Question: Question: How do I measure the absorption spectrum of a sample?

lucca_fabani is asking a question about spectral-workbench: Subscribe to answer questions on this topic

lucca_fabani asked on December 30, 2015 20:54
1,203 | 0 answers | #12549

I am starting a project for school (8th grade science project) and need to measure the absorption spectrum of methylene blue. Now I am struggling to subtract th backlight source from my spectrum. the video in the website does not look like my browser settings... any help appreciated.



What video are you referring to?
What spectrometer are you using?
What light source are you using?


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Hi Chris, I am using the v3 Spectrometer kit, I have tried different light sources, the one i am currently using is a white LED, i have tried with an incandescent light also. the video is the help video on the website where instructions on how to subtract light sources are explained... at the moment I can capture spectra and save them but I have not been able to remove the backlight source from them. thanks so much for your help!

I guess you are referring to the video on this page:, which is this video:

I have not used that feature of Spectral Workbench, and I don't know how it has changed since the video was made. Maybe someone more familiar with that feature can help.

When doing absorption spectrometry, the idea is to capture a spectrum of a light source and then put a translucent sample between the light and the spectrometer and capture another spectrum. Less light of certain wavelengths will be transmitted through the sample. When the second spectrum is captured, the exposure settings on the camera in the spectrometer cannot change. If an automatic exposure feature of the camera allows the camera to adjust to the lower light levels with the sample in place, the difference between the two spectra will not be a reliable measure of how much light the sample absorbed. Maybe someone familiar with the Public Lab spectrometer can explain how that problem is dealt with.


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Hi, lucca - what are your spectra you're trying to subtract, can you link to them?

In the new Spectral Workbench, you can subtract using the Operations system; I can help you once you post your links. Thanks!

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Maybe, the projects to measure the absorption spectrum of methylene blue are based on OTK prototypes, not in v3 Spectrometer kit. See more in:

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