Armstrong-Nome equation

The subscripts ieS and ieM refer to the ion-exchange equilibria at the solution-stationary phase and the solution-micelle interface, respectively. The [C] concentrations are the counter anion concentration in the aqueous phase, aq, including added salts, and the one on the stationary phase, s. is the micellar counterion dissociation constant, (j) is the column phase ratio, [M] is the micellar concentration and k is the anion retention fector. Equation 13.6 obtained from ion-exchange equilibria resembles the classical Armstrong-Nome equation. The Pwm Partition coefficient of eq. 13.6 can be related to the KjeM constant by [30] ... 

Exposed in several chapters is the fact that a strong point of Micellar Liquid Chromatography (MLC) is its capability to give the micellar partition coefficient of the analyzed solute. The Armstrong-Nome equation was presented in Chapters 3 and 5, Equations 3.4 and 5.1. The variations of this equation were also exposed (Eqs. 5.8 and 5.9). 

Chapter 5 discusses the unit problem that exists in the literature listing micellar partition coefficients. The Armstrong-Nome equation gives the PwM solute-micelle affinity coefficient. It is a dimensionless coefficient but valid for one surfactant molecule. The true solute micellar partition coefficient is N with N the micelle aggregation number. Equations 5.8 and 5.9 give an equivalent coefficient whose dimension depends on the concentration unit used. All equations relate linearly 1/k, the retention factor, with [M], the micellar concentration (= surfactant concentration - cmc) in mol/L or in g/L. The relations between the two coefficients are ... 

With Faruk Nome, an ex-member of the Fendler group that was spending some time as a post-doc with Armstrong, they both wrote the cornerstone article estabhshing the theory of MLC selectivity [17]. They proposed the three-phase model (see Chapter 5) and established it with experiments and a supporting theory based on the following equation ... 

Although mentioned in theories of pseudo-phase chromatography, the possibility of a direct transfer of an insoluble or a sparingly water-soluble solute, from the micelle in the mobile phase to die surfactant-coated stationary phase, was largely ignored. For this situation, a modified form of the equation of Armstrong and Nome (eq. 5.1) was derived [29], which successfully accounts for the dependence between k and [M], observed in the elution of such hydrophobic solutes ... 

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