I read this article "Determination of Cr(III) and total chromium in water samples by cloud point extraction and flame atomic absorption spectrometry" Michrochim Acta 2008.
they use NH3-NH4Cl buffer pH 2.0
Anyone with an idea how it was prepared. I have tried but the pH is from 8-10.
I have also prepare some concentration of NH4Cl alone, but pH range from 4 to 6.
Thank you
There is little buffering capacity in NH3/NH4+ at pH 2 so I prefer not to name it a buffer. Perhaps it is more correct to name it acidified ammonium solution.
You can prepare the solution by adding HCl until pH is lowered to 2.
Hello Simon, as explained above by Henrik Rasmus Andersen, you can prepare your 0.1M NH3/NH4-Cl solution by adding 0.1M HCl to 0.1M NH3 until pH reaches 2.0.
Like him, I stress that this is not a buffer: the maximum buffering capacity of a mixture of NH3 and HCl would be in the region of pH 9, i.e. the pKa of the conjugate weak acid NH4+. Ammonia (or rather, ammonium) plays no part whatsoever in the acid-base properties of the mixture around pH 2. Therefore the term "buffer pH 2.0" used in that paper is incorrect. My guess is that ammonium may play a role as a matrix modifier in the AAS procedure, for example by changing the forms of interfering substances in the flame and thus eliminating spectral interferences.
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