COMPOSITION OF KELEX(R)-100, KELEX(R)-100S AND KELEX(R)-108 - A DISCUSSION ON THE ROLE OF IMPURITIES

The composition of distilled KELEX(R) 100, KELEX(R) 100S and KELEX(R) 108 was investigated by GC/MS. Distilled KELEX(R) 100 and KELEX(R) 100S are shown to be of high and similar quality. 7-(4-Ethyl-1-methyloctyl)-8-hydroxyquinoline is the main component of these two reagents. However, the latter still contain small amounts of inert, furoquinoline-type impurities; namely 3-ethylfuro[2,3-h] quinoline and 2-(2-ethylhexyl)-3-methylfuro [2,3-h] quinoline. KELEX(R) 100S is probably obtained by fractionation of KELEX(R) 100. Except for the rate of phase separation, comparison of the composition of KELEX(R) 100 and KELEX(R) 100S does not reveal any clear reason why KELEX(R) 100S possesses improved properties compared to KELEX(R) 100, especially as far as the resistance against oxidation or the kinetics of metal extraction are concerned. KELEX(R) 108 is shown to contain mainly 7-(2-ethylhexyl)-8-hydroxyquinoline: but also important amounts of 8-hydroxyquinoline and its di(2-ethylhexyl) derivative.