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### Topic: Preparation of triethylammonium phosphate buffer 1M (TEAP) of pH ~2.8 ?  (Read 14914 times)

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#### Borek

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##### Re: Preparation of triethylammonium phosphate buffer 1M (TEAP) of pH ~2.8 ?
« Reply #15 on: June 28, 2017, 03:12:15 AM »
I just want to prepare 0.05M TEAP buffer from 1M TEAP stock solution.

You are still missing the point and I am starting to doubt you understand what the buffer is and how it works.

Buffer you need is made by neutralizing phosphoric acid and contains HTEA+ (protonated amine) and H3PO4 and H2PO4- in a ratio given by the Henderson-Hasselbalch equation, approximately

$$\frac {[H_3PO_4]}{[H_2PO_4^-]} = 0.2$$

For obvious reasons concentrations of HTEA+ and H2PO4- are identical.

In this context saying "1 M solution" doesn't mean anything without saying which substance is 1 M. In the case of buffers we often say "1 M buffer" meaning "sum of concentrations of the acid and conjugate base equals 1 M" - so in this case your stock solution would be 1 M in phosphates and about 0.17 M in TEA. Do you see why "1 M TEAP buffer" means nothing and is ambiguous?
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#### Optimist

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##### Re: Preparation of triethylammonium phosphate buffer 1M (TEAP) of pH ~2.8 ?
« Reply #16 on: June 28, 2017, 11:15:07 PM »
Hello, Borek

Buffer is the a mixture of weak acid and its salt ( conjugate base or conjugate acid , respectively) that premits solution to resist change in pH.
In Henderson-Hasselbalch equation if the concentration of weak acid is equal to that of conjugate base, the ratio of two component is one. So, pH=pKa because the log(1)=0. In this case solution is know as best buffer.

To be honest in this case I didn't get your point, it's little confusing when I am preparing TEAP buffer.
Kindly would you help me in that case. Actually I need 0.05M TEAP buffer or solution for my HPLC analysis

Regards,

#### Borek

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##### Re: Preparation of triethylammonium phosphate buffer 1M (TEAP) of pH ~2.8 ?
« Reply #17 on: June 29, 2017, 03:40:52 AM »
Let's start with something simple, examples are best approach to such problems.

Acetic acid has pKa = 4.75, so the buffer prepared from equimolar amounts of acetic acid and sodium acetate has pH is 4.75.

Please try to calculate what are concentrations of: acetic acid, acetate anion, Na+ in 1 M acetate buffer of pH=4.75.
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#### Optimist

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##### Re: Preparation of triethylammonium phosphate buffer 1M (TEAP) of pH ~2.8 ?
« Reply #18 on: June 29, 2017, 06:48:55 AM »

Acetic acid concentration = 0.5 mole
Acetate anion concentration= 0.5 mole

#### Borek

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##### Re: Preparation of triethylammonium phosphate buffer 1M (TEAP) of pH ~2.8 ?
« Reply #19 on: June 29, 2017, 09:41:43 AM »
Then it is 0.5 M in Na+, isn't it?
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#### Optimist

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##### Re: Preparation of triethylammonium phosphate buffer 1M (TEAP) of pH ~2.8 ?
« Reply #20 on: June 29, 2017, 08:34:01 PM »
yes, you are right 0.5 Na+

#### Borek

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##### Re: Preparation of triethylammonium phosphate buffer 1M (TEAP) of pH ~2.8 ?
« Reply #21 on: June 30, 2017, 03:07:50 AM »
So why is it 1 M buffer?

Or, to ask the same question I asked long ago - it is a buffer 1 M in what?
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#### Optimist

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##### Re: Preparation of triethylammonium phosphate buffer 1M (TEAP) of pH ~2.8 ?
« Reply #22 on: July 01, 2017, 09:46:23 AM »

0.1 M in TEA or 0.1 M in phosphates?

Protocol haven't mentioned about 0.1 M in TEA or 0.1 M in phosphate. it's just 0.1 M TEAP buffer.

#### Optimist

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##### Re: Preparation of triethylammonium phosphate buffer 1M (TEAP) of pH ~2.8 ?
« Reply #23 on: July 01, 2017, 09:48:43 AM »
So why is it 1 M buffer?

Or, to ask the same question I asked long ago - it is a buffer 1 M in what?

It is 1 M buffer in 0.5 M Phosphate I think ? isn't ?

#### Borek

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##### Re: Preparation of triethylammonium phosphate buffer 1M (TEAP) of pH ~2.8 ?
« Reply #24 on: July 01, 2017, 03:41:02 PM »
So why is it 1 M buffer?

Or, to ask the same question I asked long ago - it is a buffer 1 M in what?

It is 1 M buffer in 0.5 M Phosphate I think ? isn't ?

So you are starting to see why it is problematic to state "1 M TEAP buffer"?

As I told you from the very beginning - such a statement is ambiguous.
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#### Optimist

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##### Re: Preparation of triethylammonium phosphate buffer 1M (TEAP) of pH ~2.8 ?
« Reply #25 on: July 02, 2017, 01:52:57 AM »
Borek

Now I catch up what you want to say!! but anyway my HPLC protocol called it 0.05 M TBAP buffer, for time being so Let's supposed it as buffer

Still I have problem related with HPLC column, I am not getting any peak while performing HPLC analysis of my sample. I am using Water XTerra Hybride particle technology, containing inorganic ( silica) and organic (organosiloxane) column. The actual protocol ( I have seen different reference of the sample I am analyzing) used Beckman C18 RP ultrasphere Octyladecyl silane column.

What is the difference between two column? Both are RP C18.

#### Borek

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##### Re: Preparation of triethylammonium phosphate buffer 1M (TEAP) of pH ~2.8 ?
« Reply #26 on: July 02, 2017, 03:09:33 AM »
Now I catch up what you want to say!! but anyway my HPLC protocol called it 0.05 M TBAP buffer, for time being so Let's supposed it as buffer

It is a buffer, there is just not enough information to prepare it.
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#### Optimist

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##### Re: Preparation of triethylammonium phosphate buffer 1M (TEAP) of pH ~2.8 ?
« Reply #27 on: July 02, 2017, 03:22:30 AM »
What about second part my question. ? the column are they same or different?