ASTM D7220 standard test method for sulfur in automotive fuels
ASTM D7220 Standard Test Method for Sulfur in Automotive Fuels by Polarization X-ray Fluorescence Spectrometry
1. Scope
1.1 This test method specifies an energy-dispersive X-ray fluorescence (EDXRF) method for the determination of total sulfur in automotive fuels with a concentration range of 6 mg/kg to 50 mg/kg.
1.1.1 The pooled limit of quantitation of this test method as obtained by statistical analysis of inter laboratory test results is 6 mg/kg sulfur.
1.2 A fundamental assumption in this test method is that the standard and sample matrix is well matched. Matrix mismatch can be caused by C/H ratio differences between samples and standards or by the presence of other heteroatoms.
1.3 The values stated in SI units are to be regarded as the standard. The preferred concentration units are mg/kg sulfur.
1.4 This 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.
2. Referenced Documents
2.1 ASTM Standards:
D4057 Practice for Manual Sampling of Petroleum and Petroleum Products
D4177 Practice for Automatic Sampling of Petroleum and Petroleum Products
D6299 Practice for Applying Statistical Quality Assurance Techniques to Evaluate Analytical Measurement System Performance
E 29 Practice for Using Significant Digits in Test Data to Determine Conformance with Specifications
2.2 ISO Standard:
ISO 4259 Determination and application of precision data in relation to methods of test
3. Terminology
3.1 Definitions:
3.1.1 polarization X-ray fluorescence, n - typically a polarization EDXRF instrument is used. In difference to direct excitation EDXRF spectrometry, polarization X-ray fluorescence uses polarized radiation for excitation. Combined with Cartesian geometry (of excitation, sample and detection system) this results in a significant improvement of the detection limit compared to direct excitation EDXRF.
3.2 Abbreviations:
3.2.1 DBS - actual mass of Di-n-butyl sulfide, g
3.2.2 EDXRF - Energy dispersive X-ray spectrometry
3.2.3 PTFE - Polytetrafluorethylene
3.2.4 SDBS - mass % of sulfur in Di-n-butyl sulfide, typically 21.91%
3.2.5 SStd - mg/kg sulfur in the calibration standard
3.2.6 SStock - mg/kg of sulfur in the stock standard
3.2.7 STK - actual mass of stock standard, g
