Waters CORTECS 2.7 um Columns User Manual

Page 8

Waters Corporation
34 Maple Street
Milford, MA 01757 U.S.A.
T: 1 508 478 2000
F: 1 508 872 1990
www.waters.com

Waters, The Science of What’s Possible, CORTECS, UPLC, ACQUITY UPLC, Alliance, Oasis, and Sep-Pak are registered trademarks of Waters
Corporation. eCord and VanGuard are trademarks of Waters Corporation. All other trademarks are property of their respective owners.

■

Routinely maintain your water purification system to
ensure it is functioning properly.

■

Only use ultra-pure water (18

ΩOhm-cm) and highest

quality solvent possible.

■

Consider sample preparation (e.g., SPE, filtration,
centrifugation, etc.) when possible.

4. Avoid when possible:

■

100% aqueous mobile phases

■

HPLC-grade bottled water

■

“Topping off” your mobile phases

■

Using phosphate salt buffer in combination with
high acetonitrile concentrations (e.g., >70%) due to
precipitation.

b. Getting Started with CORTECS HILIC Columns

Note. CORTECS HILIC Columns are designed to retain very polar
bases. Acidic, neutral, and/or non-polar compounds will have
limited retention

Mobile-Phase Considerations:
1. Always maintain at least 3% polar solvent, such as water, in

the mobile phase or gradient. This ensures that the CORTECS
HILIC 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 high

organic content mobile phases used for HILIC separations.
Phosphoric acid is acceptable.

4. Buffered mobile phases such as ammonium formate or

ammonium acetate will produce more reproducible results
compared to unbuffered additives such as formic acid or acetic
acid. For best peak shape, maintain a buffer concentration of
10 mM.

5. If using an ACQUITY UPLC System, the weak needle wash

solvent should closely match the % organic present in the
initial mobile-phase conditions, otherwise, analyte peak shape
distortion can occur.

Injection Solvent considerations:
1. Whenever possible, injection solvents should contain 95%

acetonitrile with the polar solvent (i.e., water, methanol,
isopropanol) component to be no more than 25% of the total
volume. A generic injection solvent is 75:25 acetonitrile/
methanol. This is a good compromise between analyte
solubility and peak shape.

2. Avoid water and dimethylsulfoxide (DMSO) in the injection

solvents. These solvents will produce very poor peak shapes.
In HILIC, it is important to remember that water is the
strongest eluting solvent. Therefore, it must be eliminated or
minimized in the injection solvent. Exchange water or DMSO
with acetonitrile by using reversed-phase SPE. If this is not
possible, dilute the water or DMSO with organic solvent.

c. Troubleshooting Questions

1. Are you using 100% aqueous mobile phases?

2. W hat is the age of the mobile phase?

3. Is the mobile phase filtered through a 0.2 µm membrane?

4. Was the mobile phase prepared fresh or topped off?

5. Is the water source of adequate quality?

6. W hen was the last time the water system was serviced or

was the bottle of
water unopened?

7. Is bacterial growth a possibility (pH7 phosphate buffer is

susceptible to bacterial growth within 24 hours)?

8. If a neat standard is prepared in the initial mobile phase

conditions and injected, are the problems still observed?

9. If the sample is filtered/purified (i.e., SPE, filtration...etc.) is

the problem still observed?

10. Has the quality of the samples changed over time?