Noch fallen keine Programme dem Rotstift zum Opfer, Institute und Universitäten müssen noch keine Mitarbeiter entlassen. Aber die Wissenschaftsorganisationen in Deutschland müssen sparen und können an vielen Stellen nicht mehr investieren, denn die zugesagte Erhöhung der Forschungsetats durch den Staat bleibt aus.
The use of a reactive electrode (reactrode) consisting of graphite, a solid ion exchanger (HYPHAN) and paraffin for the batch analysis of Cd(2+), Cu(2+), Pb(2+) and Hg(2+) in aqueous samples and as a passive monitor for these metal ions is described. The metal ions are accumulated on the reactrode surface at an open-circuit potential in an ion-exchange reaction. After the accumulation, the ion exchanger-bonded metal ions are reduced to the metals which remain on the electrode surface. In a following step, the metals are anodically dissolved which is recorded by differential-pulse voltammetry. The 3s detection limits for the analysis of drinking water are: 1.1x10(-7) mol/l for Pb(2+), 5x10(-8) mol/l for Hg(2+) and 2.4x10(-7) mol/l for Cu(2+).The reactrode developed can be used for the passive monitoring of heavy metals in aqueous streams if the reactrode is mounted in a wall-jet cell which is part of a flow-through system. Using this arrangement, it has been possible to determine Hg(2+), Cu(2+) and Pb(2+) in drinking water after 20 hours of accumulation.
The tin@) complex of N-benzoyl-N-phenyl-hydroxamic acid (HX) and chloride ions [Sn'"X2CI,Jo is reduced in 2-propanol solution via two different pathways depending on the scan rate. At scan rates higher than 20mV/s, the reduction proceeds via [Sn"X2CI2J2-and [SnoX(H20)J, and at slower scan rates the reduction proceeds via [Sn"XC13]2-and [Sn°CI(H20)2]-. This is the first time that experiments have indicated the existence of tin' complexes. The studied tin'" complex can be used for the determination of tin traces in aqueous solutions. Therefore the tinIv complex is preliminarily extracted from aqueous solution and the differential pulse anodic stripping voltammograms are recorded in the organic solution after addition of 2-propanol. The 3 0 limit of detection is 4 x
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