Continuous flow-through solid phase spectrophotometric determination of trace amounts of zinc Original Research Article

A flow-through solid phase spectrophotometric sensing device for the determination of Zn(II) was developed based on the reaction of this ion with 1-(2-pyridylazo)-2-naphthol (PAN) immobilized on a Dowex cation exchanger placed in a flow-through cell. The reaction of Zn(II) with immobilized PAN and its retention on the resin developed the analytical signal. Adequate dissociation of the Zn–PAN complex left the unaltered reagent fixed on the solid support, enabling the regeneration of the sensor. The sensor allows working with several calibration lines simply by varying the sample volume injected for the determination. As an example, linear dynamic ranges from 0.2 to 4.0 μg ml−1 and from 20 to 500 μg l−1 can be obtained by using 100 and 2000 μl, respectively, with detection limits being 0.05 μg ml−1 and 5 μg l−1, respectively. The RSD (%) being 2.1 (100 μl) and 2.3 (2000 μl) and the sampling frequency 38 and 15 samples per hour, respectively. The sensor was applied to the determination of Zn(II) in real samples, namely, human hair, pharmaceutical and cosmetic preparations and water samples.