Construction of an optical sensor for copper determination in environmental, food, and biological samples based on the covalently immobilized 2-(2-benzothiazolylazo)-3-hydroxyphenol in agarose

Abstract

An optical chemical sensor has been developed for the quantitative spectrophotometric analysis of copper. The optode is dependent on covalent immobilization of 2-(2-benzothiazolylazo)-3-hydroxyphenol (BTAHP) in a transparent agarose membrane. The absorbance variation of immobilized BTAHP on agarose as a film upon the addition of 5 × 10⁻³ M aqueous solutions of Mn²⁺, Zn²⁺, Hg²⁺, Cd²⁺, Pb²⁺, Co²⁺, Ni²⁺, Fe²⁺, La³⁺, Fe³⁺, Cr³⁺, Zr⁴⁺, Se⁴⁺, Th⁴⁺, and UO₂²⁺ revealed substantially higher changes in the Cu²⁺ ion content compared to other ions investigated here. The effects of various experimental parameters, such as the solution pH, the reaction time, and the concentration of reagents, on the quality of Cu²⁺ sensing were examined. Under ideal experimental circumstances, a linear response was achieved for Cu²⁺ concentrations ranging from 1.0 × 10⁻⁹ to 7.5 × 10⁻⁶ M with an R² value of 0.9988. The detection (3σ) and quantification (10σ) limits of the procedure for Cu²⁺ analyses were 3.0 × 10⁻¹⁰ and 9.8 × 10⁻¹⁰ M, respectively. No observable interference was recorded in the detection of Cu²⁺ due to other inorganic cations. With no indication of BTAHP leaching, the membrane demonstrated good durability and quick response times. The optode was effectively used to determine the presence of Cu²⁺ in environmental water, food, and biological samples.