Solvent Handling

Observe the following recommendations when using normal phase solvents:

• Always use fresh, filtered solvents. Exchange solvents every second day.

• Prevent reactions caused by heat, light, and oxygen. Use brown, firmly closed bottles.

• Whenever possible, use stabilizers, e.g. butylated hydroxytoluene (BHT) for ethyl ether.

• Use isopropanol (IPA) to flush out the previous solvent when converting a system from normal phase to reverse phase, or vice versa.

• Store all unused channels in IPA.

• Don’t turn off the pump while it is filled with solvents with low boiling points. Generate a small flow throughout the used channels when the pump is not in use.

The following recommendations should be observed when using buffer solutions:

• Buffers and aqueous solutions are possible sources of algae contamination, for avoiding related problems, please read Algae Growth in HPLC Systems.

• For buffer concentrations of 0.1 M or higher, using the seal wash function periodically with a runtime of 0.3 min every 3 min is strongly recommended.

• Filter buffer solutions to avoid increased wear or blockages that are caused by undissolved crystals. Always use solvent inlet filters.

• Avoid conditions where mixing of buffers and organic solvents may cause precipitation, as this impairs the reproducibility of chromatographic experiments and may also reduce the system life time. For example in reversed-phase chromatography, avoid buffers (especially phosphate buffers) with a concentration higher than 20 mmol/L. For phosphate buffers, avoid compositions containing more than 65 % acetonitrile or other organic solvents.

• Use a minimum flow rate of 5 µL/min or 1 % composition per solvent channel (whatever is greater) to avoid crossflow. Crossflow can be caused by micro leaks in pump heads and can result in buffer precipitation in pump heads, channel blocking, or reduced pump head life time through wear of seals and pistons.

• Use a minimum flow rate of 50 µL/min or 1 % composition per solvent channel (whatever is greater) to avoid crossflow. Crossflow can be caused by micro leaks in pump heads and can result in buffer precipitation in pump heads, channel blocking, or reduced pump head life time through wear of seals and pistons.

• When installing tubing connections to the MCGV, use lower channels (A/D) for aqueous solvents and upper channels for organic solvents. This will redissolve precipitates more easily.

• Consider using an inline filter, for example 5067-5407 (Inline filter assembly, material: stainless steel) .

• Consider using an inline filter, for example G1311-60006 (Inline filter) .

• Consider using an inline filter.

• Never leave buffers in a system without flow. Before shutting down a system, flush it extensively with warm water to avoid clogging of valves, capillaries, or flow cells or reducing the life time of your column. If the system is not used for some time, for example more than a day depending on lab temperature, fill all solvent lines with organic solvent or water with at least 10 % isopropanol.

• Regularly maintain the LC system.

When using acetonitrile:

• Use high-quality solvents from renowned suppliers.

• Use fresh solvents and filter them.

• Minimize exposure to light and air/oxygen.

• Choose a bottle size, which fits to your application and use.

• Acids accelerate solvent aging. If possible, avoid such additives or refresh solvents more frequently.

• Pure acetonitrile ages faster. If your application allows, add about 5 % water and adjust gradient compositions.

• Do not leave acetonitrile in unused systems to avoid aging. If not in use, flush all solvent lines with a mixture of water and 10 % isopropanol.

• In case of blocked valves, flush the system with hot water. Knock at valves, flush them (see Release a Stuck Inlet Valve) or ultrasonicate them, for example in methanol.

• In case of blocked valves, flush the system with hot water. Knock at valves, flush them (see Release a Stuck Inlet Valve) or ultrasonicate them, for example in methanol.