“…Additionally, even when ion-pair agents, such as trifluoroacetic acid [14], or ion suppressing agents, such as triethylamine [15], are used, the MS response is greatly decreased. Proposed alternative solutions of using bare silica, dynamically modified silica, or alumina [16,17] have not yet not gained widespread acceptance. Despite these negative effects RP-HPLC is still the most widely used method, because of the fast equilibration time, the selectivity characteristics, and the retention reproducibility.…”