Published:Journal of Chromatographic Science,
ISSN 0021-9665Volume 41, Number 7, August 2003, pp. 350-358
Improvement of Peak Shape and Separation Performance of b-Blockers
in Conventional Reversed-Phase Columns Using Solvent Modifiers
M.J. Ruiz-Angel, J.R. Torres-Lapasió, S. Carda-Broch,
and M.C. García-Alvarez-Coque
Departament de Química Analítica, Facultat de Química,
Universitat de València, Dr. Moliner 50, 46100 Burjassot (València),
Spain
A comparative study of peak shape, elution behavior, and resolution
of 16 b-blockers (acebutolol, alprenolol, atenolol, bisoprolol, carteolol,
celiprolol, esmolol, labetalol, metoprolol, nadolol, oxprenolol, pindolol,
practolol, propranolol, sotalol, and timolol) chromatographed with hybrid mobile
phases of triethylamine (TEA)–acetonitrile and sodium dodecyl sulfate
(SDS)–propanol is performed using conventional reversed-phase columns
and isocratic elution. Both solvent modifiers (TEA and SDS) prevent the interaction
of the basic drugs with the alkyl-bonded phase. However, the protection mechanisms
of silanols on the packing are different. Whereas TEA associates with the silanol
sites (blocking ion-exchange processes or repelling the solutes), the long
hydrophobic chain of SDS is inserted in the bonded organic layer with the sulfate
group protruding outside, which makes the stationary phase negatively charged.
The effects of TEA, acetonitrile, SDS, and propanol on the elution strength,
efficiency, peak asymmetry, and resolution are examined under an experimental
design basis that is assisted by computer simulation to reach more general
conclusions. The combination of improved peak shapes, larger selectivity, and
a smaller range in retention among compounds of extreme polarity leads to the
observation that a greater number of b-blockers can be resolved with a hybrid
micellar system.
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