Environmental Engineering Reference
In-Depth Information
The high efficiency achieved by capillary GC allows the separation of
the derivatized compounds with non-polar or semi-polar stationary phases,
such as dimethyl-polysiloxane or 5% diphenyl-dimethyl-polysiloxane. Most
of the capillary columns generally utilized for OT separation, have a length of
25-30 m, an i.d. of 0.2-0.25 mm and a film thickness of 0.1-0.3
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m [11, 25,
61, 63].
Flame photometric detection (FPD), atomic emission detection (AED),
atomic emission spectrometry (AAS) and mass spectrometry (MS) are the
mostly used methods for the detection of tin species and are characterized by
detection limits down to pg levels for injected tin species [11, 25, 61, 63].
The FPD system is based on the emission of tin species in a hydrogen-rich
flame; selectivity for tin is obtained at 610 nm using a cut-off or interfer-
ence filter. However, the FPD signal may be disturbed by the coextracted
sulfur species. Dual flame FPD had been introduced to improve the selectiv-
ity of the technique, but it provided lower sensitivity than the single-flame
FPD. The new generation FPDs in which the continuous flame is replaced
by a pulsed flame, the pulsed FPD (PFPD) detector, has recently been intro-
duced. The main advantages are the increased sensitivity and lower matrix-
dependency [68].
The application of the AED detector is generally used in combination with
microwave-induced plasma (MIP-AED) rather than with inductively coupled
plasma (ICP-AED) for its high sensitivity, even if the robustness of the ICP is
a significant advantage when complex matrices are analyzed [67].
In the GC-AAS systems tin is quantified at 286.3 or 224.4 nm and the at-
omization of the compounds is mainly achieved by electrothermal (ET-AAS)
or quartz furnace (QF-AAS) [25, 28].
Mass spectrometric (MS) detection with electron impact (EI) ionization for
fragment production and a quadrupole or ion trap for ion detection, has dis-
tinct advantages over the previously mentioned detectors [6, 11, 65]. It is more
sensitive, highly selective and is able to provide structural information about
the target compounds. Especially, when a single fragment of a specific organo-
tin compound is chosen for selected ion monitoring (SIM) analysis mode.
Recently, ICP has been widely utilized as the ion source for fragment produc-
tion coupled to AES, MS or time-of-flight (TOF)-MS detection. The application
of MS in combination with isotope-dilution (ID) analysis is becoming very pop-
ular [14, 15, 26, 44, 45]. The sensitivity and selectivity of MS systems can be
further improved by tandem mass spectrometry (MS
MS) [20, 22].
The absolutely essential derivatization step in gas chromatography is not
necessary in high performance liquid chromatography (HPLC). This renders
the HPLC methods significantly simpler and faster. The separation of the un-
derivatized ionic organotin compounds may be performed with normal- or
reversed-phase, ion-pair as well as ion-exchange columns; the latter being the
most commonly applied [25, 61-64]. Implementations with HPLC, however,
are limited for organotin separation compared to GC, because of the scarce
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