Sorption of polycyclic aromatic compounds to humic and fulvic acid HPLC column materials

Two different humic acids (HA) and a fulvic acid (FA) were chemically immob ilized to a high performance liquid chromatography (HPLC) silica column mat erial. The immobilization was performed by binding amino groups in HA/FA to the free aldehyde group in hlutardialdehyde attached to the silica gel. Th e HPLC column materials were compared with a blank column material made by applying the same procedure but without immobilizing HA or FA. Also, a colu mn was made by binding carbonyl groups in HA to amino groups attached to th e silica gel. The humic substances were selected to secure appropriate vari ation of their structural features. The retention factors of 45 polycyclic aromatic compounds (PAC) to the four columns were determined by HPLC. The a dvantage of the technique is a large number of compounds can easily be stud ied. The binding procedure does not appear to cause a drastic selection bet ween the HA molecules. The k ' values obtained for the two Aldrich HA colum ns agree in general reasonably. The retention or sorption of the compounds increased with the size of the PAC and the number of lipophilic substituent s, but decreased when polar substituents were present. The PAC retention wa s much stronger to the two HA columns than to the FA and blank column, both for hydrophobic polycyclic aromatic hydrocarbons (PAH) and the polar PAC. Other factors impacting the PAC binding may be specific interactions with H A and the ionic strength of the aqueous phase. The technique has been appli ed to do direct determinations of K-oc.