Determination of 3,3'-Dichlorobenzidine in Industrial Wastewaters

A solid-phase extraction, chemical derivatization, and gas chromatography/mass spectrometry (GC/MS) method has been developed for the determination of trace 3,3'-dichlorobenzidine (DCB) in industrial wastewater samples. Instead of an octadecylsilane (ODS) cartridge, a Porapak RDX cartridge was used since the latter could be optimized for the extraction of DCB. After the pre-concentration, interfering coextractives in the sample were selectively removed from the cartridge by elution with a 1:1 mixture of acetonitrile and water. DCB was then eluted with acetonitrile and derivatized with pentafluoropropionic acid anhydride. The product was subsequently analyzed by GC/MS in either the electron impact or negative ion chemical ionization mode. Recoveries of DCB and the surrogate, DCB-d 6 , were better than 90% at spiking levels of 10, 1, and 0.1 pg/L. Based on a concentration factor of 100, the detection limits for DCB in wastewater samples were determined to be 0.1 pg/L by electron impact GC/MS detection, and 0.01 pg/L by negative ion chemical ionization GC/MS detection, respectively. This method has been successfully applied to wastewater samples collected in the Toronto area.