Abstract: An acetylcholinesterase (AChE) biosensor was prepared by cross-linking AChE and bovine serum albumin
(BSA) onto nitrogen doped carbon sphere-gold (N-Cs-Au) nanoparticles composite modified glassy carbon electrode
(GCE) and used for detecting carbofuran in spinach. The results showed that N-Cs-Au had a good electrical conductivity
and catalytic activity, effectively promoting electron transfer and consequently improving the sensitivity of AChE/N-Cs-
Au/GCE. It was found that there was a good linear relationship between the negative common logarithm of carbofuran
concentration (X) in the range from 2.3 × 10-10 to 2.3 × 10-5 g/L and the percentage inhibition of the peak current by
carbofuran (Y) as indicated by the equation: Y/% = −8.246 7X + 93.867 6 (R2 = 0.992 9). As calculated by 10% inhibition,
the limit of detection (LOD) for carbofuran was 6.763 9 × 10-11 g/L. The sensor showed recoveries of 91.417 7%–95.859 7%
for carbofuran in spiked spinach and high precision, which could meet the analytical requirements. Moreover, the sensor
was free from the interference of common heavy metals such as Pb, Cu, Cd and Mn and could provide a new method for
detecting carbofuran in foods.

Key words: carbofuran, nitrogen doped-carbon spheres-gold nanoparticles, sensor, detection