Waters 2489, Operator'S Manual

Page: 212 / 234

D-6 Solvent Considerations
Buffered solvents
When using a buffer, use a good quality reagent and filter it through a
0.45-µm filter.
Do not leave the buffer stored in the system after use. Flush all fluid line
pathways with HPLC-quality water before shutting the system down and
leave distilled water in the system (flush with 90% HPLC-quality water: 10%
methanol for shutdowns scheduled to be more than one day). Use a minimum
of 15 mL for sparge-equipped units, and a minimum of 45 mL for in-line
vacuum degasser-equipped units.
Head height
Position the solvent reservoirs at a level above the HPLC equipment or on top
of the pump or detector (with adequate spill protection).
Solvent viscosity
Generally, viscosity is not important when you are operating with a single
solvent or under low pressure. However, when you are running a gradient, the
viscosity changes that occur as the solvents are mixed in different proportions
can result in pressure changes during the run. For example, a 1:1 mixture of
water and methanol produces twice the pressure of either water or methanol
alone.
If the extent to which the pressure changes will affect the analysis is not
known, monitor the pressure during the run using the Chart Out terminal.
Mobile phase solvent degassing
Mobile phase difficulties account for 70% or more of all liquid
chromatographic problems. Using degassed solvents is important, especially
at wavelengths below 220 nm.
Degassing provides
• stable baselines and enhanced sensitivity.
• reproducible retention times for eluting peaks.
• reproducible injection volumes for quantitation.