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Quantitative Assessment of Destruxins from Strawberry and Maize in the Lower Parts per Billion Range: Combination of a QuEChERS-Based Extraction Protocol with a Fast and Selective UHPLC-QTOF-MS Assay
journal contribution
posted on 2015-06-17, 00:00 authored by Judith Taibon, Sonja Sturm, Christoph Seger, Hermann Strasser, Hermann StuppnerThe entomopathogenic fungus Metarhizium brunneum is widely applied as a biological
pest control agent. Consequently,
its use has to be accompanied by a risk management approach, which
includes the need to monitor the fate of its bioactive metabolites
in the environment, for example, in treated crops. A fast and selective
UHPLC-QTOF-MS method was developed to monitor the presence of secreted
destruxins in two model food plants for the application of this fungal
biocontrol agent, namely, strawberry and maize. The liquid chromatography–mass
spectrometric assay for destruxin trace analysis is combined with
a novel QuEChERS-based extraction protocol. The whole assay was optimized
for the application in these crops, and it allows quantitative analysis
of the major M. brunneum metabolites destruxin A, 1, destruxin B, 2, and destruxin E, 3, down to the parts per billion range. In strawberry, limits of quantitation
(LOQs) were found to be <2.0 ppb for all analytes; in maize LOQs
were found to be <3.2 ppb for destruxin A and destruxin B. Destruxin
E showed a distinctive loss of recovery in maize and was excluded
from further quantitative analysis in this crop. For both crops assay
linearities ranged from the LOQs to 100 ppb, interassay repeatabilities
(RSD) were found to be better than 16.4%, and accuracies ranged from
83.5 to 105.3% (assessed at four spiking levels between 5 and 75 ppb).