Question

Primary and secondary coulometric titration

Answer 1

Primary colorimetric determination uses a binding dye that has a known lambda max, and then you will measure the concentration (beer lambert law) based on the absorbance. Primary determination involves a functional group of the dye that intrinsically fluoresces. For example, highly conjugated (lots of double bonds!) chemicals are detectable at certain wavelengths. Example: the Bradford assay binds to proteins instantly and is absorbance is easily measured. Secondary colorimetric determination often involves enzyme catalysis in order to produce colour, which can then be subsequently measure at x wavelength... As is the case with immunological tests such as ELISA.