Diffuse Reflectance and Transmission Fourier Transform Infrared (DRIFT) Spectroscopy of Humic and Fulvic Acids

Abstract

The infrared spectra of a humic and a fulvic acid from a peat were obtained using diffuse reflectance infrared Fourier transform (DRIFT) spectroscopy and were compared with transmission Fourier transform infrared (FTIR) spectra using KBr pellets. The DRIFT spectra showed similar resolution to KBr pellet transmission spectra. Elimination of interference due to water bands is easy with DRIFT and possible changes in the spectra due to modification of H bonding and ionization of carboxylate groups in the KBr pellet is avoided. Comparison of the DRIFT spectra of humic substances with the DRIFT spectra of some reference compounds suggests that phenolic OH groups in fulvic acids are more H‐bonded than those in humic acids, but the COOH groups are similarly H‐bonded. Comparison of the C=O stretching band with those of the reference compounds suggests that either intramolecular H‐bonding between COOH and phenolic OH is not significant in humic substances or alkyl COOH groups contribute considerably in the 1720 cm−1 band. The DRIFT spectra of Na and Cu(II) forms of humic acid powders show the capability of the method for metal‐ion binding studies. The possibility of using DRIFT spectroscopy for quantitative and semiquantitative evaluation is suggested by the similarity in the Kubelka‐Munk transformed DRIFT spectra and absorbance spectra using KBr pellets.

Physico-chemical characterization of SOA derived from catechol and guaiacol – a model substance for the aromatic fraction of atmospheric HULIS

“…The main group frequencies of SOA (ν(O-H), ν(C=O), ν(C=C) aromatic , ν(C-O) of carboxylic acids and of ethers) from catechol and guaiacol are compared to natural HULIS extracts (Polidori et al, 2008;Duarte et al, 2005) and SRFA , fulvic acids from soil (Stevenson and Goh, 1971) Stevenson and Goh (1971); IR spectra from KBr pellets containing aqueous extracts of humic and fulvic acids acids from various soils, mud and peat. (2) Baes and Bloom (1989); DRIFT spectra of powders, material was extracted from peat. (3) Graber and Rudich (2006); comparing the FTIR spectrum Suwannee River fulvic acid standard reference material (www.ihss.gatech.edu) with HULIS: aqueous extracts from aerosol at a rural area in Portugal (summer and autumn) presented by Duarte et al (2005).…”

“…(3) Graber and Rudich (2006); comparing the FTIR spectrum Suwannee River fulvic acid standard reference material (www.ihss.gatech.edu) with HULIS: aqueous extracts from aerosol at a rural area in Portugal (summer and autumn) presented by Duarte et al (2005). ( and peat humic and fulvic acids (Baes and Bloom, 1989) as well as to tannic acid, which is a previously reported model compound (Cowen and Al-Abadleh, 2009) (see Table 2). The main characteristic frequencies are assigned in the same way as in the literature.…”

Chemical Differences in Soil Organic Matter Fractions Determined by Diffuse‐Reflectance Mid‐Infrared Spectroscopy

“…Fourier-transformed MidIR spectroscopy is a quick and nondestructive technology that has been used to calibrate for SOC in diverse sets of samples (McCarty and Reeves, 2000;Reeves et al, 2001;McCarty et al, 2002), indicating that the MidIR region contains spectral information related to a variety of soil chemical attributes. Th e MidIR region (4000-400 cm −1 ) is characterized by strong vibration fundamentals, and can be used for spectral interpretation of sample composition, because the MidIR spectra show peaks or bands that can be assigned to specifi c organic or mineral spectral bands (Nguyen et al, 1991;Haberhauer and Gerzabek, 1999;Baes and Bloom, 1989;Janik et al, 2007).…”

Humic substances isolated from residues of sugar cane industry as root growth promoter

“…Moreover, the presence of a wide and diffuse absorption band at 1100 cm -1 is characteristic of low-humified HS; in fact, the band is related to C-O stretching of polysaccharides. The HS in the initial humification degree has a relatively high content of preserved sugars arisen from degradation reactions (Baes and Bloom, 1989). Therefore, it is tempting to speculate a structural similarity of HA isolated from filter cake to HA from soils.…”