Liophilic Mobile Phase Additives in Reversed Phase HPLC

Abstract

The separation of basic compounds can be challenging and the use of inorganic mobile phase additives have been successfully used in chromatographic methods development. About fifteen years ago the role of these additives as ioninteraction agents for selectively adjusting retention of ionic analytes was discovered and the theory of chaotropicity was applied to reversed phase chromatography. In the last ten years the studies of the influence of these counterions on the retention of ionizable analytes and the interaction with the stationary phase in various hydro-organic eluents has expanded our knowledge of this phenomenon.The general view and understanding of the process have been significantly updated and the use of these ionic additives (liophilic ions) in the mobile phase has become regular practice in the pharmaceutical industry for optimization and fine tuning of complex separations. This paper reviews the latest developments in the field and discusses the modification and expansion of our theoretical understanding of the process. The paper also describes their application in practical separations for a wide variety of analytes, from small molecules to peptides and even chiral separations.

Search for improved fluorinated stationary phases for separation of fluorine-containing pharmaceuticals from their desfluoro analogs

“…In general, the perfluroalkyl columns show comparable selectivity to the perflurophenyl columns, suggesting no special role for aromatic vs. aliphatic stationary phases. The perchloric acidbased mobile phase shows significantly better chromatographic performance in all cases, consistent with the effect of liophilic additives on ionized basic analytes [21,22]. The UHPLC studies show comparable results, with substantially faster separations than those obtained via HPLC.…”

Investigation into reversed-phase chromatography peptide separation systems Part IV: Characterisation of mobile phase selectivity differences

“…This affects the way in which the peptides interact with the stationary phase. Both kosmotropic and chaotropic salts follow the Hofmeister series [11,12], which describes the minimum concentration required to salt out proteins [47][48][49][50][51][52]. As shown in section 3.3, both the chaotropic salts PF 6and ClO 4 -, which are also anionic ion-pair reagents yielded interesting selectivities at low pH.…”

Static vs. Dynamic Electrostatic Repulsion Reversed Phase Liquid Chromatography: Solutions for Pharmaceutical and Biopharmaceutical Basic Compounds

“…In the first case, protonated bases and anionic additives (inorganic as well as organic) provide the formation of neutral adducts and can be resolved by a reversed phase mechanism. In the second case, the anionic additives, especially those bearing a hydrophobic portion, can be adsorbed onto the stationary phase, promoting an electrostatic interaction similarly to a strong or weak anion exchange stationary phase [37][38][39][40][41]. In these elution conditions, the anionic silanols are not shielded by counterions; however, their effect on the peak distortion can be negligible.…”