It shows three
peaks corresponding to relative isomers. The sum of the three
peaks was used for determination of recoveries and precision
validation data. Figs. 1e3 show chromatograms related to three
samples spiked with red (group AeB together), yellow (group C)
and blue dyes (group D).
DAD detector higher signal was obtained by setting pertinent
wavelengths for each group of dyes. For red colorants, wavelength
for quantificationwas fixed at 515 nm as a reasonable average of the
maximum absorptions within the red colorants. For yellow dyes 2
different wavelengths were set: E102, E104 and metanil yellow
were monitored at 420 nm, while E110 and orange II were observed
at 480 nm. For blue dyes DAD wavelength was set at 620 nm.
Fortification levels for allowed food colors in foodstuffs were
chosen in accordance to legislation limits. For unauthorized dyes in
solid matrices, spiking levels was slightly lower. It was estimated
that significant quantities of colorant should be added to foodstuffs
for changing color appearance. For this reason, validation of illegal
red dye in solid matrices was carried out at the ppm order of
magnitude.