Geoscience Reference
In-Depth Information
400
400
O
O
O
(a)
(b)
380
380
OH
360
360
HO
340
340
320
320
300
300
280
280
260
260
240
240
300
350
400
450
500
550
600
300
350
400
450
500
550
600
400
400
OH
H
or lignin
OH
SH
(c)
(d)
Gly
380
O
380
H
3
C
CH
3
O
360
360
lignin
O
CH
3
OH
O
H
3
C
340
340
320
320
300
300
280
280
260
260
240
240
300
350
400 450
Emission Wavelength, nm
500
550
600
300
350
400 450
Emission Wavelength, nm
500
550
600
Figure 2.5. Excitation-emission spectra for (a)
p
-coumaric acid, (b) coumarin, (c) naringin hydrate,
and (d) lignin, alkali, 2-hydroxypropyl ether. (See Plate 4.)
waters and wastewaters (see
Section 2.4.3
). Mayer et al. (
1999
) conclude that quantitative
measurement of tyrosine, tryptophan, and protein by fluorescence alone is not possible.
First reported by Coble et al. (
1990
) for samples from the Black Sea, reports of pro-
tein-like, tyrosine-like, and tryptophan-like fluorescence are common in data reported for
freshwater (Cory and McKnight,
2005
; Fellman et al.,
2009
), marine (Coble et al.,
1990
),
estuarine (Mayer et al.,
1999
; Maie et al.,
2007
), and wastewater systems (Baker,
2001
). A
complication of assigning peaks in this way is that the names imply composition and, as
noted previously, there are a number of fluorophores present in water samples with spec-
tral overlap in the regions with proteins and amino acids. Few studies provide supporting
data based on compound specific analyses for the presence of amino acids or the array
of compounds that fluoresce in these regions. Yamashita and Tanoue (
2003
) related the
protein-like fluorophores for marine samples to tyrosine and tryptophan content obtained
from analyses of hydrolyzable amino acids. In their system, amino acid components
likely dominate their fluorescence signals; however, no other analyses were provided to
rule out the possibility that other compound classes may have contributed to these regions
of fluorescence. The influence of phenolic compounds (tannins and simple phenols) on
