An optical sensor for zinc determination based on Zincon as sensing reagent

An optical sensor has been designed for the determination of zinc by spectrophotometry. The sensing membrane is made by immobilizing Zincon as an ion pair with methyltrioctylammonium ion on triacetylcellulose membrane. In the present of Zn2+ ions in ammonia/ammonium chloride buffer at pH 9 the color of the membrane changes from purple to blue. The calibration curve was linear in the range of 0.76–30.60 μM of Zn2+ ion with a limit of detection 0.16 μM (10.5 ng ml−1). The response time of the optode was about 10–12 min, depending on the concentration of Zn2+. The sensor can readily be regenerated with hydrochloric acid solution. This optode is stable and could be stored under water for three weeks without reagent leaching. The relative standard deviation for seven replicate measurements of 7.65 and 15.30 μM Zn2+ was 3.09 and 2.82%, respectively. The sensor was successfully applied to the determination of zinc in powdered milk and hair samples.