Toward the Development of Certified Reference Materials for Effective Biodiesel Testing. Part 2: Characterization and Value Assignment

Abstract

A comprehensive feasibility study for the production of a biodiesel reference material for relevant specification parameters as provided in EN 14214 was launched because of insufficient knowledge available for most of the steps needed for the production of new biodiesel certified reference materials (CRMs). This paper summarizes the findings of this study for the characterization and final value assignment of a biodiesel reference material. Assigned values were calculated as the unweighted mean of the laboratory means of the accepted sets of results for each parameter. Uncertainties were estimated in compliance with the “Guide to the Expression of Uncertainty in Measurement” (GUM, ISO/IEC Guide 98-3:2008), including contributions from characterization, homogeneity, and stability studies. Of the 22 parameters considered overall, it could be shown that it would be feasible to prepare and certify reference material for 7 of them (ester, linolenic acid methyl ester, triacylglycerol, total glycerol, iodine value, oxidation stability, and acid value) with the approach taken thus far. For the remaining parameters, different problems were encountered. Although raising a considerable number of challenges, the development of a future biodiesel CRM for many parameters seems feasible. The provision of such a material would favor the building of a harmonized measurement system and, consequently, comparable analytical results.

New Certified Rapeseed-Based Biodiesel Reference Material for Effective Biodiesel Testing

“…The outcome of the previously organized feasibility study was that the results obtained for methanol and water content, flash point, and viscosity would be clearly insufficient for certification of a reference material because of the higher estimated standard uncertainties from the between-unit inhomogeneity. Hence, for the production of ERM-EF001 the processing of the material was improved in order to reduce potential between-unit inhomogeneity.…”

“…A few parameters had to be excluded for practical reasons, as their required sample intakes would have exceeded the 27 mL that was filled per unit (cold filter plugging point, total contamination, copper strip corrosion, cetane number, and sulfated ash content). For a few parameters (polyunsaturated fatty acid methyl esters, sodium, potassium, calcium, magnesium, phosphorus, and sulfur) the concentration level present in the material was expected to be rather low, not allowing reliable measurements thereof as already shown in the previously performed feasibility studies. − In total, 15 parameters were investigated, covering both chemical and physical properties (Table ).…”

“…Each participant was required to operate a quality system and to deliver documented evidence of its laboratory proficiency for the respective parameters in the field of biodiesel measurements by submitting results for intercomparison exercises or method validation reports. Moreover, all admitted laboratories had proven their competence in the previously organized characterization exercises for the feasibility study and the BIOREMA project . Having a formal accreditation was not mandatory, but meeting the requirements of ISO/IEC 17025 was obligatory.…”

“…However, the decision to develop a reference material is not taken lightly, largely due to the considerable resources needed to produce a CRM. This has already been explained and demonstrated in previous papers summarizing the findings of feasibility studies related to the production of biodiesel reference materials. − The information gained in these projects was used to improve critical steps in the physical production of and value assignment to the candidate CRM, to determine the priority needs of the analytical community, and to assess the potential demand for such materials, paving the way to the successful production of the first rapeseed-based biodiesel reference material.…”

“…In particular, it describes the steps of selecting and processing the material, homogeneity testing, stability testing, characterization, and value assignment, performed by robust metrological approaches according to the requirements of ISO Guides 34 and 35 . Moreover, a comparison of a few selected results from a preceding feasibility study and the presented study is given, showing the importance of performing preliminary research, which was paving the way to the successful production of ERM-EF001.…”