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Optimizing the detector
AZURA® Detector DAD 6.1L, DAD 2.1L, MWD 2.1L Instructions, V6700
For the same concentration, the peak height will be higher if the path
length is longer. Path lengths of 3 mm, 10 mm, and 50 mm are available
for the detectors. A longer path length, therefore, increases the sensitivity
of a method (see Fig. 26). The limit of detection is inversely proportional
to the path length.
Fig. 26:
Path length comparison
Wetted parts
The wetted parts of the flow cell must be chemically compatible with the
solvents and sample you are working with (see chapter „14. Chemical
compatibility of wetted materials“ on page 69). Biocompatible flow
cells (with titanium/metal-free) are available (see chapter „13. Reorders“
Pressure stability
The different flow cells can withstand various maximum pressures. The
upper pressure limits of the flow cells are 30 bar, 50 bar, or 300 bar. The
flow cell should not be subjected to the maximum pressure for a long
period of time.
Connection
Undesired effects, like the loss of resolution in the chromatogram, may be
prevented by ensuring a correct connection to the flow cell and the remo-
val of any dead volume.
Remote operation (fiber optics)
If the flow cell must be positioned outside of the detector (e.g. in an
explo sion-proof room, at higher temperatures such as in an oven, or in an
environment with radioactive substances), the devices can be optionally
equipped with fiber optic connectors. Remote flow cells are recommen-
ded for preparative applications (high flow rates), in order to protect sen-
sitive optical components from potential leakages.
For detectors with fiber optic cables the light intensity does not depend
just on the lamp and the cell but also on the quality / condition of the
fiber optic cables, the quality of the connections, the length of the fiber
optic cables, the number of bends and the bending radius.
Sensitivity is typically reduced to half that of an equivalent standard cell
when working with standard length fiber optic cables (750 mm). Overall,
sensitivity is inversely proportional to the length of the fiber optic cables.
Temperature changes around the cables may cause additional drift.
