UV-VIS Spectrophotometer

UV-VIS Spectrophotometer
Procedure No.:
Procedure Title:
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1.
UV-VIS
Spectrophotometer
Physics CR-018
UV-VIS Spectrophotometer
1
20th June 2009
Colin Belton
Xuhua Wang
If it is not already on, turn on the Spectrophotometer using the power On/Off switch (Left hand
side of instrument).
2. Turn on the computer and click on the UV Probe software (available on the desktop).
3. Click the “Connect” button to initiate communication between the computer and the
Spectrophotometer. The instrument will now begin it’s initialisation procedures and begin to
warm up. The machine should be allowed at least ½ an hour to warm up fully before proceeding
with the remainder of this procedure.
4. Select the “Spectrum Mode” using the button on the toolbar.
5. Click on the “Spectrum Method” button on the toolbar. A tabbed dialogue button will now open
to allow you to set the parameters for the measurement.
In the “Measurement” tab: Enter the wavelength range via the “Start” and “End” fields. Always enter the longer
wavelength into the “Start” field and the shorter wavelength into the “End” field. NOTE
the operational region of the spectrophotometer is between 1040-190nm.
 Select the scan speed to be Medium via the drop down menu. Medium is fine for the
broad absorption bands typical of organic materials; if you have samples with sharp
absorption features, it may be better to run a slower scan.
 Select the sampling interval as 1nm from the drop down menu.
 The “Scan Mode” should be set to “Single”.
In the “Instrument Parameters” tab: Select Absorbance from the “Measuring Mode” drop down menu. (Transmittance is also
possible)
 Select a value of 1nm from the “Slit Width” drop down menu.
 Ensure that the “Light Source Change Wavelength” is set to 360nm and the “S/R
Exchange” is set to “Normal”.
6. Set up the sample mounts in the configuration that you will use to carry out measurements
without any sample or reference in place. Close the lid of the sample compartment.
7. Run a baseline calibration by clicking on the “Baseline” button at the bottom of the screen.
Ensure that the baseline range matches that which you have previously entered in the “Spectrum
Method” dialogue. Click “OK” to run the baseline calibration.
8. To obtain a spectrum, click on “Start” and the machine will begin collecting data with the
parameters you have specified.
9. Ensure that the baseline is good by first running a scan with no sample in place. You should
obtain a flat baseline with noise distributed about zero.
10. Now insert your sample and reference into the sample mounts in the sample compartment
(Ensure that the lid is closed before taking measurements) and take a spectrum as before.
11. When the scan is finished, enter a label into the dialogue box which appears. NOTE: This does
NOT save your data.
12. To save a data set, select “Save As” from the “File” menu and enter a filename. Select “Data Print
Table (*.txt)” from the “Save As Type” drop down menu. This will save the data in an ASCII text
format which you can access using other software. Please only save data in your directory under
the “Users Data” folder.
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13. It is good practice to take another absorption spectrum with your sample oriented at 90 in the
sample mount. This will give you two data sets for the same sample and will allow you to assess
the reliability of your data, which may be affected by the uniformity of the film.
14. To shut the instrument down press the “Disconnect” button at the bottom of the screen and trun
the instrument off using the Power On/Off button. Close the software and shut the computer
down when you are finished with it.
15. Ensure that the lid to the sample compartment is fully closed when you are finished as external
light leaking into the can cause damage to the PMT.
It is quite acceptable to leave the machine running the day should it be used regularly, however it
be inactive for long periods of time (>3hours), it should be shut down to preserve the lamps. The
machine should be shut down at weekends and overnight, If you see the instrument left on late at
night or at the weekend please shut it down.
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