AUG 17, 2016 08:00 AM PDT

A Comparison of the Challenges in the Quantification of Fosetyl-Al Tree Nut Residues with CESI-MS/MS and LC-MS/MS

  • Director of Research Chemistry, DFA of California
      Dr. Wiley Hall currently serves as the Director of Research Chemistry at the DFA of California where he is in charge of fumigation and chemistry research. He received his PhD in chemistry from the University of Delaware where he researched mass spectrometry and atmospheric chemistry. Previously, he worked for the Battelle Memorial Institute in Aberdeen Maryland, developing methods to detect toxic compounds in the environment. He came to the San Joaquin Valley in 2011 and carried out post-doctoral research on methyl bromide recapture following post- harvest fumigations and new analytical methodology to measure fumigant and pesticide residues in agricultural technologies.


    The export of tree nuts to the European Union (EU) is subject to a maximum residue limit (MRL) of 1.5 ppm for the fungicide fosetyl-Al. As fosetyl-Al readily hydrolyzes to phosphonic acid, the residue of fosetyl-Al is quantitated as the “sum of fosetyl, phosphonic acid, and their salts”. Unfortunately, phosphonate in tree nut extracts can originate from several sources other than fosetyl-Al, particularly when analyzed according to the EURL-SRM method, and if levels of fosetyl-Al exceed the MRL it impacts the export of tree nuts to the EU from the US (valued at $2.7 billion in 2014). The results from a multi-instrument, inter-laboratory study have recently demonstrated the limitations of the current EU methodology, which include:: poor extraction efficiency in tree nuts, low repeatability and of particular concern, false positive results obtained when high levels of phosphate (regularly found in California tree nuts) are present. In this presentation we will discuss the use of capillary electrophoresis, coupled to tandem mass spectrometry (CESI-MS/MS), an orthogonal technique to LC-MS/MS, which has been found to offer a promising alternative addressing these challenges.

    Learning Objectives:

    • Learn about the challenges the tree nut industry is currently facing for exporting tree nuts into the EU
    • See the results produced from a multi-instrument, inter-laboratory study demonstrating the limitations of current methodology for the analysis of fungicides.
    • Learn about an alternative CESI-MS/MS based methodology for analyzing fungicides which overcomes the limitations and technical challenges present with currently utilized methods.

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