Report of the CCQM-K123: trace elements in biodiesel fuel

Abstract

The CCQM-K123 key comparison was organized by the Inorganic Analysis Working Group (IAWG) of CCQM to assess and document the capabilities of the national metrology institutes (NMIs) or the designated institutes (DIs) to measure the mass fractions of sodium, calcium, potassium, magnesium phosphorous and sulfur in biodiesel fuel (BDF). National Metrology Institute of Japan (NMIJ) and National Institute of Standards and Technology (NIST) acted as the coordinating laboratories. Results were submitted by 11 NMIs and DIs. Most of the participants used inductively coupled plasma-mass spectrometry (ICP-MS), isotope dilution technique with ICP-MS and inductively coupled plasma-optical emission spectrometry (ICP-OES) with microwave acid digestion. Accounting for relative expanded uncertainty, comparability of measurement results for each of Na, Ca, K, Mg and P was successfully demonstrated by the participants. Concerning S, the variation in results between participants, particularly those using IDMS methods was observed. According to the additional evaluation and investigation, the revised results were overlapping between IDMS measurements at the k = 2 level. However, this KC does not support S measurements. Main text To reach the main text of this paper, click on Final Report. Note that this text is that which appears in Appendix B of the BIPM key comparison database kcdb.bipm.org/. The final report has been peer-reviewed and approved for publication by the CCQM, according to the provisions of the CIPM Mutual Recognition Arrangement (CIPM MRA).

Combining Isotope Dilution and Standard Addition—Elemental Analysis in Complex Samples

“…The single results encompass the zero line with their associated expanded uncertainties, which proves the complete consistency of the data. In the case of sulfur determination in this work, the respective sample was taken from a stock solution already used in the interlaboratory comparison CCQM-K123, as described in [ 23 ]. There, the sulfur determination was carried out using double IDMS, yielding w x = 7.394(46) µg/g.…”

“…The sample preparation for sulfur determination in the biodiesel fuel matrix is described in [ 23 ]. Briefly, an ampoule (15 mL) from the CCQM-K123 study containing commercial biodiesel fuel doped with the target analyte sulfur using dibutyl sulfide was used as the sample.…”

“…Data from the new combined IDMS/standard addition approach (this work). Red solid line: average value of w (S) from BAM, applying IDMS and using the same solution [ 23 ]. Upper and lower associated uncertainties: red dotted lines.…”

“…The second example of the new combined method is the measurement of the mass fraction ( w x ) of sulfur in a biodiesel fuel matrix. These measurements were performed within an interlaboratory key comparison conducted by the IAWG of the CCQM (Inorganic Analysis Working Group of the Consultative Committee for Amount of Substance: Metrology in Chemistry and Biology): CCQM-K123 [ 23 ]. The mass fractions of several trace elements (impurities)—among them, sulfur—were determined.…”