ANALYTICAL & LAB EQUIPMENT
Extended inline vacuum degasser durability
Exploring the features of inline degassers
I
nline degassing is the silent guardian of precision and reliability in fluidic systems. Installation of an inline degasser
(see Figure 1) will drastically diminish the concentration of dissolved gases in the liquids passing through. This reduces variations, improves baseline stability, shortens startup times, and ensures more consistent results. By reducing the concentration of dissolved gases beyond the level where outgassing can occur, bubble formation will not be an issue despite changes in temperature, pressure, or compositions of the liquid managed throughout the flow path. Degassers are important
equipment components in laboratory analysis equipment such as liquid chromatography, HPLC, UHPLC, ion chromatography and mass spectrometry. Machines for semi- conductor manufacturing or assembly will also typically deliver more consistent results with a degasser included in the fluid path. The same is true for instruments in immunology, haematology, and in vitro diagnostics. An inline degasser assembly
contains a purposedly designed vacuum pump connected to one or several degassing chambers through which the liquid with dissolved gases flows. Inside the degassing chamber (see Figure 2) there is an inert gas-permeable membrane that must be compatible with the liquid to be degassed. A control board with a vacuum sensor ensures that the vacuum level is kept at a constant level to minimise fluctuations in degassing performance and wear on the vacuum pump.
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Figure 1. Example of a stand-alone inline degasser from the DEGASi family, suitable for aqueous liquids and organic solvents at flow rates from 25 µL/min up to 1000 mL/min, depending on model and configuration
MAXIMISING DEGASSER LIFETIME Modern inline degassers incorporated into instruments handling liquids with high precision and accuracy, are fortunately essentially maintenance- free. However, there are a few things to keep in mind not to shorten the lifetime of your inline degasser. Firstly, one should use a degassing
chamber compatible with the solvents that will be used. Organic solvents such as hexane, heptane, toluene, tetrahydrofurane (THF), and dichloromethane (DCM), typically demand specially designed degassing chambers. These degassing chambers are often labelled GPC to highlight their suitability in gel permeation chromatography, but they are equally suitable for normal phase and flash chromatography applications where such organic solvents are also employed. In addition, there are degassing chambers explicitly designed for hexafluoro isopropanol (HFIP) that are required when this aggressive organic solvent is used. As with any fluidic component, it is
advised not to leave your degassing chamber with liquid inside when disconnected from use. This is especially important when there are salts or buffer components dissolved into the liquid since they may precipitate. Precipitates will block the flow path and are notoriously problematic to wash out again. In
addition, buffered aqueous solutions exposed to open air may constitute an attractive environment for microbial growth, which can constrict the flow path. Finally, it is strongly recommended
to always suck solutions through the degassing chambers, rather than pumping or pushing liquids through them. The internal gas-permeable membrane material that allows gases to penetrate while blocking liquids, is designed to withstand a certain pressure difference. That limit may accidentally be exceeded if liquids are pumped too fast into the degassing chamber, which may cause irreparable damage.
REPLACEMENT OF PARTS Should a degasser chamber malfunction, it is most often either related to use with incompatible organic solvents, or a blocked flow path. If this happens, the chamber needs to be replaced. Fortunately, this is a straightforward and quick procedure in most systems. Note however, that in cases where there has been a leakage from the fluidic line into the vacuum line, there is a high risk that the vacuum sensor on the control board has been impaired. In these situations, there are often so many damaged components that one should consider exchanging the entire degasser.
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