Chemical Forums

Please login or register.

Login with username, password and session length

Sponsored links

Pages: [1]   Go Down

Author Topic: Quantitative analysis of Ca2+ in Milk  (Read 8007 times)

0 Members and 1 Guest are viewing this topic.

Alberto_Kravina

  • Assault Chemist
  • Retired Staff
  • Full Member
  • *
  • Mole Snacks: +70/-15
  • Offline Offline
  • Posts: 607
Quantitative analysis of Ca2+ in Milk
« on: March 03, 2006, 02:31:16 AM »

Does somebody of you guys know how I colud perform a quantitative analysis of Ca2+ in milk?
A titration or a gravimetric analysis would be great... :)

Thanks for any suggestion.
Logged

Albert

  • Lonely Wanderer
  • Retired Staff
  • Sr. Member
  • *
  • Mole Snacks: +112/-22
  • Offline Offline
  • Gender: Male
  • Posts: 1050
  • Half Decent Pharmaceutical Chemist
Re:Quantitative analysis of Ca2+ in Milk
« Reply #1 on: March 03, 2006, 02:37:27 AM »

Generally speaking, gravimetric analysis is always more accurate but time-consuming.
Well, I'd say an ISE for Ca2+ to be the best way of carrying out your determination. Or you can titrate it using EDTA or EGTA.
Logged

Alberto_Kravina

  • Assault Chemist
  • Retired Staff
  • Full Member
  • *
  • Mole Snacks: +70/-15
  • Offline Offline
  • Posts: 607
Re:Quantitative analysis of Ca2+ in Milk
« Reply #2 on: March 03, 2006, 02:43:22 AM »

Quote
Generally speaking, gravimetric analysis is always more accurate but time-consuming.
Well, I'd say an ISE for Ca2+ to be the best way of carrying out your determination. Or you can titrate it using EDTA or EGTA.
Yes-gravimetric analysis eats a lot of time. I thought about using EDTA (complexometry) but...doesn't the matrix interfer in this case? :) ISE is also a smart idea, by the way.
If the other methods fail I'll perform gravimetry..

My 200th post!
« Last Edit: March 03, 2006, 02:45:07 AM by Alberto_Kravina »
Logged

Albert

  • Lonely Wanderer
  • Retired Staff
  • Sr. Member
  • *
  • Mole Snacks: +112/-22
  • Offline Offline
  • Gender: Male
  • Posts: 1050
  • Half Decent Pharmaceutical Chemist
Re:Quantitative analysis of Ca2+ in Milk
« Reply #3 on: March 03, 2006, 02:48:59 AM »

I'd try to find information about EGTA: I think that the matrix shouldn't interfer. However, I've never used it.

Congratulations!
« Last Edit: March 03, 2006, 02:49:21 AM by Albert »
Logged

Alberto_Kravina

  • Assault Chemist
  • Retired Staff
  • Full Member
  • *
  • Mole Snacks: +70/-15
  • Offline Offline
  • Posts: 607
Re:Quantitative analysis of Ca2+ in Milk
« Reply #4 on: March 03, 2006, 03:07:01 AM »

Well, I'll try tomorrow...EDTA or EGTA should work...and if not...I'll find a solution (hopefully not gravimetry :ermm: )

Thanks for your useful advice! :)
Logged

Alberto_Kravina

  • Assault Chemist
  • Retired Staff
  • Full Member
  • *
  • Mole Snacks: +70/-15
  • Offline Offline
  • Posts: 607
Re:Quantitative analysis of Ca2+ in Milk
« Reply #5 on: March 03, 2006, 11:10:01 PM »

Just finished performing the analysis:

Result: 1.205 g/L Ca2+

It worked perfectly with EDTA... :)
Logged

Borek

  • Mr. pH
  • Administrator
  • Deity Member
  • **
  • Mole Snacks: +1364/-369
  • Offline Offline
  • Gender: Male
  • Posts: 20881
  • I am known to be occasionally wrong.
    • Chembuddy
Re:Quantitative analysis of Ca2+ in Milk
« Reply #6 on: March 03, 2006, 11:50:41 PM »

Can you post procedure?
Logged
ChemBuddy chemical calculators - stoichiometry, pH, concentration, buffer preparation, titrations.info, pH-meter.info

