- minimum volume: 5 mL
- use green-capped test tubes (larger diameter)
- use a blank containing your media
- ok to leave on all day, but do turn it off when done
- bulbs are cheap (UV bulbs are generally the expensive ones)
- Turn on by turning leftmost dial clockwise
- Allow the spectrophotometer to warm up for at least 15
minutes to stabilize.
- Set filter to 600 nm (or whatever)
- Zero transmittance with left knob
- Put in blank & cover with black cap
- set transmittance to 100
- absorbance for the blank should now be 0
- Measure absorbance for your sample
- Keep tube orientation the same each time you measure in case of any unevenness.
Manual's Version of Instructions
1. Turn on the SPECTRONIC® 20+ by turning the Power Switch/Zero Control (knob on the left side of instrument) clockwise. Allow the spectrophotometer to warm up for at least 15 minutes to stabilize. 2. After the warmup period, set the desired wavelength with the Wavelength Control Knob. 3. Set the filter lever to the appropriate position for the selected wavelength (not required for SPECTRONIC ® 20). 4. Adjust the meter to 0%T with the Power Switch/Zero Control (knob on the front left side of instrument). Make sure the sample compartment is empty and the cover is closed. 5. Fill a clean cell with water (or blank solution) and wipe the cell with a tissue to remove liquid droplets, dust and fingerprints. 6. Place the cell in the sample compartment and align the guide mark on the cell with the guide mark at the front of the sample compartment. Press the cell firmly into the sample compartment and close the lid. 7. Adjust the meter to 100%T with the Transmittance/Absorbance Control (knob on the front right side of instrument). 8. Remove the cell from the sample compartment and empty the water. 9. Rinse the cell twice with small volumes of the solution to be measured and fill it with the solution.