TENSAMMETRY WITH ACCUMULATION ON THE HANGING MERCURY DROP ELECTRODE .6. ERRORS OF DETERMINATION CAUSED BY ADSORPTION OF NONIONIC SURFACTANTS ON THE MATERIAL OF THE MEASURING CELL

The adosorptive loss of oxyethylated alkylphenols (Triton X-100 and Rokafenol N-3), oxyethylated alcohols (Brij-35, Marlipal 1618/40 and surfactant 18-10) and poly(ethylene glycol) of MW 9000 on cells constructed from quartz, glass, glassy carbon, PTFE, polyethylene, polypropylene, polystyrene and aluminium during the measuring process was investigated. In all instances very substantial losses were found, which completely changed the results of the determination. Apart from the vessel itself, very important losses on the ceramic frit located at the end of the salt bridge were found. The loss of all the surfactants tested on the quartz vessel is not very substantial and, after protection of the ceramic frit, a cell with such a construction gives minimum losses. The glass cell is very sensitivie to the manner of preparation of its surface. Cells constructed from PTFE and glassy carbon adsorb more specifically than others and can be used for the determination of oxyethylated alcohols but not for the determination of oxyethylated alkylphenols. Other materials used gave substantial losses of almost all the surfactants tested. Particularly bad results were obtained with polystyrene and aluminium cells. © 1990.