PerkinElmer Lambda 25, User Manual

Page: 110 / 116

Analytical Notes
109
Solvent Properties
The solvent should meet the following requirements:
•
It should dissolve the sample without reacting with it.
•
The radiation absorption in the scanning region should be low.
High absorption by the blank reduces the reference energy, thus increasing
noise.
•
Evaporation should be fairly low at ambient temperature.
In general, aromatic compounds exhibit high absorption in the UV region and hence
are not suitable as solvents for measurements in this region.
Water is virtually the only useful solvent below 195 nm, but it must be freed from
oxygen to attain best transmission.
Whenever you are going to use a solvent with unknown absorption characteristics,
scan its spectrum first to determine whether it is suitable.
The lower wavelength limits of a number of commonly used solvents are presented
in the following table.
The lower limit has been defined as that wavelength at which 10 mm of pure solvent
has a transmission of 10%.
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