Arsonophenylazochromotropic acid

Higher sensitivity is obtained in reactions of Nb with Sulphonitrophenol M (formula 33.1) (8 = 5.3-10 ) [55,62,63]. Other reagents recommended for Nb determination include Sulphonitrazo E [64], TAR [21,65], arsonophenylazochromotropic acid [66], an azo derivative of 8-hydroxyquinoline [67], and 2-(5-chloro-2-pyridylazo)-5-dimethylamino-phenol (MIBK) [68]. 

Although Y in aqueous solution can be determined by EDTA titration, Cu ions have to be removed by a lengthy procedure. However, the organic dye arsenazo (6-phenylazo-3-arsonophenylazochromotropic acid) forms a violet complex witii Y(III). 

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