In recent years microwave-induced combustion (MIC) has proven a robust sample preparation technique for difficult-to-digest samples containing high carbon content, especially for halogens and sulfur. NIST has applied the MIC methodology in combination with isotope dilution analysis for sulfur determinations, representing the first-reported combination of this robust sample preparation methodology and high accuracy quantification approach. Medium-resolution mode sector-field inductively coupled plasma mass spectrometry was invoked to avoid spectral interferences on the sulfur isotopes. The sample preparation and instrumental analysis scheme was used for the value assignment of total sulfur in coal Standard Reference Material 2682c and associated control materials. A description of the analytical procedures required is provided, along with metrological results, including an estimation of the overall method uncertainty (1.5 % relative expanded uncertainty) calculated using the IDMS measurement function and a Kragten spreadsheet approach.
Sulfur, SF-ICP-MS, Microwave Induced Combustion, Coal, Isotope Dilution Mass Spectrometry