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To use the instrument, it must first be purged with nitrogen, system checks must be conducted and the relevant values must be logged in the sheets provided.
Nitrogen purge (instrument remains switched off):
Before conducting any experiments, the instrument needs to be purged with nitrogen. The time of purging depends on how long the instrument has been inactive for:
1 day = 30 min - 1 hr
1 week = 1 hr - 2 hr
1 month = overnight
To purge the instrument:
Open the cylinder with the wrench (first drawer below the bench).
Turn the black knob and set it to 4 bar.
Open the valve connecting the cylinder to the instrument (key in the drawer below the bench).
Set the flow rate using the dials*:
Lamp = 1 L/min
Monochromator = 3 L/min
Sample = 1 (for an overnight purge, leave at 0)
*note: each dial is calibrated differently so please cross-check the values.
Steps to open nitrogen cylinder
Setting the flow rate
Switching on the instrument:
Once the instrument has been purged for the required amount of time, switch on the instrument:
Switch on the system.
After ~15 seconds, switch on the lamp (start button).
After ~30 seconds, ignite the lamp
Switch on the chiller (below the bench) and the Peltier (back of instrument).
Start the Chirascan software from the desktop.
Start the ProData Viewer from the toolbar within the Chirascan software.
Note: The lamp requires 30 minutes to warm up but system checks can be performed in the meantime. The lamp needs to cool down before it can be switched on again. Leave 5 hours between switching it on and off.
System checks
Nitrogen purge:
Switch the CD plot to the HV (v) plot. This can be done by right-clicking the y-axis label and choosing HV(v) from the drop-down list.
Take the HV value at 180 nm and 200 nm.
If the ratio of HV values at 180/200 < 1.5, the purge is complete. If not, switch off the lamp and continue purging.
If the instrument has been purged for at least a 2 hours after a period of disuse then go ahead and use the instrument, there appears to be some error with regards to the purging timing according to Applied Photophysics engineers.
Xenon lamp:
Look out for a drop at 468 nm. This is a xenon lamp line. If this drop is elsewhere, it gives a hint to a problem with wavelength calibration. In that case, please contact Khushboo ASAP.
Cuvette check (optional, but recommended):
Measure the empty cuvette.
For more information regarding sample preparation and cut-off concentration of buffers, please refer to : https://structbio.vanderbilt.edu/wetlab/cd.sample.prep.php
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