The supernatant was separated and the solid-state sample was extracted once again with
a further 20 ml of the solvents mixture. The extracts were collected and H3PO4 was added drop wise to pH 2. The SPE polyamide cartridges were conditioned by 4 ml of MeOH and 2 ml of water. The extract was flowed slowly through the cartridges (1 ml min1). SPE
columns were washed with 2 ml of water and gently vacuum-dried for 30 s. The colorants were eluted with 4.5 ml of a methanol/1% ammonia solution (1:1 v/v) in a graduated test tube. The final extractwas made up to a final volume of 5 ml with the same solvent
mixture and 20 ml of solution were injected into the HPLC.