D-optimal design for electrochemical simultaneous determination of bentazon and fenamiphos in natural waters

In this study, we proposed a new electroanalytical methodology using a boron-doped diamond electrode (BDD), associated with factorial design for simultaneous and selective determination of bentazon (BTZ) and fenamiphos (FNP). These pesticides are frequently combined for different crops and have overlapping oxidation potential signals (1.04 V and 1.13 V for BTZ and FNP, respectively). Thus, to enable simultaneous determination we used a 33 full factorial design with three parameters at three levels, using the D-optimal design. The optimised square wave voltammetry parameters were pH 4.0, frequency of 200 s−1, pulse amplitude of 10 mV, and scan increment of 4.0 mV. These parameters were used for the construction of calibration curves, which showed linear ranges of 9.90 µmol L−1 to 91.0 µmol L−1 for BTZ and 4.95 µmol L−1 to 69.0 µmol L−1 for FNP. The limits of detection (LOD) and quantification (LOQ) were 0.38 µmol L−1 and 1.27 µmol L−1 for BTZ, and 1.50 µmol L−1 and 4.98 µmol L−1 for FNP. The performance of the method was evaluated using a natural water sample collected from a supply dam. The recovery values were 117.5% for BTZ and 88.6% for FNP. The results show that the developed method is suitable for the simultaneous determination of both pesticides in samples from natural water.