Environmental Engineering Reference
In-Depth Information
been reported is the SPE method (Table 1). In the group of detection tech-
niques such as ECD, FTD and AFID applied to marine water samples, the
detection limits are at the low ng L -1 level (2-20 ppt) [21, 37]. For sediments,
the available documentation which is related to AFID, show detection limits
at the ng g -1 level (50 ppb) [37].
Concerning Q-MS techniques for water analysis, the sensitivity can be con-
sidered similar to selective detectors (ECD). The detection limits obtained in
EI ionization and SIM mode are at the ppt level (0.5-10 ppt) [9, 20, 28]. Sub-
to-low ng L -1
levels (0.1-1 ppt) are also the reported detection limits using
IT-MS in MS
MS mode [29]. To obtain optimal sensitivity in the analysis of
antifouling compounds, most of the developed analytical methods have used
the EI ionization technique. Alternatives such as CI in both positive and nega-
tive modes have been evaluated to give an idea of the sensitivity obtained
with ionization techniques [27, 28]. NCI is not a suitable ionization technique
for Irgarol 1051, the sensitivity decreases by four orders of magnitude with
respect to EI. In addition, analysis in the PCI mode does not significantly in-
crease the sensitivity, and PCI has a detection limit at the ng L -1 level (50 ppt).
SIM procedures have also been preferred with the objective of achieving very
low residue determinations because remarkable differences have been ob-
served between sensitivities obtained by full scan and SIM modes. The SIM
mode provides response factors from 10 to 150 times higher than full scan
mode (see Fig. 2, where sensitivity obtained with EI and NCI techniques was
evaluated).
When extraction methods such as SPME, HS-SPME or LLE have been
used, comparable sensitivity has been obtained in GC-MS water analyses (30;
50; 0.5-2 ppt respectively) [2, 16, 22, 24, 33]. On the other hand, sensitivity
in sediment sample analysis with extraction methods and GC-MS analysis
/
Fig. 2 GC-EI-MS and GC-NCI-MS chromatograms corresponding to a spiked seawater
sample at a concentration of 25 ng L -1
 
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