Origin and elimination of interferences from siliconization procedures in anodic stripping voltammetry

Interferences caused by organic impurities can be a serious problem in trace analysis for heavy metals by differential pulse anodic stripping voltammetry. Organic impurities, which originate from siliconization treatment of the capillary of the hanging mercury drop electrode, can cause high background currents, interfering signals and peak broadening, especially in the concentration range below 5 ppb. A new method of siliconization for glass capillaries which avoids these problems is reported. A reference electrode with a poly-acrylamide gel-stiffened internal electrolyte is recommended, to avoid difficulties such as adsorption of organic material on low-leakage diaphragms of the Vycor type, which are often used in trace analysis.