Investigations on the use of analyte protectants for multiresidue GC analysis
Matrix-induced enhancement effects are well-known to seriously affect
measurement accuracy in GC applications, mostly leading to overestimated
results, when using the convenient matrix free calibration standards.
There are various approaches on how to deal with matrix effects: Intensive
cleanup of the extracts, instrument maintenance measures including the use of
inert materials may reduce but not eliminate this effect. The use of matrixmatched
standards and the standard additions approach can effectively
overcome this problem, but they are often troublesome. The use of isotopically
labelled ISTDs is the best approach, but it is currently not feasible in
multiresidue analysis due to the high price and limited availability of the
standards.
The use of “analyte protectants” (APs) was first introduced 4 years ago, at the
EPRW in Rome, as a concept to deal with the notorious problem of matrix
effects [1-3]. APs are chemicals, that are added to sample extracts and
calibration solutions (e.g. prepared in neat solvent) to improve chromatographic
behaviour of pesticides and to equalize the matrix effects. The function of APs
is to interfere with the interactions that pesticides undergo with active sites on
the GC-inlet and column surfaces and that typically lead to degradation and/or
peak broadening in GC separations. The most effective APs are polar
compounds with the ability to undergo H-bonds such as sugars and their
derivatives. APs are added, individually or in mixtures, to extracts at
concentrations much higher than those of the pesticides to be protected.
In the initial study some representative pesticides were tested [2,3]. In this study
the influence of APs on a greater number of GC-amenable pesticides and their
applicability in routine multiresidue analysis is being investigated.
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