Knowledge Center

Sulfur in Jet Fuel by ASTM D4294

XOS Team — Thu, 18 Jun 2026 22:51:03 GMT

Background

The International Air Transport Association (IATA) reports that in 2017 alone, more than 4 billion passengers traveled by air. It is estimated that air transport will reach global growth of over 7 billion passengers by 2035. Standard jet fuel specifications are used to ensure that wherever a plane is fueled, it can continue to operate safely. Common jet fuel specifications are shown in Table 1. Jet fuel specifications require total sulfur content to be less than 0.30 wt%. In order to comply, refinery and independent laboratories rely on standard test methods such as ASTM D4294 and ISO 8754. These labs operate in fast-paced environments that require rapid, precise results and are increasingly relying on solutions that provide simple and direct integration with Laboratory Information Management Systems (LIMS).

In this study, certified standards were analyzed to demonstrate the expected performance of Petra utilizing ASTM D4294 methodology for jet fuel.

Sulfur in mineral oil standards were used to calibrate following ASTM D4294 and ISO 8754 methods using a single curve from 10 ppm to 6.0 wt%
A certified standard in a matrix similar to jet fuel with a concentration of 0.1 wt% was obtained
Samples were prepared by transferring 7 mL to a 43 mm XRF sample cup and sealed with Mylar film
Separate aliquots were prepared and analyzed for 100 seconds each
Individual measurement results and average are reported in Table 2

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Rapid sulfur measurement plus 12 other critical elements
Petra MAX delivers advanced elemental analysis powered by EDXRF, utilizing XOS patented doubly curved crystal optics coupled with a high-performance silicon drift detector and an intense monochromatic excitation beam. This industry leading technology reduces background noise and increases signal-to-noise output, enabling low detection limits and high precision. Petra MAX offers low-level detection of iron, saving the marine industry money on engine replacement and lube oil costs, while also using a next-generation interface that saves users' time.

Conclusion

Sulfur analysis using ASTM D4294 and ISO 8754 continues to be an important measurement for refinery and independent laboratories certifying jet fuel around the world. The growing demand for air travel will continue to drive the need for a rapid and precise analysis solution. That solution is Petra — delivering accurate measurement for jet fuel and other hydrocarbons without the need for complex sample preparation or consumable gasses.

How the Gulf War is Making Refineries Change Their Crude Feedstocks

nick.nugent@xos.com (Nick Nugent) — Thu, 18 Jun 2026 18:06:00 GMT

Background

The war in the Gulf has triggered one of the biggest disruptions to global crude supply in decades. The effective closure of the Strait of Hormuz, which accounts for approximately 20% of the world’s daily crude traffic, has severely reduced exports of Middle Eastern crude. Refineries worldwide are scrambling to secure feedstock, and refinery capacities are being reduced until the disruption ends.

Most refineries are configured around specific crude qualities, and inventories typically cover only a few weeks of operations. As regular Gulf supplies fail to arrive, many refiners are drawing down stocks, reducing throughput, or switching to alternative grades sourced from the Atlantic Basin, Southeast Asia, or the United States. These substitute crudes often differ significantly in sulfur content, metals, acidity, and density — parameters that directly affect unit corrosion risk, catalyst performance, and product quality.

The War's Impact

As a result, crude switching has become an operational and analytical challenge. Refiners need faster, more reliable insight into the composition of incoming feedstock to manage blending decisions, protect assets, and maintain stable operations. In this environment, real‑time elemental analysis has become increasingly important. Online crude oil analyzers allow refiners to continuously monitor chlorine as new feeds are introduced, reducing uncertainty when running variable crude feedstocks.

XOS’s Clora Online instrument in C1D2 and ATEX configurations can determine continuous analysis of total chlorine from 0.2 ppmw up to 3000 ppmw. The instrument can also be configured for aqueous streams such as process water coming from the desalter, which can determine the performance and check whether the dosing chemicals are sufficient for the amount of Cl in the crude.

