How to connect guard columns
Shodex is offering small complete columns which are used as guard columns. They are filled with the same material like the main column and are not only filtering impurities from the sample, but also improve the separation and trap substances that react with the gel material.
Guard column names are indicated with "G" in the name. The size is coded in the suffix: "4A" means an inner diameter of 4.6 and a length of 10 mm (ID: 2=2 mm, 3=3 mm, 4=4.6 mm, 6=6 mm, 7=7.5 mm, 8=8 mm, 20=20 mm. Length: A=10 mm, B=50 mm, C=100 mm, J=20 mm).
The guard column and the main analytical column can easily be connected by fittings and capillaries. Please use short capillaries with small inner diameter to avoid dead volume.
Picture overview about some examples of classical guard columns from Shodex:
List of classical guard columns:
Asahipak GF-1G 7B
Asahipak GS-10G 7B
Asahipak GS-2G 7B
Asahipak NH2P-50G 2A
Asahipak NH2P-50G 3A
Asahipak NH2P-50G 4A
Asahipak NH2P-130G 7B
Asahipak C4P-50G 4A
Asahipak ODP-50G 2A
Asahipak ODP-50G 4A
Asahipak ODP-50G 6A
CLNpak EV-G AC
CLNpak EV-G AC12C
GPC FP-G 8B
GPC H-G 8B
GPC KD-G 4A
GPC KF-G 20C
GPC KF-G 4A
GPC KF-G 8B
GPC K-G 20C
GPC K-G 8B
HILICpak VC-50G 2A
HILICpak VG-50G 2A
HILICpak VG-50G 4A
HILICpak VN-50G 2A
HILICpak VN-50G 4A
HILICpak VT-50G 2A
OHpak LB-G 6B
OHpak SB-G 6B
OHpak SB-G 8B
PROTEIN KW-G 6B
PROTEIN LS-G 4J
PROTEIN LW-G 6B
RSpak DC-G 4A
RSpak DE-G 2A
RSpak DE-G 4A
RSpak DM-G 4A
RSpak KC-G 6B
SUGAR KS-G 6B
SUGAR SC-1211G 4A
SUGAR SC-G 6B
SUGAR SP-G 6B
There are the following exceptions, which consist of a holder and exchangeable filters:
GPC HK-G and IC SI-2GF.
Picture overview about the exceptional guard columns from Shodex, which consist of holder and filters:
List of exceptional guard columns:
GPC HK-G (1 holder + 1 filter)
GPC HK-G filter (3 filters)
This guard column is used for the ultra-rapid SEC column series GPC HK-400 series (4.6 x 150 mm).
IC SI-2GF (1 holder + 1 filter)
IC SI-2GF filter (3 filters)
This guard column is used for the IC column for anions IC SI-35 2B (2.0 x 50 mm).
Why use guard columns?
Guard columns protect the main analytical column from impurities and matrix from the sample. It prolongs the life time of the analytical column. Usually 2 (sometimes 3, depending on the sample) guard columns are used for the useful life of the main column.
Guard columns can be quickly exchanged. Elevated pressure or broader peak forms can be signs, that the guard column should be checked.
When cleaning the guard column and the main column it is important to disconnect them first and to clean them separately. This prevents the transfer of impurities.
To flush out particles, that might be stuck and accumulated at the inlet frit of the guard column, it is recommended to install it in reverse flow direction and carefully pump eluent at a low flow rate.
-> Guard columns have no manual. The information about the guard columns is included in the manual for the main column.
Where to get column fittings, capillaries or column couplers?
Shodex is not offering HPLC instrument consumables like fittings, ferrules and tubes. Please contact your laboratory supplier.
Fittings, Ferrules and Tubes - Overview for connection of Shodex HPLC guard columns with main columns?
1. Fitting and ferrule types for Shodex columns:
Materials: Stainless steel (SUS) or PEEK fittings can be used
The size of the screws and ferrules are the same for all Shodex columns, i.e. no difference for micro or conventional type columns.
Screw type: unified thread standard No. 10-32 UNF
Nut 1/16 (Waters type)
Ferrule 1/16 (Waters type)
Picture: SUS-based and PEEK-based fitting, ferrule and tube
2. Tubing for Shodex Columns:
1/16 outer diameter (O.D.)
0.25 mm inner diameter (I.D.) for analytical columns
0.10 mm inner diameter (I.D.) for semi-micro columns
Length of tubing connection depends on the arrangement of columns in the oven:
approx. 10 cm in the case the connection has to be bended
approx. 5 cm in the case the columns can be arranged in line
Picture: bended SUS tube to connect guard column and main column in a short column oven; PEEK tube and fittings in line to connect guard column and main column, when sufficient space is given in the column oven. In both cases the materials can be also switched.
3. Capillary length under the ferrule for Shodex columns:
2.8 mm*: for Asahipak ODP-50, Asahipak NH2P-50, GPC KF-800, OHpak SB-800, SUGAR series
5 mm*: for Asahipak GF-HQ, Asahipak GS-HQ and IEC series
*These values are not guaranteed and should be treated as reference. Since this length is adjusted by the used ferrule for tubing, these values are not strictly fixed.
It is possible to adjust the length of the tubing under the ferrule with PEEK fittings.
How to prepare the SUS tubing and adjust the under ferrule length:
1. Prepare one tube, one screw and one ferrule.
2. Set the screw and the ferrule to the tube. At this time, the ferrule is not fixed.
3. Prepare the column, and release one plug.
4. Set the assembled tube to the column, and tighten the screw by spanner.
5. Release the screw. The ferrule is fixed to the tube.
Picture: examples for capillary length under the ferrule, it depends on the type of column housing.