INVESTIGADORES
CASTELLS Cecilia Beatriz
artículos
Título:
Effect of temperature on the chromatographic retenion of ionizable compounds. II. Acetonitrile-water mobile phases
Autor/es:
L. G. GAGLIARDI; C. B. CASTELLS *; C. RÀFOLS; M. ROSÉS; E. BOSCH
Revista:
JOURNAL OF CHROMATOGRAPHY - A
Editorial:
Elsevier
Referencias:
Lugar: Amsterdam; Año: 2005 vol. 1077 p. 159 - 169
ISSN:
0021-9673
Resumen:
The retentive behavior of weak acids and bases in
reversed-phase liquid chromatography (RPLC) upon changes in column temperature
has been theoretically and experimentally studied. The study focuses on
examining the temperature dependence of the retention of various solutes at
eluent pH close to their corresponding pKa
values, and on the indirect role exerted by the buffer ionization equilibria on
retention and selectivity. Retention factors of several ionizable compounds in
a typical octadecylsilica column and using buffer solutions dissolved in 30% v/v acetonitrile as eluent at five
temperatures in the range from 25 to 50ºC were carefully measured. Six buffer
solutions were prepared from judiciously chosen conjugated pairs of different
chemical nature. Their pKa
values in this acetonitrile/water composition and within the range of 15 to
50ºC were determined potentiometrically. These compounds exhibit very different
standard ionization enthalpies within this temperature range. Thus, whenever
they are used to control mobile phase pH,
the column temperature determines their final pH. Predictive equations of retention that take into account the
temperature effect on both the transfer and the ionization processes are
evaluated. This study demonstrates the significant role that the selected
buffer would have on retention and selectivity in RPLC at
temperatures higher than 25ºC, particularly for solutes that coelute.