A COMBINED REVERSED-PHASE AND PURGE AND TRAP CHROMATOGRAPHIC METHOD TO STUDY THE INTERACTION OF VOLATILE ORGANIC-COMPOUNDS WITH DISSOLVED HUMIC-ACID IN AQUEOUS-SOLUTIONS

A combined reversed-phase and purge and trap chromatographic method was used to study the interaction of dissolved Aldrich humic acid with volatile organic compounds in aqueous solution. Humic acid bound compounds were quantified by a purge and trap gas chromatographic method after separation from unbound compounds using C-18 solid-phase extraction columns. Partition coefficients (K(p)) were 22.7 mL/g for dichlorotoluene, 14.9 mL/g for dichlorobenzene, and 3.6 mL/g for trichloroethene. The humic-dichlorotoluene interaction was biphasic and gave a first-order rate constant of 1.8 x 10(-5) h-1 for the slower phase, and a second-order constant of 1.01 L g-1 h-1 for the faster phase. Lowering the temperature of the solutions resulted in the increased binding of dichlorotoluene to humic acid.