Alternative for mobile phase

[kayaii]

Hi guys. I'm new here and I really need some help. I'm currently doing a project which requires me to use HPLC in order to detect ascorbic acid. The problem is at my university, we don't have dihydrogen ammonium phosphate to use as the mobile phase. So, I was wondering if there are any chemicals that can replace dihydrogen ammonium phosphate as the mobile phase? Thanks in advance.

[tom jupille]

Ammonium dihydrogen phosphate is a solid, so it cannot be used by itself as a mobile phase. What you need is a solution of it at some concentration, at some pH, in some solvent. Get a chemistry prof or graduate student to explain how to prepare it at the appropriate concentration from ammonium hydroxide, phosphoric acid, and dihydrogen monoxide.

[kayaii]

Can I just change it to other chemicals? Some that might be equivalent to it as the mobile phase?

[tom jupille]

No, you can't "just" change it without changing a lot of other parameters as well. In any case, ammonium phosphate is a common chemical which should not be difficult to obtain in Malaysia.

Before we all waste a lot of time & effort, why don't you tell us something about your background & experience level, what exactly you are trying to accomplish, and what resources you have available?

[Uros]

Ammonium dihydrogen phosphate is a solid, so it cannot be used by itself as a mobile phase. What you need is a solution of it at some concentration, at some pH, in some solvent. Get a chemistry prof or graduate student to explain how to prepare it at the appropriate concentration from ammonium hydroxide, phosphoric acid, and dihydrogen monoxide.

This sounds like very dangerous substance

[kayaii]

Ok, I'll will explain in detail. First, I'm a diploma student and currently doing a final year project. The project that I've been researching for a while now is the extraction of ascorbic acid in order to find out the existence of ascorbic acid in fruits.
For the extraction, I've been using metaphosphoric acid and trichloro acetic acid as the solvents for extraction.
The only thing that is left is the analysis. Based on the journal that I've been using, it said that it uses dihydrogen ammonium phosphate as the mobile phase and a c18 column hplc. The thing is, we don't have that particular mobile phase to use and it will be too late to order them right now as the lab assistant will be on leave soon. So I'm kind of stuck right now and that's the reason why I'm trying to find an alternative way or chemicals to replace the dihydrogen ammonium phosphate. Perhaps you could recommend me the conditions of hplc for the detection of ascorbic acid other than the one that using dihydrogen ammonium phosphate.
Any help will definitely be appreciated.

[Uros]

You can check Google for application notes. What is the sample matrix?

Maybe useful link: http://www.sielc.com/Compound-Vitamin-C.html
http://naldc.nal.usda.gov/download/7342/PDF

[DR]

Look around for Ammonium Phosphate Monobasic.

A rose by any other name...

[kayaii]

Thanks for all of the suggestions.
And Uros, Thanks for the link and journal. It really helped me a lot.
Decision still have to be made. I hope the suggestions can keep on coming. All helps are welcomed and appreciated. Thanks a lot guys.

[James_Ball]

Thanks for all of the suggestions.
And Uros, Thanks for the link and journal. It really helped me a lot.
Decision still have to be made. I hope the suggestions can keep on coming. All helps are welcomed and appreciated. Thanks a lot guys.

http://www.restek.com/pdfs/59398.pdf

This one used a Potassium Phosphate buffer and C18 column.

You may want to browse through the Restek site and see if there are other combinations which you may be able to replicate with what you have on hand.