Environmental Engineering Reference
In-Depth Information
3.5
Sea-nine 211
Sea-nine 211 is an antifouling agent whose active ingredient is a halogenated
compound with two Cl atoms in its structure (4,5-dichloro-2- n -octyl-4-
isothiazolin-3-one). Similarly to Dichlofluanid and Chlorothalonil, the analy-
sis with ECD or NCI is expected to have an improved sensitivity with respect
to the EI technique. However, analytical methods developed with NCI and
EI techniques in the SIM mode do not show significant differences, with
detection limits at the same order of magnitude (1.5-2.5 ng L -1 )andusing
a pre-concentration step (SPE) [28]. With ECD, the sensitivity is equivalent
to NCI and offers detection limits at the low-ng L -1 level (2 ppt) or sub-low-
ng L -1 level (0.2 ppt) depending on the extraction method (SPME and SME,
respectively) [21, 23] in water samples. For sediment samples the developed
analytical methods applying SPME or LLE with shaking procedures have
a detection limit at ppb [26, 36], so the lower sensitivity can be related to the
extraction method (Table 1).
The EI mass spectra shows three ions (between 80 to 100%ofrelative
abundance) at m
z 169 as the base peak that corresponds to the [M - C 8 H 17 ] -
ion; the other two ions are at m
/
z 246 and 182. These fragment ions can be
attributed to the loss of a Cl atom given the [M - Cl] - ion and the loss of the
alkyl chain obtaining the [M - C 7 H 14 ] - ion, respectively. The M - ion with m
/
z
283 has a lower abundance (approx. 11%).Atotaloffourionscharacterize
the EI spectrum, which offers capabilities for quantification and confirma-
tion purposes. In addition, the PCI technique using methane, gives enough
spectral information to confirm the detection of this compound, providing
[M + H] +
/
at m
/
z 284 and adduct ions at m
/
z 310 and 322 [28]. In addition,
the sensitivity using PCI, in the MS
MS mode, is similar to that obtained with
NCI or EI in the SIM mode [28, 36]. However, when NCI-MS
/
MS is applied,
the sensitivity is improved with respect to NCI-MS in SIM mode obtaining
detection limits of 0.05 ng L -1 and 1.5 ng L -1 , respectively. In MS
/
/
MS experi-
ments, the fragmentation of the precursor ion at m
/
z 245 gives two main
z 160 and 162, which correspond to the cluster [M - ClH] -
fragment ions at m
/
ions (Table 3).
3.6
TCMTB
The analysis of TCMTB (2-thiocyanomethylthiobenzothiazole) has been
mainly focused on its determination in marine waters using MS detectors.
In spite of this compound being suitable for separation by LC, analytical
methods using GC separation have been developed with good sensitivity for
detection in environmental samples [27, 28]. The ionization techniques, NCI
and EI that have been applied have comparable sensitivity, when the SIM
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