Thanks - so glad to hear that it's informative AND fun! I'm definitely making more :)

Yay glad it was helpful!

Thanks!! Glad the video was helpful

@@YouTooBio Can I ask what if I want to measure the absorbance of methylene blue after I put carbon coated sand with it ... If I press ZERO-BLANK in the device it gives me (insert empty cuvette or distilled water)... should I do that or insert a cuvette contains MB from the stock solution ??

@@bxwn8931 1) use the same concentration of MB for the blank, 2) the spec only works for dissolved solutions - if the sand sinks to the bottom you won't get a meaningful measurement (unless the sand changes the color of the MB, in which case mix them for some amount of time, then measure just the liquid portion with the spec)

Thanks! Glad you enjoyed them!

Yay glad it was helpful!

Glad it was helpful!

Thanks so much!

Wow that's a new one! Share the fan fic when it's ready?

I want to read your fanfic now

Glad it was helpful!

Thanks!

Yay! Glad it was helpful

It's already recorded once you set it up, so you don't have to set it every time. See 3:57

Great question! If you don't have a protocol telling you what wavelength to use, then you need to determine the absorption spectrum for your sample - do this by measuring the absorbance (A) across the visible spectrum (~400-700nm), measuring every 10 or 25 nm or so. This will give you a curve showing you the wavelength with the highest amount of absorbance - that's the wavelength you'll use for subsequent experiments testing concentration of that substance. For your second question, if your sample is red, then your sample won't absorb red light - it reflects red light, and that's why it looks red! So, if you use red light (wavelengths 600-700nm) for a red sample, you'll have an absorbance near or at 0! For further reading: chem.libretexts.org/Bookshelves/Physical_and_Theoretical_Chemistry_Textbook_Maps/Supplemental_Modules_(Physical_and_Theoretical_Chemistry)/Kinetics/02%3A_Reaction_Rates/2.01%3A_Experimental_Determination_of_Kinetics/2.1.05%3A_Spectrophotometry

@@YouTooBio Ok great thanks. Last question 🙏🏻 why do we measure at certain wave length? We can get the conc. Of the sample from standard curve. But if we didn't measure at certain wavelength it will give us zero or negative. Why? I googled for the answer a lot but i didn't find a satisfying answer. Second, I heard that If we want to measure wavelength for a specific color we use the color that's before it or the color that completes it I think😅 Is that true?

It's a lot easier to measure at one set wavelength than to do a standard curve for each sample! Generally it's true that if your sample is one color, you will use the opposite color (on the color wheel) for absorbance, which has to do with why colors look the way they do. But it's hard to predict for some samples that don't have obvious color "opposites" - like a culture of bacteria. That's why you do the absorbance curve to determine the optimal wavelength to use.

Glad you liked it!

Glad you liked it!

Thanks!

Hi Kevin! The spectrophotometer in this video is a Thermo Scientific Genesys 10UV. There are some on eBay. Also, check out Sebastian Cocioba at twitter.com/ATinyGreenCell who is doing lots of biology in a DIY home lab and eagerly helps other DIY scientists!

@@YouTooBio Awesome, thank you!

Interesting problem! I don't know! It may depend on your spectrophotometer make and model. Consulting the operating manual would be my next step.

The difference is in the volume needed to measure the sample. Nanodrop needs only a couple microliters

It depends on 1) the device, does it drift? Probably not but I've seen old specs have unreliable results, so maybe? 2) whether your sample settles between preparation and measurement. The best way to check is to measure your sample as usual, re-blank, then measure your sample again. If you get two different results, then yes it's a problem to blank once before all the students measure their samples. See if your instructor will let you try that.

Yes!

Thanks!

I'm not sure - are you talking about fluorescence spectrophotometry?

Yes :(

That is outside my expertise, sorry! Maybe you can find your answer here? www.chem.uci.edu/~dmitryf/manuals/Fundamentals/Fluorescence%20Spectroscopy.pdf

2:40 "Step 1: set the wavelength"

Glad you enjoyed it!

What is your sample? If it has heavy particles, they can settle out of the solution over time, which will change the reading.

@@YouTooBio sulphuric acid, water and dissolved wood particles.. i did klason lignin treatment on empty fruit bunches and I wanted to find out the absorbance of my samples after the treatment

However, I just took the supernatant of the samples

Yeah sounds like large particles. Be sure to shake your sample before pipetting into the cuvette and then take the reading quickly

Sorry I don't know the make and model of the spectrophotometer in my video! As a scientist working without lab access, I suggest you check out Sebastian Cocioba on Twitter - he does DIY biology and would likely have lots of advice twitter.com/atinygreencell

This model is Thermo fisher genesys 10 spectrophotometer go to 2:40

Spectrovis plus is the cheapest but accuracy not too good Personally I recommend ocean insight I have STS - Vis as Edu kit with all light source, cuvette holder They used to sell as Edu Kit which is much cheaper for all components But now STS series replaced by ST spectrometer , STS and ST are same size Those ST/STS are small but they rival the big one like Shimadzu, Agilent , Thermo fisher (the one in video) in terms of accuracy of absorbance