Page 13 - BR20828_E Accucore 0713S
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can occur. Figure 14 demonstrates the
stability of the Accucore C18 column at 70°C,
where it can be seen that even with 400
injections there is no loss of performance at
these elevated temperatures with a
water/methanol mobile phase. The stability
of these columns at 70°C under more
aggressive mobile phase conditions (for
instance, pH extremes) has not been tested
to date.
Conclusion
The data presented in this article illustrates
solid-core chromatographic supports exhibit
less band broadening through eddy diffusion
and resistance to mass transfer than fully
porous chromatographic supports. As a
result, solid-core columns exhibit higher
efficiency than fully porous columns and a
lower rate of efficiency loss with linear
velocity. From the columns compared in this
study, the Accucore 2.6µm material is the
most efficient per unit length of column and
the most efficient per unit time, with the fully
porous sub-2µm performing similarly.
Impedance is a term that defines the
resistance a compound has to move down
the column relative to the performance of
that column. Sub-2µm fully porous and solid-
core materials show similar values of
efficiency, however the impedance is directly
proportional to the pressure drop across the
column. Solid-core particle packed columns
show a pressure drop that can be half or
even less that of a fully porous sub-2µm
particle packed columns. Therefore,
Accucore columns provide higher efficiency
(more resolving power) than fully porous
columns for the same nominal pressure (or
’bar for bar‘) and can, in most cases, be used
in conventional HPLC instrumentation. The
higher efficiencies of solid-core columns
result in reduced peak widths and increased
peak capacities. Narrower chromatographic
peak widths have advantages such as
improved resolution and improved
sensitivity (better signal-to-noise ratios),
particularly important in trace analysis and
impurity profiling.
Column selectivity is still the most effective
way of controlling resolution of a
chromatographic separation. To make solid-
core columns a serious contender in the
analytical laboratory, manufacturers need to
ensure these materials are available in a
range of stationary phase chemistries for
method development.
Band broadening in the column is
significantly reduced with the solid-core
chromatographic supports. However, in
order to fully harvest this gain, extra column
band broadening needs to be considered
and minimised through consideration of
system volume and optimisation of detector
acquisition parameters. Whereas UHPLC
equipment has been designed to have
reduced system volume, conventional HPLC
equipment often needs some attention when
operating with high performance columns
such as the solid-core materials.
Columns used in fast, high efficiency
separations are often stressed considerably
through chemical and physical operating
parameters. The ruggedness and durability
of these materials needs to equal or exceed
that of traditional HPLC columns. The
robustness of Accucore columns under pH
extremes and elevated temperature was
demonstrated in this paper.
References
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Figure 14: Accucore column stability at 70° C. Experimental Conditions: Column - Accucore C18 2.6
µ
m, 100 x
2.1mm; Mobile phase: 35:65 (v/v) Water/Methanol; Flow rate: 400
µ
L/min; Injection volume: 1.5
µ
L;
Temperature: 70°C; Detection: UV at 254nm (0.1s rise time, 20Hz); Order of elution: 1. Theophylline/Caffeine
(t0), 2. Phenol, 3. Butylbenzene, 4. o-Terphenyl, 5. Pentylbenzene/Triphenylene.
AR20526_E 06/12S
