Qualitative and Quantitative Analysis of Food Dyes >> Step 2

Qualitative and Quantitative Analysis of Food Dyes

Step 2 - Taking the spectrum of each dye for identification


Taking the spectrum of each dye for identification:
After collecting each dye into a separate vial (remembering to discard the intermediate mixture of the two dyes), water is added to fill each vial to about 2/3 of the height. This is to ensure that the light travels to the detector through the dye solution and not through the air when the vial is placed in the colourimeter. This is a qualitative measurement, so the exact amount of the dye is not important.

Once the spectrum of the unknown dye and its similarly colored standard dyes are taken, we can match them to determine the unknown’s identity.

Since similar dyes have similar spectra, you have to carefully compare the spectrum of your unknown to the spectra of known dyes with similar colour. In the laboratory, the program called ColourMixer (similar to the simulation above) will help you with this process.

Now that we have identified our dyes, we can quantitatively determine their concentrations