Reversed-phase chromatography comparison

The model for ionic retention and ion-pair chromatography that are discussed in Sections 15.2 and 15.3 has been tested and applied to a number of different systems and works very well in most of the cases. From colloid and surface chemistry is known that the model has its limitations, and under certain chromatographic conditions, the presented model will not be valid. The limitations of the model when applied to reversed-phase chromatography of ions still need to be found. Some are self-evident, such as if the pairing-ion concentration is close or above the CMC or when the retention factor is very low so that the accumulation in the double layer is important in comparison to the adsorption, see Ref. [7] for a discussion concerning the accumulation in the double layer. 

Burgess, R. M., R. A. McKinney, W. A. Brown, J. G. Quinn. 1996. Isolation of marine sediment colloids and associated polychlorinated biphenyls A comparison of ultrafiltration and reverse phase chromatography. Environmental Science and Technology 30 1923. 

An alternative approach for MOCA analysis by HPLC, also involving reverse phase chromatography on a yBondapak Cis column, utilizes the paired ion technique. Paired ion chromatographic (PIC) analysis is effective for the determination of compounds which may exist as ionic species in the polar mobile phase. A counter ion, such as an alkyl sulfonate for cations or tetrabutylammonium phosphate for anions, is added to the mobile phase at a concentration of approximately 0.005 M. This technique generally affords Improved efficiencies in comparison to ion exchange chromatography. For the analysis of MOCA by PIC, the following conditions apply ... 

Popa, T.V., Mant, C.T., and Hodges, R.S. Capillary electrophoresis of cationic random coil peptide standards effect of anionic ion-pairing reagents and comparison with reversed-phase chromatography. Electmphoresis 2004, 25, 1219-1229. 

This paper describes the use of poly(styrene-divinylbenzene) copolymer, PRP-1, as a reverse-phase adsorbent in the assay of the antibiotic aztreonam and related compounds. Comparisons are also made for similar assays using silica-based columns. None of the shortcomings described earlier, associated with bonded phase columns, is observed. In addition to the reverse-phase mode, the PRP-1 columns are tested in ion-pair as well as in size exclusion modes of separation. Superior resolutions are obtained in the reverse-phase chromatography of ionic compounds without the use of lon-palring agents. In addition to the normal adsorption and/or partitioning,... 

In ideal SEC, no interactions between the sample and the support should occur only the pore dimension and the pore size distribution and therefore the volumes related to the porosity and to the interparticle volume can influence the separation. This makes SEC an easy and quick method to handle and to optimize in comparison with other chromatographic techniques such as ion-exchange chromatography or reversed-phase chromatography. Analyses of proteins in SEC are in fact carried out in the isocratic mode and the choice of the mobile phase is only directed to minimize the interactions between the sample and the support surface it does not influence the retention of the analyte when ideal conditions... 

Fausnaugh JL, Kennedy LA, Regnier FE. Comparison of hydrophobic-interaction and reversed-phase chromatography of proteins. J Chromatogr 1984 317 141—55. 

Cumme, G. A., E. Blume, R. Bublitz, H. Hoppe, A. Horn, Detergents of the polyoxyethylene type comparison of TLC, reverse-phase chromatography, and MALDI MS, /. Chromatogr. A, 1997, 791, 245-253. 

Not only in HPLC, but also in modem thin-layer chromatography, the application of reversed-phase stationary phases becomes increasingly important. The advantage of the hydrophobic layers in comparison with the polar, surface-active stationary phases is the additional selectivity and a reduced hkehhood of decomposition of sensitive substances. 

Imaz, C., Navajas, R., Carreras, D., Rodriguez, C., and Rodriguez, F.A., Comparison of various reversed-phase columns for the simultaneous determination of ephedrines in urine by high-performance liquid chromatography, /. Chromatogr. A, 870 (1 2), 23, 2000. 

Hartkopf, J. and Erbersdobler, H. F., Stability of furosine during ion-exchange chromatography in comparison with reversed-phase high-performance liquid chromatography, /. Chromatogr., 635, 151, 1993. 

Dzido, T.H., Kossowski, T.E., Matosiuk, D. (2002). Comparison of retention of aromatic hydrocarbons with polar groups in binary reversed-phase high-performance liquid chromatography systems. J. Chromatogr. A 947, 167-183. 

McCalley, D.V. (2002). Comparison of conventional microparticulate and a monolithic reversed-phase column for high-efficiency fast liquid chromatography of basic compounds. J. Chromatogr. A 965, 51-64. 

Jandera, P., Urbanek, J. (1995). Comparison of chromatographic behavior of oligoethylene glycol nonylphenyl ether non-ionic and anionic surfactants in reversed-phase high-performance liquid chromatography. J. Chromatogr. A 689(2), 255-267. 

---