3. Results and discussion
3.1. MAS procedure
Simultaneous microwave assisted saponification and
unsaponifiable extraction was first applied to pasta samples and
later to other cereal-based products with different moisture and
fat content.
With respect to the conditions used by Akpambang et al. (2009)
for PAH extraction from fish and meat tissues (400 mg of lyophilised
sample added with 1.6 mL of water, 8 mL of saturated
methanolic KOH and 20 mL of n-hexane), a higher amount of sample
(5 g) was processed in order to achieve higher sensitivity. The
amount of saturated methanolic KOH was slightly increased to
10 mL, while the amount of n-hexane used was reduced from 20
to 10 mL to limit organic solvent consumption and to obtain a
more concentrated extract. Since an excess of KOH is required to
ensure complete fat hydrolysis (Pena et al., 2006), when processing
samples with more than 25% of fat, the volume of the saturated
methanolic KOH solution was increased to 20 mL. Under these conditions
fat hydrolysis was complete (no fat traces were found in the
residue obtained after evaporation of the hexane extract), and an
excess of KOH remained in the aqueous extract.
Comparative trials carried out in triplicate on different aliquots
of the same dry sample (semolina pasta) added and not with water
(2 mL) before the MAS, demonstrated that the water content of the
sample does not significantly affect the results. Nevertheless, to
obtain similar water content and uniform extraction conditions,
dry foods, such as pasta and biscuits, were added with 2 mL of
water. For what concerns extraction temperature and time, the
same conditions (120 C for 20 min) previously used for PAH determination
in fish and meat tissue (Akpambang et al., 2009) and later
for propolis samples (Moret et al., 2010) were utilised.
The effect of the MAS treatment was preliminary investigated
on C10–C40 n-alkanes mixture, internal standard mixture, paraffin
oil and printing ink solvent, which were analysed in duplicate. No
appreciable differences in the chromatographic areas were
observed with respect to the same standards which did not
undergo the MAS procedure, demonstrating that MAS does not
cause analyte losses or artefacts formation in the absence of the
matrix.
3. Results and discussion3.1. MAS procedureSimultaneous microwave assisted saponification andunsaponifiable extraction was first applied to pasta samples andlater to other cereal-based products with different moisture andfat content.With respect to the conditions used by Akpambang et al. (2009)for PAH extraction from fish and meat tissues (400 mg of lyophilisedsample added with 1.6 mL of water, 8 mL of saturatedmethanolic KOH and 20 mL of n-hexane), a higher amount of sample(5 g) was processed in order to achieve higher sensitivity. Theamount of saturated methanolic KOH was slightly increased to10 mL, while the amount of n-hexane used was reduced from 20to 10 mL to limit organic solvent consumption and to obtain amore concentrated extract. Since an excess of KOH is required toensure complete fat hydrolysis (Pena et al., 2006), when processingsamples with more than 25% of fat, the volume of the saturatedmethanolic KOH solution was increased to 20 mL. Under these conditionsfat hydrolysis was complete (no fat traces were found in theresidue obtained after evaporation of the hexane extract), and anexcess of KOH remained in the aqueous extract.Comparative trials carried out in triplicate on different aliquotsof the same dry sample (semolina pasta) added and not with water(2 mL) before the MAS, demonstrated that the water content of thesample does not significantly affect the results. Nevertheless, toobtain similar water content and uniform extraction conditions,dry foods, such as pasta and biscuits, were added with 2 mL ofwater. For what concerns extraction temperature and time, thesame conditions (120 C for 20 min) previously used for PAH determinationin fish and meat tissue (Akpambang et al., 2009) and laterfor propolis samples (Moret et al., 2010) were utilised.The effect of the MAS treatment was preliminary investigatedon C10–C40 n-alkanes mixture, internal standard mixture, paraffinoil and printing ink solvent, which were analysed in duplicate. Noappreciable differences in the chromatographic areas wereobserved with respect to the same standards which did notundergo the MAS procedure, demonstrating that MAS does notcause analyte losses or artefacts formation in the absence of thematrix.
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