Amino Acid Separation (L-Cysteine)


I'm currently do the development of the method for L-Cysteine separation by HPLC on tablet product. My reference method is based on the Agilent Method which is the Amino Acid Analysis Using Zorbax Eclipse-AAA Columns and the Agilent 1100 HPLC by John W. Henderson, Robert D. Ricker, Brian A. Bidlingmeyer, and Cliff Woodward. Before this, we already developed the method for L-Lysine based on this reference method also. 

I'm facing the problem on the derivatization of the L-Cysteine with the OPA as well as the FMOC. My concern now is either the derivatization was not complete or the reaction was not happened since there were no peak being eluted out when i tried with the API (L-Cysteine HCL Anhydrous). FYI, trials had been done using exactly the reference method i mentioned earlier. 

Next, may i know more details on DTDPA Reagent for analysis of cysteine. (Since it was mentioned on the ordering information but there was not mentioned in the procedure of the method)

Hoping someone can enlighten me why this problem happened or is there any precautions steps i need to take after this. 

Here i put my details for further discussions,

Muhammad Amran

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