A rapid on-site analysis method for the simultaneous extraction and determination of Pb(2+) and Cd(2+) in cereals

In order to achieve rapid on-site screening and solve the problem of rapid pretreatment for the determination of lead (Pb(2+)) and cadmium (Cd(2+)) in cereals by a portable electrochemical analyzer with disposable screen-printed electrodes (SPEs), a new reliable and simple extraction method for Pb(2+) and Cd(2+) in cereals was developed. The Pb(2+) and Cd(2+) in cereals were purified by a mixed solution of 1 mol L(−1) potassium iodide (KI)/5% vitamin C (VC)/ethyl acetate after being extracted by 10% HNO(3), which transfers the Pb(2+) and Cd(2+) into ethyl acetate after a reaction with KI–VC. Then, the Pb(2+) and Cd(2+) were eluted from ethyl acetate with 5% HNO(3) and were determined by an electrochemical analyzer with screen printed electrodes. Under the optimized conditions, the matrix calibration curves of Pb(2+) and Cd(2+) in rice and wheat showed good linear relationships with R(2) > 0.996. The method shows a detection limit (LOD) for Cd(2+) in rice and wheat of 6.7 μg kg(−1) and 11.5 μg kg(−1), and the corresponding values for Pb(2+) were 34.9 and 31.1 μg kg(−1), respectively. The relative standard deviation (RSD) was less than 8.7% for Cd(2+) and Pb(2+). In addition, the recoveries of the tested reference materials using this method were between 80% and 120%. From sample pretreatment to testing results, the whole process took no more than 25 min, and the operation was simple for operators, green to the environment, cheap in terms of instruments, and above all suitable for on-site detection. The results implied that this portable electrochemical method with new pretreatment may be a good choice for screening Pb(2+) and Cd(2+) in cereal samples on-site.