ULSD (Ultra-Low Sulfur Diesel) Sulfur Content Analysis

As per standard test method ISO 13032, the analysis of sulfur in ultra-low sulfur diesel is demonstrated. Regulations worldwide have restricted the sulfur amount in a number of fuels oils with specific attention to diesel fuel. For several years road diesel has been restricted to a maximum sulfur concentration between 10-15 ppm, based on the global region.

Now, these restrictions are expanded to all diesel fuel including use in off-road diesel engines and large engines. Ultra-low sulfur highway diesel fuel (15 ppm sulfur maximum) has been used in all model year 2007 and later highway diesel vehicles and engines. It is recommended to be used in all diesel vehicles and engines. Based on the standard test method ISO 13032, the analysis of sulfur in ultra-low sulfur diesel is used.


Model: Rigaku NEX QC+
X-ray tube: 4 W Ag-anode SDD
Sample type: Diesel fuel
Film: Prolene
Analysis Time: 300 sec
Environment: Helium
Sample Ring: Single position 32mm

Figure 1.

International Standard Test Method

The Rigaku NEX QC+ is compliant with ISO 13032 for the measurement of ultra-low sulfur between 8 - 50 mg/kg in diesel fuels and gasoline as described in the ISO 13032 method Scope.

Sample Preparation

For sample measurement, shake the sample bottle gently, allow bubbles to settle, and fill a 32mm XRF sample cup with 5g of the sample.


Empirical calibration was done using a suite of 6 certified diesel calibration standards as shown in Table 1

Table 1.

Element: S
Units: ppm
RMS Deviation: 0.76
Correlation: 0.99170
Sample I.D. Standard Value Calculated Value
STD 1 5.0 5.2
STD 2 10.0 10.1
STD 3 15.0 14.0
STD 4 20.0 20.9
STD 5 25.0 24.9
STD 6 50.0 49.4

Figure 2.


Instrument repeatability (precision) is determined by ten repeat analyses of a sample in static position using a 300 sec analysis time.

Table 2.

Element: S       Units: ppm
Sample Standard Value Average Value Std Dev % Relative
STD 2 10.0 10.2 0.48 4.8
STD 6 50.0 50.9 0.50 1.0

Detection Limit

Ten repeat analyses of a blank diesel sample without sulfur are taken with the sample being static and the standard deviation is determined. The lower limit of detection (LLD) is then defined as three times the standard deviation. The following typical LLDs are reported here using an analysis time of 300 s.

Table 3.

Element LLD Analysis Time
S 1.3 ppm 300 sec
S 1.9 ppm 600 sec

Note: 1 ppm = 1 mg/kg


The results shown here indicate that the Rigaku NEX QC+ EDXRF analyzer offers excellent performance for the measurement of ULSD as per standard test method ISO 13032. The versatility of the NEX QC+ also makes it a suitable tool for measuring many other elements and oil matrices as well, such as lube oils, wear metals in oils, used oil and waste oil, and other elemental analysis needs throughout the petroleum industry.

This information has been sourced, reviewed and adapted from materials provided by Rigaku.

For more information on this source, please visit Rigaku.


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