87
Dissolved Organic Matter in Natural Waters
(4-MBC), m-toluamide, galaxolide, tonalide, musk xylene, musk ketone, celestolide, triclosan, octocrylene and two alkylphenol surfactants such as p-octylphenol and p-nonylphenol. These methods consisted of extraction, clean-up,
derivatization and analysis by gas chromatography–mass spectrometry with
selected ion monitoring (GC–SIM–MS) or gas chromatography–tandem mass
spectrometry (GC–MS/MS) techniques (Mottaleb et al. 2009). To assess recovery
of target compounds from 1-g tissue homogenates, acetone was selected as optimal solvent for extracting compounds with dissimilar physicochemical properties
from fish tissue. Initial experiments confirmed that GC–SIM–MS could be applied
for analysis of lean fillet tissue (<1 % lipid) without gel-permeation chromatography (GPC), and this approach was applied to assess the presence of target analytes in fish fillets collected from a regional effluent-dominated stream in Texas,
USA. Benzophenone, galaxolide, tonalide, and triclosan were detected in 11 of 11
environmental samples at concentrations ranging from 37 to 90, 234 to 970, 26
to 97, and 17 to 31 ng g −1 , respectively. However, performance of this analytical
approach declined appreciably with increasing lipid content of analyzed tissues.
Successful analysis of samples with increased lipid content was enabled by adding GPC to the sample preparation protocol and monitoring analytes with tandem
mass spectrometry. Both analytical approaches were validated using fortified fillet tissue collected from locations expected to be minimally impacted by anthropogenic influences. Average analyte recoveries ranged from 87 % to 114 % with
RSDs <11 % and from 54 % to 107 % with RSDs <20 % for fish tissue containing <1 % and 4.9 % lipid, respectively. Statistically derived method detection limits (MDLs) for GC–SIM–MS and GC–MS/MS methodologies ranged from 2.4 to
16 ng g −1 , and from 5.1 to 397 ng g −1 , respectively (Mottaleb et al. 2009). In
a following study, improvement of the MDL has been observed between 12 and
38 ng g −1 by the GC–MS/MS methodology for the same PCPs using 2.0–2.5 g of
fish (Subedi et al. 2011).
9 Does DOM Act as Energy Source for Living Organisms
and Aquatic Ecosystem?
The concentration levels of DOC in groundwater are very variable: they reach
16–424 μM C in Asia, 42–15333 μM C in Europe, 8–2333 μM C in North America,
1108 ± 217–14167 ± 6333 μM C in Botswana (Africa), 100–3000 μM C in Brazil
(South America) (Table 2) (Mostofa et al. 2007a, Mostofa KMG et al., unpublished data; Buckau et al. 2000; Bertilsson et al. 1999; McIntyre et al. 2005; Meier
et al. 2004; Crandall et al. 1999; Schwede-Thomas et al. 2005; Pabich et al. 2001;
Michalzik et al. 2001; Anawar et al. 2002; Richey et al. 2002; Bradley et al. 2007).
Groundwater is the main source of drinking water for many developing and developed countries, including the USA. Groundwater has the advantage over surface
water of being usually free of suspended solids, bacteria and other disease-causing
microorganisms (Mostofa et al. 2009a). Interestingly, upland areas make up 30 %
Dissolved Organic Matter in Natural Waters
(4-MBC), m-toluamide, galaxolide, tonalide, musk xylene, musk ketone, celestolide, triclosan, octocrylene and two alkylphenol surfactants such as p-octylphenol and p-nonylphenol. These methods consisted of extraction, clean-up,
derivatization and analysis by gas chromatography–mass spectrometry with
selected ion monitoring (GC–SIM–MS) or gas chromatography–tandem mass
spectrometry (GC–MS/MS) techniques (Mottaleb et al. 2009). To assess recovery
of target compounds from 1-g tissue homogenates, acetone was selected as optimal solvent for extracting compounds with dissimilar physicochemical properties
from fish tissue. Initial experiments confirmed that GC–SIM–MS could be applied
for analysis of lean fillet tissue (<1 % lipid) without gel-permeation chromatography (GPC), and this approach was applied to assess the presence of target analytes in fish fillets collected from a regional effluent-dominated stream in Texas,
USA. Benzophenone, galaxolide, tonalide, and triclosan were detected in 11 of 11
environmental samples at concentrations ranging from 37 to 90, 234 to 970, 26
to 97, and 17 to 31 ng g −1 , respectively. However, performance of this analytical
approach declined appreciably with increasing lipid content of analyzed tissues.
Successful analysis of samples with increased lipid content was enabled by adding GPC to the sample preparation protocol and monitoring analytes with tandem
mass spectrometry. Both analytical approaches were validated using fortified fillet tissue collected from locations expected to be minimally impacted by anthropogenic influences. Average analyte recoveries ranged from 87 % to 114 % with
RSDs <11 % and from 54 % to 107 % with RSDs <20 % for fish tissue containing <1 % and 4.9 % lipid, respectively. Statistically derived method detection limits (MDLs) for GC–SIM–MS and GC–MS/MS methodologies ranged from 2.4 to
16 ng g −1 , and from 5.1 to 397 ng g −1 , respectively (Mottaleb et al. 2009). In
a following study, improvement of the MDL has been observed between 12 and
38 ng g −1 by the GC–MS/MS methodology for the same PCPs using 2.0–2.5 g of
fish (Subedi et al. 2011).
9 Does DOM Act as Energy Source for Living Organisms
and Aquatic Ecosystem?
The concentration levels of DOC in groundwater are very variable: they reach
16–424 μM C in Asia, 42–15333 μM C in Europe, 8–2333 μM C in North America,
1108 ± 217–14167 ± 6333 μM C in Botswana (Africa), 100–3000 μM C in Brazil
(South America) (Table 2) (Mostofa et al. 2007a, Mostofa KMG et al., unpublished data; Buckau et al. 2000; Bertilsson et al. 1999; McIntyre et al. 2005; Meier
et al. 2004; Crandall et al. 1999; Schwede-Thomas et al. 2005; Pabich et al. 2001;
Michalzik et al. 2001; Anawar et al. 2002; Richey et al. 2002; Bradley et al. 2007).
Groundwater is the main source of drinking water for many developing and developed countries, including the USA. Groundwater has the advantage over surface
water of being usually free of suspended solids, bacteria and other disease-causing
microorganisms (Mostofa et al. 2009a). Interestingly, upland areas make up 30 %