In
This
Issue
ISE for sulfide detection Because of interest in the development of new catalysts, Yu-Hong Tse, Pavel Janda, and A.B.P. Lever of York Univer sity demonstrate a highly oriented pyrolytic graphite electrode covered with N, 1Ψ, N", ^'"-tetramethyltetra-S^-pyridinoporphyrazinocobalt(I) and an ion-ex change membrane as a sulfide and 2-mercaptoethanol-selective electrode. Advantages of the electrode include fast response time (compared with some commercial sulfide potentiometric indicators that require several minutes) and no special cleaning procedures prior to measurement. This elec trode is used at pH 7; the silver sulfide electrode is used at pH 12. The detection range varies from 10-6 to ΙΟ-2 Μ. (p. 384)
φ\ηι?
«S
ISEs Most charged carriers used in ISEs are ion exchangers that do not exhibit specific interactions with the ions to be sensed. Ulrich Schaller, Eric Bakker, Ursula E. Spichiger, and Ernô Pretsch of the Swiss Federal Institute of Technology demonstrate that charged carriers need oppositely charged lipophilic sites in liquid membrane electrodes to induce the highest possible selectivity. By incorporating a defined amount of these sites, selectivity is enhanced, emf functions become theoretical, electrode resistance is lowered, and longterm stability is improved, (p. 391) Sonochemistry During cavitational collapse, temperatures as high as 5000 Κ and pressures of hundreds of atmospheres are generated; however, the duration of these extreme conditions is < 1 μβ. Electrode surfaces are efficient nucleation sites for cavitation and are therefore uniquely suited to study the physical and chemical phenomena that occur during sonication. Carolynne R. S. Hagan and Louis A. Coury, Jr., of Duke University com pare the results of sonoelectrochemical experiments with ro tating disk electrode measurements to demonstrate how acoustic cavitation influences steady-state currents, (p. 399) Microlithographic fabrication of electrodes Subnanoampere currents and the unstable configuration of mercury on an inert substrate limit the use of ultramicroelectrodes in general and mercury electrodes in particular. Sam uel P. Kounaves of Tufts University and colleagues describe the microlithographic fabrication of an ultramicroelectrode array that combines the advantages of the mercury electrode, iridium-based mercury electrode, ultramicroelectrodes, and multielement array electrodes. Capabilities of the array are demonstrated by analyzing spring water samples for cad mium, lead, and copper, (p. 418)
GC capillaries à la carte!
fused silica capillary columns with numerous standard phases chemically bonded (PERMABOND®) or non-bonded
Ο special phases for particular applications e. g. chiral phases (LIPODEX®) Please ask for further information!
MACHEREY-NAGEL
