New solid-state membrane and coated wire potentiometric sensors for the determination of Zn(II) ions based on...

The first, novel solid-state membrane sensor for Zn(II) determination is developed based on ZnS nanoparticles. ZnS nanoparticles are synthesized by chemical co-precipitation and investigated via X-ray diffraction, transmission electron microscopy (TEM), Fourier transform infrared spectroscopy (FTIR) and impedance study. X-ray diffraction shows that the prepared ZnS nanoparticles have an average domain size of 5.72 nm, which is very close to the particle size obtained from TEM observations (6.30 nm). The ZnS nanoparticles are pressed into disks and examined as electroactive solid-state membrane. Solid-state membrane and coated wire sensors are fabricated. They display linear responses over concentration ranges of 1.0 × 10^-5 to 1.0 × 10^-1 mol L^-1 Zn²⁺ ions with cationic slopes of 28.9±0.2 and 25.9±0.2 mV decade^-1 for the solid-state membrane and coated wire sensors, respectively. The lower limits of detection are 2.86 × 10^-6 and 4.60 × 10^-6 mol L^-1 Zn²⁺ ions for the solid-state membrane and coated wire sensors, respectively. The response time for the two sensors is instantaneous (1 s), and the useful lifetimes for the solid-state membrane and coated wire sensors are long (10 and 6 months, respectively). The solid-state membrane sensor is utilized for the quantification of Zn(II) ions in brass alloys and pharmaceutical preparations.