Absorbance spectra of food dyes in the red-violet color range.

(A) Schematic diagram of a color wheel illustrating the emission wavelengths (inner circle) and absorption wavelengths (outer circle) of visible light (in nanometers; nm). The inner circle represents the emission color of the indicator dye and the outer circle represents the color of the quencher required to absorb the emission. For example, ANG-2 has a peak emission wavelength of 540 nm (green), therefore it can be expected that red-violet colored dyes will quench the emission (B) Absorbance spectra of Brilliant Black BN, Carmine, Ponceau 4R, Allura Red and Amaranth, Calcium 4 Assay and BD Quencher. Grey shaded area represents the FLIPR^TETRA detection range (FDR). (C) International Numbering System for Food Additives (INS) E number, common name(s), color and peak absorption (λ max) of food dyes tested.