Internal standard

[chandra]

Hello all,
I am using tropic acid as internal standard but i am facing some problem.Some time i don,t get the peak of the internal standard in the chromatogram.Why it is happening i don,t know.The concentration of standard is 10mmol/l.

Thanks

[Don_Hilton]

There is a lot of detail not given here. GC? LC? solvent? ??

[chandra]

I am using GCMS and solvent phase which i am using is ethyl acetate and GCMS condition is as follows
Injection volume – 1µl
Injection Source – Manual
Column – HP-5MS 5% Phenyl Methyl Silox
325°C:30m x 250µm x 0.25µm
Oven Program
50°C for 3 min
then 10°C/min to 140°C for 1 min
then 20°C/min to 280°C for 3min
Derivatizing reagent is BSTFA:TMCS in which equal volume of pyridine is added and then used.

[Don_Hilton]

Some times you do not get the peak for tropic acid. Then what happens? If you inject the sample and make another run, do you see the peak? Does it show up with injection from another vial? The trick here is to figure out what is common in the loss or reappearance of the peak.

And one of the ususal questions. How long has it been since the septum was replaced on the inlet.