Waters CORTECS 1.6 um Columns - Manual (Page 9)

Waters Corporation
34 Maple Street
Milford, MA 01757 U.S.A.
T: 1 508 478 2000
F: 1 508 872 1990
www.waters.com
©2013 Waters Corporation. Waters, ACQUITY UPLC, UPLC, Oasis and
SepPak are registered trademarks of Waters Corporation. CORTECS,
VanGuard, eCord and The Science of What’s Possible are trademarks
of Waters Corporation. All other trademarks are the property of their
respective owners.
June 2013 720004750EN Rev. A VW-PDF
Mobile-Phase Considerations
1. Always maintain at least 3% polar solvent in the mobile
phase or gradient (e.g., 3% aqueous/3% methanol or 2%
aqueous/1% methanol, etc.). This ensures that the CORTECS
particle is always hydrated.
2. Maintain at least 40% organic solvent (e.g., acetonitrile) in
your mobile phase or gradient.
3. Avoid phosphate salt buffers to avoid precipitation in HILIC
mobile phases. Phosphoric acid is okay.
4. Buffers such as ammonium formate or ammonium acetate
will produce more reproducible results than additives such
as formic acid or acetic acid. If an additive (e.g., formic acid,
etc.) must be used instead of a buffer, use 0.2% (v:v) instead
of 0.1%.
5. For best peak shape, maintain a buffer concentration of 10 mM
in your mobile phase/gradient at all times.
Injection solvents
1. If possible, injection solvents should be 95% acetonitrile.
The polar solvent (i.e., water, methanol, isopropanol) should
be minimized to 25% of the total volume.
2. A generic injection solvent is 75:25 acetonitrile/methanol.
This is a good compromise between analyte solubility and
peak shape.
3. Avoid water and dimethylsulfoxide (DMSO) as injection sol-
vents. These solvents will produce very poor peak shapes.
4. Exchange water or DMSO with acetonitrile by using
reversed-phase solid-phase extraction (SPE). If this is not
possible, dilute the water or DMSO with organic solvent.
Miscellaneous tips
1. CORTECS HILIC Columns are designed to retain very polar
bases. Acidic, neutral and/or non-polar compounds will have
limited retention.
2. Optimal flow rates for small (<200 daltons) very polar bases
are in the 0.4 to 0.8 mL/min range with the CORTECS HILIC
Columns.
3. In HILIC, it is important to remember that water is the strongest
solvent. Therefore, it must be eliminated or minimized in the
injection solvent.
4. For initial scouting conditions, run a gradient from
95% acetonitrile to 50% acetonitrile. If no retention occurs, run
isocratically with 95:3:2 acetonitrile/methanol/aqueous buffer.
5. Alternate polar solvents such as methanol, acetone or isopropanol
can also be used in place of water to increase retention.
6. If using an ACQUITY UPLC System, the weak needle wash
should closely match the % organic present in the initial
mobile-phase conditions, otherwise, analyte peak shape or
retention may suffer.