Solid-surface room-temperature phosphorescence detection of serotonin, tryptamine, and gramine enhanced by inorganic salts and sodium dodecyl sulfate

Room-temperature phosphorescence characteristics of serotonin (5-hydroxytryptamine), typtamine, and gramine ([3-(dimethylaminomethyl)indole]) were studied on low-background paper substrates. Several experimental parameters were optimized for maximum signal intensity. Sodium iodide, thallium(I) nitrate, silver(I) nitrate, and lead(II) nitrate were tested as phosphorescence enhancers. The effect of sodium dodecyl sulfate on the enhancement efficiency of these inorganic salts was also studied. The pH values of the solutions were adjusted to optimize the interaction between analyte molecules and solid substrates. Under the experimental conditions for maximum phosphorescence intensity, working curves ranging from two (gramine) to four (typtamine) orders of magnitude were obtained. Limits of detection at the nanogram level were estimated for the three compounds, showing the potential of solid-surface room-temperature phosphorimetry as a detection technique for biogenic amines.