Development of a methodology based on QuEChERS-dSPE/UHPLC-PDA to quantify pesticide residues in potatoes

Pesticides have been associated to human health hazards, ranging from headaches to cancer or, reproductive and endocrine system disruption. Inappropriate use of pesticides may cause damage to the environment, increase resistance in the target pest organisms and deleterious effects of non-target organisms. The European Union (EU) set directives for pesticides usage, establishing maximum residue limits (MRLs) in fruits and vegetables. It is very important to monitor if the pesticide residues are below the MRLs in food matrices and to evaluate if they pose a risk to the health of consumer and environment. The purpose of this work was to develop a fast and sensitive analytical method to identify and quantify common pesticide residues in potatoes based on a quick, easy, cheap, effective, rugged, and safe (QuEChERS) procedure combined with ultra-highpressure liquid chromatography tandem with photodiode array system (UHPLC-PDA). The parameters that affect the QuEChERS/UHPLC-PDA efficiency, such as extraction solvent, buffered salts, stationary phases, gradient conditions, and eluents were optimized. The optimal parameters were 50% of acetonitrile (ACN) acidified with 0.1% phosphoric acid (PhA) and, magnesium sulfate: sodium chloride: disodium hydrogen citrate sesquihydrate: trisodium citrate dihydrate (1:1:1/2:1) ratio was used. Moreover, 30 min ultrasound time was added and for clean-up magnesium sulfate and primary secondary were used. The selected column was CORTECS with a gradient program combining an aqueous solution acidified with 0.1% PhA and ACN, a flow rate of 150 µL/min at 30 ºC. After optimization, the method was validated according to IUPAC guidelines. The validated method showed to be selective for the studied pesticides, and showed satisfactory performance in terms of linearity, with correlation coefficient (r2) higher than 0.997. The limits of detection (LOD) ranging from 0.005 (chlorpyrifos) to 2.581 (thiabendazole) mg/L, whereas the limit of quantification (LOQ) limit from 0.015 (chlorpyrifos) to 7.821 (thiabendazole) mg/L. In relation to the accuracy, the obtained values varied between 87.7 and 214.2 %, while in precision, the coefficients of variation remained in general below to 20 %. In terms of matrix effect, the values ranged between 87.6 and 185.8 %, which agreed with results reported by other studies.