Trace determination of zinc in standard alloys, environmental and pharmaceutical samples by fourth derivative spectrophotometry using 1-2-(thiazolylazo)-2-naphthol as reagent and ammonium tetraphenylborate supported on naphthalene as adsorbent

A highly sensitive, selective, economical and rapid method for the trace determination of zinc using fourth derivative spectrophotometry has been proposed with 1-2-(thiazolylazo)-2-naphthol (TAN) as an analytical reagent and ammonium tetraphenylborate (ATPB)-naphthalene as an adsorbent. Zn–TAN is quantitatively retained on ATPB naphthalene in the pH range 6.5–9.5. The calibration plot is linear in the concentration range 0.02–1.4 μg ml −1 Zn of DMF solution. The sensitivity of the method as determined from the slope of the calibration plot is 2.640 (d 4 A/d λ 4)/(μg ml −1). Nine replicate determinations of 5.0 μg of zinc in 5 ml of DMF give a mean signal height of 2.660 (peak to peak height between λ 1=597 nm and λ 2=585 nm) with a relative standard deviation of 1.1%. The various conditions have been optimized and the developed method has been used for the determination of zinc in standard alloys, environmental and pharmaceutical samples.