2,2′,3,4-Tetrahydroxy-3′-sulpho-5′-nitroazobenzene for spectrophotometric determination of aluminium in pharmaceutical suspensions and granite

A selective and sensitive new spectrophotometric method has been developed for the determination of aluminium. 2,2′,3,4-Tetrahydroxy-3′-sulpho-5′-nitroazobenzene (tetrahydroxyazon SN) formed an orange chelate with aluminium at pH 4. Molar absorptivity of the complex in 1:2 is 5.46 × 104 l mol−1 cm−1 at 479 nm. The method obeys Beer's law in the range of 0.005-1.079 μg ml−1. The determination of aluminium is not interfered with by earth alkaline, alkaline elements, rare earth elements, halides, phosphates, sulphates, urea, ascorbic acid, Sn2+, Sr2+, Cr3+, Cd2+, Hg2+, or Mn2+. The proposed method is rapid and simple, and it has been successfully applied to the determination of aluminium in certified pharmaceutical suspension and granite.