Influence of Epicuticular Waxes on the Photolysis of Pirimicarb in the Solid Phase

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 CHCl(3) and CHCl(3)/CH(3)OH 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 II and III were both reduced by all waxes, M included. The waxes extracted with CHCl(3)/CH(3)OH show a higher inhibition effect on K(obs) than those with CHCl(3). 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.

Determination of famoxadone, fenamidone, fenhexamid and iprodione residues in greenhouse tomatoes

“…The trial with fenhexamid showed a further decrease in the residue after 16 days. Literature data report photodegradation as being mainly responsible for pesticide dissipation in the field 20–24. A parallel experiment carried out on peaches, in the field and in greenhouses, showed a higher decrease in the studied pesticides in field 25.…”

Effect of surface waxes on the persistence of chlorpyrifos-methyl in apples, strawberries and grapefruits

“…We can hypothesize that the radiation is adsorbed by wax, and only the λ that penetrate the waxes can interact with the pesticide molecule. This decrease in radiation intensity results in a decrease in the rate of photodegradation (Pirisi et al, 1998).…”

Photolysis of pesticides: influence of epicuticular waxes from Persica laevis DC on the photodegradation in the solid phase of aminocarb, methiocarb and fenthion

“…The photodegradation under sunlight or λ > 290 nm lamps of pirimicarb (Fig 1; 1 ) and fenthion ( 2 ), is qualitatively and quantitatively affected by the presence of the amorphous waxes extracted from different fruits or drupes ( eg oranges, nectarines, tangerines and olives) 1. 2 Among the different waxes used, the behaviour of nectarine wax ( Persica laevis DC) appeared unique, showing different quantitative and qualitative effects on the photodegradation of the two compounds.…”