SPECTROSCOPIC INVESTIGATION OF FLUORESCENCE QUENCHING AGENTS .3. EFFECT OF SOLVENT POLARITY ON THE SELECTIVITY OF NITROMETHANE FOR DISCRIMINATING BETWEEN ALTERNANT VERSUS NONALTERNANT POLYCYCLIC AROMATIC-HYDROCARBONS

To better assess the applicability of nitromethane as a selective quen ching agent for alternant versus nonalternant polycyclic aromatic hydr ocarbons in HPLC, TLC, and HPTLC analysis, we measured the effect that it has on the fluorescence emission behavior of % different polycycli c aromatic hydrocarbons dissolved in binary toluene/acetonitrile solve nt mixtures. Results of these measurements revealed that the ''selecti ve quenching'' rule is obeyed for the vast majority of PAHs, with the coronene derivatives being the only major exceptions. Fluorescence emi ssion spectra are also reported for benzo[g]chrysene, naphtho[2,3g]chr ysene, 4H-benzo[c]cyclo-penta[mno]chrysene, dibenzo[ghi,mno]fluoranthe ne (commonly called corannulene), rubicene, diacenaphtho[1,2j:1',2'l]f luoranthene, 10-methyl-benzo[b]fluoranthene, 3-methoxybenzo[k]fluorant hene, and 3-hydroxy-benzo[k]fluoranthene in organic nonelectrolyte sol vents of varying polarity. Calculated emission intensity ratios failed to vary systematically with solvent polarity, and all nine of the afo rementioned solutes were thus classified as nonprobe molecules.