Fluorescence enhancement of Carbendazim in the presence of cyclodextrins and micellar media: a reappraisal

Cloud point extraction of carbendazim fungicide from strawberry samples and amperometric detection with boron doped diamond

The cloud point extraction (Tergitol® surfactant) method was used for the first time to extract and preconcentrate the fungicide carbendazim (CBZ) from strawberry samples, while electrochemical detection (boron doped diamond electrode) in association with high performance liquid chromatography (HPLC-EC) was used for the determination of CBZ. The variables of bath temperature, ultrasonic stirring time, mass of NaCl and amount of surfactant were investigated using a 24 full factorial design. Limits of detection (LOD, S/N = 3) and quantification (LOQ) of 3.42 × 10-8 mol/L (or 6.54 µg/L) and 6.84 × 10-8 mol/L (or 13.1 µg/L), respectively, were obtained for the CPE processes, considering the value of the preconcentration factor obtained (9.12). The method was validated based on linearity, intra-day and inter-day recovery tests, accuracy and precision. The proposed method was applied to strawberry samples from local commercial establishments and different procedures for washing and sanitizing strawberry fruits were also evaluated.

Development of 2D graphene oxide sheets-based voltammetric sensor for electrochemical sensing of fungicide, carbendazim

Incorporating new pollutants and environmental pollution has become a formidable issue as new pollutants are introduced into it and have become a significant concern in recent years. Detection of such pollutants needs a susceptible, selective, and cost-effective sensor that can sense their presence and quantify them at a trace level. In the present study, we have designed a 2D graphene oxide (GO)-based glassy carbon electrode (GCE) electrochemical sensor (GO/GCE) and utilized it as a sensing material for the detection and determination of CRZ. The voltammetric behavior of CRZ was studied using cyclic voltammetry (CV) and square wave voltammetry (SWV) techniques. The SWV was applied to quantify and analyze CRZ in actual samples. A better response of CRZ was noticed at GO/GCE when phosphate buffer solution of pH 4.2 was used as a supporting electrolyte for to experiment. The SWV technique achieved trace-level detection of CRZ. A linearity plot was obtained for the concentration range of 1.0 × 10^-7 M to 2.5 × 10^-4 M with a limit of detection of 1.38 × 10^-8 M. The selectivity of the modified sensor was verified by the interference study of metal ions and other pesticides with CRZ. The agricultural and environmental significance of the developed method was successfully tested by estimating CRZ in water and soil samples.

Graphene/g-carbon nitride (GO/g-C3N4) nanohybrids as a sensor material for the detection of methyl parathion and carbendazim

The widespread use of methyl parathion (MP) and carbendazim (CBZ) as pesticide molecules for controlling pests and protect crops has added pollution issues; excess usage of these can lead to atmospheric pollution through contaminating water and soil sources. In the present study, detection of these compounds at the trace level was achieved by employing graphene oxide (GO) and graphitic carbon nitride (g-C₃N₄) nanohybrid electrode assembly (GO/g-C₃N₄/GCE). The X-ray diffraction (XRD), Transmission Electron Microscopy (TEM), and Atomic Force Microscopy (AFM) techniques were also used to characterize the materials developed to reveal their purity, crystal structure, and morphology. The complete voltammetric behavior of these analytes was investigated using cyclic voltammetic (CV) and square wave voltammetry (SWV) techniques. The influence of pH was studied and it was noticed that electrochemical response was the highest at pH 7.0 for MP and at pH 4.2 for CBZ. Density Functional Theory (DFT) calculations could help us to understand the adsorption behavior of MP and CBZ onto the GO and g-C₃N₄ before their degradation due to the electrochemical reactions. SWV technique was helpful in the trace level detection of MP and CBZ. Linearity plots were obtained in the range of concentration from 8.0 × 10^-8 M to 1.0 × 10^-4 M with a limit of detection 0.824 nM for MP and 1.0 × 10^-8 M to 2.5 × 10^-4 M for CBZ with the detection limit of 2.82 nM. Significance of the developed method in the field of agricultural and environmental domains was successfully investigated by monitoring MP and CBZ in water and soil samples, and the obtained results suggested the selectivity, stability, and reproducibility of the newly developed GO/g-C₃N₄/GCE electrode assembly.

A novel sensor based on WO3·0.33H2O nanorods modified electrode for the detection and degradation of herbicide, carbendazim

In the present-day scenario, it is necessary to establish more flexible, effective and selective analytical methods that are easy to operate and less expensive. Cyclic voltammetry (CV) can be a useful technique to assess minute quantity of pollutants and in this work, an effort has been made to detect the trace quantification from the environmental samples. Herein, electrochemical sensor was fabricated using tungsten oxide nanorod (WO₃·0.33H₂O) for sensitive detection of fungicide, carbendazim (CBZ). Under optimal conditions, while studying the effect of pH on peak current, the highest peak current was observed at pH 4.2. The degradation of CBZ followed the mixed diffusion-adsorption controlled and quasi-reversible processess at the WO₃·0.33H₂O/GC electrode surface. Using WO₃·0.33H₂O/GCE sensor in SWV provided the lowest limit of detection (LOD) and limit of quantification (LOQ) values of 2.21 × 10^-8 M and 7.37 × 10^-8 M, respectively over the concentration ranges of 1.0 × 10^-7 M to 2.5 × 10^-4 M. The proposed method demonstrates potential applicability of the fabricated sensor for soil and water samples analysis in the management of creating a benign environment.

