Agilent InfinityLab LC Series 1260 Infinity II FLD User Manual 127
Optimizing the Detector
5
Finding the Best Signal Amplification
2 Set your Luminescence Units in LU.
If you are not satisfied with the LU output level of the detector or if you
want to align the output of multiple instruments with different output
levels you can scale each instrument output.
The recommended setting of the FLD is around 100 LU for the highest peak
height to get optimum signal to noise and signal range. Lower LU values
normally do not influence the performance of the instrument if PMT-Gain
Test was executed fine.
For analog out less than 100 LU is optimum to get best analog signal
performance with the default attenuation of 100 LU/ 1 V. Adapt your LU
setting such that your maximum signal level under default attenuation is
between 50 to 80 LU (analog output equivalent to 500 mV to 800 mV).
After correct PMT Setting you can scale any instrument to your favorable
LU level. We recommend not exceeding around 100 LU. The parameter of
choice is called 'Scale factor' and is applicable by the local controller, the
Instant Pilot (B.02.07 or later).
In case older revisions are used, the 'Scale factor' can be entered using the
command line of
• Agilent ChemStation:
PRINT SENDMODULE$(LFLD,"DMUL x.xx")
• Instant Pilot: Service Mode – FLD, then type
DMUL x.xx and press SEND.
• LAN/RS-232 Firmware Update Tool: via Send Instruction menu:
DMUL x.xx
• Agilent Lab Advisor Software: via Instruction menu:
DMUL x.xx
This setting is resident to the instrument even for firmware updates and is
independent of the software environment.
The level of LU is no measure of instrument sensitivity! At the lowest
concentration limit (limit of detection), the signal to noise (for example by
Raman S/N Test) is the only measure that can accurately be used to
compare chromatograms and results and to confirm the performance of the
instrument.
For low background and highest sensitivity keep the flow cell clean and
always use fresh water to prevent biological background from native
fluorescence by algae and bacteria.
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