Pyrolysis derivatization of humic substances 1. Pyrolysis of fulvic acids in the presence of tetramethylammonium hydroxide

Abstract

A BSTRACTPyrograms of Ihree fulvic acids (FAs) or ditferenl origins and Ihe corresponding pyrosrams obtaincd by reactive pyrolysis wilh Iclramclhylammonium hydroxide (TMAH) are compared. Thi! proc.cdure inlroduces bolh slriking qualilalive and quanlilalive changes in lhe pyrolylic pallems of Ihe FAs. which are discussed in lerms of Ihe usefulness of Ihis approach lo slructural sludies. Sorne non·pyrolysis compounds (probably relained in Ihe macromolecular fulvic malrix) seem lo be released when Ihe FAs are pyrolysed in lhe presrnce of TMAH. A se{ of benzenecarboxylic acid slandards was also pyrolysed bolh in lhe abscnce and in Ihe prcscncc: oC TMAH. The resulls oblained suggcsl a lhennally assisled chemolysis ralher Ihan i" s;/u melhylalioD of lhe pyrolysis produclS. Fulvic &cids; humic substances; pyrolysiS; tetramelhylammonium hydroxide. INTRODUCTlONHumic substances (HS) are widely distributed in almost all terrestrial and aquatic environments. Owing to their colloidal properties and high runctionality they play important roles in reactions and processes relaled lO the conservation and production of soil ecosystems. which have been recently reviewed [1,2].The complex. variable composition of lhe fulvic acids (FAs) (lhe alkali and acid-soluble collodial humic fraction) has been investigated by many different methods with divergent results. Overall the struclural ínformation gained by analytical pyrolysis (Py) of FA is unexpectedly much lower than that given by the other humic fractíoDS (humic acids and humíos). Thus, FA givcs low yields of Py compounds. with major components bcíng characteristic of $Oíl polysao:harides, and a small numbcr of aromatic compounds, whereas Py of humíc acids gives much richer pyrograms. This

Natural photolysis by ultraviolet irradiance of recalcitrant dissolved organic matter to simple substrates for rapidbacterial metabolism

“…Some fatty acid methyl esters were present, and these probably derived from Juncus or bacterial biomass contributions to the DOM. Although the TMAH thermolysis procedure has been applied to humic materials (Hatcher and Clifford 1994;Martin et al 1994;Saiz-Jimenez 1995), lignin (Clifford et al 1995), and plant cuticles containing cutin esters (de Leeuw and Bass 1993), the present analyses are the first applications of the procedure to dissolved organic compounds of natural waters.…”

Comparative study for separation of atmospheric humic-like substance (HULIS) by ENVI-18, HLB, XAD-8 and DEAE sorbents: Elemental composition, FT-IR, 1H NMR and off-line thermochemolysis with tetramethylammonium hydroxide (TMAH)

“…The aromatic compounds identified in HULIS were remarkably similar to pyrolysis products of HAs, FAs and lignin (Martin et al, 1994(Martin et al, , 1995del Rio et al, 1998;Chefetz et al, 2002;Li et al, 2006;Fukushima et al, 2011). All HULIS pyrograms present two distinct peaks at 32.8 min and 34.5 min (Nos.…”

Pyrolytic alkylation-gas chromatography-mass spectrometry of model polymers Further insights into the mechanism and scope of the technique

“…However, due to the known limitations of the pyrolytic technique, the results are not always in agreement with those obtained by chemical wet methods or spectroscopic techniques. For instance, carboxylic acid moieties are highly biased as potential 'building-blocks' upon conventional pyrolysis, since they undergo decarboxylation under these conditions [1]. Recently, pyrolysis in the presence of tetramethylammonium hydroxide *Corresponding author.…”