Solvolysis kinetic study and direct spectrofluorimetric analysis of the fungicide benomyl in natural waters

Abstract

<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<sup>-2</sup> M NaOH aqueous solution, various alkaline (10<sup>-2</sup> 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<sup>-2</sup> M NaOH aqueous solution and Triton X-100 solutions (pH7 and 10<sup>-2</sup> 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>

Etude des propriétés fluorescentes d’un naphtopyranone isolé de <i>Guiera senegalensis</i>

“…Plusieurs études ont montré que le pH est un facteur qui affecte fortement le signal de fluorescence des molécules organiques (Thiaré et al, 2014;Thiaré et al, 2015a;Coly et al, 2001;Coly et al, 2009). Pour le naphtopyranone, l'intensité de fluorescence augmente fortement à partir du pH 8 puis le signal devient constant entre 8 et 12.…”

“…En effet, la fluorescence est un puissant outil d'investigation des propriétés et d'analyse tant qualitative que quantitative des molécules organiques (Mbow et al, 2014). Sa précision et sa sensibilité ne sont plus à démontrer (Thiaré et al, 2014;Thiaré et al, 2015a;Coly, 2001;Coly et al, 2001;Coly et al, 2009 Pour étudier la variation de l'intensité de fluorescence en fonction du pH de la solution, des concentrations appropriées de solutions d'acide chlorhydrique ou de soude ont été utilisées pour faire varier le pH. Un échantillon de la solution diluée du naphtopyranone a été placé dans la cuve en quartz et les spectres de fluorescence ont été enregistrés entre 200 et 300 nm pour l'excitation et entre 350 et 500 nm pour l'émission avec une vitesse de balayage de 480 nm/min.…”

Cyclodextrin-enhanced photo-induced fluorescence of tau-fluvalinate, molecular modelling of inclusion complexes and determination in natural waters

“…7 This feature can be related to the micropolarity of the CD core. 21,22 Under these conditions, it is probable that the micro polarity of CDs would allow TFV, which possesses a notable polar region, to nd a more satisfactory adsorption site within. On the other hand, this micropolarity permits a higher affinity of CDs core to the weakly water-soluble TFV molecules.…”

Development, Validation and Application of a Spectrofluorimetric Method for the Quantification of Nevirapine in Pharmaceutical Formulations Tablets and Suspensions

“…The fluorescence signal intensity of many fluorophores is sensitive to changes in the pH of the medium [89]. The pH is an important factor in chemical reactions, so solutions of phosphoric acid (0.1 M) and NaOH (0.1 M) were used to get the pH variations between 2 and 13.…”