Nanomolar detection of 4-aminophenol using amperometric sensor based on a novel phthalocyanine

Abstract

Novel cobalt (II) tetra-β-[N(2-(1,3-benzothiazole))carboxamide] phthalocyanine (CoTBTCAPc) has been synthesized for the first time. The dark green colored complex was characterized by different physicochemical and analytical techniques. Cyclic voltammetric studies revealed that the synthesized complex is redox-active nature. The CoTBTCAPc modified glassy carbon electrode (GCE/CoTBTCAPc) showed a stagnant charge transfer behavior for the redox probe whereas, composite hybrid of CoTBTCAPc with carbon nanoparticles (CNP) coated on GCE (GCE/CNP-CoTBTCAPc) showed facile and better charge transfer compared to the bare GCE. The GCE/CoTBTCAPc and GCE/CNP-CoTBTCAPc fabricated electrodes exhibited a decrease in over potential with the increase in oxidation peak current. Electrochemical oxidation of 4-aminophenol (4-AP) at nanomolar concentration was obtained in phosphate buffer pH 7.0 electrolytic media. The modified electrodes showed linear electrochemical response in the concentration range of 40–800 nM and the detection limit (LOD) was found as 13 and 11 nM (S/N = 3) for GCE/CoTBTCAPc and GCE/CNP-CoTBTCAPc electrodes respectively. Differential pulse voltammetric (DPV) technique showed linear response for the 4-AP oxidation in the concentration range of 100–1000 nM with sensitivity of 0.0328 and 0.4179 μA nM−1 cm−2 for the phthalocyanine and CNP-phthalocyanine modified electrodes respectively. In contrast, the amperometric sensor displayed linear response in the concentration range of 100–900 nM with sensitivity values of 0.4008 and 0.8887 μA nM−1 cm−2 and LOD of 40 and 30 nM for GCE/CoTBTCAPc and GCE/CNP-CoTBTCAPc electrodes respectively. The GCE/CNP-CoTBTCAPc showed selectivity for 4-AP even in the presence of interfering organic and inorganic species. This stable and simple sensor offers an opportunity for the electrochemical sensing of 4-aminophenol in real sample analysis like 4-AP in paracetamol tablets.