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3-3
2.4 Electrical Connection
The system utilizes Universal Switching Power Supply, and will
accept voltages from 90 – 260 VAC, 50-60 Hz.
WARNING: Do not bypass the safety ground connection as
a serious shock hazard could result.
2.5 Solvent Preparation
Proper solvent preparation will prevent a great number of pumping
problems. The most common problem is bubble formation, which may
affect the flow rate consistency. Aside from leaky fittings, the problem
of bubble formation arises from two sources: solvent out-gassing and
cavitation. Filtration of HPLC solvents is also required.
2.5.1 Solvent Out-gassing and Sparging
Solvent out-gassing occurs because the mobile phase contains
dissolved atmospheric gases, primarily N
2
and O
2
. These dissolved
gases may lead to bubble formation and should be removed by
degassing the mobile phase before or during use. The best practical
technique for degassing is to sparge the solvent with standard
laboratory grade (99.9+%) helium. Helium is only sparingly soluble
in HPLC solvents, so other gases dissolved in the solvent diffuse into
the helium bubbles and are swept from the system. Solvent filtration is
not an effective alternative to helium degassing.
It is recommended that you sparge the solvent vigorously for 10 to
15 minutes before using it. Then maintain a trickle sparge during use
to keep atmospheric gases from dissolving back into the mobile phase.
The sparged solvent must be continually blanketed with helium at 2 to
3 psi. Non- blanketed, sparged solvents will allow atmospheric gases
to dissolve back into the mobile phase within four hours.
Solvent mixtures using water and organic solvents (like methanol or
acetonitrile) hold less dissolved gas than pure solvents. Sparging to
reduce the amount of dissolved gas is therefore particularly important
when utilizing solvent mixture.
Even with sparging some out-gassing may be occur. A back
pressure regulator installed after the detector flow cell will help
prevent bubbles from forming and thus limit baseline noise.
WARNING: Always release pressure from the pump slowly. A rapid
pressure release could cause the pulse damper diaphragm to rupture.