfate solutions, pure and natural waters. Natural water samples were obtained from a commercially available mineral water and from a heavily polluted urban creek. Very well-defined waves were always obtained showing a half-wave potential near to the valuc previously reported for NO, oxidation. It was demonstrated that neither 0, or NOT exert any influence in the nitrite oxidation response. The detection limits calculated were within the range of 2.6 to 9.7 / L M , the highest being associated to the polluted water sample on carbon fiber and the lowest to mineral water on gold ultramicroelectrodes.

organic chemistry, review organic chemistry, review Z 0200 03 -266 Further Studies on the Mechanism of the Peroxyoxalate Reaction -[kinetic studies]. -(BAADER, W. J.; SILVA, S. M.; OYAMAGUCHI, K. H.; CISCATO, L. F. L. M.; STEVANI, C. V.; Chemilumin. Turn Millennium (2001) 33-38; Inst. Quim., Univ. Sao Paulo, 05599 Sao Paulo, Brazil; EN)