decreased recovery of a carboxylic acid

[roche_peter]

Question: We are obtaining a decreased percent recovery, of a carboxylic acid product, when it is dissolved in an 86% water / 14% placebo diluent, compared to when it is dissolved in 100% water as diluent. Details as follows:



Mobile Phase: 40% Methanol + 0.1% Trifluoroacetic acid.

Flow rate: 1.3ml per minute. Injection Volume 10µl, Column Temperature 30 C

Column: X-Bridge, C18, 3.5µm, 4.6 x 100mm, Waters

Placebo: Contains PVA, Succinic acid, Sodium Succinate, NaCl, Sodium EDTA, Taurine, pH = 6.3



Has anyone got any experience of this phenomenon that can make some suggestion for obtaining an increased recovery for this carboxylic acid, when it is diluted in 86% H2O + 14% Placebo?



Is it acceptable to prepare the standards in the H2O+Placebo matrix, rather than using water as the diluent?

[Uwe Neue]

It could be adsorption to the placebo matrix, most likely to the PVA, together with adsorption to the vial. You have sufficient operational space to change the composition of the sample and standard by adding methanol and or TFA. Maybe 20% methanol would solve the problem already.