Simultaneous quantification of carbaryl, chlorpyrifos, and paraquat in a municipal wastewater treatment plant by SPE-RP-HPLC–PDA-FD method

Three commonly used pesticides, carbaryl, chlorpyrifos, and paraquat, were quantified by using solid-phase extraction (SPE) technique and high-performance liquid chromatography with photodiode-array and fluorescence detectors (HPLC–PDA-FD) in wastewater treatment plant. After solid-phase extraction, separation, and quantification were done using a C₁₈ analytical column, an isocratic mobile phase consisting of acetonitrile/water (70%:30% v/v) at a flow rate of 1 mL/min, and a column oven maintained at 35 °C. Analyte concentrations were detected simultaneously at 230 nm, 254 nm, and 270 nm. PDA detection at 230 nm gave LOD and LOQ values of 0.65 mg/L and 1.98 mg/L, 0.39 mg/L, and 1.17 mg/L, for carbaryl and chlorpyrifos, respectively. Fluorescence emission peaks, λ_exc (270 nm) and λ_em (320 nm), were chosen for detection. FD gave LOD and LOQ values of 0.98 mg/L and 2.96 mg/L, 1.57 mg/L, and 4.76 mg/L, for carbaryl and chlorpyrifos, respectively. Calibration curves based on integrated peak area counts gave satisfactory linearity (R² ≥ 0.9995). Although exhibiting low detector sensitivity for paraquat at 230 nm, this method is deemed best suited for routine analysis in Wastewater Treatment Plants (WWTPs). The developed and validated method using lower-cost dual detectors, PDA-FD, as a substitute for the higher-cost mass spectrometry is suitable for routine quantitative and qualitative analysis of carbaryl, paraquat, and chlorpyrifos in wastewater and environmental samples.

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