Comprehensive experimental and theoretical investigations on chromium (III) trace detection in biological and environmental samples using polymeric membrane sensor
In the current work, a new highly selective and sensitive sensor based on PVC membrane for accurate trace detection of chromium (III) ions as the environmental contaminant based on 4-Isopropylcalix[4]arene (4-IPC4) was developed. The electrode demonstrated a working range from 1.0 × 10−6 to 1.0 × 10−1 M with 19.45 ± 0.21 mV and 9.0 × 10−7 M of Nernstian slope and detection limit, respectively. The pH of the electrode was independent of the potential response over the range of 3.0 to 5.5. The developed sensor revealed acceptable repeatability for at least three months with fast response time (less than 15 seconds). The impedance changes of the solution/electrode interface were investigated using the EIS technique. The proposed sensor was used successfully for direct detection of Chromium (III) ions in biological and environmental samples and the obtained values validated by AAS and ICP techniques with the recovery values varied from 99.6 to 101.9% for the concentration range of 15.0 to 75.0 ppm. Moreover, the electrode was successfully applied as an indicator electrode for potentiometric titration of Cr3+ cation with standard EDTA solution. The characterisation of the proposed sensor and its selective membrane were carried out using FT-IR, UV-Vis, and SEM techniques. The adsorption energy as an important parameter of trapping has been calculated at B3LYP/3-21G (d) level via using the density functional theory (DFT). The strong interactions were resulted by natural bond orbital (NBO) calculations between lone pair of O with lone pair* of chromium (III) ions which revealed that the charge transfer plays important role in the formation of the complex.
