I am currently developing a residual solvent analysis method by Gas chromatography equipped with a flame ionization detector. My sample is an API with a phosphate salt attached. One of the residual solvents of interest is triethylamine. When my sample is spiked with the residual solvents, all other solvents show recovery except for triethylamine with a recovery of ~75 %. I think it is because of the triethylamine reacting with the phosphate salt in the sample. I have tried adding a base such as NaOH to remove the phosphate salt from the sample first, then adding the triethylamine, but the recovery is still not showing. The sampler used is the headspace sampler and the diluent is NMP.
Please let me know if you have any advice on how to make the recovery better.