Determination of zinc (II) in pharmaceuticals based on a flow-through bulk optode

A method based on flow injection (FI), was applied for the determination of Zn (II) using a flow-through bulk optode membrane that incorporates 1-(2-pyridylazo)-2-naphthol in a plasticized poly (vinyl chloride) membrane entrapped in a cellulose support. The calibration graph plotting the reflectance at 562 nm versus [Zn (II)] was linear in the range 0.16-3.27 mgl(-1) (2.5 x 10(-6)-5 x 10(-5) M) with a detection limit of 0.10 mgl(-1). The variation coefficients of the sensor response for 0.33 mgl(-1) of Zn (II) were +/-0.11% for consecutive measurements (n=10), +/-0.19% between days (n=5) and +/-0.22% between different membranes (n=6). The sensor can be readily regenerated with the same acetic/acetate carrier of pH 3.9. The FI method proposed was applied to the determination of zinc (II) in pharmaceuticals.