A new chemically modified electrode is constructed based on multiwalled carbon nanotube/chitosan modified glassy carbon electrode (MWCNTs-CHT/GCE) for simultaneous determination of acetaminophen (ACT) and mefenamic acid (MEF) in aqueous buffered media. The measurements were carried out by application of differential pulse voltammetry (DPV), cyclic voltammetry (CV) and chronoamperometry (CA) methods. Application of DPV method showed that the linear relationship between oxidation peak current and concentration of ACT and MEF were 1 mM to 145 mM, and 4 mM to 200 mM, respectively. The analytical performance of this sensor has been evaluated for detection of ACT and MEF in human serum, human urine and a pharmaceutical preparation with satisfactory results.

A glassy carbon electrode (GCE) modified with carbon nanotube/chitosan (MWCNTs-CHT/GCE) was used for the sensitive voltammetric determination of levodopa (Lev) and serotonin (Ser). The measurements were carried out using cyclic voltammetry (CV), differential pulse voltammetry (DPV) and chronoamperometry (CA). Under the optimum conditions the electrode provides a linear response versus Lev and Ser concentrations in the range of 2.0-220.0 mM and 0.5-130.0 mM, respectively, using DPV. The modified electrode was satisfactorily used for determination of Lev and Ser in human serum and urine with satisfactory results.

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A novel, sensitive and selective adsorptive stripping procedure for simultaneous determination of iron, copper and cadmium is presented. The method is based on the adsorptive accumulation of thymolphthalexone (TPN) complexes of these elements onto a hanging mercury drop electrode, followed by reduction of adsorbed species by voltammetric scan using differential pulse modulation. The influences of control variables on the sensitivity of the proposed method for the simultaneous determination of iron, copper and cadmium were studied using the Derringer desirability function. The optimum analytical conditions were found to be TPN concentration of 2.0 mM, pH of 9.5, and accumulation potential at À 0.4 V vs. Ag/AgCl with an accumulation time of 60 s. The peak currents are proportional to the concentration of iron, copper and cadmium over the 1 -80, 0.5 -100 and 1 -100 ng mL À1 ranges with detection limits of 0.5, 0.4 and 0.9 ng mL À1 , respectively. The R.S.D. at a concentration level of 20 ng mL À1 of iron, copper and cadmium were 2.5%, 0.9% and 1.5% (n ¼ 6), respectively. The procedure was applied to the simultaneous determination of iron, copper and cadmium in the tap water and some synthetic samples with satisfactory results.

The present work demonstrates that simultaneous determination of adrenalin (AD) and paracetamol (PAR) can be performed on single-walled carbon nanotube/chitosan/ionic liquid modified glassy carbon electrode (SWCNT-CHIT-IL/GCE). The electro-oxidations of AD and PAR were investigated with cyclic voltammetry (CV), differential pulse voltammetry (DPV) and also chronoamperometry (CA) methods. DPV experiments showed that the oxidation peak currents of AD and PAR are proportional to the corresponding concentrations over the 1-580 µmol/L and 0.5-400 µmol/L ranges, respectively. The RSD at a concentration level of 15 µmol/L AD and 15 µmol/L PAR were 1.69% and 1.82%, respectively. Finally the modified electrode was used for simultaneous determination of AD and PAR in real samples with satisfactory results.