A spectropolarimeter works much like a UV/Vis Spectrophotometer, only with a twist. The light is literally twisted in a helical waveform, and the absorption of left and right circularly polarized (Twisted) light is measured. This effect is called Circular Dichroism, so the machine is often referred to as a CD machine.

Only compounds that are asymmetric, that is, compounds in which the mirror image of the compound cannot be superimposed on itself, will show an absorption in the CD machine. For most everyday types of chemistry, we don't worry about whether or not a compound is asymmetric, but in drugs and in biological compounds, this asymmetry becomes extremely important. For example, a drug made with the incorrect stereoisomer (mirror image) will have no effect on the body at all, while the correct stereoisomer will have a correct effect.

CD machines are not found in many graduate schools, and are extremely rare in undergraduate schools like BHSU. Our JASCO J-41A may be the only machine of this kind in a several-hundred-mile radius. While this instrument was built before the days of computer interfaces, we have made our own data interface and can acquire data in a digital format. We also have a thermostated cell holder, so we can study the CD of a sample as a function of its temperature. This allows us to monitor the denaturation of proteins and DNA.

We use our CD machine at BHSU to support biochemical research, and in classes like Chem 460 Biochemistry, and Chem 434, Instrumental Analysis.