Development of novel response surface methodology-assisted micellar enhanced synchronous spectrofluorimetric method for determination of vandetanib in tablets, human plasma and urine

A highly sensitive and accurate novel response surface methodology (RSM)-assisted micellar enhanced synchronous spectrofluorimetric method was developed and validated for determination of vandetanib (VDB) in tablets, human plasma and urine. The method relied on enhancement of the fluorescence behavior of VDB in polyoxyethylene hydrogenated castor oil 40 (HCO 40) micellar medium and measuring the fluorescence using synchronous scan approach (Δλ = 50 nm). Key factors affecting VDB fluorescence were optimized by RSM using Box-Behnken design. These factors were the type and volume of surfactant and pH of the buffer medium. Under the optimum conditions, the fluorescence-concentration plot was linear over the range 40-600 ng mL^-1; the limits of detection and quantification were 5.22 and 15.82 ng mL^-1, respectively. The suggested method was successfully applied to the analysis of laboratory-prepared tablets, spiked human plasma and urine samples. The results were statistically compared with those acquired by a pre-validated liquid chromatography-tandem mass spectrometric reference method and the results obtained from both methods were found to be in good agreement.

Utility of Cremophor RH 40 as a micellar improvement for spectrofluorimetric estimation of sorafenib in pure form, commercial preparation, and human plasma

An easy, quick, simple and accurate spectrofluorimetric method was recognized and validated for evaluation of sorafenib (SOR) in pure form and biologically in plasma. Cremophor RH 40 (Cr RH 40) used for enhancing the fluorescence activity of SOR in phosphate buffer (pH 7). Cr RH 40 improved the native fluorescence of SOR remarkably in water. The fluorescence spectrum of SOR was observed at 405 nm after excitation at 265 nm. The linearity appeared to be in the range of 5 to 600 ng ml^-1 for pure and from 9 to 500 ng ml^-1 for plasma using the protein precipitation (ppt) method while from 10 to 500 ng ml^-1 for plasma using liquid-liquid extraction method. The precisions and the accuracy of the estimated method gave satisfactory results. The recommended method was effectively applied for determination of SOR in human plasma with high recovery values. The results of some compounds that are possibly found in plasma were studied. The proposed method was also focused on real volunteers and a drug dissolution test.

Micellar Enhanced Spectrofluorimetric Method for the Determination of Ponatinib in Human Plasma and Urine via Cremophor RH 40 as Sensing Agent

An impressively simple and precise spectrofluorimetric procedure was established and validated for ponatinib (PTB) quantitation in biological fluids such as human plasma and human urine. This method depends on examining the fluorescence characteristics of PTB in a micellar system of Cremophor RH 40 (Cr RH 40). Cr RH 40 enhanced the intrinsic fluorescence of PTB distinctly in aqueous water. The fluorescence spectra of PTB was recorded at 457 nm following its excitation at 305 nm. Maximum fluorescence intensity was attained by addition of 0.7 mL of Cr RH 40 and one mL of phosphate buffer to PTB aliquots and then dilution with distilled water. There is a linear relationship between the fluorescence intensity of PTB and its concentration over the range 5–120 ngmL⁻¹, with limit of detection and limit of quantification equal to 0.905 ngmL⁻¹ and 2.742 ngmL⁻¹, respectively. The accuracy and the precisions of the proposed method were checked and gave adequate results. The adopted method was applied with a great success for PTB quantitation in different biological matrices (spiked human plasma and urine) giving high recovery values.

A new method to determine the new C-Met inhibitor “Cabozantinib” in dosage form and human plasma via micelle-enhanced spectrofluorimetry

A highly sensitive and simple micelle-enhanced spectrofluorimetric method was developed for the determination of cabozantinib (CBZ) in its pharmaceutical formulation and spiked human plasma without any derivatization.

Spectrofluorimetric determination of benzoimidazolic pesticides: effect of p-sulfonatocalix[6]arene and cyclodextrins

