The permitted sulfur limit in fuel oils has been decreased to 10 ppm in many regions. This application note demonstrates that
the performance of the Rigaku Micro-Z ULS meets the requirement of ASTM D2622-10, in the analysis of ultra-low sulfur in automotive
Recent developments in ultra-low sulfur (ULS) fuel have improved fuel efficiency and created cleaner exhaust gas. Globally,
the permitted sulfur limit in fuel oils has been decreased to 10 ppm in many countries and regions.
For compliance verification, X-ray fluorescence (XRF) spectrometry is the definitive analysis tool for use at distribution
terminals and refineries, as well as mobile or stationary testing laboratories. In recent years, there has been an increasing
need for an instrument which does not require the use of helium gas, for instances when acquisition or delivery of helium
to the analysis site is difficult.
The Micro-Z ULS (ultra-low sulfur) is a newly developed sulfur analyzer which does not require helium gas in operation. This
application note demonstrates that Micro-Z ULS can meet the requirements of ASTM D2622-10.
The Micro-Z ULS is a benchtop wavelength dispersive X-ray fluorescence (WDXRF) spectrometer with fixed optics optimized for
sulfur analysis. The atmosphere in the optics path of the Micro-Z ULS is a vacuum, so that helium gas is not required. The
spectrometer is designed to minimize the restrictions in installation such as the need for cooling water, a special power
supply, and installation space. The Micro-Z ULS is equipped with an air-cooled 40 W Cr-target X-ray tube and a doubly curved
RX-9 analyzing crystal optimized for low concentration sulfur.
The Micro-Z ULS has a built-in operation panel, which enables simple and easy operation for daily analysis. The counting time
was 300 s for peak and background measurements in this experiment.
Approximately, 4 mL of each sample was poured into a liquid cell with sample film of 2.5 Ám Mylar« film (Chemplex« 100).
Standard and Calibration
"Number 2 diesel fuel" standards and isooctane-based standards provided by VHG Labs, Inc. were used for calibrations of diesel
fuel and gasoline respectively.
Figure 1: Calibration curve for each material of Micro-Z ULS; (a) diesel fuel, (b) isooctane (for gasoline).
Repeatability tests were carried out using a representative sample for each material. For each sample, two aliquots were prepared
and analyzed using the calibration Figure 1; this process was repeated 20 times. The term "r" represents "repeatability" defined
by the following formula in ASTM D2622-10 (1):
The difference between successive test results obtained by the same operator with the same apparatus under constant operation
conditions on identical test material would exceed the values calculated by equation 1 only in one case in every 20.
The test results, where the maximum value for each fuel is smaller than r, prove that the performance of the Micro-Z ULS meets
the requirement of ASTM D2622-10 for diesel fuel and gasoline.
Low concentration sulfur in petroleum-based fuel can be routinely analyzed with high accuracy and precision on the Micro-Z
ULS, a benchtop WDXRF spectrometer with fixed optics, which does not require He gas, external water for cooling the X-ray
tube, or special power supply. This application note demonstrates that the performance of the Micro-Z ULS meets the requirement
of ASTM D2622-10, which has become strict in the recent versions of ASTM D2622.
(1) ASTM D2622-10(2010), "Standard Test Method for Sulfur in Petroleum Products by Wavelength Dispersive X-ray Fluorescence
Spectrometry," ASTM International, p. 12.
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