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Analysis of Residues of Dithianon - Analytical Observations and Method Report

Dithianon is a foliar fungicide with protective and curative action used to control a variety of foliar diseases on a wide range of crops including table and wine grapes, pome fruit, stone fruit, berries, spinach, lettuce, brassica crops, solanaceous crops and rice.
Using the original citrate buffered QuEChERS method (EN 15662) very low recoveries of dithianon are obtained from commodities with high pH. Also low recoveries are obtained when dSPE cleanup with PSA. Acidification during the QuEChERS extraction step helps to improve the recovery rates. Sulfuric acid offers better protection than formic acid or acetic acid. If no ILIS is used to compensate recovery losses extraction with 1% sulfuric acid is indicated, especially for commodities having high natural pH. Using dithianon-D4 as IS recovery losses can be effectively compensated provided that it is added at a very early step in the procedure. As losses of dithianon are very rapid in high-pH commodities it is of paramount importance to conduct analysis as fast as possible and keep sample temperature low. Acidification during sample comminution helps to reduce losses further.
The report on analytical observations can be found here: Link to Observations Report.

In the proposed method the pesticide is extracted using the QuEChERS method under acidic conditions (either acidified with sulfuric acid or with formic acid in combination with Dithianon-D4 as IS) and directly analysed by LC-MS/MS in the ESI (neg.) mode without dSPE cleanup involving PSA-sorbent: Link to Method.



Published 03-05-2016, 10:52:01

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