Analytical methods of calcium in milk

[almohandes]

Could someone help with a way (or method) of how to determine the content of calcium in milk at a high school level.

 

[stamba]

I think that you can determin it in this way

In one beaker which volume is 250 cm3, put 50 cm3 of your sample. Add 5 cm3 of NaOH which has 2 mol/dm3 and on tip of a spoon indicator mureksid. You do titration with 0.025 mol/dm3 EDTA until color is changed from blue to violet-blue.

You can calculate concentration of Calcium on this way:


(mmol/dm3 Ca2+) / dm3 = (V x M x 1000) / 50

I am so sory for this formula, but I have no idea how to use that service this forum has.

 

[thunderfvck]

Add NaOH, collect the Ca(OH)2 that is formed, mass the Ca(OH)2, determine the number of moles of Ca(OH)2 which corresponds to...

Ca(2+) + 2 OH(-) --> Ca(OH)2

should tell you how many moles of Ca(2+) is there...

Something like that anyway.

Ca(OH)2 is insoluble.

 

[stamba]

No you can't do in that way, beaucouse you also have magnesium ions in milk, they will also form Mg(OH)2, which is also insoluble in milk.If you plan to heat the milk, you will get nothing beaucouse many organic supstances will fall down as insoluble substances.

As far as I know this is the only way, but if anyone knows any other, better way, plaese write.

 

[almohandes]

thanks stamba and thunderfvck and yes if some one knows of more way please write, because I am not really sure if i get it yet.

 

[almohandes]

im going to try titrating with EDTA, I think it might work
so, I am going to analyse milk for calcium content using:

EDTA-4 + Ca+2 ---> CaEDTA-2

 

[Gokul43201]

I concur with stamba. EDTA titration is also used to determine Ca-hardness in water.

 

[Naeem]

Ya , Mohandes, Kaifal Haal, Khair, Could you look at the Breaking Plates problem and suggest something,

Thanks,

 

[chem_tr]

Calcium determination may be done in milk after denaturizing it with trichloroacetic acid; the proteins may interfere the process. Alternatively, milk is boiled and the powder burnt in a furnace, so that all organic matter is broken down, afterwards you can titrimetrically (as stamba wrote; the pH of the medium must be at least 12 in order not to encounter the interference of magnesium ion) or atomic absorbance (this is more reliable as it is much more sensitive).

Please look in AOAC (Association of Official Analytical Chemists) to read a much better and reliable treatment.

There may also be spectrophotometric (colorimetric-based) and gravimetric (pyrophosphate-based) techniques. Flame photometry is another fast technique.

 

[GCT]

A very simple way...observe the nutrition details, which is frequently 30 percent of daily value. Find the related data; how much, exactly is the daily value? Use factor label method for the rest.