Crown ether modified poly(hydroquinone)/carbon nanotubes based electrochemical sensor for simultaneous determination of levodopa, uric acid, tyrosine and ascorbic acid in biological fluids

Abstract

Tyrosine (Ty) is an important amino acid that converts to levodopa (L-DOPA) which is used for treatment of Parkinson's disease (PD). Also, there is a correlation between UA levels and the risk of progression of PD as significantly low level of serum uric acid (UA) is a biomarker for Parkinson. Thus, it is important to detect L-DOPA and UA in presence of interfering compounds for monitoring PD disease. An electrochemical sensor is fabricated by the modification of glassy carbon electrode with successive layers of carbon nanotubes (CNT), poly(hydroquinone) (PHQ) and benzo-12-crown-4 (CE) for the simultaneous determination of L-DOPA, UA and Ty in biological fluids. CE is introduced for the first time as a receptor for L-DOPA, UA, Ty and ascorbic acid (AA). Stable host-guest complexes are formed between CE and these biologically compounds. L-DOPA, UA, Ty and AA are determined in the concentration ranges of 0.005–20 μM, 0.005–25 μM, 0.03–170 μM and 0.1–50 μM with detection limit values of 0.221 nM, 0.769 nM, 1.31 nM and 3.32 nM, respectively. Furthermore, the sensor possessed excellent anti-interference capability for simultaneous determination of L-DOPA, UA, Ty and AA or folic acid (FA). Recovery tests of the studied compounds were attained with excellent results.