Waters CORTECS 2.7 um Columns - Manual (Page 6)

6 CORTECS 2.7 µm Columns
Table 5. Mobile Phase Buffer Recommendations for CORTECS 2.7 µm 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
4
CH
2
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
4
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 No Traditional low pH buffer, good UV transparency.
Phosphate 2 7.20 6.20– 8.20 Non-volatile No
Above pH 7, reduce temperature/concentration
and use a guard column to maximize lifetime.
c. Solvents
To maintain maximum column performance, use high quality HPLC
or MS grade solvents. Filter all aqueous buffers prior to use through
a 0.2 µm filter. Solvents containing suspended particulate materials
will generally clog the outside surface of the inlet of the column.
This may result in higher backpressure or distorted peak shape.
d. Pressure
CORTECS 2.7 µm Columns are compatible with HPLC, UHPLC,
and UPLC pressures. Table 6 provides the maximum operation
pressure for each column dimension.
Table 6. Maximum Operation Pressure
Column i.d. Maximum Operating Pressure
2.1 mm 15,000 PSI [1034 bar]
3.0 mm 15,000 PSI [1034 bar]
4.6 mm 9,000 PSI [620 bar]
e. Temperature
CORTECS 2.7 µm Columns can be used at temperatures up to 45 °C
to enhance selectivity, reduce solvent viscosity, and increase
mass transfer rates.
Note. Working in combinations of extreme pH, temperature and
pressure may result in reduced column lifetime.
IV. COLUMN CLEANING, REGENERATION, AND
STORAGE
a. Cleaning and Regeneration
Changes in peak shape, peak splitting, shouldering peaks, shifts in
retention, change in resolution, or increasing backpressure may
indicate contamination of the column. Flush with a neat organic
solvent to remove the non-polar contaminant(s), taking care not to
precipitate any buffered mobile phase components. If this flushing
procedure does not solve the problem, purge the column with the
following cleaning and regeneration procedures.
Use a cleaning routine that matches the properties of the samples
and stationary phase type (reversed-phase, normal-phase or
HILIC) to help solubilize the suspected contaminate. Flush with
20 column volumes of solvent at 45 °C. Return to the initial
mobile phase conditions by reversing the sequence.
If using a reversed-phase column, purge the column with a
sequence of progressively more non-polar solvents (i.e., water-to-
methanol-to-tetrahydrofuran-to-methylene chloride).
If using a HILIC column, purge the column with a sequence of
progressively more polar-organic solvents (i.e., acetonitrile-
to-acetonitrile/methanol-to-acetonitrile/water-to-water).
If column performance has not improved after regeneration/
cleaning procedures, contact your local Waters representative for
additional support.