Ethion residue removal efficiency using individual and combined effects of ultrasonication (US), ozonation (O3), ultrasonication and ozonation (US/O3) was investigated. A 1 mg·L-1 standard ethion was subjected to an ultrasonic irradiation (3W input power) device with different frequencies of 108, 400, 700, 1000 kHz, and to an ozone with a concentration of 200 mg· mL-1 with various exposure times (0, 15, 30, 45 and 60 minutes). Reduction of residual ethion was determined by gas chromatography with flame photometric detection (GC-FPD). It was found that 1000 kHz ultrasonic irradiation for 60 minutes was the most effective treatment for reducing ethion concentration. Additionally, ozone could reduce the concentration of standard ethion after 60 minutes of exposure. Ultrasonic irradiation in combination with ozone had a synergistic effect in reducing standard ethion concentration, with the highest rate occurring within the first 15 minutes. Ethion concentration was reduced to 75.43% after ultrasonic irradiation at 1000 kHz and ozone exposure for 60 minutes. The effectiveness of the combined scheme for reducing of ethion residues on tangerine was also determined by GC-FPD. The ethion residue on fresh tangerines after ultrasonic irradiation and ozone washing was reduced by 73.03% after 60 minutes. The present study demonstrates that ultrasonic irradiation and ozone exposure could be used to reduce ethion residues in treated tangerine in order to meet the Standards for Pesticide Residue Limits.
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