The International Energy Agency warns that as long as Gulf disruptions persist, refinery operations outside the region will be constrained by feedstock availability. In that environment, the ability to rapidly qualify and manage alternative crudes is becoming not just a competitive advantage, but a prerequisite for keeping refineries running safely and efficiently.

Product Highlight: Clora Online

Continuous, Real-Time Chlorine Analysis for Corrosion Control
Clora Online delivers reliable, continuous chlorine analysis using MWDXRF technology in compliance with ASTM D7536. By monitoring desalted crude in real time, your plant can prevent corrosive hydrochloric acid formation, protect critical equipment, and optimize performance, reducing downtime and safeguarding refinery assets.

Precision Comparison Between EDXRF and ICP for Ni, Fe, and V

XOS Team — Wed, 17 Jun 2026 19:24:45 GMT

Background

As petroleum professionals continue to refine their production processes, products such as crude oil can contain higher concentrations of problematic metals like nickel (Ni), iron (Fe), and vanadium (V). In the face of tightening regulations and increased demand for sweeter crudes, refiners are looking to buy lower cost oils that contain the metals mentioned above, with the intent of assessing their concentration levels throughout the refining process.

The reason these metals need to be continually monitored is due to their problematic effects on refining processes. For example, nickel and iron rapidly deactivate process catalysts used in hydrotreaters and FCC units which leads to off-specification coke and increased, unplanned costs to refiners. In addition to this, regulations for sweet crude will tighten in January 2019 to lower the allowable limit to 8ppm and 15ppm for nickel and vanadium, respectively. To compound the challenge of attaining a sweet crude and mitigating risk of damages from metals, refineries and other petroleum certification sites, such as terminals and third party labs, must adhere to regulations that require them to utilize D5708B methodology, which specifies ICP analysis. There is, however, an option for users to screen samples before ICP using XRF analysis.As mentioned, there are two well-known methods for elemental analysis: X-ray fluorescence (XRF), and inductively coupled plasma (ICP). In ICP measurements in compliance with method D5708B, also known as Inductively Coupled Plasma Optical Emission Spectroscopy (ICP – OES), samples must be digested with sulfuric acid, constantly stirred under gentle heat, then burned off in a muffle furnace to remove the carbon. After this, the sample must be reconstituted with nitric acid before finally being analyzed. ICP analysis is a highly precise form of elemental quantification, however, it involves exhaustive sample preparation and lengthy wait times for results – usually between 6 to 12 hours.

XRF analysis involves exposing the sample to X-rays to produce an emission at an energy level that is characteristic of the element of interest. This method involves minimal sample preparation and provides results in minutes. Energy DIspersive X-ray Fluorescence (EDXRF) is an improved version of the XRF technique. EDXRF applies state-of-the-art monochromating and focusing optics enabling a dramatically higher signal-to-background ratio. This technique also reduces background noise delivering lower limits of detection and significantly better precision.

Challenge

While professionals in the petroleum industry must adhere to the D5708B method, those looking to save downtime during the process may consider EDXRF as a cost-effective, in-house alternative. While some may utilize an in-house ICP setup, many professionals, such as those working at pipelines, have to send samples out. This is yet another necessary burden these professionals must deal with as the costs and downtime will ramp up significantly when products come back from ICP analysis out of spec. By testing in-house and getting results in less than five minutes, refineries, terminals, and labs will be able to make real-time decisions when products are off-spec and can improve their overall processes when products are within spec.

Solution

Those tethered to ICP can still utilize EDXRF for screening purposes. By utilizing Petra MAX in-house, powered by EDXRF, users can pre-screen their samples before sending them out for ICP testing. Likewise, even those with access to an in-house ICP process can save hours by first screening the samples with Petra MAX, then running off-spec or near off-spec with ICP. In this paper we will review and discuss data that covers elemental analysis across ICP and EDXRF methods with an emphasis on comparing the precision performance between the two.

Testing Precision

ASTM runs a Proficiency Testing Program (PTP) where they send out samples of crude oil several times per year to be tested at independent labs and refineries around the world. The results are then published which includes statistics on many test results, such as the average concentration values for Ni, V and Fe by ICP - see Table 1. XOS obtained sample retains from eight different PTPs and tested these samples on different Petra MAX analyzers.

