Open AccessComparison of Primary Laser Spectroscopy and Mass Spectrometry Methods for Measuring Mass Concentration of Gaseous Elemental Mercury
Author(s) -
Abneesh Srivastava,
Stephen E. Long,
James E Norris,
Colleen E. Bryan,
Jennifer Carney,
Joseph T. Hodges
Publication year - 2020
Publication title -
analytical chemistry
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 2.117
H-Index - 332
eISSN - 1520-6882
pISSN - 0003-2700
DOI - 10.1021/acs.analchem.0c04002
Subject(s) - chemistry , mercury (programming language) , analytical chemistry (journal) , mass spectrometry , inductively coupled plasma mass spectrometry , primary standard , isotope dilution , spectroscopy , sorbent , environmental chemistry , chromatography , physics , quantum mechanics , computer science , programming language , statistics , mathematics , organic chemistry , adsorption , calibration
We present a direct comparison between two independent methods for the measurement of gaseous elemental mercury (GEM) mass concentration: isotope dilution cold-vapor inductively coupled plasma mass spectrometry (ID-CV-ICP-MS) and laser absorption spectroscopy (LAS). The former technique combined with passive sorbent tube sampling is currently the primary method at NIST for mercury gas standards traceability to the International System of Units (SI). This traceability is achieved via measurements on a mercury-containing reference material. The latter technique has been recently developed at NIST and involves real-time measurements of light attenuation caused by GEM, with SI traceability based in part on the known spontaneous emission lifetime of the probed 6 1 S 0 -6 3 P 1 intercombination transition of elemental mercury (Hg 0 ). Using a steady-flow Hg 0 -in-air generator to produce samples measured by both methods, we use LAS to measure the sample gas and in parallel we collect the Hg 0 on sorbent tubes to be subsequently analyzed using ID-CV-ICP-MS. Over the examined mass concentration range (41 μg/m 3 to 287 μg/m 3 Hg 0 in air), the relative disagreement between the two approaches ranged from (1.0 to 1.8)%. The relative combined standard uncertainty on average is 0.4% and 0.9%, for the LAS and MS methods, respectively. Our comparison studies help validate the accuracy of the ID-CV-ICP-MS primary method as well as establish the LAS technique as an attractive alternative primary method for SI-traceable measurements of GEM.