Environmental Engineering Reference
In-Depth Information
4.4
Chlorothalonil
Few applications using LC-MS have been reported in the literature. To the best
of our knowledge this technique has scarcely been applied for the determin-
ation of Chlorothalonil in marine waters and sediments. Limited information
is also available for the determination of the biocide boosters, that are re-
viewed in this chapter, by LC-MS analysis (Table 3).
For structural information of Chlorothalonil, as is usual in optimization
procedures, the operational parameters of interfaces and fragmentor volt-
age are optimized. APCI has been reported as the selected interface for the
analysis of Chlorothalonil. Typically, the capillary voltage and the corona cur-
rent are the most relevant operational parameters of APCI that are observed
in both PI and NI modes. Comparing both operation modes, Chlorothalonil
has been shown to exhibit a higher sensitivity under PI mode than under
NI mode. Contrary to compounds such as Diuron or Irgarol 1051, that show
a low fragmentation rate at low fragmentor voltage (70-75 V), the mass spec-
tra of Chlorothalonil is characterized by the presence of two predominant
ions. One of them is the molecular ion [M]
-
; in addition the spectra show
afragmentionatm
z 246. This ion, which has a high abundance, corres-
ponds to [M + OH - HCl]
-
(Table 4). An interpretation of this pattern of frag-
mentation is that Chlorothalonil is known to degrade under high temperature
conditions leading to the substitution of a Cl atom by the hydroxyl group in
the aromatic ring [19, 47]. Under SIM conditions and SPE pre-concentration,
it is feasible that the analytical method can detect Chlorothalonil at the ng L
-1
level (1-2 ppt) in seawater samples [19, 47].
/
4.5
Dichlofluanid
Data concerning the determination of Dichlofluanid by LC-MS using the
APCI interface have been published [19, 47, 51, 52]. On-line SPE methods
have been developed for trace detection in seawater samples and sediments
with limits of detection of 4-5 ng L
-1
and 1.6 ng g
-1
, respectively [19, 51]
(Table 3).
The optimum conditions of sensitivity were working with APCI in nega-
tive mode. To study the structural information for the determination of
Dichlofluanid, different fragmentor voltages have been applied, in the range
of 25-200 V. When fragmentor voltage values were applied in the range
70-110 V, Dichlofluanid suffers an appreciable fragmentation. The pattern
of fragmentation shows a main ion at m
/
z 199, which has been assigned
to [M - SCCl
2
F]
-
(Table 4). This result is in agreement with most of the
reports where fragmentation experiments for Dichlofluanid have been car-
ried out [19, 47, 52]. An additional fragment ion at m
/
z 155 with a low
