Agriculture Reference
In-Depth Information
techniques have appeared in the last few years for pesticide residues and plant
toxins [7
9]. In these papers, the validation of the methods has demonstrated the huge
amount of work that is necessary, not only to initially validate the methods, but also to
maintain comprehensive AQC that is also essential to check continuing method
performance.
There are two options:
-
i. Determine the responses of each analyte in blank samples and in samples
spiked at the anticipated screening reporting limit (SRL). Thus, there will be a
numerical output and a cutoff value below which there is a de
ned certainty
that the analyte is below the SRL. The advantage of this approach is that
normal statistics can be applied and the numbers of samples used for method
validation can be limited to, say, 20. The disadvantage is that using GC
-
MS or
MS, the SRL will vary with each batch of samples that is subsequently
analyzed and calibration standards will need to be included so that the SRL is
reestablished. This is time consuming especially with respect to large numbers
of analytes.
ii. If a numerical response is not used, then the situation becomes
LC
-
“
detected
”
or
“
Hence, with no numerical response, normal statistics no longer
apply and according to the recently published protocol for validation of
Macarthur and von Holst [2], many more blank and spiked samples are
necessary to give con
not detected.
”
dence for the number of pesticides now being analyzed
during each multiresidue determination.
Qualitative screening multiresidue methods may be used in parallel with estab-
lished validated quantitative MRMs in order to demonstrate the absence/presence of
unexpected analytes. For ef
multiresidue extraction and
cleanup procedure that is used for the quantitative MRMs may be used for the
qualitative MRMs.
It has been recognized for a number of years that full-scan, high-resolution mass
spectrometry (HRMS) offers a means of multianalyte detection of a wide range of
contaminants. Recent publications provide examples of the use of HRMS technol-
ogies (ToF-MS, Orbitrap, etc.) to detect and identify pesticides [10], veterinary
drugs [11], mycotoxins [12], and plant toxins [7].
ciency, the same
“
generic
”
3.3 ELEMENTS OF THE ANALYTICAL WORKFLOW
3.3.1 Sample Preparation
Laboratory samples should be prepared before processing according to regulations
pertaining to
For example, for
pesticide residues, Commission Regulation (EU) No. 212/2013 [13] lists the foods in
groups and de
“
Parts of the product to which the action level applies.
”
nes the parts of the products to which the MRLs apply. So this may
