The 2016 Joseph W. Richards Summer Research Fellowship — Summary Report: Single Drop Electroanalysis for Low Cost Quality Control Testing of Oxidative Pharmaceuticals

Abstract

Q uality control analysis of biochemically relevant pharmaceuticals is an important process in the drug industry. The therapeutic value of a drug mainly depends on the purity of the active pharmaceutical ingredient (API). Various chromatographic, spectroscopic, titrimetric, and electrochemical methods have been used in pharmaceutical industry for the estimation of APIs in drugs.1 Electroanalytical methods can be tailored to provide unique advantages such as high sensitivity, low cost, portability, fast assay time, and automation features. These are attractive for industrial-scale analytical applications. Fig. 1. (A) Schematic representation of single drop analysis using a MWCNT-COOH modified SPE (WE) with a carbon counter electrode (CE) and a silver pseudo-reference electrode (RE). (B) CVs (i) at lower concentration range and (ii) at higher concentration range. (C) Oxidation peak currents versus concentration of 50 µL droplets of varying concentrations of analytes placed on2 Moreover, measurements in micro-volume droplets of pharmaceutically important compounds allow miniaturized design, ease of operation, opportunities for throughput analysis, and less sample consumption.3 In this study, we measured oxidative pharmaceuticals as single 50 µL drops on screen printed electrodes (SPEs) modified with carboxylated multiwalled carbon nanotubes (MWCNT-COOH). Acetaminophen (a pain-killer), ascorbic acid (a dietary supplement), nicotinamide adenine dinucleotide reduced form (NADH) (a dietary supplement), and Nicotine (the active agent of antismoking pharmaceuticals) were analyzed. The relationship between polar/nonpolar interactions of analytes and surface carbon nanostructures in influencing sensitivity and limit of detection was understood.Cyclic voltammograms (CVs) of various concentrations of the four analytes prepared in pH 7.0 phosphate buffer were obtained on SPEs, [110 CNT, carbon counter electrode and silver pseudo-reference electrode, Dropsens Ltd.,Llanera (Asturias) Spain] upon which 50 µL drops were added (Fig.