SPECTROSCOPIC INVESTIGATIONS IN MOLECULARLY ORGANIZED SOLVENT MEDIA -PART-3 - EXAMINATION OF THE NITROMETHANE SELECTIVE QUENCHING RULE IN AQUEOUS ANIONIC PLUS CATIONIC AND ANIONIC PLUS NONIONIC MIXED SURFACTANT SOLUTIONS

Applicability of the nitromethane selective quenching rule for discrim inating between alternant versus nonalternant polycyclic aromatic hydr ocarbons (PAHs) is examined for 20 representative PAH solutes dissolve d in micellar sodium dodecylsulfate (SDS) + cetyltrimethylammonium bro mide (CTAB), SDS + dodecyltrimethylammonium bromide (DTAP), SDS + Brij -35, and SDS + sodium octanoate (SO) mixed surfactant solvent media. E xperimental results show that nitromethane quenched fluorescence of al l 8 alternant PAHs studied in the four different solvent systems. Unex pected quenching behavior was observed, however, in the case of nonalt ernant PAHs. Nitromethane quenched fluorescence emission of nonalterna nt PAHs dissolved in the SDS + SO solvent media, which is contrary to the selective quenching rule. In the case of the mixed anionic + catio nic surfactant solvent media, nitromethane quenching selectivity was r estored at concentration ratios of approximately 4:1 (anionic:cationic ) or less.