Influence of epicuticular waxes on the photolysis of pirimicarb in solid phase

PIRISI, FILIPPO MARIA;ANGIONI, ALBERTO;Cabitza M;Cabras P;Maccioni E.

1998-01-01

---

Abstract

The influence of epicuticular waxes extracted from different fruits on the photodegradation of pirimicarb (I) in the solid phase was studied. Waxes were extracted with CHCl3 and CHCl3/CH3OH from nectarines (N), oranges (O-R), and mandarin oranges (M). All of the waxes affect the qualitative behavior of the photodegradation of I: the formation of photoproducts N-formylpirimicarb (II) and demethylpirimicarb (III) was hindered. This influence was found to be independent of the light sources (sunlight or lamp > 290 nm) and of the solvents employed in the extraction of the waxes. The photodegradation rate (K-obs) of I was reduced to a different extent by the presence of waxes, from N and O, and was increased from M (irrespective of the extraction solvent). The photodegradation rates of HH and WI were both reduced by all waxes, M included. The waxes extracted with CHCl3/CH(3)0H show a higher inhibition effect on K-obs than those with CHCl3. The scales of rate reduction were similar under sunlight and artificial light. Inhibition of the photodegradation rate does not correlate with UV absorbance of waxes or with their content on the surface of the fruits.