eJournal ISSN 2196-3460

»Volume 2017 Issue 01 (November)

Improvement of Ethoxyquin Yields and Recoveries from Pears through the Addition of Ascorbic Acid

Anne Benkenstein, Sabine Mögle, Ellen Scherbaum and Michelangelo Anastassiades

EU-Reference Laboratory for Pesticides Requiring Single Residue Methods (EURL-SRM)
hosted at Chemisches und Veterinäruntersuchungsamt Stuttgart
Schaflandstraße 3/2
70736 Fellbach, Germany
Email: Anne.Benkenstein@cvuas.bwl.de

Keywords:

Ethoxyquin, Pesticides, Residues, Pears, Ascorbic acid, Analysis, LC-MS/MS, Environmental

Abstract

Ethoxyquin (EQ) is a quinoline-based antioxidant widely applied to inhibit superficial scald (formation of brown spots) in pears and apples. EQ typically shows low recoveries when extracted from commodities with low antioxidative potential such cereals, most vegetables, and some fruits (including pears). The impact of adding ascorbic acid (AA) at different stages of the procedure to protect EQ was studied, u sing pears with incurred EQ residues as well as pears that were superficially spiked in the laboratory. It was shown that extensive degradation occurs during milling, irrespective if conducted cryogenically or at ambient temperature. By adding AA to the sample prior to milling (1 g AA per 100 g sample) EQ losses declined dramatically. In the case of cryogenic milling a single addition of AA prior to milling provided sufficient protection throughout the procedure. During ambient milling, however, AA consumption was much higher requiring supplementary AA addition prior to QuEChERS extraction for sufficient protection. The average EQ r ecoveries (spiked to pear homogenates at 0.05 mg kg^-1 and 0.2 mg kg^-1) reached 98 % if AA had already been added to the blank pears during milling and 86 % if AA was added directly after EQ spiking. RSDs ranged between 1 % and 8 %. From 2014 onwards 82 pear samples from the local market were analyzed for EQ residues with the analysis involving addition of AA prior to milling. Three pear samples analyzed in 2014 (all from Italy) were found to contain ethoxyquin residues at levels between 0.25 and 0.58 mg kg^-1. There have been no further findings of EQ in pear samples since 2015.