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DIOXIN 2003 BOSTON SESSION SUMMARY REPORT Rapid Screening Methods Keith Worrall & Takeshi Nakano. This session is comprised of approximately 19 presentations covering a variety of screening methods for POPs.
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Presenters are from Australia, Japan, United Kingdom, Norway, Spain, Sweden, USA, Netherlands and Hong Kong will participate in the session.
For a considerable amount of time, High Resolution GC High Resolution Mass Spectrometry (HRGC-HRMS) methods have been the legislative and accepted methods for the determination of Dioxins, Furans and similar compounds in the analytical laboratory.
Whilst very accurate, these methods can be time consuming and costly. The aim of this session is to present methods that are being proposed for the rapid screening of a wide variety of matrices.
There are a number of possible methods of screening, in this session the emphasis is split between bioassay monitoring, instrumental methodsand bio-monitoring.
In the first of the Oral presentations, Leeuwen and colleagues report on the validation of a wide range of screening methods, with good accuracy and repeatability obtained.
Anderson and colleagues have worked on a comparison of a rapid biological screening method(EPA 4425) and chemical analytical methods.
In a study concentrating upon ash, exhaust gas and soil samples, they have concluded that the comprehensive screening of a site using method EPA 4425,
followed by confirmation analysis of 10-20% of the samples by HRGC-HRMS methods presents the possibility for substantial project savings for a large site.
This work is complemented nicely by the work of Leeder and colleagues, who present their work looking at the applicability of EPA method 4025 for dioxin site assessment.
The conclusions are that the method does provide an effective approach to the assessment of sewage treatment plants, being low cost, and having improved turnaround times when compared with EPA method 8290.
The assay employs an efficient clean-up method to remove possible interfering compounds such as PAHs, which results in good correlation with HRGC-HRMS techniques.
Nishi and colleagues have developed an immunochromatographic test highly specific for PCBs, allowing possible results to be obtained at the point of sampling.
Rivera and colleagues have studied the use of mosses as bio-monitors. The properties of mosses make them a suitable substrate for monitoring,
The conclusions demonstrate that the congener profiles are maintained following deposition on the moss, indicating that no metabolic or transfer effects occur within the organism.
Ohno and colleagues are presenting an enzyme linked immunoassay (ELISA) technique that shows high selectivity to 3 out of the 4 non-ortho PCBs.
The assay demonstrates virtually no reactivity to other PCBs, PCDDs or PCDFs, providing a rapid and specific method for the mass screening of environmental samples, prior to confirmatory analysis of high concentration samples.
The final Oral presentation is by Engwall and colleagues, and reports their findings from an international intercalibration study of dioxin-like compounds in cod liver using bioassays.
Intercalibration studies are one of the most effective methods for evaluating the accuracy of methods, in this case covering a number of different bioassay methods.
The study showed that a good percentage of the participating laboratories gave values within 60-106% of the ‘true’ value, indicating a good degree of accuracy and showing good agreement with chemical analysis by HRGC-HRMS.
The authors also point at possible problems with interfering compounds that can elevate the determined TEQ, and also suggest work to be performed to reduce the risk of false negatives.
A large amount of the presented work in the session looks into the application of various immunoassay and bioassay methods as a tool for the rapid screening of samples for PCDD/Fs and PCBs.
The methods work for a variety of different matrices, for example human blood (Usuki), flyash(Miyata, Matsuyama), PCB oil (Takigami) environmental samples (Fujihara, Kobayashi).
Most of the methods employ some specific clean-up practices to remove compounds such as PAHs, and other Ah antagonists, which can result in high determined values when compared with HRGC-HRMS methods or reference values.
In contrast the work of Nording and colleagues focuses on the bio-analysis of PAHs in soils, and has produced a method recommended for semi-quantitative analysis of PAHs.
The method is far simpler to implement in the field and the authors view is that this far outweighs the lower accuracy as a tool for rapid field screening.
Ikeda and colleagues present some work complementary to that presented by Rivera, where Blue Mussels are utilized as bio markers to monitor the levels of pollution across a wide range of estuaries, beaches, canals and offshore.
C.S. NG and W.C. Chung have taken a slightly different approach to speeding up analysis by producing a simplified extraction and clean-up method for application in foodstuff samples.
an effective method has been produced which accounting for the 1-2 days saved during clean-up could increase sample turnover and reduce turnaround times significantly.
An instrumental approach to screening has been taken by Worrall and colleagues, with the development of a GC-MS/MS method, allowing profiles of congeners to be detected and reported, giving the possibility of the ‘finger-print’ of a source to determined.
Screening a number of areas in the south of Norway for chlorinated paraffin’s, compounds for which there are several thousand components in a single commercial mixture.