Relationship between the retention characteristics on an alumina column and physico-chemical parameters of some environmental pollutants

The retention behavior of 16 environmental pollutants was studied on alumina and porous graphitized carbon (PGC) columns using n-hexane as eluent. The relationship between the logarithm of the capacity factors determined on the alumina column and the physico-chemical characteristics of the solutes was elucidated by principal component analysis (PCA) followed by two-dimensional nonlinear mapping. The 12 original variables can be reduced to four with only a 10% loss of information. The logarithm of the capacity factor formed a cluster with the hydrogen donor and acceptor properties of the solutes and their Taft's constant on the two-dimensional nonlinear map of PC loadings indicating that both steric and electronic parameters play a considerable role in the retention mechanism on alumina support. Alcohols, aromatics and chlorinated alkanes formed separate clusters on the two-dimensional nonlinear map of PC variables suggesting that their retention mechanism may be different on the alumina column. Solutes were not retained on the PGC surface proving that under normal-phase conditions the retention capacity of alumina can be higher than that of PGC.