Spectrophotometry (Absorbance)

[@nurulhasan3953]

Oh my. How on earth am I finding this class so late today? Your explanation is digestible, very well understandable as opposed to my university lecture. Great job, Mam.

[@OldSchoolChemistry]

Hi Nurul, that makes me so pleased. I am glad it was helpful. God bless you in your class!

[@RITHINHN]

Now I saw your channel and I was simply shocked by seeing number of subscribers,even after great teaching, and then I saw the number of videos you made , but again there was plenty of them , mam you are really consistent and you definitely get very big success one day 😀

[@OldSchoolChemistry]

Rithin thank you for your kind comment! I hope your class goes well💕

[@juwairiyaiffat8714]

thank you soo much..you told me exactly what i needed to understand lab experiments in my graduation.

[@OldSchoolChemistry]

Hi Juwairiya, I’m so glad. Good luck with graduation!😊

[@adellsspeedarts3978]

Thank you ! It helped me a lot, I am studying for my Graduation and Spectofotometry is one of my questions

[@OldSchoolChemistry]

Good Luck!!

[@Sim_2002]

Tha satisfaction when u r searching for an information and you find an excat image of what u had in mind.... I'm glad i found your channel......i have a project presentation and i was in need of it thankyou mam!!!

[@OldSchoolChemistry]

Hi Sim, that is wonderful news and makes me so happy. Thank you for sharing! I hope your project goes well!!

[@kennyyemi5752]

What a great teacher you are! You just opened my eyes!

[@OldSchoolChemistry]

Hi Kenny, that makes me so happy! Thank you for sharing😊

[@nightstars_0]

This is the first time I have seen you and you look very beautiful. It clearly seems to me that you are a wonderful teacher or doctor. You have an amazing way of conveying information in a smooth manner. Thank you.💗

[@OldSchoolChemistry]

Hi Nightstars, Thank you for your kind comments. I am glad they were helpful. I hope your class goes well:)

[@guptasomil888]

Hi @OldSchoolChemistry I have a compound and want to calculate the absorptivity on dried basis, and also need to compare with standard solution absorptivity.. please give me a calculation formula to calculate the same.

[@OldSchoolChemistry]

Hi Guptasomil, I am sorry I don't know what that formula is. I hope you find it easily!

[@Kikipoo9952]

I just wanted to say I really love your bangs. Really few people pull them off and you do it wonderfully :D

[@OldSchoolChemistry]

Hi Kiyaan, I appreciate your comment. Thank you for that! :)

[@Amna313]

omg thank you so much! I have final biochemistry lab exam on Sunday, this was so helpful🥹🤍!

[@OldSchoolChemistry]

Hi Amna, I am glad it was helpful. God bless you on your test tomorrow!

[@mtfhs]

Thank you Mrs. Laub, Your explanations are much clearer than my professors :)

[@OldSchoolChemistry]

Hi Marco, I am glad it was helpful! Good luck in your class:)

[@hypatiatv1]

U deserve MUTCH MORE followers, exellent explanation, simple and efective.

[@OldSchoolChemistry]

Hi Hypatia, I appreciate that, thank you! Please subscribe if you haven’t already. I hope chemistry goes well. Thanks!!💕

[@hypatiatv1]

@@OldSchoolChemistry Ok, i am your follower alredy, pls like my comment up, thanks.

[@lalayatem3758]

You’re amazing at teaching! This makes so much more sense , thank you. God bless

[@OldSchoolChemistry]

Hi Lalaya, I am so glad it was helpful for you. God bless you too! Thank you:)

[@estelamino6356]

Thanks so much. Very clear step by step...

[@OldSchoolChemistry]

Hi Estelamino, I am glad you think so! Thank you for your comment:)

[@jaishrisahu3031]

Mam you explained it so clearly.thank you for this video❤ And you have a soothing voice .

[@OldSchoolChemistry]

Thanks you Jaishri. I appreciate your kind words. Please subscribe if you haven’t already. I hope chemistry goes well for you!😁

[@migamundi]

Thank you!! It was very clear!! Helped me a lot!!

[@OldSchoolChemistry]

I’m so glad! Be healthy and safe😊

[@تتاسعيد]

Thanks dr , keep going

[@exe.m1dn1ght]

i had to watch the video twice because first time i couldn't stop looking at those beautiful eyes and smile

[@mdmahfuj8805]

Absolutely outstanding 🔥💝 masallah From Bangladesh 🇧🇩

[@OldSchoolChemistry]

Hi MD Mahfuj, thank you. It was God's blessing! Sending love to you in Bangladesh!

