Environmental Engineering Reference
In-Depth Information
factory solvent for the extraction of these compounds. A solvent evaporation
step is not required, so the aqueous extract obtained can be pre-concentrated
by a SPE procedure. Mean recoveries obtained with this procedure are higher
than 80% and precision, lower than 40%, indicating the suitability of its use
for the extraction of Irgarol 1051 and M1 [25].
3
Gas Chromatography-Mass Spectrometry
3.1
General Remarks
Gas chromatography is a commonly used technique in the analysis of booster
biocides such as Irgarol 1051, Chlorothalonil, Dichlofluanid, Sea-nine 211
or TCMTB (Table 1). In general, the separation of most of these com-
pounds is performed using non-polar GC-capillary stationary phases such as
methyl polysiloxane or phenyl-methylpolysiloxane (DB-1, HP-1, DB-5, HP-5,
ZB-5, DB-225, BPX-5, SE-54), and gradient temperatures from (60-80
◦
Cto
280-320
◦
C). The splitless injection mode is generally preferred because of
its robustness but on-column [20] and PTV [29] have also been used. On
the other hand, the use of splitless injection has the limitation of low sample
capacity (up to 2
L). However, non-volatile co-injected compounds can be
retained in the liner altering the sensitivity and usually an adsorbent is placed
on the liner (i.e. carbon). To avoid this limitation of the splitless mode, on-
column or PTV injectors can be an alternative because they allow a sample
volume of up to 5
µ
L.
Typically, common detection systems such as ECD or FTD have been used
for coupling to GC. In particular, ECD has been applied for the detection
of halogenated compounds (i.e. Chlorothalonil, Dichlofluanid) in environ-
mental samples offering high sensitivity and good reproducibility. However,
interference can be frequently observed as well as low identification capabil-
ity. MS detectors provide unambiguous component identification and also the
use of library spectra. In this sense, the use and acceptance of MS systems
has increased over the last years. The number of applications using GC-MS
is the result of the efficiency of GC separation as well as the good qualitative
information and high sensitivity of MS systems (Table 1). GC-MS methods
have been developed for the simultaneous determination of all GC amenable
booster biocides in seawater and sediment samples; also, some publications
include the simultaneous determination by GC-MS of degradation prod-
ucts, M1 (2-methylthio-4-tert-butylamino-6-amino-s-triazine) which is a sta-
ble transformation product of Irgarol 1051 [15] or DMSA (
N
-dimethyl-
N
-
phenyl-sulphamide), a degradation product of Dichlofluanid [34]. Applica-
tions of GC-MS using ionization techniques based on EI, negative chemical
µ
