Sample matrices of different origin were spiked with all the target
compounds at a concentration between 1 and 10 lg/mL and
injected into the GC system using the two selected ratios for standards,
namely sample:MSTFA volume ratios of 2:1 and 2:3. Fig. 2
shows that the second condition led to a marked improvement in
the detection of polyphenols. This enhancement was especially high for most of the compounds in raspberry jam. This could be
attributable to this matrix containing a higher amount of sugars,
which interfere with the derivatization reaction of the target analytes.
On the other hand, a considerable decrease in response for
phloretin 20-O-glucoside, cyanidin-3-O-glucoside, and cyanidin-3-
O-rutinoside was observed in apple samples compared with the
other two fruit samples, likely due to the higher content of organic
acids in this matrix. Although a decrease was noticed for these
three compounds in a certain matrix, in general a considerable
increase was observed in the responses for most of the compounds
when using a 2:3 ratio. This finding may be attributable to the fact
that fruit matrices contain a high concentration of co-extractives,
such as sugars and organic acids, which reduce the derivatization
efficiency of polyphenols. Consequently, a sample:MSTFA volume
ratio of 2:3 was used for further analyzes.