CONCENTRATION OF METAL-IONS IN WATER AS E LECTRICALLY NEUTRAL COMPLEXES ON A POLYTETRAFLUOROETHYLENE FILM

A PTFE-seal-tape of 20 cm long, 1.3 cm wide and 0.1 mm thick was place d on the surface of an aq. solution of 400 to 500 ml. Chloroform vapor was introduced into the solution and circulated in a closed system fo r 30 min. Then, the film was picked up and the solute held on it was e luted with CHCl3. As solutes, Hg(II), Pb(II), Ag(I) and Cd(II)-dithizo nates and Co(II), Ni(II), Cd(II) and Zn(II)-PAN complexes were used (d ithizone: diphenylthiocarbazone; PAN: 1-(2-pyridylazo)-2-naphthol). Fo r Cd(II)-PAN benzene vapor was circulated, and for Zn(II)-PAN, CHCl3 v apor was circulated for 1 h. Recoveries of metal dithizonates and PAN complexes were more than 80%. In an acidic solution, free dithizone is collected almost completely by the PTFE film, but can be removed from the film while keeping metal dithizonates on the film by circulating CHCl3 vapor in an alkaline solution. When air or carbon tetrachloride vapor was circulated, metal complexes were not collected by the PTFE f ilm. The PTFE film surface is assumed to be covered with a thin layer of liquid CHCl3 upon circulating CHCl3 vapor in aq. solution. The pres ent method is applicable to solutes with a large chloroform/water part ition constant.