Simple washing technique for removal of pesticides and heavy metals from vegetables and mussels

Abstract

Washing is a common practice at home and industry to avoid contamination of germs and dangerous diseases and to remove residual contaminants (pesticides and heavy metals) from vegetables. A commercial vegetable washing solution was tested for the removal of nine organophosphate pesticides (dichlorvos, ethoprophos, disulfoton, parathion-methyl, fenchlorphos, chlorpyrifos, prothiofos, azinphos-methyl and malathion) by soaking the vegetables in the washing solution. Meanwhile, in the heavy metals removal study, the samples were washed with sodium acetate chelating solution to remove four heavy metals, namely arsenic, lead, cadmium and nickel. Method validation study was carried out for the analysis of pesticides and heavy metal residues in term of linear range, repeatability, recovery, limits of detection and limits of quantification. The optimum washing practices for pesticides removal were achieved with five minute washing time, 15 mL washing solution and at temperature of 27°C with swirling. The optimized conditions for heavy metals removal were 1 hour chelating time at temperature of 29.5°C and sodium acetate concentration of 500 mg/L. Results showed that six of the pesticides residues were within the safe permitted levels except for ethoprophos (1.4 - 0.15 ppm) and disulfoton (0.25 - 0.03 ppm). Meanwhile, the removal effectiveness for pesticides and heavy metals from the real samples were in the range of 16.7% - 97.3% and 5.5% - 100.0%, respectively. Among the heavy metals studied, only nickel (0.16 ppm) in long beans achieved the safe permitted level after washing with sodium acetate solution. The results also suggested that continuous process is a better technique compared to combined or individual process since the continuous process achieved lower residual contaminant levels than the allowed maximum residue limit for certain pesticides and heavy metals.