An analytical procedure utilizing infrared techniques has been developed for the quantitative determination of glutamic and α-ketoglutaric acids for samples containing milligram quantities of these acids. The infrared spectra of the samples in KBr pellets was determined on a Beckman IR-8 infrared spectrophotometer using double beam, slow scan, gains of 5.2% to 5.6% and attenuation to 97% T at 3846.2 cm−1. For preparation of the pellets, approximately 400 mg of KBr (IR grade, E. Merck, Darmstadt, Germany), was used. Better dispersion of the sample was achieved by mixing a part of the KBr with the sample in an agate mortar and combining this mixture with the rest of the KBr in the capsule of a Wig-L-Bug (Crescent Dental Mfg. Co., Chicago, Ill.) along with a nylon ball (⅛ in.). Twenty seconds agitation completed the mixing. The mixture was transferred to the die and the pellet prepared in the usual manner.
Frances L. Estes, Albert L. Myers, and Sharon Briney, "The Analysis of Mixtures of Glutamic and α-Ketoglutaric Acids by Infrared Spectroscopy," Appl. Spectrosc. 24, 131-132 (1970)