Environmental Engineering Reference
In-Depth Information
A post-column derivatization method for PST analysis was developed in the late
1970s and involved using a silica-based stationary phase (Buckley et al.
1978
).
Post-column derivatization allows continuous analysis (via post-column oxidation)
of toxins and subsequent detection by fl uorescence. The toxins are separated on an
ion exchange column (Oshima et al.
1989
; Oshima
1995
). This method is valued for
producing results that correlate well to those produced by MBA. A post-column
method for analysis of PSTs was standardized by a biotoxin working group of the
European Committee for Standardization (CEN) and was approved as the European
Norm EN 14194 (CEN
2002
). However, a pre-column derivatization approach
(employing a single reverse phase column) was developed, in which peroxide or
periodate was used as the oxidation agent (Lawrence et al.
1991
). For instrumental
analyses, the pre-column approach is much simpler than the post-column approach,
and this pre-column method was approved by the Association of Offi cial Analytical
Chemists (AOAC) in June 2005. This so-called pre-column derivatization liquid
chromatography has high accuracy and precision, and produces data that are signifi -
cantly correlated to MBA data.
Generally, pre-column derivatization is more sensitive for detecting lower toxin
levels than the post-column derivatization method. However, the pre-column
method provides a total toxin value, because the following toxins co-elute: GTX2
and 3, GTX1 and 4 and dcGTX2 and dcGTX3. Therefore, the post-column oxida-
tion method is more accurate for individual PSP toxin analysis (RodrÃguez et al.
2010
). Nevertheless, HPLC methods of PSP toxin analysis are slow, costly and
technically demanding. For these reasons, HPLC methods are usually carried out
only in centralized laboratories.
5.2.2
Liquid Chromatography-Mass Spectrometry (LC-MS)
Liquid chromatography-mass spectrometry (LC-MS) is a technique that allows
identifi cation of unknown compounds, elucidation of structural properties of mole-
cules and quantifi cation of known compounds. LC-MS has been advocated by
Quilliam (
1998
) as a universal analytical method for all marine toxins (Humpage
et al.
2010
). Its main advantages are high specifi city, high sensitivity, rapid analysis,
automation, elimination of false positives, and limited sample preparation, com-
pared to other methods, which require complex derivatization and cleanup proto-
cols. However, the main drawbacks of this technique are initial high capital
equipment cost, the requirement for having highly skilled technicians, and the need
for calibration standards (which are not available for all biotoxins).
5.3
Immunosorbant Assays
Immunoassays are biochemical assays that utilize antibodies for analysis. Antibodies
obtained from a conjugate with STX shows the highest sensitivity for STX, dcSTX
and GTX2, 3, whereas, antibodies obtained from a conjugate with neoSTX has high
Search WWH ::
Custom Search