Spectrochemical investigations in molecularly organized solvent media: Evaluation of nitromethane as a selective fluorescence quenching agent for alternant PAHs dissolved in micellar solvent media

Applicability of the nitromethane selective quenching rule for discriminating between alternant versus nonalternant polycyclic aromatic hydrocarbons (PAHs) is examined for 29 representative PAH solutes dissolved in micellar cetyltrimethylammonium bromide (CTAB) and micellar sodium dodecylsulfate (SDS) solvent media. Experimental results show that nitromethane quenched fluorescence emission of only the 17 alternant PAHs in the cationic CTAB surfactant solvent media as expected. Emission intensities of nonalternant PAHs, except for the few exceptions noted previously, were unaffected by nitromethane addition. Unexpected quenching behavior was observed, however, in the case of nonalternant PAHs dissolved in micellar SDS solvent media. Nitromethane quenched fluorescence emission of nonalternant PAHs studied in the SDS solvent media, which is contrary to the selective quenching rule.