Highly Selective Potentiometric Determination of Zn (II) Ions Using Polymeric Membrane Sensor

Zn (II) ions are the second most abundant transition metal in organisms after iron, and are involved in numerous aspects of biological metabolism. Zinc plays an important role in synthetic routes within cells, sense of taste and smell, normal growth of the human body, protection from accelerated aging, and normal brain function. Although zinc is a relatively nontoxic element, it can be toxic if consumed in large quantities [1]. Uptake by humans owing to high environmental concentrations causes pulmonary manifestations, fever, chills, and gastroenteritis. Thus, the determination of trace amounts of zinc ion is currently of great interest in many scientific fields, including medical analysis and environmental monitoring [2].The present work deals with developing a high selective membrane electrode based on C-methylcalix[4]resorcinarene for accurate determination of trace amount of zinc (II). The amounts of ionophore, PVC, plasticizer and the ionic additive were optimized in the preparation of the membrane. The effects of various parameters such as pH, composition of the membrane, different cation interferences and concentration of internal solution were investigated. The electrode exhibited a linear response with a near Nernstian slope of 28.6±0.21 (mV per decade of activity) over the pH range from 3 to 7 with a satisfactory concentration range of 1.0×10−6 to 1.0×10−1 M. The value of 6.5×10-7M was obtained as lower detection limit for the fabricated zinc (II) selective electrode. The developed sensor exhibited good reproducibility over a period of about 12 weeks with a fast response time of less than 20 seconds. The proposed sensor was successfully applied as an indicator electrode for the potentiometric titration of a zinc(II) solution with EDTA. The validation of the developed electrode was done using atomic absorption spectrometry (AAS) and inductively coupled plasma technique (ICP) which confirmed the accuracy and precision of fabricated electrode in successful determination of zinctrace amount in environmental, industrial and pharmaceutical samples.