Each crude oil sample was homogenized and then pipetted into a sample cup. The cup was sealed with a sample film and then vented before analysis with Petra MAX. Analysis time for each sample was five minutes, and the results were averaged; see Table 1.

Conclusion

EDXRF delivers comparable results to ICP in five minutes or less. In addition, users have minimal sample preparation and can achieve results with the push of a button. Those looking to save time and money in elemental quantification by screening samples before ICP analysis can achieve comparable results with Petra MAX.

Product Highlight: Petra MAX

A Unique Sample Introduction System to Eliminate Centrifuge

Particulate solids and water have shown to cause underreported sulfur measurements by as much as 40%. Such a significant error can cause misclassification of sour crude oil as sweet crude oil. With global regulatory trends lowering sulfur levels in refined products from diesel to marine fuel, underreporting sulfur may cause refiners to miscalculate the costs associated with processing incoming crude oil. Many D4294 analyzers are designed with the X-ray detector focused on the bottom of a sample cup where settling occurs, as depicted in Diagram 1. Since particulate solids and water settle over time, it is difficult to obtain accurate sulfur measurements due to the changing concentration of interferences. Because traditional D4294 XRF instruments take their measurement from the bottom of the sample, settling occurs at the focal point of the analysis rendering the analyzer’s automatic interference correction, ineffective. To prevent biased results, many laboratories centrifuge all crude oil samples prior to analysis by traditional D4294 instruments. This increases the amount of processing and time it takes to perform the measurement. To combat the effects of settling in crude oil, Petra MAX delivers a new, innovative sample chamber that rotates the sample on its side, providing a clear measurement window for more accurate results. See Diagram 2.

New Gen 4 Software Offers an Advanced Workflow

The new Gen 4 software upgrade for Petra Series offers novel features for a simple, intuitive operation including preset measurement configurations, streamlined custom calibration set-up, enhanced LIMS compatibility, and additional matrices like water and catalysts.

To match the expanding measurement capabilities of Petra Autosampler, users will now be able to set unique preset measurements with adjustable parameters for quick access to pre-determined measurement types. For example, a terminal frequently running crude oil samples can set a crude oil preset which includes a 300s measurement time, a preselected matrix type and calibration curve, and a default number of sample repeats - see Figure 1. Additionally, this preset can be set as the default measurement. The presets can be set directly after users scan their QR-coded cup or sample bottle with a single push of a button before loading the sample into the analyzer. All this information can be found on the main scan screen to reinforce the high throughput and efficient workflow that Petra offers.

Once a sample begins its measurement, live results will begin to populate for the elements of interest. Users can continue to load samples, work with a different instrument, or view their historical results. When a sample is not being measured, completed measurements can be averaged on-screen using the built-in averaging function. When running repeats, results will be automatically averaged and viewable as a separate file without the need to export data. Those looking to export their data can do so either through their network, USB drive, or as a printable CSV or PDF.

Precision Comparison Case Study — Petra MAX (EDXRF®) vs ICP (IP 501 & IP 621)

XOS Team — Tue, 16 Jun 2026 18:54:41 GMT

Background

As petroleum professionals continue to refine their production processes, products such as crude oil, residual fuel oils, and VGO can contain higher concentrations of problematic metals like nickel (Ni), iron (Fe), and vanadium (V). In the face of tightening regulations and increased demand for sweeter crudes, refiners are looking to buy lower-cost oils that contain these metals, with the intent of assessing their concentration levels throughout the refining process.The reason these metals need to be continually monitored is due to their problematic effects on refining processes. For example, nickel and iron rapidly deactivate process catalysts used in hydrotreaters and FCC units, which leads to offspecification coke and increased, unplanned costs to refiners. To compound the challenge of attaining a sweet crude and mitigating the risk of damage from metals, refineries, and other petroleum certification sites, such as terminals and thirdparty labs, must adhere to regulations that might require them to utilize IP 501 and IP 621 methodology. There is, however, an option for users to screen samples before ICP using XRF (X-ray fluorescence) analysis or to supplement their wet chemistry procedures with the use of XRF to further improve their processes.

