Edible oil-based switchable-hydrophilicity solvent liquid–liquid microextraction for the determination of lead in food samples using flame-atomic absorption spectrometry

Edible oil-based switchable-hydrophilicity solvent liquid–liquid microextraction (EO-SHS-LLME) was used prior to the determination of lead as its metal chelate with ammonium pyrrolidine dithiocarbamate (APDC) by flame-atomic absorption spectrometry. Optimum extraction conditions were achieved using 600 µL of coconut oil as the extraction solvent, pH of sample solution adjusted to 4.50 and containing 1.0% (w/v) APDC, within 5.0 min complexation time, a 300 µL of 2.0 M sulfuric acid as the hydrophilicity switching-off trigger, and 150 µL of 8.0 M nitric acid as the back-extraction solution within 4.0 min back-extraction time. The limits of detection and quantification were found as 2.8 and 9.4 µg g⁻¹, respectively. Good linearity was obtained with coefficients of determination (R²) higher than 0.9961. Intraday and interday precision, expressed in terms of relative standard deviation, were less than 4.0% and 4.6%, respectively, while the linear dynamic range was from 12.6 to 175.0 µg g⁻¹. Accuracy was checked by addition-recovery tests and percentage recoveries were found to be within the range of 97.1–106.0%. The proposed method was applied for the determination of lead in food samples (i.e., carrot, fish, onion, potato and yam) and satisfactory results were achieved.