ASTM D 7757 : 2017

1.1This test method covers the determination of total silicon by monochromatic, wavelength-dispersive X-ray fluorescence (MWDXRF) spectrometry in naphthas, gasoline, gasoline-ethanol blends, reformulated gasoline (RFG), ethanol and ethanol-fuel blends, and toluene at concentrations of 3 mg/kg to 100 mg/kg. The precision of this test method was determined by an interlaboratory study using representative samples of the liquids described in 1.1 and 1.2. The pooled limit of quantitation (PLOQ) was estimated to be 3 mg/kg.

1.2Gasoline samples containing ethanol and other oxygenates may be analyzed with this test method provided the matrix of the calibration standards is either matched to the sample matrices or the matrix correction described in Annex A1 is applied to the results. The conditions for matrix matching and matrix correction are provided Section 5, Interferences.

1.3Samples with silicon concentrations above 100 mg/kg can be analyzed after dilution with appropriate solvent. The precision and bias of silicon determinations on diluted samples have not been determined and may not be the same as shown for neat samples (Section 16).

1.4A fundamental assumption in this test method is that the standard and sample matrices are well matched, or that the matrix differences are accounted for (see 13.5). Matrix mismatch can be caused by C/H ratio differences between samples and standards or by the presence of other interfering heteroatoms; observe the cautions and recommendations in Section 5.

1.5The values stated in SI units are to be regarded as standard. No other units of measurement are included in this standard.

1.6This standard does not purport to address all of the safety concerns, if any, associated with its use. It is the responsibility of the user of this standard to establish appropriate safety and health practices and determine the applicability of regulatory limitations prior to use.

1.7This international standard was developed in accordance with internationally recognized principles on standardization established in the Decision on Principles for the Development of International Standards, Guides and Recommendations issued by the World Trade Organization Technical Barriers to Trade (TBT) Committee.