Determination of Pesticide Residues in Tomato Samples from Kaduna State Agricultural Markets Using HPLC

Tomatoes are among the most widely cultivated and consumed vegetables in Nigeria, with Kaduna State in the North West zone being a significant production hub. The extensive use of organophosphate and pyrethroid pesticides to enhance yields has raised concerns about residue levels in commercially sold produce. This study determined pesticide residue concentrations in tomato samples obtained from three agricultural markets in Kaduna State using High-Performance Liquid Chromatography with UV detection. A total of thirty samples were collected over two harvest seasons, and residues of chlorpyrifos, cypermethrin, and lambda-cyhalothrin were targeted for analysis. Sample preparation involved acetonitrile-based QuEChERS extraction followed by dispersive solid-phase clean-up. Calibration was performed using certified reference standards. Chlorpyrifos was detected in 60% of samples, with 25% exceeding the Codex Alimentarius maximum residue limit of 0.5 mg/kg. Cypermethrin was detected in 40% of samples, with lower proportions exceeding regulatory limits. Seasonal variation was observed, with dry season samples showing higher residue burdens. The findings indicate inadequate adherence to pre-harvest intervals and pesticide application guidelines among tomato farmers in the region. Targeted farmer education programmes and stricter market-level residue monitoring are recommended. Keywords: pesticide residues, tomato, HPLC, Kaduna State, chlorpyrifos.