Combinations of specific eluents and reversed-phase solid-phase extraction cartridges were found to prevent matrix effect due to phospholipids.

Following this discovery, a reproducible method was developed and successfully validated for ramipril and ramiprilat. Additional stability tests were performed in the presence of glucuronide and diketopiperazine metabolites of ramipril and ramiprilat to demonstrate the method specificity.

We have shown that high pH modifiers are sufficient to induce a signal enhancement for the majority of compounds detected under LC-ESI+-MS/MS.

This strategy demonstrated its usefulness by removing co-eluting isobaric interference, and reducing chemical background ions from the mobile phase, while drastically improving S/N.