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Determination of Level of Quantification (LoQ) for Measuring Chlorobenzenes in Stack Emissions

Pentachlorobenzene (QCB) and tetrachlorobenzenes (TeCBs) meet the criteria of persistence, bioaccumulation and primarily form anthropogenic sources. Virtual elimination from the environment of this type of substance is the main objective of the Toxic Substance Management Policy.

The Level of Quantification (LoQ) will be the benchmark for achieving virtual elimination for the release of chlorobenzenes from combustion facilities. LoQ is defined as the lowest concentration of target compounds that can be quantified confidently. It is determined by assessing the variability (standard deviation) of replicate measurements of analytes at a concentration near the detection limit.

A landfill gas incinerator at a municipal solid waste disposal site was chosen for the study. A total of 10 stack gas samples spiked with chlorobenzenes were collected. Samples were Soxhlet extracted with solvent, cleaned-up by passage through a modified silica column, and analyzed using GC-MS and the internal standard quantification (Isotope Dilution) method. LoQ was determined as ten times the standard deviation of the repeated sampling and analysis. LoQ for measuring chlorobenzenes (individual congener of QCB and TeCBs) in stack emissions is estimated as 5.3 ng/sample or 1.5 ng/m3 on a 3½-m3-gas sample.

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