Waters 2489, Overview And Maintenance Manual

Page: 142 / 150

June 11, 2015, 715004752 Rev. A
Page 142
C.1.5 Water
Use water only from a high-quality water purification system. If the water system
does not deliver filtered water, filter it through a 0.45-µm membrane filter before use.
C.1.6 Using buffers
When you use buffers, dissolve salts first, adjust the pH, then filter to remove
insoluble material.
C.1.7 Tetrahydrofuran
When using unstabilized tetrahydrofuran, ensure that your solvent is fresh. Previously
opened bottles of tetrahydrofuran contain peroxide contaminants, which cause
baseline drift.
C.2 Solvent miscibility
Before you change solvents, refer to the table below to determine the miscibility of
the solvents to be used. When you change solvents, be aware that,
• changes involving two miscible solvents may be made directly. Changes
involving two solvents that are not totally miscible (for example, from
chloroform to water), require an intermediate solvent (such as isopropanol);
• temperature affects solvent miscibility. If you are running a high-temperature
application, consider the effect of the higher temperature on solvent solubility;
• buffers dissolved in water can precipitate when mixed with organic solvents.
When you switch from a strong buffer to an organic solvent, flush the buffer out of the
system with distilled water before you add the organic solvent.
Warning:
Tetrahydrofuran contaminants (peroxides) are potentially explosive
if concentrated or taken to dryness.
Table C–1: Solvent miscibility:
Polarity
index
Solvent
Viscosit
y CP, 20
°C
Boiling
point °C
(1 atm)
Miscibilit
y number
(M)
λ
Cutoff
(nm)
–0.3 N-decane 0.92 174.1 29 ––
–0.4 Iso-octane 0.50 99.2 29 210
0.0 N-hexane 0.313 68.7 29 ––
0.0 Cyclohexane 0.98 80.7 28 210
1.7 Butyl ether 0.70 142.2 26 ––
1.8 Triethylamine 0.38 89.5 26 ––