307 / 413
•
5
•
2007.01
Pharmaceutical
pHidelity™ C18 Columns
Physical Characteristics:
3µm Column, 4.6mm
cat. #
price
30mm
9579335
$440
50mm
9579355
$440
100mm
9579315
$455
150mm
9579365
$470
ordering
note
For guard cartridges for these columns, visit our website at
www.restek.com.
To order a column with a Trident
™
inlet fitting, add -700 to the
column’s catalog number.
particle size: 3µm
pore size: 200Å
pH range: 1 to 12
temperature limit: 80°C
pHidelity
™
C18 Guard Cartridges
qty.
cat. #
price
10 x 2.1mm
3-pk.
957930212
$131
10 x 4.0mm
3-pk.
957930210
$131
20 x 2.1mm
2-pk.
957930222
$131
20 x 4.0mm
2-pk.
957930220
$131
retained (Figure 2A). In contrast, using an extend-
ed range pHidelity™ C18 column and a mobile
phase pH above the highest pKa of the analytes, the
compounds will be uncharged and more
hydrophobic, resulting in greater retention (Figure
2B). The analysis of basic compounds using a high
pH mobile phase is an easy way to increase reten-
tion and to enhance resolution and peak shape.
This makes a simpler task of method development,
especially for complex test mixtures.
Non-silica-based chemistries have been developed
in attempts to overcome the pH constraints of con-
ventional silica-based HPLC columns, but silica-
based phases offer a number of advantages, includ-
ing high efficiencies, consistent lot-to-lot repro-
ducibility, and predictable selectivities. Silica-based
pHidelity™ pH-stable columns offer selectivity
similar to conventional materials, but with dramat-
ically increased column lifetime, even under the
most harsh conditions. Figure 3 shows equivalent
comparisons of a pHidelity™ C18 column and a
conventional C18 column in an accelerated life-
time test under high pH conditions, at pH 10 and
60°C. This test demonstrates that pHidelity™
columns have a much greater lifetime when used in
caustic environments than conventional C18
columns. Additionally, the pHidelity™ packing
material is based on a true silica particle, ensuring
a more C18-like selectivity than any competitive
column based on non-silica or hybrid materials.
If your separation would benefit from extended
pH conditions, we recommend you take advantage
of pHidelity™ column for extreme-pH stability,
C18-like selectivity, and long lifetimes. To discuss
your separation, or for more information, please
contact Restek’s HPLC technical service group,
and we will be happy to discuss how you can
improve your analysis, and make fewer column
replac ments, by using pHidelity™ column.
Figure 2
Using a high pH mobile phase is an easy way to
improve peak retention, resolution, and symmetry in a test mix of
compounds varying in pKa values.
Sample:
Inj.:
10µL
Conc.:
100µg/mL each component
Sample diluent: acetonitrile
Column:
C18
Dimensions:
150 x 4.6 mm
Particle size:
3µm
Pore size:
200Å
Conditions:
Mobile phase:
20mM ammonium acetate
(pH 4):acetonitrile 50:50
Flow:
0.75mL/min.
Temp.:
ambient
Det.:
UV @ 254 nm
1. lidocaine
2/3. verapamil/diphenhydramine
4. nortriptyline
LC_PH0363
LC_PH0392
A) Poor separation of bases under typical conditions
conventional C18
column, pH 4
B) Complete separation of bases on a pHidelity™ column at pH 11
Column:
pHidelity
™
C18 (cat.# 9579365)
Dimensions:
150 x 4.6 mm
Particle size:
3µm
Pore size:
200Å
Conditions:
Mobile phase:
10mM ammonium bicarbonate
(pH 11): acetonitrile:
tetrahydrofuran, 35:55:10 (v/v/v)
Flow:
1.5mL/min.
Temp.:
ambient
Det.:
UV @ 254 nm
1. lidocaine
2. verapamil
3. diphenhydramine
4. nortriptyline
Lifetime comparison.
Hours exposed to 50mM triethylamine (TEA), pH 10, 60°C
0.0000
0.1000
0.2000
0.3000
1.0000
1.1000
1.2000
1.3000
Conventional C18
pHidelity C18
90
80
70
60
50
40
30
20
10
0
Efficiency (Normalized)
Figure 3
pHidelity™ C18 columns - exceptional performance under
accelerated high pH stability testing conditions.