Boric acid is used in photographic processing solutions, for example, fixing solution and developing solution. It is said that weak acid such as boric acid can not be detected by ion chromatography, because the dissociation of weak acid is very small. A complex of boric acid with mannitol is a strong acid. When mannitol was added to buffer eluent of ion chromatography, boric acid in sample solution reacted with mannitol in the eluent to form a strong acid complex and could be detected by ion chromatography. This method has been applied to determination of boric acid in photographic processing solution. It was possible to determine boric acid and other anions, such as acetic acid, S0₃^2-, Br-, SO₄^2-, and S₂O₃^2-, in photographic solutions without any pretreatment of sample solutions.