Study of hypersensitive colour reactions of tin(IV) with 2,6,7-trihydroxyphenylfluorone derivatives in the presence of nitrilotriacetic acid and mixed surfactants

Abstract

The hypersensitive colour reactions of tin(IV) with three 2,6,7-trihydroxy-9-phenyl-3-fluorone derivatives, namely 4,5-dibromophenylfluorone (4,5-DBPF), o-hydroxyphenylfluorone and o-nitrophenylfluorone, in the presence of both nitrilotriacetic acid and cetyltrimethylammonium bromide–Tween-80 are described. It is shown that the molar absorptivities of these complexes are 1.42 × 106(560 nm), 1.0 × 106(525 nm) and 1.03 × 106(538 nm) dm3 mol–1 cm–1, respectively, indicating that the proposed technique is the most sensitive spectrophotometric method for the determination of tin(IV) developed so far. The system has been investigated in detail. The tin(IV) complex is formed at pH 2.8–3.9. Beer's law is obeyed for tin(IV) in the range 0.05–0.7 µg per 10 ml. The complex is stable for at least 2.5 h. The molar ratio of tin(IV) to 4,5-DBPF was found to be 1 : 4. Tolerance limits are given for 27 foreign ions by using tartrate, mandelic acid and lactic acid. The method was successfully applied to the determination of trace amounts of tin(IV) in a zinc-base alloy, a lead–copper alloy and alloy steels with low molybdenum contents.