Units of CD spectroscopy

The relationship between CD signal (in absorbance units) and sample concentration and pathlength is analogous to the Beer-Lambert law for absorbance, namely  

A general summaiy of possible CD imits and their interrelationship follows. In absorbance units we write 

CD is often given in terms of the eUipticity, 0. 6 is obtained ftom the ratio of the minor and major axes of the ellipse traced out by the electric field vector of the elliptically polarized light that emerges ftom a circularly dichroic sample onto which linearly polarized light was inddent. 

Most CD spectrometers, although they actually measure differential absorbance, produce a CD spectrum in ellipticity, with imits 0, in millidegrees, versus rather than AA versus X. Most CD machines will perform the conversion from ellipticity to absorbance units on request. 

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