October 18, 2021, 12:36:30 PM
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Topic: year 13 3.1 titration internal. Calcium and magnesium content in raw milk  (Read 4317 times)

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Offline emzy

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I recently carried out the investigation internal. I wanted to investigate how mg and ca concentration changed when i heated raw milk, between 35 and 75 degrees centigrade. Used the EDTA salt complex and titrated with MgCl2 using erioT indicator. I thought it went well, got concordant results, but I have a trend which increases as I heat it. I'm pretty sure this makes no sense chemically and I've looked on internet but nothing seemed to fit or was too complicated. Could someone please suggest whats happened and if there is anyway I can still use my results to pass this internal, or point me to some websites which would help me as I can't find anything. Would be much appreciated, thanks :)

Offline Borek

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Please elaborate and/or show your results, it is not clear to me if I understand what have happened.
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Offline emzy

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temperature         average titre of MgCl2(L)           n(ca2+ and Mg2+)
35                       0.024067                                 3.98x10-4
47                       0.032328                                 4.09x10-4
56                       o.o228                                    4.208x10-4
66                       0.0226                                    4.26x10-4
74                       0.0224067                               4.306325x10-4

The ammount of EDTA i added was constant at 9.908x10-4 mol each titration. Its not a big increase but is still an increasing trend. I read that calcium and magnesium ions are tied up to proteins but don't really understand how. could they be protein bound at a low temperature so not as many available to complex with my EDTA at low temperatures and when I heat it the proteins degrade therefore relaesing them to complex with the EDTA?

Offline Borek

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Its not a big increase but is still an increasing trend. I read that calcium and magnesium ions are tied up to proteins but don't really understand how. could they be protein bound at a low temperature so not as many available to complex with my EDTA at low temperatures and when I heat it the proteins degrade therefore relaesing them to complex with the EDTA?

That would be a logical conclusion. Protein denaturation can be involved.

Don't worry about not understanding details about how calcium and magnesium are bonded with proteins. Think about it this way - EDTA complexes both cations, same may happen with proteins. Details will be different, but general idea very similar.
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Offline emzy

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thanks, So I might not have totally stuffed a four day internal.
For our report we need to explain the scientific ideas that caused our trend. I've been researching the internet but cannot find any expected outcomes or explanations for this titration. Could you please explain how this works? when proteins begin to denature does this leave ca++ ions in the milk or do they bond to a weaker substance thats then 'kicked off' by the EDTA?

Offline JGK

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the extent to which proteins bind metals thereby reducing the amount of free iond in solution detectable by titration is usually a function of their secondary (general three-dimensional form of local segments of proteins) and tertiary (its three-dimensional)  structures.

In protein denaturation, which can be caused by heat, secondary and tertiary structure is lost and the bound metal released into solution as indicated by the rise in mesure concentration.
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Offline emzy

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Ok thank you very much for your help
I can use that to search for more information
 :)

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