Simple Derivatization–Gas Chromatography–Mass Spectrometry for Fatty Acids Profiling in Soil Dissolved Organic Matter

Abstract

Dissolved organic matter is an important component of the global carbon cycle that allows the distribution of carbon and nutrients. Therefore, analysis of soil dissolved organic matter helps us to better understand climate change impacts as it is the most dynamic and reactive fraction in terrestrial ecosystems. Its characterization at the molecular level is still challenging due to complex mixtures of hundreds of compounds at low concentration levels in percolating water. This work presents simple methods, such as thermochemolysis– or derivatization–gas chromatography, as an alternative for the analysis of fatty acids in dissolved organic matter without any purification step. The variables of the protocols were examined to optimize the processing conditions for the C9–C18 range. As a proof of concept, fatty acid distributions of soil percolating water samples from a long-term field experiment were successfully assessed. The variability of dissolved organic acid distributions was pronounced through depth profile and soil treatment but no major change in composition was observed. However, although the optimization was done from C9 to C18, detection within the C6-C32 fatty acids range was performed for all samples.

Volatile Variation of Theobroma cacao Malvaceae L. Beans Cultivated in Taiwan Affected by Processing via Fermentation and Roasting

“…First, 0.1 g of crude fat was correctly measured and placed into a spiral test tube, 1 mL NaOH (1N) and 1 mL C-15 authentic sample solutions were added. The mixture was saponified at 85 °C for 15 min in the water bath, cooled, and 1 mL boron trifluoride (14%) was added and the derivation reaction was allowed to proceed on 100 °C water bath for 15 min [ 64 ]. After being cooled, 2 mL of n-hexane and 5 mL of saturated saline were added and left to stand until phase separated.…”

Linkages between the molecular composition of dissolved organic matter and soil microbial community in a boreal forest during freeze–thaw cycles

“…So the release of long-chain alkanes by FTCs in our experiment may be attributed to the rupture of microbial cell membranes, while the variation of short chains might be attributed to variation in microbial decomposition. Fatty acid methyl esters (Me) can be generated by the cyclization of fatty acids (FAs) and phenolic hydroxyl groups ( Musadji and Geffroy-Rodier, 2020 ). Generally, long-chain FAs ascribe to microbial degradation or microbial lipid fragments ( Sousa et al, 2007 ), and FAs are typically combined with long-chain fatty alcohols or sterols to form esters ( Chiavari et al, 1994 ).…”

Droplet Microfluidic-BasedIn SituAnalyzer for Monitoring Free Nitrate in Soil

“…Both methods can provide high spatial and temporal resolution and cause minimal disruption to the surrounding soil environment. However, currently, these two techniques require long sampling times to collect a sufficiently large sample for the subsequent lab-based analysis, 22 which is manually intensive and costly.…”