Environmental Engineering Reference
In-Depth Information
ionization (NCI) and positive chemical ionization (PCI) are discussed in the
following sections for the booster biocides, which have been the focus of
attention in several publications as a consequence of their frequency of detec-
tion in the marine environment.
3.2
Irgarol 1051
Analysis of Irgarol 1051 in marine waters and sediments has normally been
focused on survey studies for determining in particular the presence of this
compound and its main degradation product (M1) or the simultaneous pres-
ence of other booster biocides or organotins. The presence of Irgarol 1051 has
been well documented reflecting its wide distribution in coastal and estuarine
waters, harbours and marinas [3] from the Côte d'Azur (France) [9], western
Mediterranean [38], UK coastal [14], western Japan [15] to Biscayne Bay in
Florida [16]. In addition, to measure environmental residue concentrations,
analytical skills have also been used to investigate the degradation, environ-
mental transport and fate of Irgarol 1051. Irgarol 1051 is a triazine herbicide
and is amenable to analysis by GC and similarly, the degradation products of
triazines, such as M1, are generally also amenable to separation by GC. How-
ever, LC separation and APCI ionization are also favoured as an analytical
approach, in particular for M1, compared to its GC analysis [44].
The typical EI GC-MS spectrum of Irgarol 1051 has a base peak M
+
ion and
abundant fragment ions that correspond to the [M - NC(CH
3
)
3
]
+
(m
/
z, 182)
and the [M - CH
3
]
+
(m
z, 238) ions (Table 3). Most of the triazines that have
methyl, ethyl or larger alkylamino groups as ring substituents, have either
basepeaksormajorionscausedbythelossofasmallalkylradicalfromthe
M
+
ion by the alpha-cleavage reaction [39]. The three GC-MS ions have a rela-
tive abundance of 98%atm
/
z
253. The spectrum operating in PCI mode, exhibits the characteristic M
+
ion
as a base peak and a fragment ion that corresponds to [MH - NC
4
H
7
]
+
(m
/
z 182, 75%atm
/
z 238 and a base peak at m
/
/
z,
198). In addition, adduct ions that correspond to [M + C
2
H
5
]
+
(m
/
z, 282) and
[M+C
3
H
5
]
+
z, 294) were observed with low abundance (10-27%). With
the NCI GC-MS spectrum, however, the [M - H]
-
ion is the base peak (m
(m
/
/
z,
252) and only one low-abundance molecular ion [M]
-
z, 253) is also ob-
served. In this sense, considering the identification power that is offered by
the EI spectrum on the basis of the number of fragment ions and relative
abundance, EI has been used by most authors. The lack of mass spectrum li-
braries for CI conditions is also a limitation, especially for the identification
of degradation products.
From the point of view of sensitivity, pre-concentration of the samples is
a decisive step to achieve lower limits of detection (sub-to-low ppt). A com-
mon pre-concentration procedure included in the development of analytical
methods using different detection systems (ECD, FTD, AFID, MS) that has
(m
/
