Waters CORTECS 1.6 um Columns User Manual

Page 4

CORTECS Columns

table 2: Buffer Recommendations for Using CoRteCs Columns

additive/Buffer

pKa

Buffer
range

Volatility
(±1 pH unit)

used for
mass Spec

Comments

tfa

0.30

Volatile

Yes

Ion pair additive, can suppress MS signal, used in the
0.02-0.10% range.

acetic acid

4.76

Volatile

Yes

Maximum buffering obtained when used with ammonium acetate
salt. Used in 0.1-1.0% range.

formic acid

3.75

Volatile

Yes

Maximum buffering obtained when used with ammonium formate
salt. Used in 0.1-1.0% range.

acetate
(nH

CooH)

4.76

3.76 – 5.76

Volatile

Yes

Used in the 1-10 mM range. Note that sodium or potassium salts
are not volatile.

formate
(nH

CooH)

3.75

2.75 – 4.75

Volatile

Yes

Used in the 1-10 mM range. Note that sodium or potassium salts
are not volatile.

Phosphate 1

2.15

1.15 – 3.15

Non-volatile

Traditional low pH buffer, good UV transparency.

Phosphate 2

7.20

6.20– 8.20

Non-volatile

Above pH 7, reduce temperature/concentration and use a guard
column to maximize lifetime.

II. CoLUMn Use

To ensure the continued high performance of CORTECS Columns, follow these guidelines:

a. sample Preparation

1. Sample impurities often contribute to column contamination. One option to avoid this is to use Waters Oasis

Solid-Phase Extraction

Cartridges/Columns or Sep-Pak

Cartridges of the appropriate chemistry to cleanup the sample before analysis. For more information,

visit www.waters.com/sampleprep

2. It is preferable to prepare the sample in the operating mobile phase or a mobile phase that is weaker than the mobile phase for the

best peak shape and sensitivity.

3. If the sample is not dissolved in the mobile phase, ensure that the sample, solvent and mobile phases are miscible in order to avoid

sample and/or buffer precipitation.

4. Filter sample with 0.2 µm membranes to remove particulates. If the sample is dissolved in a solvent that contains an organic modifier

(e.g., acetonitrile, methanol, etc.) ensure that the membrane material does not dissolve in the solvent. Contact the membrane
manufacturer with solvent compatibility questions. Alternatively, centrifugation for 20 minutes at 8000 rpm, followed by the
transfer of the supernatant liquid to an appropriate vial, could be considered.

5. For Hydrophilic Interaction Chromatography (HILIC) separations, the samples must be prepared in a high percentage of organic

solvents (e.g., 95% acetonitrile). See “Getting Started with CORTECS HILIC Columns”.

b. pH Range

The recommended operating pH range for CORTECS Columns is 2 to 8 for the C

+ and C

chemistries, and 1 to 5 for the HILIC chemistry.

See Table 2 for more characteristic details of CORTECS chemistries.