Material; Pressure Stability; Connection; Remote Operation (Fiber Optics) - Knauer Azura DAD 2.1L Benutzerhandbuch

37 Optimizing the Detector
:
Molar absorptivity coefficient (wavelength- and tem-
perature-dependent)
b: Path length
c: Analyte concentration (temperature-dependent)
For the same volume of sample, the apparent concentration of
the sample will appear to be higher if the path length is longer.
Optical path lengths of 3 mm, 10 mm, and 50 mm are available
for the detectors. A longer path length increases the signal
intensity as more light is absorbed and thereby may enhance
the sensitivity of a method (see figure 27).
Fig. 27 Path length comparison

Material

The flow cell materials must be chemically compatible with the
solvents and sample you are working with. Stainless steel and
metal-free flow cells are available. The metal-free variants are
bio-inert.

Pressure Stability

The different flow cells can withstand various maximum pres-
sures. The upper pressure limits of the flow cells are 30 bar,
100 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 chromato-
gram, may be prevented by ensuring a correct connection to
the flow cell and the removal of any dead volume.

Remote Operation (Fiber Optics)

The detectors can be operated with a spatially separated flow
cell which is connected with fiber optics. This provides
enhanced security for hazardous, explosive, or toxic work pro-
cesses. Sensitivity is typically reduced to half that of an equiva-
lent 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 drift.
KNAUER DAD 6.1L, DAD 2.1L, MWD 2.1L User Manual V6700, Version 1.0