5. Measurement methods

We'll confine ourselves to the measurement of circular dichroism, which, as we said earlier, is the approach mainly used today, and which can be carried out in three ways.

• The most obvious method is to measure the absorbance of the solution with right-hand circularly polarized light, then with light polarized in the opposite direction, and make the difference. However, this requires very high precision, as the difference between the two absorbances is usually very small (ΔA/A can typically be of the order of 10 ^-4 ).

• Another possibility is to measure the ellipticity of the light beam leaving the solution when illuminated with plane polarized light. Since the minor axis of the ellipse is very small compared with the major axis, plane polarized light of very high...