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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

<p>A direct spectrofluorimetric method for the quantitative analysis of benomyl in natural waters is described. Benomyl is an instable, fluorescent fungicide that mainly decomposes into carbendazim and n-butyl-isocyanate in organic and aqueous solutions. The kinetics of benomyl solvolysis reactions were investigated in organic solvents (methanol and acetonitrile) and in aqueous solvent systems, including β–cyclodextrin (β-CD), sodium dodecyl sulfate (SDS), dodecyltrimethylammonium chloride (DTAC), cetyltrimethylammonium chloride (CTAC), cetyltrimethylammonium hydroxide (CTAOH), Brij-700, Triton X-100 and water, at different pH and/or NaOH concentrations. The benomyl fluorescence signal was found to be quasi-completely stable in 10^-2 M NaOH aqueous solution, various alkaline (10^-2 M NaOH) organized media, β-CD neutral solution and Triton X-100 aqueous solutions of different pH. Based on these results, a direct spectrofluorimetric analytical method was developed for the determination of benomyl in 10^-2 M NaOH aqueous solution and Triton X-100 solutions (pH7 and 10^-2 M NaOH), with wide linear dynamic range (LDR) values of two to three orders of magnitude, very low limit of detection (LOD) and limit of quantification (LOQ) values of, respectively, 0.002-0.5 ng/mL and 0.007-2.0 ng/mL, and small relative standard deviation (RSD) values of 0.2-1.7 %, according to the medium. This direct spectrofluorimetric method was applied to the evaluation of benomyl residues in natural waters, with satisfactory recovery values (87-94%).</p>

The fenvalerate pyrethroid insecticide was determined in various types of natural waters of Senegal by means of a newly-developed, simple, rapid and very sensitive photochemically-induced fluorescence (PIF) method. The PIF method was optimized with respect to the irradiation time, solvent and pH. The obtained calibration curves yielded correlation coefficients very close to unity. The limit of detection (LOD) and of quantification (LOQ) values were very low (LOD = 0.01-0.66 ng/ml and LOQ = 0.04-2.20 ng/ml, according to the solvent), and the relative standard deviation (RSD) values were small, ranging between 0.1 and 1.5 %, which indicated a very good analytical sensitivity and a great repeatability of PIF. Recovery studies were performed on spiked distilled water, tap water, sea water, well water, river water and draining water samples of Senegal, using the liquid-liquid extraction (LLE), solid phase extraction (SPE), and standard addition procedures. Satisfactory recovery results (about 85-121%) were obtained for the determination of fenvalerate in an aquatic environment.Keywords: fenvalerate; insecticide; photochemically-induced fluorescence (PIF); aquatic environment ОПРЕДЕЛУВАЊЕ НА ИНСЕКТИЦИДОТ ФЕНВАЛЕРАТ ВО ПРИРОДНИ ВОДИ СО ФОТОХЕМИСКИ ИНДУЦИАРАН ФЛУОРЕСЦЕНТЕН МЕТОДПиретоидниот инсектицид фенвалерат е определен во различни типови природни води на Сенегал по пат на ново разработен, едноставен, брз и многу осетлив фотохемиски индуциран флуоресцентен (PIF) метод. Методот беше оптимизиран земајќи ги предвид времето на ирадијација, растворувачот и pH. Добиените калибрациони криви дадоа коефициенти на корелација многу блиски до еден. Вредностите за границата на детекција (LOD) и границата на квантификација (LOQ) беа многу ниски (LOD = 0,01-0.66 ng/ml и LOQ = 0.04-2.20 ng/ml, во зависност од растворувачот) додека вредностите на релативната стандардна девијација (RSD) беа мали и се движеа од 1 до 1,5%, што укажува на висока аналитичка сензитивност и одлична повторливост на PIF методот. Извршено е испитување на аналитичкиот принос на спајкувана дестилирана вода, вода од чешма, морска вода, изворска вода, речна вода и дождовница од Сенегал со примена на течно-течна екстракција (LLE), цврсто фазна екстракција (SPE) и со постапка на стандардни адиции. Беа добиени задоволувачки резултати за аналитичкиот принос (околу 85-121%) за определување на фенвалерат во водна средина.Клучни зборови: фенвалерат; инсектициди; фотохемиски индуцирана флуоресценција; водна средина