Jenway 6285 - Manual (Page 37)

Glossary of Terms
Filters
- There are three types of filter commonly used in fluorimeters, Band-pass
filters, Cut-Off filters and Interference filters. The first two offer a low-cost general
purpose option while the more expensive interference filters offer precise selection of
excitation or emission wavelengths. Often one type will be used for excitation and
another for emission depending on the proximity of interfering wavelengths.
An excitation filter is fitted between the light source and the sample to limit the
wavelengths reaching it to those absorbed by the analyte but not by any other
substance in the sample matrix.
An emission filter is fitted between the sample and detector to restrict the
wavelengths reaching the detector to those due to the fluorescence of the analyte,
while blocking those due to scatter and stray light.
Band-pass filters - can be used to isolate excitation or emission wavelengths, their
broad transmittance spectra enable them to be used in many applications. However
when used for both excitation and emission great care must be taken that their
transmittance ranges do not overlap. Most useful of those available are the UG1 filter
with transmittance from 320 to 380nm, BG28 from 380 to 500nm and VG9 from 480
to 580nm.
Cut-off filters
- (low cut) will pass all wavelengths above their designated cut-off
point, this makes them ideal as an emission filter, blocking any stray radiation from
the shorter wavelength excitation source; but beware of scatter which will be at
longer wavelengths and so will be transmitted with the fluorescence.
Interference filters
- are available across the full wavelength range and are
specified by their peak wavelength and spectral bandwidth (SBW). With typical
SBWs of 10nm their performance is close to that of a monochromator and all
unwanted wavelengths can be excluded.
TET - Total Energy Transfer
IFM
- Intelligent Filter Modules. Filters are pre-programmed with their peak
wavelength and type. These are identified by the system, enabling error messages to
be generated and displayed should the wrong filters be fitted or their positions be
incorrect.
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