Prime The Needle-Wash Pump - Waters Alliance e2695 Operator's Manual

5. In the Purge Injector dialog box, adopt the default value of 6.0 volumes,
and then press Enter.
Result:
predetermined flow rate, flushing the sample loop with the selected
volume.
6. To prevent a compression test from running, leave the Compression
Check check box blank the first time you use the system.
You cannot perform a compression test before the seal pack is
Rule:
adjusted.
7. Press OK.

Prime the needle-wash pump

The needle-wash pump flushes the needle in the sample management system,
preventing carryover of sample between injections. The needle wash also
extends the life of the injector seals by flushing buffered mobile phase and
sample from the needle.
Select a needle-wash solvent
Use a needle-wash solvent based on the sample and mobile phase chemistries,
making sure all solutions and buffers are miscible and soluble.
A gradient separation typically involves the initial use of a weak solvent
combination, whereas final conditions usually combine stronger solvents. In
general, it is best to choose a needle-wash solvent similar to final gradient
conditions. For example, in a separation with an initial gradient of 80%
water/20% methanol, and a final gradient of 10% water/90% methanol, an
effective needle-wash solvent would be 20% water/80% methanol.
The choice of a needle-wash solvent similar, but not equivalent, to final
gradient composition ensures solubility of early eluting peaks. When sample
solubility in the mobile phase is pH-dependant, choose a needle-wash solution
that is similarly pH-adjusted. If acids are used, avoid long-term exposure of
the needle-wash system to halide-containing acids.
Using samples containing strongly hydrophobic components can require
experimentation to determine the best needle-wash solvent. In these cases,
the use of a needle-wash solvent such as 20% water/80% methanol with
tetrahydrofuran (THF) or dimethylsulfoxide (DMSO) [1-5 mL THF or
DMSO/99-95 mL needle-wash solvent] may be superior.
Prepare the sample management system for operation
The solvent management system gradually attains a
July 29, 2013, 715003794 Rev. B 109