Development of Electrochemical Sensors for the Analysis of Drugs and Detection of Water Toxins

Abstract

The current research work is intended at the designing of a various electrochemical sensors for the analysis of pharmaceutical drugs and detection of toxic heavy metal ions. Three types of electrochemical sensors were prepared and characterized. These include nanosensors, DNA biosensors and surfactant based electrochemical sensors. In the electrochemical nanosensors, TiO2 nanoparticles and COOH functionalized MWCNTs were used as receptors for the sensing of oxymetazoline drug (OMZ). The designed nanosensor helped in the sensing of OMZ with a 4.4 nM detection limit. In the second type of electrochemical sensor, DNA was used a receptor over the surface of transducer. The designed DNA biosensors were employed for the detection of a number of Schiff bases, i.e., 2-((3-chlorophenylimino)methyl)-5-(diethylamino)phenol (2-CPMP), 2-((2,4dichlorophenylimino)methyl)-5-(diethylamino)phenol (2-DPMP), 5-(diethylamino)-2((3,5-dimethylphenylimino)methyl)phenol (5-DDPMP) and 5-(diethylamino)-2-((2,6diethylphenylimino)methyl)phenol (5-DDMP). All the Schiff bases were found to interact with DNA and interestingly the oxidation signal of 5-DDMP registered 30 times increase at the fMWCNTs fabricated DNA biosensor compared to DNA biosensor alone. Moreover, surfactant based electrochemical sensors were also designed and applied for the simultaneous detection of several toxic heavy metal ions. For this purpose, 1-dodecanoyl3-(4-methoxyphenyl)-2-thiourea and 1-(3-chlorophenyl)-3-dodecanoylthiourea were used as recognition layers for the simultaneous and sensitive sensing of four and six metal ions, respectively. The electrochemical behavior of the targeted analytes at the developed sensors was probed by adsorptive stripping differential pulse voltammetry (ASDPV) and cyclic voltammetry (CV). The performance parameters of the developed sensors were evaluated from EIS, CV and ASDPV. The conditions i.e. concentration of modifiers, type of electrolyte, pH of medium deposition potential and deposition time were optimized for getting the highest current response to achieve the lowest detection limits of the targeted analytes. The modified electrodes were tested for real samples to check their validity for practical applications. The results revealed all the designed sensors to demonstrate the qualities of excellent sensitivity, selectivity and reproducibility