Analysis of pesticide residues in potato varieties using modified quechers multi-residue method combined with gas chromatography tandem mass spectrometric detection

Regular monitoring of pesticide residues in potatoes (Solanum tuberosum L.) is important to ensure a low risk of pesticide toxicity to consumers. An efficient, modified quick easy cheap effective rugged safe-dispersive-solid-phase extraction (QuEChERS- d-SPE) was optimized and validated for quantification of pesticide residues (metalaxyl, chlorpyrifos, lambda-cyhalothrin, and cypermethrin) in popular Kenyan potato varieties "Shangi," "Tigoni," and "Dutch Robyjn," grown under controlled field conditions using gas chromatography with tandem mass spectrometry (GC-MS/MS). An evaluation of the effect of five spraying frequencies (unsprayed, 5, 7, 10, and 14-day intervals) of metalaxyl-based fungicides on residue levels in harvested potatoes was simultaneously done. Metalaxyl residue levels in the varieties were determined for each spraying regime. Method validation showed good linearity (r2) of 0.988-0.999, detection limit (0.37-0.61 mu g/L), quantification limit (1.20-1.84 mu g/L) while recovery (71%-94%), and precision (relative standard deviation of 2.3%-24.1%) were used to determine the accuracy of the method. Pyrethroids (cypermethrin and lambda-cyhalothrin) and organophosphates (metalaxyl and chlorpyrifos) were detected in the potato samples. Residue levels of the compounds were not significantly different (p = 0.05) between varieties except for chlorpyrifos. Cypermethrin was the residue compound detected at the highest mean level with 17.4 mu g/L, followed by metalaxyl, chlorpyrifos, and lambda-cyhalothrin, at 2.88, 1.05, and 0.15 mu g/L, respectively. Residue levels at different spraying frequencies varied statistically between varieties (p = 0.05). Dutch Robyjn sprayed at seven days' intervals had the highest residue level of 9.49 +/- 0.26 mu g/L. QuEChERS-d-SPE with GC-MS/MS has shown suitability for routine pesticide residue monitoring in potatoes. The potatoes grown under the controlled experimental conditions did not present any concern for human health, as the pesticide residues detected were below Codex maximum residue levels of 500 mu g/L. Potato field production in Kenya is characterized by intensive pesticide application.There is limited data available locally about the type of pesticide or their residue levels present in potatoes.Pyrethroids and organophosphates were detected and quantified in the potato samples.Cypermethrin was the highest residue compound detected, though below Codex MRLs while lambda-cyhalothrin was the lowest.Highest residue in cypermethrin in Dutch Robyjn, metalaxyl in Shangi, and chlorpyrifos and lambda-cyhalothrin in Tigoni.