Identification and Limit of Detection of Benzene, Chlorobenzene, Benzoic Acid, Phthalic Acid, and Mellitic Acid in Water Solutions Using Excitation, Emission, and Single-band Synchronous Fluorescence Spectroscopy

Abstract

Introduction: This paper first introduces the use of computer-simulated single-band synchronous fluorescence (SF) obtained from experimental excitation and emission fluorescence spectra of a pure compound in solution. The simulation produces a single narrow band with a peak wavelength that identifies the compound. Methods: The method is used to show single peak identification of benzene, chlorobenzene, benzoic acid, phthalic acid, and mellitic acid in water solutions. Synchronous fluorescence spectroscopy (SFS) is a variant of fluorescence technique in which excitation and emission scans are simultaneously acquired and multiplied with a predetermined wavelength difference (Δλ) between the two. Commercial instruments have this option to get the SFS signals. Results: In response to the Δλ selected, the result will be an SFS signal producing a series of peaks that could be assigned to compounds. Instead of running the same experiment with different Δλ values to identify the compounds, our simulation program determines a specific Δλ value that generates a narrow SF band with a distinctive peak wavelength for identification purposes. Conclusion: Finally, binary mixtures of chlorobenzene with each compound in water are prepared. The SFS of the solution is acquired and compared with the SFS bands of the components for identification purposes. With the commercial lamp fluorimeter employed, the limits of detection are obtained at the ng/g concentration level with fluorescence emission. Possible limits of detection at lower concentrations are discussed using a laser source. The presence of these molecules in astrochemical studies is discussed.