The effect of the addition of a macrocyclic host (H) such as p-sulfonatocalix[6]arene (C6S), native and modified cyclodextrins (CDs), on the fluorescence of benzoimidazolic fungicides (P), like Benomyl (BY) and Carbendazim (CZ), has been studied. The fluorescence of BY in water at pH 1.000 and 25.0 degrees C was increased in the presence of C6S, alphaCD and hydroxypropyl-beta-CD (HPCD). The association constants determined by fluorescence enhancement showed weak interactions (K(A) approximately 10(1) to 10(2) M(-1)) between the fungicide with both CDs, whereas they were stronger with C6S (K(A) approximately 10(5) M(-1)). Molecular recognition of BY for C6S was mainly attributed to electrostatic interactions, and for CDs to the hydrophobic effect and hydrogen bond formation. On the other hand, the fluorescent behaviour of CZ in the presence of C6S at pH 6.994 was interpreted as the formation of two complexes with 1:1 (P:H) and 1:2 (P:H(2)) stoichiometry, the latter being less fluorescent than the free analyte. Relative fluorescence quantum yield ratios between the complexed and free BY (phi(P:H)/phi(P)) were 2.00+/-0.05, 1.40+/-0.03 and 2.8+/-0.4 for C6S, alphaCD and HPCD, respectively. The analytical parameters improved in the presence of C6S and CDs. The best limit of detection (L(D), ng mL(-1)) was 17.4+/-0.8 with HPCD. The proposed method with C6S and HPCD was successfully applied to fortified samples of tap water and orange flesh extract with good recoveries (91-106%) and R.S.D. (< or = 2%) by triplicate analysis. The method is rapid, direct and simple and needs no previous degradation or derivatization reaction.

Complexation study of brilliant cresyl blue with beta-cyclodextrin and its derivatives by UV-vis and fluorospectrometry

The complexation reactions of brilliant cresyl blue (BCB) with beta-cyclodextrin (beta-CD), mono[2-O-(2-hydroxypropyl)]-beta-CD (2-HP-beta-CD), mono[2-O-(2-hydroxyethyl)]-beta-CD (2-HE-beta-CD), and heptakis(2,6-di-methyl) -beta-CD (DM-beta-CD) were investigated using UV-vis and fluorospectrometry. The complexation between BCB and CDs could inhibit the aggregation of BCB molecules and could cause its absorbance at 634nm gradually increasing. The fluorescence of BCB was also enhanced with the addition of CDs. The fluorescence enhancement was more notable in neutral and acidic media than in basic media. Hildebrand-Benesi equation was used to calculate the formation constants of beta-CDs with BCB based on the fluorescence differences in the CDs solution. The stoichiometry ratio was found to be 1:1. The complexing capacities of beta-CD and its three derivatives were compared and the results followed the order: 2-HP-beta-CD>2-HE-beta-CD>DM-beta-CD>beta-CD. The effect of temperature on the formation of BCB-beta-CD inclusion complexes has also been examined. The results revealed that the formation constants decreased with the increase of temperature from 1038.9 to 491.6l/mol. Enthalpy and entropy values were calculated and the values were -25.77kJ/mol and 35.04J/kmol, respectively. The thermodynamic measurements suggest that the inclusive process was enthalpic favor. The release of high-energy water molecules and Van der Waals force played an important role in the inclusive process.

Fluorescence enhancement of carbendazim fungicide in cucurbit[6]uril

The potential increase in fluorescence of a benzimidazole-type fungicide (carbendazim) due to complexation with cucurbit[6]uril is reported. The fluorescence of the probe carbendazim in aqueous Na2SO4 solution (pH=7.61) at room temperature is found to increase by a maximum factor of approximately 10.0 and blue-shifted up to approximately 11+/-1 nm with the increase in cucurbit[6]uril concentration up to approximately 5 mM. This fluorescence enhancement is the result of formation of a 1:1 guest-host inclusion complex, in which the guest carbendazim is incorporated inside the hydrophobic cavity of the host curbit[6]uril through the amido-ester part. Such mode of inclusion is supported by NMR spectral measurements, in which upon encapsulation, the resonance of the methyl-protons of the amido-ester moiety is shifted significantly to upfield in the (1)H NMR spectrum. Also, to assess the formation of inclusion complex, solid samples prepared by co-evaporation have been studied, using differential scanning calorimetry (DSC). Measurement of the enhancement as a function of cucurbit[6]uril concentrations yielded a value of the equilibrium constant (Ka) of 271+/-10 M(-1) at 25 degrees C. From the temperature dependence of the equilibrium constants, DeltaH and DeltaS values have been negative in sign, indicating the dipole-dipole interactions and the steric factors associated with the formation of this inclusion complex. It might be proposed that the spectral changes due to the inclusion of carbendazim are the result of decrease in the polarity of the surrounded media rather than the loss of carbendazim rotational mobility.

Partial least-squares with residual bilinearization for the spectrofluorimetric determination of pesticides. A solution of the problems of inner-filter effects and matrix interferents

This paper demonstrates for the first time the power of a chemometric second-order algorithm for predicting, in a simple way and using spectrofluorimetric data, the concentration of analytes in the presence of both the inner-filter effect and unsuspected species. The simultaneous determination of the systemic fungicides carbendazim and thiabendazole was achieved and employed for the discussion of the scopes of the applied second-order chemometric tools: parallel factor analysis (PARAFAC) and partial least-squares with residual bilinearization (PLS/RBL). The chemometric study was performed using fluorescence excitation-emission matrices obtained after the extraction of the analytes over a C18-membrane surface. The ability of PLS/RBL to recognize and overcome the significant changes produced by thiabendazole in both the excitation and emission spectra of carbendazim is demonstrated. The high performance of the selected PLS/RBL method was established with the determination of both pesticides in artificial and real samples.