SUGGESTED PRELIMINARY STANDARDS FOR CALIBRATION OF OPTICAL ROTATORY DISPERSION AND CIRCULAR DICHROISM INSTRUMENTS

Two approaches have been used in the present study in an effort to define preliminary circular dichroism (CD) standards. The first involved a careful reexamination of 10-camphorsulfonic acid using the Kronig-Kramers transform to compare optical rotatory dispersion (ORD) and CD curves. The second approach utilized tris(ethylenediamine) cobalt triiodide hydrate, a compound relatively easy to prepare and resolve and one for which three independent sets of absolute rotation values have been reported. Experience has shown that the angle measuring portion of a recording spectropolarimeter may not be in correct adjustment, and that the error may be a function of the full scale reading. This section of the instrument should therefore be checked against suitable ORD standards before attempting to use ORD values to establish a CD calibration. It is clearly undesirable to use ordinary UV or visible spectrometric values as a substitute for polarimetric values in deciding the optical purity of an intended standard. © 1969, American Chemical Society. All rights reserved.