Good Practices for Use of the Multi-Channel Gradient Valve in Agilent Quaternary Pump Modules

Answer

This Information Applies To: Agilent Quaternary Pumps with Multichannel Gradient Valves

Issue:

The correct use and maintenance of multichannel gradient valves (MCGVs) in Agilent Quaternary Pump modules will prevent blockage or damage of this assembly. It will help ensure the MCGV functions correctly and reliably.

Resolution:

Warning: Use the proper PPE and precautions when handling hot water and solvents.

General:

• Before operating the quaternary pump, flush the pump and vacuum degasser with water.  
• Flushing with water is especially recommended if the pump has been turned off for some time (for example, overnight) and volatile solvent mixtures are used in the channels. It purges the solvent used for storing the system.
• Always use the pump with solvent inlet filters, as filters prevent particles being drawn into the MCGV and eventually into the pump head check valves. To stop the growth of algae, further information is available on Prevent Blocking of Solvent Filters
• When using the quaternary pump at low flow rates (for example, 0.2 mL/min) check all 1/16- inch fittings for any signs of leaks. 
• When powering up, stabilize the system by running for 10-20min with a new or a different mobile phase. 

Purge Valve:

• Check the purge valve frit and column frit weekly. With the purge valve open and flowing at 5 ml/min with water, the pressure should read less than 10 bar. If it's greater than 10 bar, then consider changing the purge frit. A blocked purge valve frit will typically be black (pump seal wear) or yellow colored.
• Whenever pump seals are replaced, the purge valve frit should also be replaced.

MCGV Channels:

• Use the lower channels A and/or D for buffer solutions and C and/or B for organic solvents: This prevents blockage due to salt precipitation as the salt can fall back into the aqueous solution and be dissolved. It is best to have the organic channel directly above the salt solution channel. 
• The use of an inline filter (G1311-60006) can avoid or reduce such effects by filtering crystals.
•  At least once a week, set the MCGV to 25% for all channels to energize all valves in MCGV and help to prevent them sticking. 

Bottles/ Solvents:

• The solvents cabinet should be on top of the pump or at a higher level.
• When using buffers or other salt solutions, flush the system with water before switching it off. The seal wash option should be used when salt concentrations of 0.1 M or higher will be used for long time periods.
• Small particles can permanently block capillaries and valves. Therefore, always filter solvents through 0.22 μm filters before flowing through the HPLC.
• Avoid or minimize the use of solvents that may corrode parts in the flow path. Consider specifications for the pH range given for different materials like flow cells, valve materials etc. and recommendations in subsequent sections.

After an installation:

• Flush with isopropanol. It is the best solvent to get air out of the system and it is miscible with almost all solvents. It is also the solvent that is used to switch from reverse phase to normal phase (and vice versa)

After runs:

• HPLC grade water is the best solvent to redissolve buffer crystals. It is suitable for systems using buffers and before changing solvents.
• After the installation of normal phase seals (PE seals; pack of 2- 0905–1420): a mix of hexane + 5% isopropanol is suitable for its good wetting properties

Piston seals:

• Check the pump pistons for scratches when changing the piston seals.
• Scratched pistons will cause micro leaks and will decrease the lifetime of the seal.
• Pressurize the system according to the wear in procedure after changing the piston seals. For further information, see the piston seal wear in procedure.

Learn how to effectively operate your Agilent Quaternary Pump: Agilent InfinityLab LC Series 1260 Infinity II Isocratic and Quaternary Pumps user manual on Agilent.com