Operating principles of a spectrofluorometer

1) Rhodamine B is most frequently used as a quantum counter, but the advantage of rhodamine 101 is that its fluorescence 

A reference channel (quantum counter or photodiode) has two advantages (i) it compensates for the time fluctuations of the lamp via a ratiometric measurement (ratio of the output signals of the photomultiplier detecting the fluorescence of the sample to the output signal of the reference detector) (ii) it permits correction of excitation spectra (see below). 

Emission and excitation spectra were deflned in Chapter 3 using the following expression for the measured fluorescence intensity 

It is important to recall that Ip is proportional to the concentration only in dilute solutions [A(Ae) 0.05) Eq. (6.1) is then reduced to 

2) In contrast, a spectrophotometer measures an absorbance, a quantity that is ejq)ressed on an absolute scale. 

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