respect to the traces obtained for the same sample by applying
classical solvent extraction or PLE.
Method repeatability for different food types was tested by
replicate analyses of the same spiked or unspiked sample (n = 4–
6). Good repeatability with relative standard deviation (RSD)
always lower than 9 was found for all the product types.
Since no certified reference material (with known amount of
mineral oil) is commercially available, method accuracy was
assessed with recovery tests performed on 4 different cerealbased
foodstuffs of different composition (dry pasta, bread, biscuits
and plum cake), using the standard addition procedure described
in Section 2.4.
Table 1 reports the amounts of MOSH and MOAH added, average
MOSH and MOAH recoveries, and RSD. The average recoveries
ranged from 89 to 104 for the MOSH and from 85% to 108% for the
MOAH with RSD lower than 10.
For the semolina pasta, recoveries obtained (4 replicate analyses)
for MOSH and MOAH at 2 different fortification levels were
practically quantitative, with RSD lower than 8.
Concerning the bread samples, standard addition was performed
on the extra virgin olive oil used to prepare the bread as
described in Section 2.4. The amount added is expressed for the
whole product (before cooking). For recovery calculation, the loss
of water occurring during cooking was also considered. The sample
prepared with the unspiked oil presented a little contamination
coming from the flour, which, for recovery calculation (3 replicates),
was subtracted from the contamination of the spiked sample.
Extraction yields over 90% were obtained also in this case.
The biscuit sample used for recovery test was a baby food product
containing 8% fat (extra virgin olive oil). Fig. 1 reports MOSH
and MOAH traces of the unspiked and spiked samples, and of the
respect to the traces obtained for the same sample by applyingclassical solvent extraction or PLE.Method repeatability for different food types was tested byreplicate analyses of the same spiked or unspiked sample (n = 4–6). Good repeatability with relative standard deviation (RSD)always lower than 9 was found for all the product types.Since no certified reference material (with known amount ofmineral oil) is commercially available, method accuracy wasassessed with recovery tests performed on 4 different cerealbasedfoodstuffs of different composition (dry pasta, bread, biscuitsand plum cake), using the standard addition procedure describedin Section 2.4.Table 1 reports the amounts of MOSH and MOAH added, averageMOSH and MOAH recoveries, and RSD. The average recoveriesranged from 89 to 104 for the MOSH and from 85% to 108% for theMOAH with RSD lower than 10.For the semolina pasta, recoveries obtained (4 replicate analyses)for MOSH and MOAH at 2 different fortification levels werepractically quantitative, with RSD lower than 8.Concerning the bread samples, standard addition was performedon the extra virgin olive oil used to prepare the bread asdescribed in Section 2.4. The amount added is expressed for thewhole product (before cooking). For recovery calculation, the lossof water occurring during cooking was also considered. The sampleprepared with the unspiked oil presented a little contaminationcoming from the flour, which, for recovery calculation (3 replicates),was subtracted from the contamination of the spiked sample.Extraction yields over 90% were obtained also in this case.The biscuit sample used for recovery test was a baby food productcontaining 8% fat (extra virgin olive oil). Fig. 1 reports MOSHand MOAH traces of the unspiked and spiked samples, and of the
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