INFLUENCE OF HYDRODYNAMIC CONDITIONS OF THE SOLUTION ON THE SENSITIVITY OF STRIPPING ANALYSIS OF TRACE-METALS

Possibilities to increase the sensitivity of stripping analysis by opt imising the hydrodynamic conditions of the solution during the deposit ion and rest period are evaluated. Rotation rates as high as 13 000 rp m can be applied during the deposition step at a mercury film rotating disc electrode for Zn, Cd, Pb, Ln and Tl determinations when 10-20 mg /l of Hg2+ for the renewal of the mercury film is added. Because of th e extreme sensitivity on the properties of the mercury film in the cas e of Ga only 4000-5000 rpm are recommended. The highest stirring effic iencies using a magnetic stirrer are equivalent to 2500-3000 rpm when a rotating disc electrode is used. The effect of the duration of the r est period is not significant for square wave stripping voltammetry, h owever, analytical signals can be increased 10 and more times when pot entiometric stripping analysis is applied.