As mentioned, there are two well-known technologies for elemental analysis: X-ray fluorescence (XRF in various methods and forms such as energy-dispersive XRF (EDXRF) or wavelength-dispersive XRF (WDXRF)) and wet chemistry (ICP and AAS), which includes methods such as IP 501 and IP 621. With IP 501 and IP 621, samples must first go through a time-consuming and sensitive sample preparation process which involves breaking down the sample, mixing it with other materials, digesting it in acid, and then diluting it in water. Only after this lengthy and complicated process is the sample then measured with either ICP OES (IP 501) or ICP-OES/AAS (IP 621). Both methods are considered highly precise, however, not only do they typically take 4-10 hours to complete, but due to the multiple complex steps, they require specially trained operators. In addition, the multiple steps may increase the likelihood for variability within the process and negatively impact precision.

Better Precision with EDXRF®

XRF analysis involves exposing the sample to X-rays in order to produce an emission at an energy level that is characteristic of the element of interest. This method involves minimal sample preparation and provides results within minutes. EDXRF is one of the more well-known forms of XRF technology. High-Definition X-ray Fluorescence (EDXRF®), XOS’ patented technology, is an improved version of the EDXRF technique that applies state-of-the-art monochromating optics, enabling a dramatically higher signal-to-background ratio. This technique also reduces background noise, delivering lower limits of detection and significantly better precision at even lower concentration levels.

Challenge

While professionals in the petroleum industry might be more familiar with IP 501 and IP 621 or feel they need to adhere to these methods in particular, those looking to reduce downtime during the process may consider a cost-effective, faster, in-house alternative. Some labs may have the luxury 2 of running these wet chemistry methods inhouse, but many professionals, such as those working at terminals, pipelines, and smaller labs, may have to send samples out for testing. This not only results in higher costs, but more importantly, significant turnaround time for the data—which can occasionally result in increased downtime when products come back from IP 501/621 analysis as being out of spec. By testing in-house and getting results in less than five minutes, refineries, terminals, and labs will be able to make real-time decisions based on the faster availability of that data.

Solution

Petra MAX, powered by EDXRF®, can be used as a cost-effective screening tool, enabling users to pre-screen their samples before sending them out for wet chemistry testing and make critical decisions faster. Likewise, even those with access to in-house ICP/ AAS processes can save hours of sample preparation time by first screening the samples with Petra MAX, then running off-spec or near off-spec with wet chemistry.

Case Study

Recently, a large European refinery was interested in testing the performance of Petra MAX as a potential addition to their in-house testing process, as they saw great value in obtaining Ni, V, and Fe results in under 5 minutes. This refinery performed an elemental analysis study comparing the precision performance between Petra MAX (EDXRF®) and ICP (IP 501 and IP 621) with VGO and fuel oils. In this paper, we will review the study performed and discuss the data provided by the refinery.

Testing Precision

The refinery prepared and measured 10 different VGO samples both on Petra MAX and with IP 621 for Ni, V, and Fe. A second set of 10 fuel oil samples were also run on Petra MAX as well as with IP 501 for Ni and V, in addition to a single sample for Fe. The samples run on Petra MAX were measured for a 5-minute measurement time, with sample preparation limited to pouring 7-8 ml into a sample cup and applying the sample film.

Product Highlight: Petra MAX

Comparing Precision Between EDXRF and ICP Data from ASTM PTP Study

In another whitepaper, we compared the precision of EDXRF® to ASTM D5708B, a common Inductively Coupled Plasma (ICP) method for the determination of nickel, vanadium, and iron in crude and residual fuel oils. The ICP data was obtained from an ASTM Proficiency Testing Program (PTP). This data demonstrated that EDXRF® (Petra MAX) delivers comparable results to ICP but can be obtained much faster – in five minutes or less. Read the full paper here.

Did you know?

