Which technique is used to separate red food dye from a mixture of food dyes?

The technique used to separate red food dye from a mixture of food dyes is paper chromatography. This method is particularly effective for separating and identifying different components in a mixture based on their differing rates of migration across a stationary phase (the paper) when a solvent moves through it.

In paper chromatography, the mixture is placed on a piece of chromatography paper, and a solvent carries the components up the paper. Because different substances travel at different speeds, they will separate into distinct spots along the paper. For food dyes, this technique allows for clear separation, enabling the identification of the red dye based on its unique retention factor (Rf) value compared to other dyes present in the mixture.

The other methods listed would not be suitable for this specific purpose. Fractional distillation is used to separate components in a liquid mixture based on differing boiling points, often for liquids, not colored dyes in a solution. Filtration is intended for separating solids from liquids or gases but would not work effectively for separating dissolved dyes from each other. Simple distillation, similar to fractional distillation, separates substances based on boiling points but is generally used for purifying liquids rather than separating mixtures of soluble substances like food dyes.