Bio-Rad Aminex Organic Acid and Alcohol Analysis Columns - Manual (Page 5)

Interferences caused by anions, cations, organics, salts, insolubles, and
particulates can be reduced or eliminated using Micro-Guard cartridges.
Micro-Guard cartridges are strongly recommended for use with Bio-Rad’s HPLC
columns.
The Micro-Guard HPLC column protection system consists of a disposable guard
cartridge in a standard guard cartridge holder, or an anion and a cation cartridge in
a double deashing holder. The deashing holder is used with the Aminex HPX-42A
silver form column. The deashing format can also be used with other columns
which use water as a mobile phase.
The guard column must be replaced before contamination extends to the main
column. The replacement frequency cannot be standardized, since it depends on
sample preparation conditions. In general, the column should be checked
periodically with a standard sample. When some change in the measured data is
observed, the guard column should be replaced immediately.
3.1 Installing Guard Columns
To install a cartridge, unscrew the end nut from one end of the holder. Attach the
solvent tubing from the injector to the Micro-Guard holder with the Parker-style nut
and ferrule included with each new cartridge holder. While the cartridge may be used
initially in either direction, changing the direction of the used cartridge may cause
particulate matter to flow off the cartridge and contaminate the analytical column.
Attach a short piece of tubing leading from the cartridge holder to the main HPLC
column in a fashion similar to the inlet tubing (see instructions for cartridge holder).
Place the guard column into the holder and secure the holder finger tight, using both
end nuts. Further tightening is unnecessary and may damage the seal or holder.
Never use tools to over tighten this seal.
To store a cartridge out of its holder between uses, protect its Kel-F frit assemblies
from dirt and scratches. Store it in its zip-locking bag, with a few drops of
recommended storage solvent to keep the cartridge from drying out.
3.2 Purging the Guard Column
Flush approximately 10–15 ml of mobile phase through a new guard column at a
flow rate of 0.2–0.3 ml/minute. With resin-based HPLC columns, it is not unusual
to find yellow eluant coming off the column initially for a short period. This material
is polysulfonate formed during column storage. Repeat this procedure each time a
new guard column is installed. The analytical column now may be attached to the
Micro-Guard column.
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