Hi all,

I came across a method for determination of total aromatic amines that uses the following mixture:

- HCl 1 M

- Ethanol

- p-dimethylamino-benzaldehyde 5% in ethanol

- 15.7% citric acid in 6% NaOH

I observed the formation of color occurs after the addition of p-dimethylamino-benzaldehyde, but color decreases after the addition of citrate. Why do we need to add citrate if it apparently decreases absorbance?