Incorporation of graphene oxide–NiO nanocomposite and n-hexyl-3-methylimidazolium hexafluoro phosphate into carbon paste electrode: application as an electrochemical sensor for simultaneous determination of benserazide, levodopa and tryptophan

The benserazide (BZ) and levodopa (LD) are two important catechol drugs to inhibit dopamine production outside the brain. On the other hand, BZ is effective on tryptophan (Trp) metabolism as an inhibitor aromatic amino acid decarboxylase. A voltammetric sensor based on carbon paste electrodes modified with graphene oxide–NiO nanocomposite and n-hexyl-3-methylimidazolium hexafluoro phosphate (n-H-3MIHF) as a binder is proposed to detect and quantify of BZ, LD and Trp in drug and urine samples. In square-wave voltammetry technique, BZ, LD and Trp were given sensitive oxidation peaks at 156, 312 and 740 mV, respectively. At a best electrochemical conditions, the enhanced oxidation peak currents represented the excellent analytical performance of simultaneous detection of BZ, LD and Trp in the ranges of 0.1–600, 0.1–700 and 5.0–700 μM, with a low limit of detection of 0.05 μM for BZ, 0.05 for LD and 1.0 μM for Trp (S/N = 3), respectively. To further validate its possible application, the proposed sensor was successfully used for the determination of above compounds in tablet and urine with satisfactory results.