Determination of tin(IV) alloys and in canned food by visible spectrophotometric technique using pyrimidine azo compounds in presence of mixed surfactants

摘要

The complex of tin(IV) with 5-(4'-nitro-2',6'-dichlorophenylazo) (I) and 5-(4'-chlorophenylazo)-6-hydroxypyrimidine-2,4-dione (II) in the presence of nonyl phenoxy polyethoxyethanol (NPE) and cetyltrimethylammonium bromide (CTAB) has a sensitive absorption band with lambda_(max) 517 and 488 nm, respectively. Under the optimal conditions, Beer-Lambert law is obeyed over the range 0.05-1.50 and 0.05-1.30 mug ml~(-1) Sn(IV) with molar absorptivity being 9.50 X 10~4 and 1.05 X 10~5 L mol~(-1) cm~(-1) using ligand I and II, respectively. As compared with the visible methods which uses bromopyrogallol red (BPR) as the chromogenic reagent (lambda_(max) = 550 nm) and that using phenylfluorone (lambda_(max) = 360 nm), our method is highly sensitive and selective because the complexes have a high and sharp absorption band. In addition, the present method is simple and rapid, no heating or standing time is needed. By means of the mixed surfactants, the precipitation caused by the ion association of cetyltrimethyl-ammonium cation and I_3~- anion is avoided if iodide is used for separating micro amounts of tin(IV) from a sample matrix. An application of the proposed method to the determination of tin(IV) in a variety of alloys and in a canned food was made with satisfactory results.