Determination of 2-ethylhexyl Nitrate in Diesel Oil Using a Single Excitation Emission Fluorescence Spectra (EEF) and Chemometrics Analysis

Abstract

A highly sensitive spectrofluorimetric method has been developed for the determination of 2-ethylhexyl nitrate in diesel fuel. Usually, this compound is used as an additive in order to improve cetane number.The analytical method consists in building the chemometric model as a first step. Then, it is possible to quantify the analyte with only recording a single excitation-emission fluorescence spectrum (EEF), whose data are introduced in the chemometric model above mentioned. Another important characteristic of this method is that the fuel sample was used without any pre-treatment for EEF.This work provides an interest improvement to fluorescence techniques using the rapid and easily applicable EEF approach to analyze such complex matrices. Exploding EEF was the key to a successful determination, obtaining a detection limit of 0.00434% (v/v) and a limit of quantification of 0.01446% (v/v overlapping of the spectral information might be overcome by using multicomponent analysis such as partial least squares (PLS) [21]. This method allowed an approach using the full spectral region rather than unique and isolated analytical bands. PLS performs data decomposition into spectral score and loading matrices prior to model building with the aid of these new variables, using spectral and concentration data. The algorithm was based on the ability to mathematically correlate spectral data to a property of interest while simultaneously accounting for all other significant spectral factors that interfered in the spectrum.The full cross-validation leave-one-out procedure was applied, which consists of systematically removing one of the training samples in turn, and using only the remaining ones for the construction of the latent factors and regression models [22].The predictive capability of calibration model was expressed by the determination coefficient (R-square), root mean square error of cross validation (RMSECV), and standard error of prediction (SEP).The optimal number of principal components (PCs) was chosen in function of the first local minimum based on the RMSEC curve after cross validation in the calibration set. Predictive capability of model was evaluated by predicting the external prediction set with commercial formulation. Results and DiscussionConventional fluorescence may be preferred to determine one fluorophor concentration or when the mixture being analyzed contains only a limited number of compounds with fluorescence properties and a quenching effect are not to be expected. Ignoring the excitation spectra by using only the emission spectra could not be enough to obtain the solutions of the problem. So, besides the emission spectra, it seems essential to include also the analysis of excitation spectra possessing abundant information. The determination in diesel oil may contain many fluourophors. This task is further complicated by the fact that the fluorophors of interest have different characteristic excitation and emission ranges in the different samples. An inherent problem of many fluorimetric ...

Absolute absorption cross section of 2-EHN in IR region

“…Pioneering studies have been carried out on 2-EHN, [13], [14], [15] but no data are available for the spectral signature of the vapors in the mid-IR domain. To complete and develop the previous studies, we propose here a thorough analysis of its IR spectrum in the gaseous phase.…”

“…In a second step, we propose different complementary approaches for the quantitative analysis in the gas phase based on a chemometric method. Indeed all the studies mentioned above [10][11][12][13][14][15] used the chemometric approach while atmospheric spectroscopy uses directly the absorption cross section data. Comparisons between the two complementary methods are therefore needed and useful.…”