Alberto_Kravina

  • Assault Chemist
  • Retired Staff
  • Full Member
  • *
  • Mole Snacks: +70/-15
  • Offline Offline
  • Posts: 607
Re:Quantitative analysis of Ca2+ in Milk
« Reply #7 on: March 04, 2006, 07:43:23 AM »

I'll post it ASAP - I left the sheet where I wrote down the procedure in the lab- I should get it on monday afternoon... :)
« Last Edit: March 06, 2006, 04:09:12 AM by Alberto_Kravina »
Logged

Alberto_Kravina

  • Assault Chemist
  • Retired Staff
  • Full Member
  • *
  • Mole Snacks: +70/-15
  • Offline Offline
  • Posts: 607
Re:Quantitative analysis of Ca2+ in Milk
« Reply #8 on: March 06, 2006, 04:08:07 AM »

OK, here is the procedure:

Take 25 mL of milk, add 5-10 mL of conc. HCl, filtrate it (this took quite a while in my case...this goddam solution didn't want to go through the funnel...it took more than 20 minutes... :( ).
Make sure that 100% of the milk goes thoruogh the funnel!
Pour the filtrate in a 100 mL volumetric flask and fill it.

Now take 20 or 25 mL with a transfer pipette and put it in an Erlenmeyer flask, add ammonia (c=0.1 mol/L) until you reach a pH of 9-10 and titrate with EDTA (c=0.01 mol/L)

Indicator: Murexide

That's it!
« Last Edit: March 06, 2006, 04:09:52 AM by Alberto_Kravina »
Logged

Borek

  • Mr. pH
  • Administrator
  • Deity Member
  • **
  • Mole Snacks: +1364/-369
  • Offline Offline
  • Gender: Male
  • Posts: 20881
  • I am known to be occasionally wrong.
    • Chembuddy
Re:Quantitative analysis of Ca2+ in Milk
« Reply #9 on: March 06, 2006, 05:34:21 AM »

I wonder how much Ca2+ is lost with filtrate :(
Logged
ChemBuddy chemical calculators - stoichiometry, pH, concentration, buffer preparation, titrations.info, pH-meter.info

Alberto_Kravina

  • Assault Chemist
  • Retired Staff
  • Full Member
  • *
  • Mole Snacks: +70/-15
  • Offline Offline
  • Posts: 607
Re:Quantitative analysis of Ca2+ in Milk
« Reply #10 on: March 06, 2006, 05:45:48 AM »

I wonder how much Ca2+ is lost with filtrate :(
Yeah - As I said - I improvised....maybe the filtration process interfers in this case because Ca2+ ions could be lost... but you can't titrate the milk directly.. :P
I don't think that vacum filtration is a solution, byw. Maybe centrifugation, but in this case you have to work with very small amounts of sample.
« Last Edit: March 06, 2006, 05:47:15 AM by Alberto_Kravina »
Logged

mike

  • Retired Staff
  • Sr. Member
  • *
  • Mole Snacks: +121/-35
  • Offline Offline
  • Gender: Male
  • Posts: 1245
Re:Quantitative analysis of Ca2+ in Milk
« Reply #11 on: March 06, 2006, 01:30:30 PM »

Quote
(this took quite a while in my case...this goddam solution didn't want to go through the funnel...it took more than 20 minutes...  ).

Acidic solutions tend to swell filter paper and make filtering very difficult.
Logged
There is no science without fancy, and no art without facts.

Alberto_Kravina

  • Assault Chemist
  • Retired Staff
  • Full Member
  • *
  • Mole Snacks: +70/-15
  • Offline Offline
  • Posts: 607
Re:Quantitative analysis of Ca2+ in Milk
« Reply #12 on: March 07, 2006, 02:22:48 AM »

Quote
Acidic solutions tend to swell filter paper and make filtering very difficult.
True! But I in this case the acidic conditions are required to precipiatate the substances that could interfer...but maybe another separation method would be nice.... :)
« Last Edit: March 07, 2006, 02:50:59 AM by Alberto_Kravina »
Logged
Pages: [1]   Go Up
 

Mitch Andre Garcia's Chemical Forums 2003-Present.

Page created in 0.089 seconds with 24 queries.