[@kaansarper5820]

you are really good at it !!!!!!! nice explanation

[@OldSchoolChemistry]

Hi Kaan, Thank you. I am glad you think so! I appreciate your comment;)

[@rouh]

Wonderful explanation.. thank you

[@cxltrsn37]

Hello. Just found this vid and it's very helpful. I'd just like to ask, where can you find and how can you know what wavelength to use in a specific solute? Thank you so much!

[@mariamhunak3026]

Amazing explanation!

[@OldSchoolChemistry]

Hi Mariam, I am so glad. Thank you for your comment! :)

[@bensonboyi1040]

You are good teacher 😊

[@OldSchoolChemistry]

Hi Benson, thank you! I appreciate you watching:)

[@fafa.paupieres5143]

Merci beaucoup c'est très clair à présent!

[@OldSchoolChemistry]

Hi FaFa - I am glad it was clear. I had 2 years of French in college. It is fun to read your French. Thanks for making me smile!!

[@fafa.paupieres5143]

@@OldSchoolChemistry haha yeah I m french! I learn english at school (my english is not perfect)I will pass my exam (le baccalauréat) thursday. I listen your video with the subtitles and it was clear merci beaucoup:)

[@OldSchoolChemistry]

@@fafa.paupieres5143 Your English is very good!

[@chococipie3849]

I understand it so well! Thank you so much for the explanation :)

[@OldSchoolChemistry]

Hi Choco, I am so glad! I hope your class goes well. Please subscribe if you have not already. Thanks! :)

[@amalinanaimah9266]

Oh my god. I love you so much thank you so much for this 💕💕💕

[@OldSchoolChemistry]

Hi Amalina, I’m glad this was helpful. I hope your class goes well💕

[@farahquba757]

Hi! Love this video. Can you please do a video explaining a spectrophotometer procedure for the determination of caffeine contents please?! Thank you

[@OldSchoolChemistry]

Hi Farah! It should be similar to the procedure I showed. Set your spectrophotometer wavelength to 275 nm. Good luck!!

[@farahquba757]

@@OldSchoolChemistry with what i know, i should use wavelength 670nm, but that is after extraction of caffeine and reaction with citric acid, naoh, glacial acetic acid and phosphomolybdic acid in order to form a blue solution. is that necessary?

[@OldSchoolChemistry]

For a blue solution that is perfect!

[@mohammadilhamaziz7855]

thanks for the explanation miss 😊

[@OldSchoolChemistry]

Hi Mohammad, my pleasure. Thanks for watching:)

[@naveenprasath5102]

Thank you mam for this video, I really learn from it

[@harjitkaur1601]

Thank you! Very clear

[@OldSchoolChemistry]

I’m so glad. I hope your class goes well😊

[@qingyuanzhou3984]

Thank you so much ms🎉

[@KatyLynnWinery]

I basically understand the principle of the spectrophotometers use. It is most often talked about in terms of one specific solute. If you have a mixture of multiple types of sugar such as in the boiling of starch/ various grains breaking them into a fermentable sugar how do I get a idea of how much sugar is in the solution measured? Do I have to find the wavelength for each know sugar In question or can related absorbance to increase overall starch converted now to some sugar?

[@OldSchoolChemistry]

Hi R. Finch, if I’m understanding correctly you have a mixture and want to identify the concentration of one solute. Create a beer lambert plot for that one solute based on lambda max ( maximum absorption of that sample). Then run the sample at the same wavelength to determine concentration of that specific solute in the sample. I hope that helps. Please subscribe if you haven’t already.

[@santhoshgudibanda1192]

Nice madam

[@mohfa1806]

thank you ..great explanation

[@OldSchoolChemistry]

Hi Mohamad, I’m glad. I hope your class goes well!!😊

[@ayaelmasry744]

Thank you very much 💖😊

[@0anniegrace]

Thank you so much!

[@OldSchoolChemistry]

I hope your class goes well!!🧡

[@marah1258]

Thanks a lot professor 🤍🤍🤍

[@OldSchoolChemistry]

Hi Marah, You are welcome. I hope chemistry goes well for you!😊

[@doniadaramly7894]

How can I determine molar absoptivity theoritacally? And does it have any relationship to maximium wavelength that determined by woodward fieser rule and alpha beta unsaturated?

[@OldSchoolChemistry]

Hi Doniadarmly, Honestly, I am not sure. Lambda max for wavelength gives you the maximum asborption at a particular wavelength for a specific substance. To determine molar absorptivity using the formula you would need the absorbance, concentration, and length of the cuvette. I hope that can at least point you in the right direction. It would be advisable to talk to your professor. Thanks!

[@doniadaramly7894]

@@OldSchoolChemistry thank you 💕 I am wondering what the importance of determining lambda max?

[@OldSchoolChemistry]

It tells you what nanometer to set your spectrophotometer machine to. It can then read for that particular solution color (lambda max). Thanks!

