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.

The session is divided in two parts; 7 oral presentations 12 poster format presentations.

The session covers a diverse range of possible screening methods, developed by colleagues from a wide range of nationalities.

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 methods and 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 samples, and soil 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.

Kobayashi and colleagues present an evaluation of an

ah-immunoassay

® screening method for PCDD/Fs and dioxinlike compounds.

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.

The range of sample matrices covered offers a useful tool for routine

environmental screening

.

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

moss

es as

bio-monitors

. The properties of mosses make them a suitable substrate for monitoring,

as any contamination present will not be taken from the substrate on which they grow, or transferred to internal tissues.

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 flyash

(Usuki), (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.

High levels detected in Blue Mussels corresponded well with areas known to be affected by high discharges of PCDD/F’s.

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.

Given the relatively complex nature of foodstuff samples, the determined concentrations and good recoveries presented

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.

Borgen and colleagues have developed a method in which a number of challenges due to the complexity of the analytes needed to be overcome.

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.

Analysis by electron capture negative-ion ionisation gives greater selectivity allowing a survey to be conducted.