AI Summary & Key Takeaways
AI InsightThe sorbent trapping method in contrast, yielded expanded uncertainties of approximately 1%relative at all sampling points, with an LOQ of 0.001μg/m3.
📌 3 Key Takeaways
Özet
Primary mercury gas standards, traceable to the SI, have been developed which can be used to underpin a NISTtraceability framework for the calibration of vapor phase continuous emission monitoring systems (CEMS). A gasstandard, which is based on a commercial gas generator, has been certified for gaseous elemental mercury outputat specified generator output set points. The standard, termed the NIST Prime (NP) was certified at selected setpoints in the range 0.25μg/m3to 38μg/m3by isotope dilution inductively coupled plasma–mass spectrometry(ID-ICP-MS) using two alternative approaches, based on directly coupled gas sampling, and activated carbonsorbent trapping. Both approaches have been used to provide NIST traceability for electric utility mercury CEMS.The directly coupled method yielded expanded measurement uncertainties ranging from approximately 5.5%relative at 0.5μg/m3, to approximately 1% relative at 38μg/m3, and an estimated limit of quantitation (LOQ) of0.06μg/m3. The sorbent trapping method in contrast, yielded expanded uncertainties of approximately 1%relative at all sampling points, with an LOQ of 0.001μg/m3.