
4
HTEC-500
4. Mobile Phase Preparation
Prepare the mobile phase according to the Eicom technical information. The mobile phase preparation
depends on what you are measuring with the HTEC-500. Please read below to find a general method
for mobile phase preparation. Also, the following points should be noted because the ECD has a higher
sensitivity compared to other detectors:
• Use ultrapure water (the resistance of the water needs to be at least 18.2 mega-ohm/cm). Any
solvent, such as mobile phase, or water applied to this system should be stored in a glass bottle.
• Use glass instruments for the preparation of mobile phase. Before use, these instruments should be
rinsed out by water and then by ultrapure water.
• Use reagents of super grade or HPLC grade quality. The following are our recommendations: for
sodium 1-Octanesulfonate, use Nacalai (code 3179-62, available at Eicom); for sodium
1-Decanesulfonate, use TCI (code I-0348 available at VWR); and for EDTA-2Na use Dojindo
(code 372.24). Separation patterns or ECD can be influenced by the use of other reagents.
• Methanol and buffer solution/water must be measured separately and then mixed. Otherwise the
methanol concentration will be higher than the designated level due to the solubility of methanol in
water.
• Do not use a sonicator for dissolving salts in the mobile phase. This may raise the background current
of the ECD.
• When all reagents are added, plug the bottle and shake and mix it thoroughly. Check if all reagents
are dissolved.
• Filtration is good for removing unwanted particles but can be a source of chemical contamination.
We do NOT recommend you to filter the mobile phase but rather encourage you to avoid any
contamination during the preparation of the mobile phase. Using less glassware and always putting a
cap or cover on the top of the containers helps to reduce chances of contamination. If you must filter
the mobile phase, use a chemically clean apparatus and do not store the mobile phase in plastic
bottles after the filtration.
• A filter at the end of the inlet tubing placed in the mobile phase can also be a cause of chemical
contamination or bacterial growth. Eicom does not recommend you to use these type of filters. If you
need to use one, please replace the filter frequently and keep it clean. Instead of these filters, we
recommend you to set a precolumn before the separation column. (If using the PP-ODS column,
please use in-line filter #PP-LF, before the precolumn and put a precolumn before the injectors.) The
precolumn filter after the HPLC pump does not prevent contamination of the HPLC pump.
• Mobile phase can only be used for one week from the date of opening/preparation. Bottles should
be well sealed while it is being used for HPLC. Do not add new mobile phase to the bottle of old
mobile phase. This is to avoid the breeding of various germs in the system.