Simultaneous use of evolving factor analysis of fluorescence spectral data and analysis of pH titration data for comparison of the acid-base properties of fulvic acids

• Type: Article in International Scientific Journal
• Date: 1996

Authors

daSilva, JCGE (Author) FCUP; Machado, AASC (Author) Other; Silva, CSPCO (Author) Other

Journal

Title: Analytica Chimica Acta

Vol. 318

Pages: 365-372

ISSN: 0003-2670

Publisher: Elsevier

Indexing

ISI Web of Knowledge - 31 Citations

Scopus - 32 Citations

Scientific classification

FOS: Natural sciences > Chemical sciences

Other information

Authenticus ID: P-00H-5NG

DOI: 10.1016/0003-2670(95)00456-4

Abstract (EN): Three fulvic acids (fua) extracted from a Portuguese pinewood soil (dry pine needles, fua1, leaf litter, fua2, and lower soil horizon, fua3) have been studied by synchronous molecular fluorescence spectroscopy (SyF) at variable pH and by potentiometric pH titrations. The number of macroscopic acid-base systems and their pK(a)s were calculated by analysis of the SyF-pH hyphenated data with a self-modeling curve resolution technique (evolving factor analysis, EFA). Four macroscopic acid-base systems were detected in the fulvic acid samples (with pK(a)s around 3.0, 4.5, 7.0 and 9.0). The concentrations of the groups responsible for the acid-base systems were calculated by a standard non-linear least squares adjustment of pH potentiometric titration curves using the pK(a) values obtained by EFA. The procedure detected differences between the three fua: the concentration of carboxylic groups increased from fua1 to fua3 but, in contrast, the concentration of the phenolic groups decreased. These results correlate well with the expected extent of humification of the samples.

Language: English

Type (Professor's evaluation): Scientific

No. of pages: 8