Internal standard

[smkh]

Hello every one;

I want to start developing method of bioequivalence study on LC-MS/MS for lisinopril , I want to ask any one have agood experience about this drug, can I use Enalapril malete as internal standard .......
all papers that i read it use enalaprilat as internal standard , no body use the maleat one
I will try it but iwould like to know if there is any reasons, or if any body know any thing of its problems

thanks alot

[alpesh]

hi smkh
we have successfully used enalapril maleate as IS in lisinopril bioequivalence study. the extraction method was solid phase with HLB cartridge of waters. we have performed several study with this method. it will work on any API instruments, we have done it on API 3000

[smkh]

hi alpesh

thank u for replying

Im trying enalapril maleate as internal standard and it gives me good results in tuning m/z 234

but no peak appears when do injection on LC........
using mobile phase isocratic 70%MEOH,30%H2O;0.1%FA without column:?:

[alpesh]

gh

[alpesh]

hi
u can use 100 X2.1 mm 5 µm Id column
also try to take another ion
also bypass LC and inject standard into MS manually to check whether LC is giving problems
hope this will help
alpesh