Double-walled carbon nanotube based carbon paste electrode as xanthine biosensor

We describe the first usage of a double walled carbon nanotube (DWCNT) modified carbon paste electrode as biosensor transducer. Xanthine was chosen as a substrate for evaluation of the electrode performance. Proper amount of DWCNT and xanthine oxidase enzyme were mixed with proper amount of graphite and mineral oil for attaining the xanthine biosensor. Results were compared with previous work that includes multi-walled carbon nanotube and single-wall carbon nanotube based carbon paste electrode xanthine biosensors. A linearity was obtained in the concentration range between 2–50 μM xanthine under the response time of 150 s with the equation of y?=?0.0441x + 0.2013 and RSD value of 4.20%. This system was applied to the determination of xanthine in canned tuna fish samples and recovery was calculated as 99.20%?±?0.07.