Application of recycled battery graphite decorated with poly hippuric acid/ multiwalled carbon nanotubes as an ecofriendly sensor for serotonin

A novel modified sensor based on electropolymerization of hippuric acid (HA) using cyclic voltammetry within the potential window - 1 to 1.5 V for 10 cycles at a scan rate 100 mV s^-1 over multiwalled carbon nanotubes (MWCNTs) on battery graphite electrode (BGE). Poly (HA)/MWCNTs/BGE sensor exhibited two linearity ranges 3.00 × 10^-3 to 1.00 µM (5.29 × 10^-4 - 0.18 µg/ml) and 5.00 to 1.00 × 10³ µM (0.88- 176.22 µg/ml) with limit of detection (LOD) of 0.06 × 10^-2 µM (1.06 × 10^-4 µg/ml) and limit of quantification (LOQ) of 2.00 × 10^-3 µM (3.52 × 10^-4 µg/ml). The poly (HA)/MWCNTs/BGE sensor was successfully applied to the determination of SER in the presence of tryptophan and in human blood serum with recovery ranges 98.31-105.47% with RSD values 3.02- 4.77%. Green chemistry metrics : national environmental index (NEMI), analytical greenness metric (AGREE), Raynie and Driver, green analytical procedure index (GAPI), and the analytical eco-scale were employed and indicated that the proposed sensor can be classified as an excellent green method, achieving an analytical eco-scale score of 84.