|Abstract Title:||Development of a Continuous Calibration Method for Gaseous Elemental Mercury Measurements|
|Presenter Name:||Teodor Andron|
|Company/Institution:||Jožef Stefan Institute|
|Session:||Special Session - Metrological Traceability for mercury analysis and speciation|
|Co-Authors:||Teodor Andron,Jože Kotnik,Milena Horvat|
Abstract Information :
Lumex RA-915M is a commonly used portable gaseous elemental mercury (GEM) analyser. The device continuously monitors GEM in ambiental and polluted air in the concentration range between 0.5 and 50000 ng m-3. Hg(0) is detected through atomic absorption spectroscopy (AAS) with Zeeman background correction. Although very reliable, the analyser is precalibrated at the manufacturer with spyked calibration standards at much higher concentrations than the ones found in ambiental areas for Hg(0). We have developed a continuous calibration method in order to do on-site calibration that would cover the working range of ambiental GEM analysis. The results are traceable to NIST 3133 Hg(II) certified reference material. The NIST 3133 is mixed in an impinger with 3% m/V SnCl2 ,by the aid of peristaltic pumps. This solution is purged with N2 in order to release the Hg(0) and carry it into the analyser. This set-up provides continuous and stable signals that can be used for calibration. Calibration and measurements have been performed in different intervals of concentration, varying from 4 to 40 ng m-3, the relative combined uncertainty of measurement results varying from 6.3 to 9 % for a coverage factor of 2. In order to evaluate the analyzer and our calibration method, we have compared the results with Sir Galahad which is an automated mercury analyser with atomic fluorescence spectroscopy, and manual double amalgamation method which also detects mercury through atomic fluorescence spectroscopy. All 3 methods have comparable results, Sir Galahad having a relative combined uncertainty of 7.2% and double amalgamation manual method having a relative combined uncertainty of 2.7%. The biggest contributors to the uncertainty were sample repeatability for Lumex and uncertainty coming from calibration for Sir Galahad and double amalgamation manual method.