Agriculture Reference
In-Depth Information
coextracts (e.g., sugars and/or fatty acids). The dSPE is based on the addition of the
sorbent material to an aliquot of the sample extract to remove matrix interferences.
The sorbent is subsequently separated from the extract bulk by centrifugation.
Various sorbents, such as primary
secondary amine (PSA), silica gel, octadecylsi-
lane-bonded silica gel (C
18
), graphitized carbon black (GCB), or their combinations,
are used for this purpose [26,27]. It is noteworthy that in the case of multitarget
methods, the dSPE step is often omitted as it might otherwise decrease recoveries of
some analytes [28]. The main advantages of QuEChERS over traditional extraction
techniques are high sample throughput (15 versus 60 min per sample), use of small
amounts of organic solvents (10 versus 25
-
100ml), less glassware, and employment
of relatively inexpensive laboratory equipment [26,27].
The use of QuEChERS in mycotoxin analysis was reported by several authors who
applied this protocol mainly to cereals and cereal-derived products. In addition to
these types of samples, wine, eggs, beer, fruits and vegetables, spices, oilseed, silage,
milk, and meat were also matrices extracted for mycotoxins by employing a
QuEChERS-type procedure (Table 8.2). Regarding the target analytes, the majority
of studies focused on legislatively regulated mycotoxins and/or
Fusarium
mycotox-
ins. Several papers reported methods with broader scope, which in addition to the
above analytes also included ergot alkaloids, alternaria toxins, and other mycotoxins
produced by
Penicillium
and
Aspergillus
species. QuEChERS was also employed for
simultaneous multiclass extraction of mycotoxins with other contaminants such as
pesticides and veterinary drugs [24,29
-
31]. Table 8.2 provides an up-to-date over-
view of publications dealing with applications of QuEChERS to mycotoxin analysis
and summarizes time demands of the extraction step [24,28
-
45].
The optimal QuEChERS-based extraction protocol largely depends on the type of
matrix to be examined. Therefore, many modi
-
cations of the original QuEChERS
design have been developed to
fit particular sample types. The most important
parameters of the QuEChERS method, which have a signi
cant impact on recovery
and other performance characteristics of the method, are the composition of extraction
mixture, extraction time, type and amount of salts added, and the ratio between
organic solvent volume and sample weight (matrix dilution factor, ml/g) [26]. Cereals
and cereal-based products represent typical dry matrices that are frequently extracted
for mycotoxins using QuEChERS. The matrix dilution factors applied to such
samples are usually either 2.0 or 2.5 (i.e., 4 or 5 g of test sample and 10 ml of
organic solvent). The volume of water used in published studies varied signi
cantly
and was in the range of 2
10ml. The soaking of the sample matrix and/or prolonged
extraction times were shown to be crucial in achieving suf
-
ciently high recoveries of
mycotoxins using QuEChERS-based extraction of cereals and similar dry sam-
ples [24,29]. However, longer extraction times ultimately result in diminished sample
throughput. On the other hand, matrices with naturally high water content, such as
vegetables, fruit, milk, beer, and wine, do not require soaking and can be processed at
much higher throughput even without the addition of water (see Table 8.2).
Regardless of the type of matrix, the extraction ef
cacy should always be assessed
based on naturally contaminated reference materials rather than with the use of spiked
samples. Improvement in recoveries of some problematic (acidic) analytes can be
