Non-hygroscopic water-soluble crystals of ammonium d-10-camphorsulfonate(ACS) were prepared and proposed as a practical secondary standard substance for the calibration of circular dichroism(CD) to replace deliquescent d-10-camphorsulfonic acid(CSA). ACS gave the same CD, ORD and molar rotation, [M]D, as CSA within an error of 1%. The molar ellipticity, [θ]290.5+7910 (c=0.06, water) was obtained by the CSA standard solution method, by which CD and [M]D were critically measured with a CD apparatus and a high precision polarimeter, respectively. The [M]25D+52.06 or [α]25D+20.88 (c=6, R.S.D. 0.1%) was used to check the optical purity.
The Japan Society for Analytical Chemistry