Spectrofluorimetric determination of beta-blockers atenolol and bisoprolol fumarate residues in Senegal natural waters

A spectrofluorimetric method was developed to determine residues of two β-blockers, atenolol (AT) and bisoprolol fumarate (BF), in Senegal's natural waters. The electronic absorption and fluorescence spectral properties of both β-blockers were investigated in several organic solvent mixtures [e.g., MeOH/H2O (60/40 v/v), cyclodextrins (β-cyclodextrin, HP-β-CD], and in the presence of surfactants (SDS, Triton X, Tween 80). After optimization, satisfactory analytical figures of merit were obtained for the determination of both β-blockers: concentration linear dynamic range of over one to two orders of magnitude, limits of detection (LODs) from 1.3 to 5.4 ng/ml for BF and from 1.2 to 3.7 ng/ml for AT, limits of quantification (LOQs) from 4.5 to 18.1 ng/ml for BF and from 4.0 to 12.5 ng/ml for AT. Relative standard deviations (RSDs) were between 2.1 and 5.3 %, according to the β-blockers. The spectrofluorimetric method was applied to the analysis of fortified river water and wastewater (effluent) collected in Senegal and France and spiked with both β-blockers. It yielded good recovery values, from 93.3 to 107.8 % for AT and from 97.4 to 108.9 % for BF. Our results demonstrated the simplicity, rapidity, and sensitivity of the spectrofluorimetric method to quantify residues of β-blockers in environmental waters

Rapid removal of fungicide thiram in aqueous medium by electro-Fenton process with Pt and BDD anodes

International audienceThe electro-Fenton (EF) process was used to assess the electrochemical degradation of the fungicide thiram and its complete removal from water using an undivided electrolytic cell equipped with Pt or BDD anode and carbon felt cathode. Hydroxyl radicals, produced homogeneously in bulk solution from electrochemically generated Fenton's reagent (• OH) and heterogeneously on the anode surface (M(• OH)) from oxidation of water, reacted with thiram leading to its fast oxidation. Oxidative degradation and mineralization kinetics were monitored by chromatographic analysis (HPLC) and total organic carbon (TOC) measurements. The electrochemical degradation of thiram by hydroxyl radicals followed a pseudo-first-order reaction kinetics with an absolute rate constant kabs(Thir) of 5.54 (± 0.03) × 10 9 M-1 s-1 , determined by competition kinetics method. The TOC removal rate values were found significantly higher with BDD anode than Pt anode. Thus, almost complete mineralization (92%) of thiram solution was obtained when using BDD anode. 2 These results highlight the major role of heterogeneous BDD(• OH) formed in the mineralization of thiram. The contribution of homogeneous • OH in mineralization of thiram was found relatively low due to its specific aliphatic structure. The efficiency of the EF process was evaluated by determining mineralization current efficiency and energy consumption per gram of TOC removed. Degradation by-products and inorganic ions, such as nitrate (NO3 −), nitrite (NO2 −), ammonium (NH4 +) and sulfate (SO4 2−) formed during mineralization process, were identified by GC-MS and ionic chromatography analyses and a plausible mineralization pathway was proposed

Determination of Flumethrin and Tau- Fluvalinate Pyrethroid Insecticides in Surface and Groundwater by Photochemically Induced Fluorescence (PIF)

International audienceFlumethrin and tau-fluvalinate pyrethroid insecticides were determined in natural water using photochemically induced fluorescence (PIF). As these pesticides are not naturally fluorescent, PIF using ultraviolet irradiation was employed to produce highly fluorescent derivatives. This method was optimized for irradiation interval, solvent and pH. The calibration curves were linear with limits of detection (LOD) from 0.5 to 73.8 ng mL−1 without matrix effects. Applications were carried out in aqueous solutions on tap water, seawater, well water and river water from Niayes, Senegal and the Brest, France using solid phase extraction and standard addition procedures. The samples were analyzed with mean recoveries between 99.0 and 109.0%. The analytical performances of these systems were favorable compared with published photoinduced fluorescence methods for the determination of pyrethroids. The results show that the developed PIF method is suitable for the determination of trace organic pollutants in natural waters

Photodegradation study of the fenvalerate insecticide by 1H NMR, 13C NMR, and GC-MS and structural elucidation of its transformation products

International audienceThe photolysis of fenvalerate, a pyrethroid insecticide, was studied in acetonitrile by 1H nuclear magnetic resonance (NMR) and 13C NMR to identify the site of bond cleavage and gas chromatography-mass spectrometry (GC-MS) to establish the chemical structure of fenvalerate photoproducts. Ultraviolet (UV) irradiation of fenvalerate solutions was performed for 18 h with a solar light simulator, and the photolysis reaction obeyed first-order kinetics. Photolysis half-life time (t1/2) values ranged between 15.25 and 21.63 h (mean photodegradation percentage = 51.7 %) for 1H NMR and between 4.55 and 8.06 h (mean photodegradation percentage > 80 %) for 13C NMR. We observed five sites of bond cleavage, namely carbonyl-tertiary carbon, tertiary carbon-tertiary carbon, carbonyl-oxygen, carboxyl-tertiary carbon, and aromatic carbon-tertiary carbon, yielding photoproducts formation. GC-MS was associated with 1H NMR and 13C NMR to obtain a complete photodegradation mechanism. Before UV irradiation, two chromatogram peaks were obtained, due to the two fenvalerate isomers. Under irradiation, both peaks decreased, and new peaks appeared, corresponding to photoproduct formation. After a 12- to 13-h irradiation, 99.39 % of fenvalerate was degraded with a mean rate constant of 0.305 h–1. The chemical structure of the formed photoproducts was identified, either by using the National Institute of Standards and Technology (NIST) mass spectral database or by interpreting the mass spectra. Finally, a detailed mechanism was proposed for fenvalerate photodegradation

Development of thermochemically induced fluorescence (TIF) method for the determination of insecticide deltamethrin in Senegalese natural waters

International audienceA simple and sensitive thermochemically induced fluorescence (TIF) method was developed to determine deltamethrin, an insecticide which has toxic effects on human beings and animals. After optimisation at different pH, temperature was increased from 25 to 50°C. TIF method is based on the thermolysis transformation of naturally non-fluorescent pesticides into a fluorescent thermoproduct. The thermolysis kinetics reaction investigated in water at optimal pH 12 and after 4 minutes heating at 40°C made it possible to obtain a low mean half-life time (t1/2 = 1.41 ± 0.06 min), which shows that deltamethrin degrades very rapidly due to heat. The obtained calibration curve gave correlation coefficients close to unity. The limit of detection (LOD = 4.4 ng mL−1) and quantification (LOQ = 15 ng mL−1) values were very low, showing the high sensitivity of the TIF method. TIF method was applied to determination of deltamethrin residues in tap and well waters by standard addition procedure, with satisfactory recovery values between 107.6 and 111.4%. The relative standard deviation (RSD) value of the measured concentrations in spiked water samples was less than 6%, which demonstrated good reproducibility of the TIF method