To test linearity standard mixtures of four different concentrations (from 1 to 250 mgL 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