SULFUR DETERMINATION BY ENERGY DISPERSIVE X-RAY FLUORESCENCE (ED-XRF): D4294
(Equivalent Test Methods: IP 336, ISO 8754, and AFNOR M07-053)
This test method is applicable to all the petroleum products mentioned in Test Method D2622 (see previously). The applicable concentration range of sulfur is 0.015 to 5.0 mass %. There can be interferences from spectral lines and matrix matching. Generally, spectral interference will arise from elements at concentrations greater than one-tenth of the sulfur concentration (for example, water, lead, alkyls, silicon, potassium, calcium, phosphorous, and halides). Matrix interferences arise from different C/H ratio or oxygen present in the standard and samples. Both types of interferences are compensated for in the modern instruments with the use of built-in software. High oxygen-containing fuels M-85 and M-100 should be analyzed using calibration standards that match the sample matrix. Suspended water if any in the sample must be removed or thoroughly homogenized and immediately analyzed. Compared to other test methods for sulfur determination, this method has high throughput (2 to 4 min per sample), minimal sample preparation, good precision, and is capable of determining sulfur over a wide concentration range. The equipment specified in most cases is less costly than that required for alternative methods.
TEST SUMMARY
The sample is placed in a beam emitted from an X-ray source. The resultant excited characteristic X radiation is measured, and the accumulated count is compared with counts from a previously prepared calibration standard to obtain the sulfur concentration. Two groups of calibration standards are required to span the concentration range, one from 0.015 to 0.1 %, and the other from 0.1 to 5.0 %.
TEST PRECISION
Repeatability: 0.02894 (X + 0.1691)
Reproducibility: 0.1215 (X + 0.05555)
Where X is the average of two results.
There is no bias.
