Waters 2489, Обзор и руководство по обслуживанию

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June 11, 2015, 715004752 Rev. A
Page 147
C.7.3.2 Vacuum degassing
The longer the solvent is exposed to the 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.
The in-line degasser is available as an option or factory-installed in the Waters 2695
Separations Module, XE model.
C.8 Wavelength selection
C.8.1 UV cutoffs for common solvents
The table below shows the UV cutoff (the wavelength at which the absorbance of the
solvent is equal to 1 AU) for some common chromatographic solvents. Operating at a
wavelength near or below the cutoff increases baseline noise because of the
absorbance of the solvent.
Table C–2: UV cutoff wavelengths for common chromatographic solvents:
Solvent
UV cutoff
(nm)
Solvent
UV cutoff
(nm)
1-Nitropropane 380 Ethylene glycol 210
2-Butoxyethanol 220 Iso-octane 215
Acetone 330 Isopropanol 205
Acetonitrile 190 Isopropyl chloride 225
Amyl alcohol 210 Isopropyl ether 220
Amyl chloride 225 Methanol 205
Benzene 280 Methyl acetate 260
Carbon disulfide 380 Methyl ethyl ketone 330
Carbon tetrachloride 265 Methyl isobutyl
ketone
334
Chloroform 245 Methylene chloride 233
Cyclohexane 200 n -Pentane 190
Cyclopentane 200 n -Propanol 210
Diethyl amine 275 n -Propyl chloride 225
Dioxane 215 Nitromethane 380