Nickel(II) tetrasulfonated phthalocyanine (p-NiTSPc)-modified carbon fiber microelectrode (CFME) was used for the first time to investigate the electrochemical quantification of diuron in an agrochemical formulation. The surface morphology and elementary analysis of unmodified carbon fiber microelectrode (CFME) and p-NiTSPc-CFME were performed using atomic force microscopy (AFM) and energy dispersive X-ray spectroscopy (EDX), respectively. Cyclic voltammetry (CV) was used to investigate the electrochemical behaviour of diuron, while square wave voltammetry (SWV) was used for quantitative analysis of diuron. Upon variation of some key analytical parameters, a calibration curve was plotted in the concentration range from 21.450 to 150.150μM, leading to a detection limit (DL) of 8.030μMmg/L (3.3σ/m) and a limit of quantification (LQ) of 20.647μMmg/L. The fabricated p-NiTSPc-CFME was successfully applied for quality control in a commercialized formulation of diuron. The standard additional method was used, and the recovery rate of diuron was found to be 98.4.

In Benin, synthetic insecticides are the main pest control option used by farmers to protect and enhance their production. However, failures to control the target pests are often observed after application and may be related to agricultural practices or insecticide quality. The present work was designed to assess a rapid, simple, and reliable analytical method for detecting and quantifying the most commonly used insecticides (λ-cyhalothrin and acetamiprid) in Benin. The analytical standard technical grade separation was performed by gradient reversed-phase high-performance liquid chromatography on a C₁₈ stationary-phase column. The mobile phase consisted of a mixture of acetonitrile/water using a gradient flow. The flow rates were 1 and 1.4 mL·min⁻¹ for λ-cyhalothrin and acetamiprid, respectively. The analysis times were 15 and 20 min, with retention times of 2.35 and 7.94 min for λ-cyhalothrin and acetamiprid, respectively. Results reveal that most of the surveyed farmers were not educated (70% < Primary School Certificate) and were men (95%). Of the main insecticides applied by farmers, λ-cyhalothrin and acetamiprid were found to be the most technical-grade ones. Furthermore, the analysis of insecticides showed that the concentrations obtained in our study often differed from the ones mentioned on insecticide labels. The proposed method is useful for quantifying insecticides in various technical and commercial formulations with little interference from additives.

We report an approach to the manual manufacture of carbon fiber microelectrodes modified by electrodeposition of gold nanoparticles and nickel phthalocyanine tetrasulphonated composite (CFME-AuNPs/pNiTSPc), for the sensitive determination of butylhydroxyanisol (BHA) using cyclic voltammetry (CV) and differential pulse voltammetry (DPV). Atomic force microscopy (AFM), Scanning electron microscopy (SEM) and Energy dispersive Xray spectroscopy (EDX) were used for the topographical, morphological and elemental characterizations of CFME, CFME-AuNPs, CFME-pNiTSPc and CFME-AuNPs/pNiTSPc, respectively. Furthermore, electrochemical impedance spectroscopy (EIS) technique was used to evaluate the charge-transfer rate of the tested sensors. To establish optimum conditions for the electroanalysis of BHA, various parameters were studied such as the effect of scan rate, pH and the electrolysis potential. CFME-AuNPs/pNiTSPc showed better signal of BHA with a higher active surface area of 0.195 cm² compared to those of CFME-pNiTSPc (0.182 cm²), CFME-AuNPs (0.142 cm²) and CFME (0.130 cm²). In phosphate buffer solution (PBS 0.1M; pH 3), good linearity (R² = 0.998) was obtained between peak current intensities and BHA concentrations in the range from 10 to 70 µM, leading to a detection limit (LOD) of 3.60 µM (S/N=3) and a quantification limit (LOQ) of 12 µM (S/N=10). The interfering effect of certain species likely to affect the BHA oxidation signal was also evaluated, followed by the application of CFME-AuNPs/pNiTSPc in real water and mitosyl ointment samples. Recovery values of BHA were acceptable ranging from 96 to 99%, indicating that the developed sensor proved to be very sensitive and effective for detecting traces of BHA.

This study reports the development of a simple and sensitive electrochemical sensor based on activated screen-printed electrodes modified by electrodeposition of nickel(II) tetrasulfonated phthalocyanine film (poly-NiTSPc), denoted SPE-A-polyNiTSPc, for the direct determination of BPA in landfill leachate samples. BPA concentrations in raw landfill leachate solutions and in residual solutions after a reverse osmosis (RO) treatment were determined, using differential pulse voltammetry (DPV) on SPE-A-polyNiTSPc, to be 29.7 mgL⁻¹ and 6.4 µgL⁻¹, respectively. The obtained BPA concentrations were very close to those found by the accredited lab in the same samples, which were 29.6 mgL⁻¹ and 6.0 µgL⁻¹, respectively. The applicability of SPE-A-polyNiTSPc for BPA bioremediation was investigated in landfill leachate samples using Trichoderma harzianum fungus in a microbial fuel cell (MFC), where the kinetics data were modeled. The first results showed an IC₅₀ of 175 mgL⁻¹ BPA, indicating that the inhibition factor could be negligeable for MFC experiments at 30 mgL⁻¹ BPA. The biodegradation kinetics was found to be of first order, with a kinetic constant of 0.795 h⁻¹ at 22 °C and a half-degradation time of 0.872 h for an initial concentration of 29 mgL⁻¹. The developed MFC displayed higher stability, offering a maximum power of 100 mWm⁻³.