OXIDATION OF HUMIC SUBSTANCES PRIOR TO THE DETECTION OF PCBs AND PAHs IN NATURAL WATERS BY FLUOROMETRY ON SOLID SORBENT

A method for the detection of PCBs in water, based on extraction/concentration with tab-shaped elements cut from C18 fiberglass SPE disks coupled with a fluorescence detection has been applied to natural waters. Due to the known complexing property of the naturally present Natural Organic Matter (NOM) with respect to non polar organic pollutants, NOM was shown to compete with the solid phase for PCB adsorption thus reducing the capability of the method.

In order to obviate the negative effect of NOM on the sensitivity of the method, a prior oxidation treatment with KMnO₄ was tested on PCB3, PCB77 and Aroclor 1221. This pretreatment was also tested for the detection of pyrene, perylene and benzo[a]pyrene taken as representative polycyclic aromatic compounds.

In all cases, with respect to the signal in pure water and depending on the dissolved organic carbon concentration (DOC), the signals with no treatment could be lowered to less than 20%, while the signals obtained following oxidative treatment was found to be very close with more than 90% of recovery.