Multivariate curve resolution of synchronous fluorescence spectra matrices of fulvic acids obtained as a function of pH

• Type: Article in International Scientific Journal
• Date: 2006

Authors

Joaquim Esteves G E da Silva (Author) FCUP; Roma Tauler (Author) Other

Journal

Title: Applied Spectroscopy

Vol. 60

Pages: 1315-1321

ISSN: 0003-7028

Publisher: SAGE

Indexing

ISI Web of Knowledge - 22 Citations

Scopus - 22 Citations

Scientific classification

FOS: Engineering and technology > Other engineering and technologies

Other information

Authenticus ID: P-004-G64

DOI: 10.1366/000370206778999111

Abstract (EN): Synchronous fluorescence spectra (excitation wavelength range between 280 and 510 ran and wavelength interval of 25 nm) of three samples of fulvic acids (FA) were obtained as a function of the pH, in the range from 2.0 to 10.5, and as a function of the FA concentration, in the range from 20 to 180 mg/L. FA were obtained from composted livestock materials (IsFA), composted sewage sludge (csFA), and Laurentian soil (laFA). Three-dimensional spectral matrices were obtained (wavelength, pH and FA concentration) and multivariate curve resolution (MCR) was used to calculate spectra and fluorescence intensity profiles for the detected components. Cluster analysis of the calculated spectra showed the existence of similar and unique fluorescent properties in the three FA samples. Some of the calculated fluorescence intensity profiles have a shape compatible with acid-base species distribution diagrams, which allowed pKa values to be estimated, namely, a well-defined acid-base equilibrium with pKa 5.7 +/- 0.2 (IsFA), 6.9 +/- 0.4 (csFA), and 5.5 +/- 0.2 (laFA); and other acid-base systems not well defined with pKa at about 3.0 and 8.6. Other spectral variations revealed the existence of inner-filter effects or self-quenching as the concentration of FA increases.

Language: English

Type (Professor's evaluation): Scientific

No. of pages: 7