Reference method for PCDDs and PCDFs in pulp and paper mill effluents: section 2


Section 2: Contamination and Interferences

Solvents, reagents, glassware, and other sample processing hardware may yield artifacts and/or elevated baselines that could lead to elevated detection limits and/or loss of ability to detect PCDDs/PCDFs that may be present. Reagents should be of the highest available purity. In some cases, reagents may require further purification before use.

Proper cleaning of glassware is extremely important. Glassware should be rinsed with solvent and washed with a detergent solution as soon after use as is practical. Sonication of glassware filled with a detergent solution can also be performed as an aid to cleaning.

It shall be demonstrated that all materials used in the analysis are free from interferences by running reference matrix blanks initially and with each sample set. High purity water is used as the reference matrix blank.

Interferences co-extracted from samples will vary considerably from source to source depending upon the exact nature of the sample matrix. Interfering compounds may be present at concentrations several orders of magnitude higher than any PCDDs/PCDFs that may be present. Interfering co-extractants must therefore be eliminated or reduced to the maximum extent practicable in order to ensure reliable quantification of trace amounts of PCDDs/PCDFs. The cleanup procedures described in this report can effectively remove many potential interferents.

Despite rigorous cleanup procedures, matrix interference will still be a possibility. If detection limits are seriously affected by excessive background (non-discrete interference), the sample extract will have to be re-processed using alternative cleanup techniques (Creaser and Haddad, 1989; NCASI Method, June 1990).

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