Determining Glucose Concentration using a Calibration Curve
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- เผยแพร่เมื่อ 21 พ.ย. 2020
- This video shows you how to make a serial dilution of glucose solution and carry out a quantitative Benedict's test to generate data. It takes you through how to use a colorimeter, plot a calibration curve and use the curve to find out the concentration of an unknown glucose solution.
This is a required A Level practical and skill for all A level Biology specifications including PAG 5.2 for OCR A.
biologybreakdown.co.uk
my teacher rushed it through the practical thanks so much for making life so much easier (just dropped a sub)
Glad you found it useful, there is quite a lot to do in this practical, lots of new skills, especially so early on in the course! Good luck! 😊
2:39
Can i know what is 2 cm cubed that u added to each concentration?? Is it distilled water ?
Hi! You have 7 tubes. In 5 of the boiling tubes you put 2cm cubed of each concentration you have just made from the serial dilution. Then in your 6th boiling tube you can add 2cm cubed of distilled water to act as your 0% sucrose solution and in your 7th tube 2cm cubed of your unknown concentration. Hope this helps! 😊
Plz i have a submission for uni id you can reply quickly i would really appreciate ig. I also want to ask abot using that graph to determine unkown concentrations, do we use the curve of best fit or do i have to draw a line of best fit too to work the unkowns??
If I can see the graph I can advise further 😊. Email it to me mrsh@biologybreakdown.co.uk
Hello Again Mrs H, Just another quick question....
What kind of Benedict's Reagent do you use in this experiment? I read the description and it says 'quantitative Benedict's test', but I'd just like to confirm this. Did you use a Quantitative Benedict's Solution, or a Qualitative Benedict's Solution?
I ask this because after heating and cooling the solution, your different glucose samples all seem to remain blue, and that's a property of Quantitative B.Sol, but then, the concentrations of glucose used are relatively low to produce any significant colour change.
Thanks a lot, and honestly this procedure has helped be so much already, that this teensy snag won't hurt!!! (but i'd like there to be no shortcomings at all 😅)
Hi yes, you’re very right. This is quantitative Benedict’s solution which gives a white precipitate and our technician tells me this works better for making calibration curves. If you need to know any more technical details I will have to ask her, I’m just the teacher! 😂😊
@@BiologyBreakdownwithMrsH ahh ok thanks a lot Mrs. H, and no, I don’t have any more questions. 😃🫶
Hi! The procedure is very helpful, thanks a lot! But I have just a small question. Would it be better if we filter out the precipitate before measuring the absorbance of the clear solution? Thanks again!
Hi, filtering could work if you have good enough filters, I’d have to check with the technician. Ideally a centrifuge is the best option but we don’t have one at our school so wait for the precipitate to settle. As long as we don’t disturb the precipitate our results tend to be ok 😊
@@BiologyBreakdownwithMrsH Hi, thanks for your quick response! Could you please expan on the technique you used to extract just the solution without disturbing the precipitate? I think the video mentions something about squeezing the dropper before placing it in the liquid…..
Sure! squeeze the dropping pipette before you put it into the solution, keep it squeezed while you put it in, once in the solution (above the precipitate) gently release the squeeze and the pipettes should fill. Gently remove the pipette from the solution and then squeeze the contents out into the cuvette. I doubt you will be asked this in an exam but it’s good to know. Lots of students put the pipette into the solution and then squeeze and this will blow outwards and disturb the precipitate. Try it using water first just to see what I mean 😊
@@BiologyBreakdownwithMrsH Thanks a ton Mrs H!! ❤
I am an IBDP student and am planning on using glucose spectrophotmetry as a part of my Biology HL IA, and the procedure you’ve used is very straightforward. This video helps me a lot!! 🫶🫶
Wow, that sounds pretty impressive! Good luck 😊
If i have data that looks more like curve, do the curve have to go throght all the points ??
Hello! Not necessarily! Would you like to send me a photo of your graph and I can take a look? mrsh@biologybreakdown.co.uk
@@BiologyBreakdownwithMrsH OMG thank you so much for replying and willing to help, submission was yesterday and i was so busy trynna finiah that i forgot about my comment. But still thank you because you just re-assured me by saying that it's not necessarily that it would go through all points, bcause my points didn't make a perfect curve. All the best, here's a sub from me ❤❤
Bless you! And good luck 😊
Fingers crossed unis mark by the same rules as GCSE and A Level 🤞🤞