A promising electrochemical sensor was developed by electrodeposition of gold nanoparticles on a carbon paste (CP) electrode. This sensor electrode (CPE-Au nano ) was used to determine paracetamol (ACOP) and some neurotransmitters, such as dopamine (DA), epinephrine (EP), norepinephrine (NP), levodopa (L-DOPA) and serotonin (5-HT). Cyclic and differential pulse voltammetry studies indicated that the oxidation of paracetamol at the electrode surface proceeded through a two electron reversible step and was fundamentally controlled by adsorption. Further modification of the sensor by mixing the CPE-Au nano with Nafion Ò showed good sensitivity and effectively resolved the overlapping anodic peaks of these neurotransmitters (NTs) with ACOP. Also, the interfering effect of physiologically common interferences, namely ascorbic acid (AA) and uric acid (UA), on the current response of paracetamol has been studied. Nafion Ò proved to increase the sensitivity of the current signal of the sensor for the oxidation of the compounds studied. Paracetamol gave a well defined oxidation peak at 430 mV in pH 7.4, which was used to quantitate the drug in the two ranges of 50 nM-50 mM and 90-270 mM with a detection limit of 7.7 nM and 28 nM, respectively. The procedure was successfully validated for the assay of paracetamol in pharmaceutical formulations. The applicability of the developed method to determine the drug in human urine samples is also illustrated.

An effective electrochemical sensor for the selective determination of dopamine (DA) in the presence of ascorbic acid (AA) and uric acid (UA) in 0.04molnormalL−1 universal buffer solution (pH 7.4) is introduced. The sensor is based on a carbon paste (CP) electrode modified with gold nanoparticles. In a mixture of DA, AA, and UA, the sensor shows high selective response toward DA and no response for AA or UA. The effect of various experimental parameters including time of deposition of gold nanoparticles on the CP electrode, pH, and scan rate on the voltammetric response of DA was investigated. At the optimum conditions, the concentration of DA was determined using differential pulse voltammetry in a linear range of 1.0×10−7 to 5.0×10−6molnormalL−1 and 5.0×10−6 to 1.3×10−4molnormalL−1 with correlation coefficients of 0.9995 and 0.9988 and a detection limit of 5.9×10−9 and 8.2×10−8molnormalL−1 , respectively. The modified electrode can be used for the determination of DA spiked into human serum samples, and excellent recovery results were obtained over a wide concentration range of DA. Moreover, validation parameters, such as reproducibility, sensitivity, and recovery were evaluated successfully in the determination of DA in diluted human urine.

A promising electrochemical sensor was developed using carbon paste electrode, gold nanoparticles and Nafion. This sensor is sensitive for the determination of catecholamine compounds, namely dopamine (DA), epinephrine (EP), L-norepinephrine (NP), and L-DOPA, as well as serotonin (5-TH), in the presence of interference molecules such as uric acid (UA) and ascorbic acid (AA). Cyclic voltammetry, differential pulse voltammetry, and electrochemical impedance spectroscopy were used to verify the behavior of the studied compounds in the physiological pH of the body. Simultaneous determinations of DA with 5-TH and L-DOPA with acetaminophen (ACOP) give very good peak separations. The linear response was obtained for L-DOPA in the ranges of 2.0 × 10 −7 to 2.0 × 10 −5 mol L −1 with correlation coefficient 0.9990 and a second range of 5.0 × 10 −5 to 3.0 × 10 −3 mol L −1 with correlation coefficient 0.9985. LOD was found to be 1.45 × 10 −9 mol L −1 and 2.84 × 10 −6 mol L −1 , respectively. The utility of this modified electrode was demonstrated for the determination of L-DOPA in human urine.

Daclatasvir (DAC) is listed on the World Health Organization's list of essential medicines needed in a basic health system, therefore, electrochemical and impedance spectroscopic methods are necessary.

A novel and effective electrochemical sensor for the determination of morphine (MO) in 0.04 mol L(-1) universal buffer solution (pH 7.4) is introduced using gold nanoparticles electrodeposited on a Nafion modified carbon paste electrode. The effect of various experimental parameters including pH, scan rate and accumulation time on the voltammetric response of MO was investigated. At the optimum conditions, the concentration of MO was determined using differential pulse voltammetry (DPV) in a linear range of 2.0 × 10(-7) to 2.6 × 10(-4) mol L(-1) with a correlation coefficient of 0.999, and a detection limit of 13.3 × 10(-10) mol L(-1), respectively. The effect of common interferences on the current response of morphine namely ascorbic acid (AA) and uric acid (UA) is studied. The modified electrode can be used for the determination of MO spiked into urine samples, and excellent recovery results were obtained.