Supercritical fluid extraction of primary aromatic amines from characterized soil samples; comparison with sonication extraction

Abstract
The extraction of the following primary aromatic amines from soil samples was studied: 1,4‐phenylenediamine, 2,4‐diaminotoluene, benzidine, 4,4'‐methylenebis(2‐chloroaniline), 3,3'‐dimethylbenzidine, and 3,3'‐dichlorobenzidine. An extensive comparison of supercritical fluid extraction (SFE) with sonication extraction was performed. The SFE method yielded significantly higher recoveries and equivalent or better precision than sonication extraction for all eleven matrices studied. Characterization data for these matrices was evaluated to determine characteristics which affect primary aromatic amine recovery and to study the potential mechanisms involved in adsorption on the soil. It was determined that amine recovery was affected by the percent clay, the surface area, and the cation exchange capacity of the soil. Adsorption likely involves cation exchange groups including silanols on the surface of the clay materials in the soil.