Selection of suitable stationary phases and optimum conditions for their application in the separation of basic compounds by reversed‐phase HPLC

Abstract

In this review, some aspects of the separation of basic compounds by HPLC are discussed with especial reference to work carried out by the author. Procedures for column evaluation are explained, together with the effect of mobile phase modifier, pH, temperature, nature of buffer, and sample overloading on the chromatography of basic compounds. Some evaluations of new column types, such as embedded polar group phases, monoliths, and hybrid inorganic/organic phases are presented.

Photo‐polymerized lauryl methacrylate monolithic columns for CEC using lauroyl peroxide as initiator

“…24 mm. Similar efficiencies were achieved for RP columns, in particular XTerra RP18 and XBridge C18, two columns with low-silanophilic activity [43], with theoretical height plates ranged between 16-25 mm. In any case, it can be observed that symmetric peaks were obtained in CEC due to suppressed electrostatic interaction between the neutral solutes and the positively charged monolithic surface, then; these stationary phases were suitable for the analysis of basic compounds.…”

Selectivity of some basic solutes on a poly(methyltetradecylsiloxane)‐silica stationary phase

“…Some solutes have better peak shapes at one pH and other solutes have better shapes at another pH, as previously observed by McCalley [4,7]. On the PMTDS-SiO 2 stationary phase, higher retention factors were observed with tricine and tris buffers at nominal pH 8 than with phosphate buffer at nominal pH 8 ( Table 1).…”

“…The development of stationary phases that separate ionizable solutes by a combination of hydrophobic and ion-exchange mechanisms, providing enhanced selectivity for some difficult-toseparate compounds [2,3], is an area of increasing interest. Such specialized stationary phases offer the flexibility of using simpler mobile phases, thereby avoiding ion-pair reagents, exotic buffer systems, extreme pH conditions and complex mobile-phase preparations [4][5][6][7].Thermally immobilized polysiloxane stationary phases occupy a prominent place, having been studied for more than 20 years in our research group [8][9][10][11]. They show interesting selectivities for basic solutes due to the combination of hydrophobic and ion-exchange properties [12][13][14], consistent with the Neue et al [3] ''three site model''.…”

Stationary phase characterization and method development

“…The datasets are smaller than those discussed above, and the goal was not necessarily a characterization of the stationary phases per se. For example, McCalley recently reviewed his test procedure for the suitability of stationary phases for the analysis of basic compounds in an article in the Journal of Separation Science [104]. The test uses nine bases of very varied structure at different pH and mobile phase compositions to assess the properties of stationary phases [105,106].…”