Waters 1500-Series, Руководство оператора

Страница: 179 / 188

Mobile phase solvent degassing C-11
Note:
Vacuum degassing can change the composition of mixed solvents.
In-line degassing
In-line degassing removes gases from the eluent as it passes through a
gas-permeable membrane enclosed in a vacuum chamber. The vacuum in the
chamber accelerates the rate at which the dissolved gas diffuses through the
gas-permeable membrane. This method provides an automatic, continuous
method of removing dissolved gasses, and allows for quick eluent changeover.
Waters makes two in-line degassers: part numbers WAT079700 (2 Eluent)
and WAT079800 (4 Eluent). Contact Waters for details.
The longer a solvent is exposed to a vacuum, the more dissolved gases are
removed. Two factors affect the amount of time the solvent is exposed to the
vacuum:
• Flow rate – At low flow rates, most of the dissolved gas is removed as the
solvent passes through the vacuum chamber. At higher flow rates, lesser
amounts of gas per unit volume of solvent are removed.
• Surface area of the degassing membrane – The length of the degassing
membrane is fixed in each vacuum chamber. To increase the length of
membrane, you can connect two or more vacuum chambers in series.
Heating
Heating to remove dissolved gas is usually not effective unless you boil the
eluent, and doing so is not practical or safe for mixed, flammable, or volatile
eluents. However, raising the temperature even slightly raises the partial
pressure of the eluent, and thereby reduces the rate of resolubilization of a
gas.
Vacuum sonication
Sonication in combination with a vacuum degasses eluents very quickly. This
technique does not change the composition of mixed eluents appreciably.
Caution:
Apply vacuum only to suitable vessels. The brown gallon
bottles in which eluent is shipped are not designed for vacuum
degassing. There is a high risk of implosion if these bottles are used for
vacuum degassing.