Fabrication of novel coated pyrolytic graphite electrodes for the selective nano-level monitoring of Cd2+ ions in biological and environmental samples using polymeric membrane of newly synthesized macrocycle

• Newly synthesized macrocycle for determination of Cd2+ ion.
• PME, CGE and CPGE (coated pyrolytic graphite electrode) were fabricated.
• CPGE exhibits the best detection limit of 7.58 × 10−9 mol L−1.
• Quantification of Cd2+ ion in waste water, soil and medicinal plants.

Novel 5-amino-1,3,4-thiadiazole-2-thiol unit based macrocyclic ionophore 5,11,17-trithia-1,3,7,9,13,15,19,20,21-nonaazatetracyclo[14.2.1.14,7.110,13]henicosa-4(20),10(21),16(19)-triene-6,12,18-trithione (M1), was synthesized and characterized. Preliminary studies on M1 have showed that it has more the affinity toward Cd2+ ion. Thus, the macrocyclic ionophore (M1) was used as electroactive material in the fabrication of PVC-membrane electrodes such as polymeric membrane electrode (PME), coated graphite electrode (CGE) and coated pyrolytic graphite electrode (CPGE) were prepared and its performance characteristic were compared with. The electroanalytical studies performed on PME, CGE and CPGE revealed that CPGE having membrane composition M1:PVC:1-CN:NaTPB in the ratio of 7:37:54:2 exhibits the best potentiometric characteristics in terms of detection limit of 7.58 × 10−9 mol L−1, Nernstian slope of 29.6 mV decade−1 of activity. The sensor was found to be independent of pH in the range 2.5–8.5. The sensor showed a fast response time of 10 s and could be used over a period of 4 months without any significant divergence in its potentiometric characteristics. The sensor has been employed for monitoring of the Cd2+ ion in real samples and also used as an indicator electrode in the potentiometric titration of Cd2+ ion with EDTA.

Potentiometric characteristic plots showing variation of membrane potential with the concentration of Cd2+ ions based on macrocyclic ionophore (M1) with different plasticizers.Figure optionsDownload as PowerPoint slide