I. Sanemasa et al., CONCENTRATION OF METAL-IONS IN WATER AS E LECTRICALLY NEUTRAL COMPLEXES ON A POLYTETRAFLUOROETHYLENE FILM, Bunseki Kagaku, 42(8), 1993, pp. 479-484
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.