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Author Topic: Standard addition method Photometric urea  (Read 589 times)

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skunny

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Standard addition method Photometric urea
« on: December 01, 2018, 10:18:56 AM »

Hi

I wanted To do the Standard Addition Methode to determiniert Urea due to a complex matrix  of my sample. I am totale confused whether i am about to do this right because I do not have a lot of experience. So I was really hoping whether somebody could take a look at what I’m about to do and tell me whether it makes sense or not
Thank u !

 First I would like to prepare that Urian standard solution : u would solve 100mg in 100 ml water , I mean fill it up in a volumetric flask.

For my sample I would need to separate my sample  from the fatty matrix so I would do an extraction with diethylether, And my urea would be in the aqueous phase.

I would prepare five volumetric flasks(100ml)

1. 1ml sample + 1 ml standard solution
2. 1ml sample + 2 ml standard solution
3. 1ml sample + 3 ml standard solution
4. 1ml sample + 4 ml standard solution
5. 1ml sample + 0 ml standard solution

And then fill it all up with water.

For the actual measurement I wanted to take 1ml of each solution I prepared (as I mentioned above) + the substance that gives it the color and then measure....

Does that make sense ? I cam completely unsure! Thank u so so much !
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Borek

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Re: Standard addition method Photometric urea
« Reply #1 on: December 01, 2018, 09:41:42 PM »

Logic looks OK.

At the moment it is impossible to say if it is all 100% correct, as there are still a lot of details that don't make the procedure foolproof - for the urea to stay in water you need low pH, standard solution needs to have concentration in a correct range for the method and so on. But I assume you omitted them intentionally.
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skunny

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Re: Standard addition method Photometric urea
« Reply #2 on: December 02, 2018, 03:03:52 AM »

thank you so much, I will try it like that, hopefully everything turns out good =)
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skunny

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Re: Standard addition method Photometric urea
« Reply #3 on: December 03, 2018, 07:29:03 AM »

I have another question to the calculation. I determine urea with this photometric methode and also by kjeldahl. (in analytical chemistry is a method for the quantitative determination of nitrogen contained in organic substances plus the nitrogen contained in the inorganic compounds ammonia and ammonium (NH3/NH4+)

Now I don't know how I can compare my results. Because when I evaluate the results from the kjeldahl method, my result is shown in percent. And with this photometric method I don't get it in percent but in mg/ml. I don't know how to compare my results or how to modify the equation of the photmetric method to get a result in percent =/ can anyone help?
 
I was thinking to just multiply by 100..but I'm not sure..Thank u!
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