To test linearity standard mixtures of four
different concentrations (from 1 to 250 mg
L 1) were prepared and analyzed. To construct
calibration plots for E 104 and
E 142 the sum of the peak areas was measured.
The coefficients of determination of
the food colorants varied from 0.9992 to
0.9999. The equations of the calibration
curves, coefficients of determination, and
the wavelengths selected for detection of
the colorants are presented in Table II.
To test peak area and retention time repeatability
a standard mixture of colorants
(c = 50 mg L 1) was analyzed by
HPLC (n = 15); the results are shown in
Table III. Retention time relative standard
deviations (RSD) were from 0.50%
(E 131) to 3.02% (E 151). Calculation of
peak areas resulted in RSD between
0.39% (E 133) and 4.38% (E 151). The lim