[@doniadaramly7894]

@@OldSchoolChemistry thanks alot 👏🧡

[@fabioverdi6291]

Hello there. Help with a question ? A compound absorb light in 227 nm. The standard curve calibration for the compound is Abs = 372x + 0,6432 which the concentration is g/100mL. The technique was standard addition method from fluoxetine hydrochloride (C17H18F3NO.HCl - molar mass = 345,79 g/mol). So determine the concentration in mol/L in the analysed solution. Show all calcs progression.

[@OldSchoolChemistry]

Hi Fabio, you would have put the analyzed sample in the spectrophotometer machine and gotten an absorbence reading. Take the absorbency value of the sample and plug it into your equation as Abs. Then solve for x which is the molarity of the solution. Good luck!

[@fabioverdi6291]

@@OldSchoolChemistry Hello thanks for your return. It's an exercise question i don't have equipment to use. Let me post the full question: Standard addition is an analytical technique of extreme importance to an analyst, as it eliminates the interfering effect in most determinations. Fluoxetine is widely used as fluoxetine hydrochloride, also known as Prozac®. This is indicated in the treatment of depression, associated or not with anxiety. This compound absorbs ultraviolet light at a wavelength of 227 nm. It has in its structure a stereocenter, being a chiral drug. It is known that only the (R) -fluoxetine isomer has activity, while the other enantiomer has no pharmacological action and there is no evidence of toxicity to the organism. In an industry, when performing the Fluoxetine analysis, the following analytical calibration curve was obtained, in which the concentration is in g / 100 mL: Abs = 372 CFluoxetine + 0.6432. Knowing the analysis was performed according to the standard addition technique and that the molar mass of fluoxetine hydrochloride (C17H18F3NO.HCl) is 345.79 g / mol. Determine the mol / L concentration in the analyzed solution.

[@OldSchoolChemistry]

Hi Fabio, I am missing something. You need the absorbance of the sample to calculate the g/100ml concentration which is x in the equation. Once you have that you can use molar mass to cover it to molarity. I’m sorry I could not be more helpful! I would ask your professor how you determine the absorbance in this problem. Thanks!

[@fabioverdi6291]

@@OldSchoolChemistry I thinks i need to use this equations but i dont know how. S= k . Ca y = m*x + b Y = S x = Vs m = k . Cs / Vt b = k.Cx.Vx / Vt It's a friend whom sent me and i couldn't to do it. I researched i found this 3B4 equation. ( www.mathcentre.ac.uk/resources/uploaded/3b4printableversion.pdf ). But i dont know the source from y value which has been used. I have the alternatives but idk which is the correct nor how to reach on it. 2,25x10-5 mol/L 5,58x10-5 mol/L 5,0x10-5 mol/L 9,69x10-5 mol/L 3,08x10-5 mol/L

[@OldSchoolChemistry]

Hey Fabio, I’m not familiar with all the symbols either. Good luck!!

[@petecastro749]

I would like to ask, if the concentration is not given and the absorbance is questionable how do we determine the absorption coefficient?

[@OldSchoolChemistry]

Hi Pete, if you know the wavelength and ion you are testing, you can look up the coefficient. Are you trying to determine the coefficient or are you trying to find the concentration of an unknown solution? If determining the concentration, use A1/A2 = C1/C2. Thanks.

[@UniChannel-pg8ol]

amazing!!!

[@OldSchoolChemistry]

Hi Uni:) Thank you for your comment!

[@UniChannel-pg8ol]

@@OldSchoolChemistry bless You teacher thanks!!!

[@OldSchoolChemistry]

@@UniChannel-pg8ol Hi Uni:) God bless you!!

[@UniChannel-pg8ol]

Amen⭐🪽🙏

[@elisapiahossain2859]

thank you so so much!!!

[@OldSchoolChemistry]

Hi Elisa, you are welcome. Thank you for your comment:)

[@adellsspeedarts3978]

I am here again, I discovered that I don´t quite understand what transaminance is, I know you don´t speak about this topic in this video, but I´m just curious what is it, do you think that you could briefely tell me about it ? I would be grateful

[@OldSchoolChemistry]

Hi! Transmittance is how much light passes through a substance. It is the ratio of the amount of light that got through over the initial amount of light that was put in. Absorbance is how much light is absorbed. The mathematical relationship is: Abs= -log T. Here is a great video for you www.khanacademy.org/science/chemistry/chem-kinetics/spectrophotometry-tutorial/v/spectrophotometry-introduction

[@adellsspeedarts3978]

Thank you, It helped me a lot

[@edouardamenie3885]

In my case I don't have any concentration ... how can I calculate the concentration from the absorbance

[@OldSchoolChemistry]

Hi Edouarda, there are 3 ways to find concentration. One, you need at least 2 absorbance values and one concentration value to calculate an unknown concentration. Set the values up as a ratio and solve for the unknown. Two, look at beer lambert graph. Match the given absorbency to the corresponding concentration. Third, use the formula Abs=abc. You need Abs,a,b and solve for c which is concentration. Your question will fall in one of those categories. I hope it goes well!!

