Page 17 - BR20828_E Accucore 0713S
Basic HTML Version
Technical Note 20542
From Equation 1, pressure is inversely proportional to
the square of the column ID and therefore decreasing the
column ID results in a significant increase in pressure. In
practical terms however, if the column is run at a typical
linear velocity, the pressure measured will also be typical
for that system set-up. Mobile phase linear velocity is the
flow rate normalized for the column cross-section.
For instance, if a method is transferred from a 4.6 to a
2.1 mm ID column, all other operating parameters kept
unchanged, and the 2 columns are run at the same linear
velocity, then the measured pressure drop across both
columns will be the same.
Effect of Mobile Phase Viscosity on Pressure
Column operating pressure is affected by the mobile
phase composition. Viscosity is a property of each
solvent, which varies with temperature. The proportion
the solvent is mixed with other mobile phase components
and the operating temperature will determine the mobile
phase viscosity. The pressure drop across the column
itself will also have an effect on the viscosity since it
affects the effective column temperature. Figure 3 shows
how water viscosity varies with the addition of aceto
nitrile or methanol. Water/methanol mixtures are more
viscous than water/acetonitrile mixtures and therefore
using methanol as the organic modifier in reversed-phase
LC produces higher pressure drops across the column.
When mobile phase gradients are used the mobile phase
composition and therefore the viscosity changes during
the run, which results in a change of pressure during the
chromatographic run.
Conclusion
•
Pressure is dependent on column length, ID, and
particle size
•
Pressure is dependent on mobile phase flow rate
and viscosity
•
Accucore 2.6 µm particle packed columns show
approximately half of the pressure of a sub-2 µm fully
porous particle packed column and approximately
double that of a 3 µm fully porous particle packed
column
•
Accucore columns can be run at high flow rates on
conventional HPLC equipment and are rated to 600 bar
Figure 3: Mobile phase viscosity changes with the composition.
Water/methanol mixtures can be up to 80% more viscous than
water/acetonitrile mixtures.
TN20542_E 10/12M
USA and Canada
+1 800 332 3331
Australia
1300 735 292
(free call domestic)
China
+86 21 68654588
+86 10 84193588
+86 20 83145199
800 810 5118
France
+33 (0)1 60 92 48 34
Germany
+49 (0) 2423 9431 20 or 21
India
+91 22 6742 9494
+91 27 1766 2352
Japan
+81 3 5826 1615
United Kingdom
+44 (0) 1928 534 110
New Zealand
0800 933 966
(free call domestic)
All Other Enquiries
+44 (0) 1928 534 050
Technical Support
North America
+1 800 332 3331
Outside North America
+44 (0) 1928 534 440
For more information, visit our website at
©2012 Thermo Fisher Scientific Inc. All rights reserved. All trademarks are the property of Thermo Fisher Scientific Inc. and its subsidiaries.
This information is presented as an example of the capabilities of Thermo Fisher Scientific Inc. products. It is not intended to encourage use of these
products in any manners that might infringe the intellectual property rights of others. Specifications, terms and pricing are subject to change.
Not all products are available in all countries. Please consult your local sales representative for details.
