Determination of Total Hydrocarbons in Contaminated Soil with “Thin Layer Sorptive Extraction Coupled with Attenuated Total Reflectance–Fourier Transform Infrared Spectroscopy”

Abstract

Soil analysis using infrared spectroscopy has been proposed as an alternative to conventional soil analysis to detect soil contamination. This study therefore aims to develop an innovative, in situ, rapid, precise, and inexpensive method that is easy to implement in order to assess soil contamination with hydrocarbons. This work describes the development and validation of a new extraction method by thin-layer sorptive extraction and attenuated total reflectance-Fourier transform infrared spectroscopy (TLSE-ATR-FTIR). First, this method allows the preconcentration of thermodesorbed pollutants on a polymer thin film and then, their quantification by ATR-FTIR using a standard addition method. A five factor fractional factorial design was used to identify the most significant factors impacting the analysis. These factors include soil texture, total organic carbon (TOC), humidity, and concentrations of contaminants. The results showed that TOC, nature (clay, sandy, and loamy) of the soil, and the concentration of pollutants can affect the infrared absorbance. The analytical method has been validated by verifying the different performance criteria such as linearity, accuracy, precision, and quantitation limit. The comparison of the results obtained by TLSE-ATR-FTIR to the results of conventional analyses carried out by accredited laboratories confirms that the use of the proposed method can become an effective alternative to the current methods for the determination of the total hydrocarbons in soils.