Eluent Degassing Methods - Waters 600e User Manual

reported a 95-percent reduction in sensitivity of the fluorescence of borate-benzoin
complex in air-equilibrated ethanol.
different types of compounds. Aromatic hydrocarbons, aliphatic aldehydes, and ketones
are especially susceptible.
B.6.2 Eluent Degassing Methods
You can degas eluents by sparging, heating, sonication, and vacuum. Sparging, however,
is the method of choice for online degassing. Sparging combines the convenience of short
initial degassing time, ease of maintaining the eluent condition during operation, and
complete control within the framework of the 600E system.
Sparging
Sparging, or bubbling a gas through eluent, removes unwanted gas from solution while
saturating the eluent with the sparging gas.
Sparging brings the eluent to a state of equilibrium that can be maintained by keeping
either a blanket of gas over the eluent or a constant, low-rate dispersion of the sparge gas
through the eluent.
Sparging with either nitrogen or helium is effective in reducing background absorbance in
a UV detector and the quenching phenomenon caused by dissolved oxygen in a
fluorescence detector.
Sparging with Helium
Helium sparging tends to give a more stable baseline on a refractive index detector than
air-equilibrated eluents. Also, the absolute mass of dissolved gas is considerably lower
than with air-equilibrated eluents. Somewhat better pumping reproducibility is obtained
from helium-sparged eluents in a piston pump.
Helium sparging gives stable baselines and improved sensitivity in a fluorescence
detector, and prevents the reabsorption of atmospheric gases. Also, eluents sparged with
helium will generally be well-degassed by the time they reach the pump because the
helium diffuses out of the eluent into the atmosphere through the Teflon tubing that
connects the reservoirs to the pump. The eluent arrives at the pump with less than 1
atmosphere partial pressure of helium.
1. C.A. Parker and W.J. Barnes, Trans. Faraday Soc., 82 (1957) 606.
218 Eluent Considerations
1
The amount of quenching by oxygen varies with