Absorption Spectrum of Janus Green B using a Genesys 30 on Live Display Mode 

Thank you very much!

I have never experienced this issue before. When I Googled it, this is the first link listed. www.researchgate.net/post/what_can_cause_a_dark_current_error_on_a_spectrophotometer Sound like you have an issue with your bulb. Either not working or this is a misalignment in the light path. What model of Spec are you using?

Thanks for the question Carlos. I did not use a calibration manual to prepare the 25 mg/mL solution of Janus Green B. I performed a serial dilution from the Stock solution. Our Stock solution of Janus Green B was 500 mg/L. I did a 1:10 dilution (0.5 mL Stock + 4.5 mL solvent) to obtain 50 mg/mL. This was followed by a 1:2 dilution (1.5 mL 50 mg/mL + 1.5 mL solvent) to obtain the 25 mg/mL solution. Why did I chose 25 mg/mL? I did a number of trials to ensure the dye was not too concentration or too dilute. I discovered that 25 mg/mL gave the best dynamic range of values. Hope this helps answer your question.

@@ProfessorDrewCollop ok thank you very much teacher. Excellent your comment. I'm going to look here in Venezuela to see if that chemical is found. I have the same equipment but we verify with a solution of potassium dichromate and sulfuric acid, in our laboratory we analyze rums and whiskeys. and I would like a standardized procedure.

We also use Cupric Sulfate, Methyl Orange, or Safranin in our labs to teach students to use the Spectrophotometer. The only reason I selected Janus Green B for the video was because it was already in my lab. When the students actually complete the lab, they use one of the other chemicals. They all give a very nice result.

@@ProfessorDrewCollop 61 / 5000 Translation results Thank you very much, I am attentive to another analysis of you thanks

We must have 40 or more in our labs. Never had an issue with them. We use them in our teaching labs, so cuvettes are not an option for us, based on the cost of so many we would need. We found some really good short tests tubes that work very well. A standard sized test tube is too large for the lid to close. Let me know if you want to know the exact product we use.

@@ProfessorDrewCollop Thank you for the info!

@@ProfessorDrewCollop If you don't mind me asking, how long have you had these for now, so far it seams like about the best answer for student labs

Not sure when we got the first one. Probably 3 years ago. We did not move them into the curriculum until Fall 2020. With the pandemic, we needed to revise the labs and that was our opportunity to introduce the Genesys 30. I know another faculty member that was using an older product. When they tried this model out, they decided to switch immediately. So far I have not had any issues, nor heard of any problems from other faculty. I would recommend it.

@@ProfessorDrewCollop Thank you much for all the information!

You might want to check your audio, as there is voice over for 50% of the video. At the half way mark I state that I am just going to be running the samples for larger number of wavelengths and I stop the voice over at that point, as it would be superfluous to continue speaking.

@@ProfessorDrewCollop Yes; indeed. Could you please share the plots of the final output, on x-y axis? Also, in practical terms, what characteristics can it measure in wastewater?

Sorry, I cannot add the final graph to this video, as this is an activity I get my students to perform after watching the video. If you really wanted it, you could graph it yourself. Plot wavelength (nm) as your independent variable (horizonal axis) and Absorbance (no units) as your dependent variable (vertical axis). The Spectrophotometer measures absorbance of different wavelengths of light by a sample. As a Biologist, I do not work with waste water. I suppose you could analyze the turbidity of the water as a function of how many particles are in it. We have some Chemists and Chemical Engineers, within our department, that work with waste water. If you are really interested, I could put you in touch with them. The Spectrophotometer works best for a single known chemical, with a known wavelength of maximum absorbance.