Aminoacid analysis

[tony83]

Hello, I have a problem with aminoacid analysis,(24 aminoacid)
I used a OPA method with FLD detector
Eluent A : 40mM NaH2PO4 pH 7,8
Eluent B : ACN/MeOH/Water 45:45:10

gradient
time A B
0 100 0
40,5 59,5 40,5
41 39 61
43 39 61
44 18 82
44,5 0 100
46,5 0 100
49 100 0

Is impossible all separetion the peaks overlopped and i see only 15 aminoacid
Can help me?
Thanks

[unmgvar]

have you injected all of them separately as well to see who falls where?

[tony83]

the problem is cisteine and cistine because i can't see them..... Why? OPA is derivation for primary amine and Cisteine is a primary amine....
I hope that this method is correct for aminoacid with S-S group

thanks
bye