Enhancing of hydroquinone and catechol oxidation using a graphite and graphene composite polymer modified paste electrode

An innovative electrochemical redox response of hydroquinone (HQN) and catechol (CCL) was analysed using a bare graphite and graphene composite paste electrode (BGGCPE) and polymerised L-leucine modified graphite and graphene composite paste electrode (LCN-MGGCPE) was successfully developed in 0.2 M phosphate buffer solution (PBS) with pH 6.0 at a 0.1 V/s scan rate. Fabricated electrode using simple and cost-effective method, the polymerised LCN-MGGCPE surface shows more electrochemical activity, sensitivity and selectivity towards the determination for HQN and CCL. Cyclic voltammetry (CV), linear sweep voltammetry (LSV), Differential pulse voltammetry (DPV), and electrochemical impudence spectroscopy (EIS) were utilised as analytical techniques while LCN-MGGCPE and BGGCPE surface characterisation were studied using a scanning electron microscopy (SEM) technique. LCN-MGGCPE exhibited superior electrochemical activity compared to BGGCPE towards the oxidation responses of both HQN and CCL. Additionally, the effect of pH studies, scan rate change for HQN, and concentration change of analyte molecule were examined, with the 0.025 to 0.500 V/s scan rate varied and revealing an adsorption-controlled process. The concentration changes of CVs methods ranged from 0.2 to 320 μM, DPVs ranged from 0.2 to 1100 μM and LSVs ranged from 0.2 to 850 μM, the calculated a limit of detection (LOD) of CV, DPV, and LSV, is 0.020 μM, 0.026 μM, and 0.011 μM and a limit of quantification (LOQ) of 0.068 μM, 0.088 μM, and 0.035 μM. The electrochemically developed LCN-MGGCPE shows good reproducibility, repeatability, stability, sensitivity and simultaneous analysis of analyte molecules were studied. This study presents a promising pathway for the growth of effective sensors for the determination of HQN in medicinal and water sample applications.