CHE 450G: Practical Inorganic Chemistry

U of KY Dept of Chemistry

Spectronic 21D Instructions

This handout explains how to use the Spectronic 21D UV/VIS Spectrophotometers found in various laboratories in the building. You probably won't use these familiar instruments in our class, but if the other spectrophotometers are busy, you might have to.

a picture of the instrument

Step by Step Instructions

Sign in on the logbook.
Turn on the instrument using the power switch on the right side. Let it warm up for at least 10 minutes -- 30 minutes is preferable.
Select the desired wavelength by turning the wavelength selector knob (it's the one on the left).
Fill a cuvette with a blank solution (usually distilled water) and place it in the sample compartment. The cuvette should be at least 3/4 filled. There should be no air bubbles in your cuvette or fingerprints on it (...because you don't touch the optically clear sides of your cuvettes, this won't be a problem, RIGHT?). Close the lid to the sample compartment.
On the lower left side of the instrument, use the 100%T dial to adjust the reading on the display to 100%T (transmittance) or 0% (absorbance). If you can't get the readout to this value, you can try moving the Sensitivity switch to M (medium) or HI (high).
Remove your blank, replace it with your sample and close the sample door lid. Set the MODE SELECTOR to transmittance or absorbance (depending which you want to measure).
The reading will be displayed on the digital readout. Record your data. You can run as many samples as you wish without recalibrating (steps 4 and 5) as long as you don't change the wavelength:
- Important: Whenever you change the wavelength, you will need to rezero (steps 4 and 5)! If you are making measurements over a long period of time at one wavelength, you may want to periodically recheck your zero calibration.
When you are finished with the instrument, turn the power off. Make sure you remove and clean your cuvettes and clean up the area around the instrument.
Sign out on the logbook.

As always, be sure to report any problems to your TA immediately.

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