The test is not valid unless, in the chromatogram obtained with solution (1), the resolution factor between the peaks corresponding to sodium chloride and trichloroammineplatinate is at least 2.0.

We adopted the linear combination method of absorbances to assay the contents of compound alcoholic solution of benzoic acid directly without isolation of its components.

ConclusionAfter improvement, it is reliable, simple, convenient, accurate, sensitive, stable for extraction, and it can offer a feasible basis for revision of the standard.