PolyCyclic Acetate peptid - residual solvent

[Ivo]

Hi!
I am in the middle of validation of method for residual solvents in some Poly-Cyclic Acetate Peptide. The problem occurred with spiked sample with Anisole which is prepared in 1% Acetic/H2O solution. After injection of about 12 samples, the problems start with lost of standards and sample for about 50% (recovery). Extra washing up system with blanks between samples helps in the beginning but than, system get bed recovery again. My guess for now is that Acetic acid from sample has big influence on recovery... Acetic acid peak disappeared in sequences where I got lost of Anisole... it seems that merge with peak of Acetone.
Does anyone have experience with such an analysis and maybe some solution for problem?
Method properties:
Column: VF-624 70x0.53x3.0
Injector temp: 150 C
Detec. Temp: 300 C (FID)
Carrier: He, constant flow 6.7 ml/min
Split: 12:1
Inj. volume: 1 uL

Thanks,
Ivan

[chromatographer1]

My guess is that you are contaminating the injector with peptide and this is causing your problem.

I would suggest a headspace analysis for anisole of your sample after adding a non-volatile strong mineral acid like sulfuric acid to acidify the solution. Why methoxybenzene would be lost in your matrix is unclear to me, but acidic solution might be a solution?

good luck,

Rod

[Ivo]

Thanx Rod

I was thinking about HS, but right now I am limited with this method (not mine). I will certainly try to make new HS method and presented it to owners of method.

Best wishes,
Ivan