Penetrative and Dislodgeable Residue Characteristics of ¹⁴C-Insecticides in Apple Fruit

Abstract

Infinite- and finite-dose laboratory experiments were used to study the penetrative and dislodgeable residue characteristics of (14)C-insecticides in apple fruit. The differences in dislodgeable and penetrated residues of three radiolabeled insecticides ((14)C-thiamethoxam, (14)C-thiacloprid, and (14)C-indoxacarb), applied in aqueous solution with commercial formulations, were determined after water and methanol wash extractions. The rate of sorption and extent of penetration into the fruit cuticles and hypanthium of two apple cultivars were measured after 1, 6, and 24 h of treatment exposure, using radioactivity quantification methods. For all three compounds, 97% or more of the treatment solutions were found on the fruit surface as some form of non-sorbed residues. For indoxacarb, sorption into the epicuticle was rapid but desorption into the fruit hypanthium was delayed, indicative of a lipophilic penetration pathway. For the neonicotinoids, initial cuticular penetration was slower but with no such delay in desorption into the hypanthium.

Determination of imidacloprid and its relevant metabolites in tomato using modified QuEChERS combined with ultrahigh‐pressure liquid chromatography/Orbitrap tandem mass spectrometry

“…Then 5‐OH IMI, 4‐OH IMI and 4,5‐diOH IMI are dehydrated into olefin IMI, which is further oxidized to carbonyl IMI. This metabolic pathway is different from the reported ‘four‐way’ mechanism shown in Fig. .…”

“…Possible structures of metabolites were confirmed by MS (Fig. ), which was carried out on both chlorine‐containing isotopic ions and the characteristic fragment ions similar to those of standard compounds (according to the metabolites of IMI in the literature).…”

“…[6][7][8][9] The environmental behavior of IMI metabolites in soils, animals and plants has been researched extensively, but there has been no comprehensive study on the forced metabolic mechanism of IMI. Summarizing various research studies, the metabolic pathway of IMI can be summed up in four ways [10][11][12][13][14][15][16] (i) denitrification directly generates guanidine IMI, which is then further oxidized to carbonyl IMI (urea IMI); (ii) reducing nitro to nitroso derivatives, nitroso into guanidyl IMI; (iii) oxidizing imidazolidine rings, forming 5-OH IMI, 4-OH IMI or 4,5-dihydroxyl IMI (4,5-diOH IMI), then dehydration into olefin IMI; (iv) IMI forms different conjugates with coexisting small molecules (amino acids, maltose, glucose, succinic acid, etc.) ( Fig.…”

Spatial and temporal distribution of trunk-injected imidacloprid in apple tree canopies

“…Legislative restrictions by the US Environmental Protection Agency (EPA) and European law on registration, evaluation and authorization of chemicals (REACH) have led to elimination, restriction or registration limitations for many pesticides . Further, more restrictive standards regarding environmental impacts, worker exposure and dietary risks for use of pesticides have been implemented …”

“…2,3 Further, more restrictive standards regarding environmental impacts, worker exposure and dietary risks for use of pesticides have been implemented. 4 Along with these changes, new protective compounds, such as the EPA-designated reduced-risk and organophosphate alternative pesticides, received expedited registration for agriculture use. Among them, a class of neonicotinoid insecticides was introduced with expectations of minimal impact on non-target organisms, human health and contamination of the environment.…”