Optical Analysis Authenticated Electrical Impedance Based Quantification of Aqueous Naphthalene

Abstract

Graphical AbstractSchematic representation of the system under investigation and variation of its electrical and optical properties with varying concentration of naphthalene.Polyaromatic hydrocarbons (PAH) are organic compounds with fused benzene rings that have toxic and mutagenic properties, and have been well documented for their detrimental effect on animal and plant health. Naphthalene, a two-ring PAH, is a common water pollutant which has been linked to the disruption of immune system as well as deformation of red blood corpuscles in human and thereby raising substantial concerns. The present study quantitatively estimates naphthalene in its aqueous solution by employing electrical impedance spectroscopy (EIS), which is simultaneously supported by UV-vis spectral analysis. Naphthalene solutions of varying concentrations (0.2-1 ppm) are prepared and subjected to EIS as well as UV-visible spectroscopy. For the EIS based studies, the data is recorded for the frequency range of 1 KHz -1 MHz and electrical parameters such as capacitance, conductance and admittance are observed to increase from 3.5 pF -7.2 pF, 2.3 µS -6.1 µS and 2.4 µS -27.3 µS, Optical Analysis Authenticated Electrical Impedance Based Quantification of Aqueous Naphthalene Article 31 respectively, with varying naphthalene concentration in its solution. On the other hand impedance values are observed to decrease with the same. Naphthalene is itself a non-polar molecule and the formation of instantaneous dipoles originating from the interaction of such molecules governs the overall dielectric nature of the solution. UV-vis spectroscopic measurements of the solutions reveal the characteristic absorbance maxima at 216 nm for all the concentrations under investigation. Absorbance values are observed to increase with the relative strength of naphthalene in the solution and such values vary in the range of 0.02 -0.16 au for the peak obtained. Thus by corroborating the electrical and the optical parameters, this study establishes a quick and handy method for detection of naphthalene in aqueous solutions and ascertains a framework for further work that can be done to formulate a naphthalene sensing device. CONCLUSIONSElectrical parameters including the impedance, admittance, capacitance and conductance of naphthalene solution of varying strength are measured by employing impedance spectroscopy in this study. Formation of instantaneous dipoles in the system is observed to govern the effective dielectric behavior of the naphthalene solution. Spontaneous formation of a dipole induces a polarity in the neighboring non-polar constituent molecules. Increment of the non-polar molecule concentration in the system augments the formation of instantaneous dipoles and hence the effective dipole moment of the system increases. Coefficient of sensitivity in terms of impedance is also calculated for the measuring system, from which a decent change in impedance is observed for a variation of naphthalene concentration of a unit ppm. Spectrophotometric analyses of the solu...