Abstract
Monosodium glutamate (M. S. G.) often contains L-cystine which shows a prominent peak in the high-sensitivity square wave A. C. polarogram. The cystine in M.S.G. was confirmed by comparing its summit potential with that of the standard cystine solution in the supporting electrolyte of high-purity M.S.G. The summit potential of cysteine wave observed after the reduction of cystine with sodium sulfite also coincided well with that of pure cysteine added to M.S.G. By the method of standard addition the cystine content in a commercial M.S.G. was found to be 00.12%. Trace of lead did not interfere with the determination.
