A NUCLEODUR C18ec column (Macherey–Nagel, Dueren,
Germany, 150 mm 4.6 mm i.d.), with a medium density octadecyl
modification, endcapped with spherical shaped 3 lm particles
and with a carbon load of 17.5% was used for the separation.
The mobile phase consisted of eluent A, ammonium acetate 1%
(pH 7.0, adjusted with ammonium hydroxide); and eluent B,
methanol:acetonitrile (80:20). The gradient elution program is
shown in Table 1. The injection volume was 20 lL. The flow rate
was 1.2 mL min1
, the column temperature was maintained
between 38–40 C and the mobile phase was passed through
0.45 lm membrane filter. The food colorants were determined at
427–624 nm.
3. Results and discussion