A novel optical chemical sensor for germanium determination in food and environmental samples

Abstract

A colorimetric optode for germanium (Ge⁴⁺) detection was developed by incorporating 2-(((3,5-dimercapto-4H-1,2,4-triazole-4-yl)imino)methyl) phenol (DMTMP) and the liquid ion-exchanger trioctylmethylammonium chloride (Aliquat-336) into a cellulose triacetate (CTA) matrix plasticized with tri-(2-ethylhexyl) phosphate (TEHP). The transparent optode quantitatively preconcentrates Ge⁴⁺ from aqueous samples, inducing a distinct color change (λ_max = 545 nm). Optimal equilibration was achieved in 5.00 min in borate medium and 25.0 min in natural water. On the other hand, an optode sample without Aliquat-336 showed no change in color corresponding to the Ge⁴⁺-DMTMP complex after equilibration with the same aqueous solution containing the Ge⁴⁺ ions. The uptake of Ge⁴⁺ is pH dependent and at pH 7.50 the maximum uptake was greater than 97.5 percent. In the detection of the Ge⁴⁺ ion, no significant interference of more than 750 times the concentration of the number of potentially interfering ions was detected. This optode showed a linear increase in absorbance at 545 nm with a peak absorbance of 545 nm for a concentration range of 6.00 to 174 ng mL⁻¹ of G⁴⁺ ions in aqueous solution over 5.00 min. The detection and quantification limits were assessed as 1.75 and 5.75 ng mL⁻¹, respectively. The optode proposed in this study has been proven to be reusable. The optode is an effective tool for the detection of germanium in food and environmental samples with high accuracy and selectivity.