Additive effects on surfactant adsorption and ionic solute retention in micellar liquid chromatography

A Submicellar Liquid Chromatographic Method for Quantitative Determination of Muscle Relaxant Drug Baclofen in Solubilized System

“…Several reports reveled that the high organic solvent content in the mobile phase decreases the thickness of the surface coating [1][2][3]. A systematic perusal of literature reveled that hitherto methods [4,5] using high submicellar liquid chromatography to optimize chromatographic conditions are developed and validated.…”

Evaluation of Some Empirical Retention Models for High Submicellar Liquid Chromatographic Separation of Aromatic Diamines

“…Most studies in MLC use a short-chain alcohol such as methanol, propanol, butanol, or pentanol [1,2] as an additive to micellar mobile phases to improve the peak shape and efficiency and increase the elution strength [3,4]. These organic modifiers decrease the mobile phase polarity and affect the amount of surfactant adsorbed on the stationary phase; also, micelle parameters, such as the CMC and surfactant aggregation number (i.e., number of surfactant monomers associated in a micelle), are altered through addition of modifier [5][6][7].…”

Stationary-phase effects on efficiency in micellar liquid chromatography

“…However, the problem of reduced efficiency in MLC still remains [3,4] despite extensive study [2][3][4][7][8][9][10][11][12][13]. Reduced efficiency in MLC has been attributed to several factors, including (i) poor wetting of the hydrophobic stationary phase by the aqueous mobile phase [2]; (ii) slow mass transfer between the micelles, the bulk aqueous phase, and the stationary phase; and (iii) dynamic modification of the stationary phase due to surfactant adsorption [3,4,8,[16][17][18][19][20][21][22][23], which further reduces mass transfer within the stationary phase.…”

“…With conventional porous HPLC phases (pore diameters of 150Å or less), the micelles are largely excluded from the pores by steric constraints and therefore do not have access to the analytes except when they have diffused out of the pores into the interstitial region. In addition to steric constraints, it is well known that surfactant monomers adsorb onto the stationary phase [5,7,8,12,19,21,22]. When ionic surfactants are employed, the resulting charge buildup on the stationary phase within the pores gives rise to a Donnan-like potential that will tend to repel like charged species from the pore, especially large structures such as micelles whose dimensions (typically 30-60Å [24]) are commensurate with pore diameters of typical (small-pore) ODS phases most commonly used in RPLC.…”