I am analyzing 20 amino acids now with ethyl chloroformate and MSTFA which is two steps derivatization. Based on the reference, they use ethyl chloroformate and MTBSTFA , but I don't have MTBSTFA now. So my result is not good because several amino acids cannot be detected and I don't know if t is related to MSTFA. Has anyone analyze amino acids with ethyl chloroformate and MTBSTFA and give me some advice?