Remediation of fungicide residues on fresh produce by use of gaseous ozone

Abstract

Ozone fumigation was explored as a means for degrading organic fungicide residues on fresh produce. Fungicides sorbed onto model abiotic glass surfaces or onto grape berries were fumigated separately in a flow-through chamber. Gaseous ozone at a constant concentration of 150 ± 10 ppmv (µL•L -1) selectively oxidized fungicides sorbed to model surfaces. Over 140 min, boscalid and iprodione levels did not change significantly based on a single-factor analysis of variance (ANOVA) at the 95% level of confidence (p = 0.05); however, pseudo-first-order losses resulted in observable rate constants of ozonolysis, k ozonolysis (min -1), of 0.0233 ± 0.0029 (t 1/2 ? 29.7 min), 0.0168 ± 0.0028 (t 1/2 ? 41.3 min), and 0.0127 ± 0.0010 (t 1/2 ? 54.6 min) for fenhexamid, cyprodinil, and pyrimethanil, respectively. The relative degradation of fungicides on berries at gaseous ozone concentrations of 900 ± 12 ppmv (µL•L -1) over 2 h was similar to that on glass; decreases in residue concentration were observed for only fenhexamid (~64%), cyprodinil (~38%), and pyrimethanil (~35%) with corresponding k ozonolysis (min -1) of 0.0085 ± 0.0021 (t 1/2 ? 81.5 min), 0.0039 ± 0.0008 (t 1/2 ? 177.7 min), and 0.0036 ± 0.0007 (t 1/2 ? 192.5 min). Heterogeneous rate constants of gaseous ozone reacting with a sorbed fungicide, k O3(M -1•min -1), were calculated for both surfaces and indicate losses proceed ~15-fold slower on grapes. The kinetics and mechanism of fungicide removal, supported by gas chromatography- and liquid chromatography-mass spectrometry product analyses, is discussed in the context of facilitating compliance with maximum residue level (MRL) tolerances for fresh produce. © 2011 American Chemical Society.