Amperometric flow injection analysis of glucose using immobilized glucose oxidase on nano-composite carbon nanotubes-platinum nanoparticles carbon paste electrode.

We report a novel amperometric glucose biosensor based on glucose oxidase (GOx) immobilized on a carbon nanotube (CNTs)-poly(diallyldimethyl-ammonium chloride) (PDDA)-platinum nanoparticle (PtNPs) modified carbon-paste electrode (CNTs-PDDA-PtNPs/CPE). The CNTs-PDDA-PtNPs composite materials were characterized by TEM and electrochemical techniques. Cyclic voltammetric results reveal direct electron transfer of the immobilized GOx, indicated by two quasi-reversible redox peaks at a potential of 0.37V (vs. Ag/AgCl) in phosphate buffered solution (PBS) (0.10M, pH 7). The biosensor provides good glucose oxidation activity and retention of GOx electrocatalytic activity due to CNTs-PDDA-PtNPs enhancement of the redox response. The carbon paste electrode was installed as working electrode in a flow through electrochemical cell of a flow injection (FI) system. Glucose was quantified using amperometric measurements at 0.5V vs. Ag/AgCl and PBS carrier (0.10M, pH 7.0) at a flow rate of 1.0mLmin-1. The linear working ranges for glucose measurements were 0.1-3mM (r2=0.995) and 5-100mM (r2=0.997), with corresponding sensitivities of 0.127 and 0.060 (μAs) mM-1, respectively. The system provides good precision of 2.8% R.S.D with a calculated detection limit (3S/N) of 15μM. The proposed method was successfully applied to determination of glucose in food and pharmaceutical samples with throughput of 200 samplesh-1.