The quenching of the fluorescence of three anthropogenic fulvic acids
(FA) provoked by Cu(II) (pH 6.0), Fe(III) (pH 4.0) and UO22+ (pH 3.5),
was analyzed by a non-linear method and by Stern-Volmer plots. The FA
samples were extracted from composted sewage sludges (csFA), composte
d municipal wastes (mwFA) and composted livestock wastes (IsFA). Synch
ronous-scan fluorescence (SyF) spectra were collected as a function of
metal ion concentration. Spectral data were treated by a self-modelin
g mixture analysis method (SIMPLISMA) to detect the SyF spectral band
with the strongest quenching and to calculate the corresponding quench
ing profile. The analysis of these profiles by a non-linear method all
owed the estimation of conditional stability constants (K) and of the
percentage of non-complexing fluorophores. The same quantitative infor
mation was obtained by the modified Stern-Volmer equation taking into
account the existence of fluorophores that do nor participate in the c
omplexation. Good agreement was found between the results of the two p
rocedures. The log K calculated by the non-linear method were (standar
d deviation in parenthesis): csFA, Cu(II), 4.22 (5); Fe(III), 5.0 (1);
UO22+, 5.2 (2); mwFA, Cu(II), 4.21 (3); Fe(III), 5.6 (2); UO22+, 4.7
(3); 1sFA, Cu(II), 4.51 (8); Fe(III), 5.5 (2); UO22+, 3.6 (2). (C) 199
8 Elsevier Science B.V.