Carboxylic acid content of a fulvic acid determined by potentiometry and aqueous Fourier transform infrared spectrometry
1991; Elsevier BV; Volume: 255; Issue: 1 Linguagem: Inglês
10.1016/0003-2670(91)85082-4
ISSN1873-4324
Autores Tópico(s)Marine and coastal ecosystems
ResumoThe carboxylic acid content of a fulvic acid is determined quantitatively using aqueous Fourier transform infrared spectrometry and potentiometry. The combined method minimizes interferences from other acidic or carbonyl functional groups in the fulvic acid mixture. Potentiometry alone provides only operational estimates of the acid content, which vary by up to 15% as the inert salt (sodium chloride) concentration increases from 1 to 500 mM. Quantitative IR spectra are collected in aqueous solutions fo varying pH using an attenuated total reflectance cell designed for liquids. Changes in the area ratio of IR peaks due to protonated and deprotonated carboxylic acid groups correlate strongly (r2 = 0.995) with base consumed in potentiometric titrations. The carboxylic acid content of this fulvic acid is 9.09 ± 0.28 (± 1 standard error) meq carboxylic acid per gram of carbon.
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