[@edouardamenie3885]

@@OldSchoolChemistry Abs= abc I got my absorbance and the path length is 1 so b=1 ... but I don't know how to get the constant a 😭😭 If I may show you the work cause I have been on this since morning

[@OldSchoolChemistry]

@@edouardamenie3885 If you know the compound, you can look up the molar absorptivity which is a.

[@zainabdheyaafalih3620]

Why was the sample cooled to room temperature before measuring the absorbance?

[@OldSchoolChemistry]

Hi Zainab, in my example in the video students simply diluted a stock solution of copper (II) sulfate. This was done at room temperature for each concentration so temperature was not a variable. Absorbance can be used as an experimental technique when running experiments. It is possible a professor would ask you to run samples of solutions at different temperatures to identify concentrations impacted by the rate of the reaction. This would be a very specific request. Most absorbance labs and Beer Lambert plots are run to identify the concentration of an unknown substance. Temperature will be constant in this type of experiment. Rate can also be determined with absorbance labs. This is focusing on concentration versus time. My guess would be the temperature must be at room temperature to serve as a constant and not a variable. I hope that helps!

[@zainabdheyaafalih3620]

Thank you so much 🥰🥰 My experiment is about amino acid assay by ninhydrin colorimetric method so l want to know why we cooling the sample .... agein thank you so much 😘😘😘😘

[@OldSchoolChemistry]

Most likely to maintain temperature as a constant and for the amino acids to be stable. I hope it goes well!

[@ninacurry4228]

Thank you so much for this video! You explained it so well. =)

[@OldSchoolChemistry]

Hi Nina, you are welcome and thank you for your comment. I hope i your class goes well!!

[@petecastro749]

Since the volumes assigned to us start with 0 yet the absorbance reading showed a value greater than 0

[@OldSchoolChemistry]

Absorbance will always be greater than zero if it is a colored solution. The ions in the solution will absorb some of the light energy as the light passes through the solution. Thanks!

[@isaksmith656]

Nice

[@OldSchoolChemistry]

Hi Isak, thanks for the comment!

[@robertzfindingz3512]

molar .. moles in the manameter .. avogadro's number is to the 23rd .. chemistyry can be fun ... --- compounds ... all very elemental watson .. electron shell spin valence and isotropic .. -- the beaker .

[@OldSchoolChemistry]

It sounds like a poem:)

[@robertzfindingz3512]

@@OldSchoolChemistry sorta .. just random jazz .. or random associated chemistry terms .. i'll bet u have a master's maybe even a phd in chem .. --- and some teaching experienc ....

[@OldSchoolChemistry]

@@robertzfindingz3512 Lots of teaching experience and Master's in Teaching Science...only a BS in chemistry. I also have experience working as a chemist - it helps! Keep sharing your "random jazz!"

[@terzatloukalova7762]

Love your video

[@OldSchoolChemistry]

Hi Ter, I am so glad. Please subscribe if you have not already. Thanks!

[@vikasvb1716]

This is awesome

[@OldSchoolChemistry]

I hope your chemistry class goes well!!😊

[@OldSchoolChemistry]

Hi Vikas, I’m sorry I do not have an Instagram page. Maybe I should get one!

[@vikasvb1716]

@@OldSchoolChemistry yes mam thank you so much for replying me

[@amailyakter6589]

excellent

[@OldSchoolChemistry]

Hi Amaily, thank you for your comment. Enjoy chemistry😊

[@idkanymore1510]

thank you, im currently taking ochem 2

[@OldSchoolChemistry]

Horikta, I’m proud of you being in o-chem 2. It is a tough class. Good luck!

[@theradzlis]

hi. love your vid. do you have a video on colorimetry? will you make one? =D

[@OldSchoolChemistry]

Colorimetry is the same principle, just a less expensive instrument. You still plot absorbable versus concentration.

[@masror_ah]

Im just really disappointed that these 6 minutes are WAY TOO better than that one hour literally more than one hour that our teacher spent to (pretend that he was) explain it.

[@OldSchoolChemistry]

Hi Masror - I'm sorry about your professor. I have sat in similar classes as a student. I am glad this was helpful. I am proud of you for looking for outside support. I hope you do well in your class! Please subscribe if you have not already. Thanks:)

[@SiddharthSingh-zd7ny]

Aniruddha apko like karta hai mam

[@OldSchoolChemistry]

Hi Siddharth, thank you. I like you too!😊