Investigation of the chromatographic behaviour of some selenium species--comparison with their octanol-water partitioning.
The retention behaviour of selenites (Se(IV)), selenates (Se(VI)), seleno-dl-methionine (Se-Met), selenocystine (Se-Cyst), selenocystamine (Se-CM) and selenourea (Se-U) was investigated using a Discovery end-capped reversed-phase column as stationary phase and different mobile phase conditions. Extrapolated to 100% aqueous mobile phase retention factors (logk(w)) of the investigated Se species, determined using different methanol fractions (phi) as organic modifier, were compared with the corresponding actual values. The proper operation of this column even at 100% aqueous phase proved to be valuable for the accurate determination of logk(w) values of Se-CM and Se-Cyst, presenting a convex curvature logk=f(phi) at low MeOH fractions, often neglected in the extrapolation procedure. The effect of the presence of n-decylamine as well as saturation of the mobile phase with n-octanol was also studied. For ampholytic Se-Met and Se-Cyst the effect of n-decylamine in retention reflected the predominance of zwitterionic nature in the case of Se-Met in contrary to the non-zwitterionic species found in the case of Se-Cyst, in accordance with our previous findings concerning partitioning experiments in the n-octanol/water system. Finally, an attempt was made to correlate logk(w) values with the logarithm of n-octanol/water distribution coefficient, logD, of the investigated Se species and an indicative logD value of Se-U was derived.
Tsopelas
Fotios
F
Laboratory of Inorganic and Analytical Chemistry, School of Chemical Engineering, National Technical University of Athens, Iroon Polytechniou 9, Athens, Greece.
Tsantili-Kakoulidou
Anna
A
Ochsenkühn-Petropoulou
Maria
M