Vanish dynamics of chlorpyrifos in spinach and effect of post-harvest washing on spinach safety.

The residue vanish dynamics of chlorpyrifos in spring open-field spinach(Spinacia oleracea L.)after sprayed with 750 fold dosage(48%emulsion),and the effect of post-harvest washing on microbe and chlorpyrifos of spinach were investigated to direct the safety management of spinach from field to market.The results showed that the first class degradation dynamic model of chlorpyrifos in spinach was C=9.542 2 e-0.361t,which predicted the half-life period of chlorpyrifos was 1.92 d,and the safe interval time for spring open-field spinach was 12.6 days when met the standard of GB 2763—2005,which required maximum residue limit of chlorpyrifos was 0.1 mg·kg -1 .Postharvest washing for 1 minute by tap water,5 mg·kg -1 chlorine dioxide(ClO2),10 mg·kg -1 ClO2,100 mg·kg -1 hypochlorite(NaClO)and ultrasonic(26 kHz and 450 W)respectively reduced 1 log total bacterial counts,but there still existed 270 cfu·g -1 coliform after treated by 10 mg·kg -1 ClO2,which meant the microbe safety was still a problem,even if some disinfectants were used for commercial washing.NaClO was found to help reducing the residue of chlorpyrifos and ultrasonic was a good washing assistant technology for reducing the residue of chlorpyrifos and microbe counts.The single washing and disinfecting technology could not entirely assure the safety of spinach,so the combined technologies including two or more technologies were suggested to improve the safety of spinach and postharvest fruits and vegetables.