Paper substrate room-temperature phosphorimetry of polyaromatic hydrocarbons enhanced by surface-active agents

The effect of the presence of surfactants of different character (sodium dodecyl sulfate, sodium decyl sulfate, Brij 35, and dodecyltrimethylammonium chloride) on the paper-substrate room-temperature phosphorescence (PS-RTP) of several polyaromatic hydrocarbons (PAHs) and carbazole was studied. Thallium nitrate was used as a heavy-atom perturber. When an anionic surfactant was added or when analytes were spotted from micellar solutions, enhancements of the sensitivity ranging between factors of 2 and 9 were found. On the other hand, the PS-RTP signal was totally quenched in the presence of the cationic surfactant. Similar effects were found for the phosphorescence of the paper background. Absolute limits of detection in the range of 0.2-3 ng were obtained in the presence of sodium dodecyl sulfate. A discussion on the possible mechanisms producing the observed effects is included.