Accurate elemental analysis of low silicon, sulfur and chlorine content in petroleum products and automotive fuels

This data sheet describes the analysis of low-level silicon, sulfur and chlorine in petrochemical products and automotive fuels with the Epsilon 4 Oil & Fuels. Click to also learn about the Epsilon 1 Sulfur in Fuels, XRF Sulfur Analyzer

Analysis of silicon, sulfur and chlorine in petroleum products and automotive fuels is crucial to conform to increasingly stringent environmental regulations. Additionally, high concentrations of these elements have detrimental effects on engine performance and often need to be determined at low levels.
X-ray fluorescence spectrometry (XRF) is widely used for the analysis of these elements. Simple sample preparation, high accuracy and precision and good detection limits are the principle reasons for this choice.

This application note describes the analysis of low-level silicon, sulfur and chlorine in petrochemical products and automotive fuels.

Instrumentation and software.

Measurements were performed using an Epsilon 4 EDXRF spectrometer, equipped with a 10W, 50 kV silver anode X-ray tube, 6 filters, helium purge facility, high-resolution silicon drift detector, spinner and a 10-position removable sample changer. Automatic data processing was performed using Epsilon software. Moreover, the proprietary silver anode X-ray tube, prevents line overlaps with chlorine resulting in a lower chlorine detection limit compared to rhodium-anode or palladium-anode based X-ray

tubes (Figure 1).

Sample preparation

A series of commercially available diesel standards from VHG Labs Inc. (U.S.) were used to set up calibrations for Si, S and Cl. Aliquots (7.5 g) of these standards were poured into a liquid cell, assembled with a 2.5 µm Mylar® supporting foil and placed in the sample changer carousel.

Measurement conditions

Two measuring conditions were used for the low-level Si, S, and Cl analysis, resulting in a total measurement time of 10 minutes per sample (Table 1).

Table 1. Measurement conditions

table1.PNG

Figure 1. Spectrum of 100 mg/kg chlorine in diesel fuel, demonstrating the excellent resolution between the chlorine Kα and silver Lα lines (from X-ray tube)

figure1.PNG

Accurate calibrations and detection limits

The calibration graph for chlorine in diesel fuel (Figure 2) illustrates a good correlation between the certified concentrations and the measured intensities.


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Introduction

Analysis of silicon, sulfur and chlorine in petroleum products and automotive fuels is crucial to conform to increasingly stringent environmental regulations. Additionally, high concentrations of these elements have detrimental effects on engine performance and often need to be determined at low levels. X-ray fluorescence spectrometry (XRF) is widely used for the analysis of these elements. Simple sample preparation, high accuracy and precision and good detection limits are the principle reasons for this choice.

This application note describes the analysis of low-level silicon, sulfur and chlorine in petrochemical products and automotive fuels.

Instrumentation and software.

Measurements were performed using an Epsilon 4 EDXRF spectrometer, equipped with a 10W, 50 kV silver anode X-ray tube, 6 filters, helium purge facility, high-resolution silicon drift detector, spinner and a 10-position removable sample changer. Automatic data processing was performed using Epsilon software. Moreover, the proprietary silver anode X-ray tube, prevents line overlaps with chlorine resulting in a lower chlorine detection limit compared to rhodium-anode or palladium-anode based X-ray

tubes (Figure 1).

Sample preparation

A series of commercially available diesel standards from VHG Labs Inc. (U.S.) were used to set up calibrations for Si, S and Cl. Aliquots (7.5 g) of these standards were poured into a liquid cell, assembled with a 2.5 µm Mylar® supporting foil and placed in the sample changer carousel.

Measurement conditions

Two measuring conditions were used for the low-level Si, S, and Cl analysis, resulting in a total measurement time of 10 minutes per sample (Table 1).

Table 1. Measurement conditions

table1.PNG

Figure 1. Spectrum of 100 mg/kg chlorine in diesel fuel, demonstrating the excellent resolution between the chlorine Kα and silver Lα lines (from X-ray tube)

figure1.PNG

Accurate calibrations and detection limits

The calibration graph for chlorine in diesel fuel (Figure 2) illustrates a good correlation between the certified concentrations and the measured intensities.


Figure 2. Calibration graph of chlorine in diesel. Each standard was measured in duplicate.


figure2.PNG


The high sensitivity of Epsilon 4 is excellent for the quantification of low-level silicon, sulfur and chlorine in petrochemicals and automotive fuels. This is illustrated by the RMS values of the calibrations and the lower limits of detection (LLD), for the three elements in diesel fuel, (Table 2).


Table 2. Calibration results and detection limits


table2.PNG

Method repeatability

Method repeatability is another important aspect of analysis and is an inherent characteristic of Epsilon 4. To test the repeatability of the method, a sample containing the three elements was measured 20 times. Fresh aliquots of this sample were used and new cups were prepared to measure each of the 20 replicates. The average concentration and RMS values (1 sigma) are shown in Table 3. The method was validated by comparing the  average  concentration with the certified concentration.


Table 3. Results of the repeatability test


table3.PNG

Conclusions

The results clearly demonstrate that the Epsilon 4 EDXRF spectrometer is capable of analyzing low silicon, sulfur and chlorine content in petrochemicals and automotive fuels, in line with stringent international test methods. The combination of a proprietary silver anode X-ray tube and excellent detector resolution, high sensitivity and powerful software contribute to the accuracy and repeatability of the results.

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