Because of their important fluorescence properties, coumarins are widely applied in sensing devices. In this paper, the electronic inductive, mesomeric, and electromeric substituent effects on the electronic absorption and fluorescence spectra of 11 substituted coumarins, including NH 2 , NMe 2 , NEt 2 , OH, CF 3 , CH 3 , COOH, Cl, and Br substituents, have been quantitatively studied by means of structure-reactivity relationships. We have applied the Hammett, Brown-Okamoto, and Yukawa-Tsuno correlations to the coumarins electronic absorption and fluorescence spectra wavenumbers and Stokes shifts. The Stokes shift of coumarins decreased when the electron-donor inductive/ mesomeric power of the substituent increased. This Stokes shift decrease was more pronounced when the solvent polarity increased, which might be explained by the electromeric effect increase.

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In this present paper, we investigate the development of simple, rapid, accurate, reproducible and sensitive methods for the determination of serotonin (5-HT) in urine. For this purpose stationary fluorescence was used as method. With regard to the analysis of serotonin, the liquid-liquid extraction (LLE) solid phase extraction (SPE) and standard addition procedures were used. Several physicochemical factors affecting the sensitivity of the fluorescence intensity of serotonin were optimized, including the system of solvent (organic, micellar), the pH and the salts. The study of the analytical performances of the method led to very low limits of detection (LOD) varying between 0.1 and 3 ng/mL and to limits of quantification (LOQ) ranging between 0.4 and 10 ng/mL. This confirms the sensitivity of the method. Thus the low values of standard deviations (DRS) (between 0.3 and 6.6%) testify the good reproducibility of the measurements with satisfactory covering rate (89 to 111%). Accordingly, our results show that the spectrofluorimetric method is simple, fast and sensitive and can be applied to the routine analysis and does not require expensive equipment nor tiresome chemical pretreatments.Keywords: serotonin, effects of solvent, method of analysis of fluorescence direct, analysis of urine

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In alkaline medium, the complex formed between putrescine and orthophthalaldehyde was studied using spectrofluorescence. The derivative is kinetically stable 24 h after complexation. The stoichiometry of the complex is 1:1 at maximum fluorescence intensity, also 24 h after complexation.