Storage Methods for
HPLC Columns
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Silica-based HPLC columns are generally not recommended for storage
with alkaline mobile phases, as the silica substrate can easily
hydrolyze in alkaline conditions.
On the contrary, silica is
stable under weakly acidic conditions or lower, making these
conditions suitable for long-term storage of silica columns.
The method of column storage varies depending on the type of column
and the analysis conditions. Solvent replacement for storage does
not require much time; generally, flowing the solvent for about 10
minutes is considered sufficient.
1. Silica-based Reversed-Phase
Columns (e.g., ODS)
Cadenza CD-C18, CL-C18, CX-C18, CW-C18,
HS-C18
Unison UK-C18, UK-C8, UK-C1, UK-Phenyl
Presto FF-C18,
Dacapo DX-C18
For columns that are frequently
used, it is common to store them after replacement with an
acetonitrile/water solvent. However, since this solvent is not pH
adjusted, concerns arise about silica substrate hydrolysis and
column degradation if stored for several weeks or more. Therefore, a
weakly acidic storage solvent is recommended.
Typically, IMTAKT
columns are shipped with the following mobile phase solvent for
stability reasons:
acetonitrile / water / acetic
acid = 60 / 40 / 0.1
Adding a little amount
of acetic acid lowers the pH inside the column, enhancing its
storage stability. Therefore, an acidic mobile phase containing
organic solvents, as described above, is recommended for
post-analysis column storage. However, encapsulation with strong
acids (such as TFA or formic acid) might lead to acid hydrolysis and
detachment of the stationary phase ligands. Acetic acid, being a
weak acid, is ideal for silica column storage.
2.
Silica Columns
Unison UK-Silica
Since silica packing material is susceptible to degradation from pH
levels above neutral and from water exposure, it is recommended to
store it in high concentrations of organic solvents under weakly
acidic conditions.
acetonitrile / water / acetic acid = 90 / 10 / 0.1
If cleaning of the silica stationary phase is also required, polar
solvents such as the following can be considered.
acetonitrile / water / acetic acid = 20
/ 80 / 0.1
3. Amino
Columns
Unison UK-Amino
Amino columns are durable in aqueous mobile phases. Volatile salts
(e.g., 100mM ammonium acetate) are suitable for cleaning the amino
stationary phase.
After cleaning, the following encapsulating solvent is recommended
for storage, which can be directly replaced from a 100mM ammonium
acetate mobile phase:。
acetonitrile / water = 90 / 10
4.
Mixed-mode (Multi-mode) Columns
Scherzo SS-C18, SM-C18, SW-C18, Nardis ND-NX,
ND-RX
Ion exchange ligands are incorporated into intact multimode
columns, so volatile salts (e.g., 100mM ammonium acetate) are
recommended for column cleaning.
[Cleaning Example]
Acetonitrile / 100mM Ammonium
Acetate = 50 / 50
After cleaning, the following encapsulating
solvent is recommended for storage, which can also be directly
replaced from a 100mM ammonium acetate mobile phase:
acetonitrile / water / acetic
acid = 60 / 40 / 0.1
5.
Size Exclusion (SEC) Column
Intrada SEC
The IMTAKT SEC column "Intrada SEC" is suitable for both aqueous and
non-aqueous SEC. For aqueous systems, the following encapsulating
solvent is recommended:
acetonitrile / water / acetic
acid = 50 / 50 / 0.1
For non-aqueous
systems, methanol is recommended.
6. Storage in Cleaning Solvent
If the cleaning solvent is chemically stable and less likely to
cause hydrolysis or other chemical changes to the column, it is also
feasible to store the column tightly capped in the cleaning solvent.
This method can reduce operational costs by eliminating the need to
replace the storage solvent.
7. Storage in Mobile Phase
Frequently replacing the column with different cleaning and storage
solvents can alter the column packing state and potentially shorten
the column life. If analysis is conducted daily with the same mobile
phase and column cleaning is not required, storing in the mobile
phase can be cost-effective. If replacing solvents results in long
times to reach mobile phase equilibrium for subsequent analyses,
maintaining the column in the mobile phase overnight without
cleaning might be a viable option to minimize solvent costs and
fixed expenses.
8. Additional Notes
HPLC columns are in their best condition when they leave the
manufacturer. Even if not used after purchase, they can degrade
during long-term storage, or due to equilibration with the initial
mobile phase, or by flowing analysis mobile phases and cleaning or
storage solvents through them. To ensure optimal performance during
analysis, care must be taken when handling cleaning and storage
solvents.
Also, if HPLC columns dry out internally, they can
suffer fatal damage. No matter which storage method is used, make
sure to firmly seal both ends of the column to prevent internal
drying.
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