2.3.2. Pretreatment of food samples
Samples from several fresh parts of lamb and chicken (muscles
and the liver), fish, honey, and milk were selected for analysis and
purchased from local supermarkets to be examined by the developed
method to pretreat lamb muscles and liver, chicken, and fish
samples, and to homogenize the samples (5 g), 15 mL of ACN and
5 g sodium sulfate were added [17]; the samples were place in an
ultrasonic bath for 5 min; and then, they were centrifuged for
10 min at 4000 rpm. Next, the supernatant liquid phase was separated
and applied to the remaining solid sample, again. At last
30 mL ACN was collected and the solid sample was discarded. The
collected ACN was concentrated to 1 mL under N2 bubbling at
40 °C. Then, it was diluted with an aqueous solution (pH 12.0) to
20 mL and left in an ultrasonic bath for 10 min. Finally, the proposed
extraction method was applied to this prepared solution.
SAs bound to sugars could affect the residue analysis of honey.
In addition, hydrolysis experiments showed that a considerable
amount of bound SAs may be released in acidic environments [18].
Thus, the 5-g honey sample, which was stored at 4 °C, was dissolved
in 5 mL of 2 mol L1 HCl and shaken for 20 min. Then, it
was diluted to 10 mL and the pH of the filtered sample was adjusted
to 12 by the addition of 10 mL of NaOH solution (2 mol L1
).