Laboratory Analysis of Flue Gas Desulfurization Wastewater
Wastewater from flue gas desulfurization (FGD) systems in power plants can contain constituents that may interfere with certain laboratory analyses, due to high concentrations of total dissolved solids (TDS) or the presence of elements known to cause matrix interferences. EPA has observed that, during inductively coupled plasma – mass spectrometry (ICP-MS) analysis of FGD wastewater, certain elements commonly present in the wastewater may cause polyatomic interferences that bias the detection and/or quantitation of certain elements of interest. These potential interferences may become significant when measuring trace elements, such as arsenic and selenium, at concentrations in the low parts-per-billion range.
As part of a recent sampling effort for the Steam Electric Power Generating Effluent Guidelines rulemaking, EPA developed two standard operating procedures (SOPs) that were used in conjunction with EPA Method 200.8 to conduct ICP-MS analyses of FGD wastewater. The SOPs describe critical technical and quality assurance procedures that were implemented to mitigate anticipated interferences and generate reliable data for FGD wastewater.
EPA regulations at 40 CFR 136.6 already allow the analytical community flexibility to modify approved methods to lower the costs of measurements, overcome matrix interferences, or otherwise improve the analysis. The draft SOPs developed for FGD wastewater take a proactive approach toward looking for and taking steps to mitigate matrix interferences, including using specialized interference check solutions (i.e., a synthetic FGD wastewater matrix).
EPA’s draft SOPs are being made available to laboratories contemplating ICP-MS analysis of FGD wastewater, either for adoption as currently written or to serve as a framework for developing their own laboratory-specific SOPs.