Suitability of Thin-Layer Chromatography-Flame Ionization Detection with Regard to Quantitative Characterization of Different Fossil Fuel Products. II. Calibration Methods Concerning Quantitative Hydrocarbon-Group Type Analysis

Abstract

Time-consuming external standard-based calibration methods are usually performed for hydrocarbon group type analysis (HGTA) of fossil fuels, regardless of the instrumental chromatographic technique. In this work, HGTA of a broad variety of coal and petroleum products is performed using a modern thin-layer chromatography-flame ionization detection (TLC-FID) system and a rapid method based on internal normalization. Repeatability, linear intervals, and sample load ranges for quantitative application of this method are detailed for different products that cover a broad range of boiling points and chemical functionalities in the field of fossil fuels: a heavy oil and its derived hydrocracked products, raw and chemically-modified petroleum asphaltenes, a coal-tar pitch, several coal extracts, and coal hydroliquefaction products. Results from external standard calibration and a normalization method (both obtained by TLC-FID) are in agreement, and they are validated using TLC-ultraviolet scanning. The use of the latter demonstrates that TLC-FID can also be applied to products such as coal extracts and hydroliquefaction products, despite these products being more volatile than petroleum asphaltenes or heavy oils. For preparative purposes when external calibration is necessary, preparative TLC and SPE are less time-consuming alternatives to MPLC fractionation, providing similar results.