In addition to providing easy, highly precise and accurate results for Ni, V, and Fe, as well as nine other elements, Petra MAX complies with ISO 8754 and ASTM D4294 for sulfur all in one measurement—an even greater time savings for petroleum labs.

Results

As shown in Tables 1, 2 and 3 for VGO, and Tables 4, 5, and 6 for fuel oil, the results of Petra MAX compare quite favorably to that of the ICP methods (IP 501 and IP 621) between the two different sample types and across multiple element concentrations and measurements. The differences between the Petra MAX results and the IP 501 and IP 621 results are all well within reproducibility for those methods and in almost all cases, even with repeatability, are great indicators of comparable accuracy. Given its minimal sample preparation, rapid 5-minute results and ease of use, Petra MAX is a valuable tool for industry professionals to determine Ni, V, and Fe concentrations in VGO and fuel oils.

Conclusion

Petra MAX, powered by EDXRF, delivers comparable results to IP 501 and IP 621 in five minutes or less. In addition, users have minimal sample preparation and can achieve results with the push of a button. Those looking to save time and money in elemental quantification by screening samples before ICP analysis can achieve comparable results with Petra MAX.

This study resulted in the refinery purchasing Petra MAX—a decision that has since saved them significant sample preparation and testing time while simultaneously reducing turnaround time for metal and sulfur analyses. Speak with one of our experts today to see how XOS analyzers can save your business time and money.

ASTM Crude Oil Proficiency Testing Program: ICP (D5708B) vs. XRF (D8252) for Ni and V

XOS Team — Tue, 16 Jun 2026 17:20:20 GMT

Background

Crude oil can naturally contain metals like nickel (Ni) and vanadium (V). These metals need to be monitored due to their negative effects on refining processes. For example, nickel rapidly deactivates process catalysts used in hydrotreaters and FCC units which leads to off-specification coke and increased, unplanned costs to refiners.

In the face of tightening regulations and increased demand for sweeter crudes, refiners are looking to buy lower cost oils that contain minimal amounts of the metals mentioned above, with the intent of assessing their concentration levels throughout the refining process.

In addition to this, NYMEX regulations for sweet crude were made more stringent January 2019 to lower the acceptable limits to 8ppm and 15ppm max, for nickel and vanadium respectively. Currently NYMEX specifies that refineries and other petroleum certification sites, such as terminals and third-party labs, must utilize method ASTM D5708B¹ to determine these two elemental concentrations.

ASTM D5708B

ASTM D5708B is an older (1995) and widely used method that uses Inductively Coupled Plasma Optical Emission Spectroscopy (ICP – OES) test method (IP 501/IP 621 European equivalent). Samples must be digested with sulfuric acid, constantly stirred under gentle heat, then burned off in a muffle furnace to remove the carbon. After this, the sample must be reconstituted with nitric acid before finally being analyzed.

ICP analysis is widely accepted and sensitive form of elemental quantification; however, it involves exhaustive sample preparation and lengthy wait times for results—usually between 6 to 12 hours. Although ICP is currently the specified method, there is an alternative method that many are using for screening that covers these two elements, has a greater range, measures faster, and is typically more precise than the ICP method D5708B.

ASTM D8252

ASTM D8252² is an X-ray Fluorescence (XRF) method that is gaining traction in the crude oil industry. This method involves exposing the sample to X-rays to produce an emission at an energy level that is characteristic of the element(s) of interest and covers both Energy Dispersive XRF (EDXRF) and Wavelength Dispersive XRF (WDXRF). The main advantage to this method is how quickly results are given and how simple it is to prepare a sample (see product spotlight on Petra MAX, XOS’ D8252 compliant EDXRF analyzer).

Despite not being the specified method, several locations are adopting D8252 to screen samples. This is incredibly useful for several reasons, the first being that to perform D5708B it is required to know the rough concentration of the metals in your sample and D8252 removes this guess work. Another reason screening is useful is due to the fluid nature of the business; it pays to know that there is an issue as soon as it is happening, not 8 hours after the fact. With D8252, a sample can be flagged before ICP analysis, potentially saving thousands of dollars and preventing countless headaches. So, the question remains, how do these two methods compare to one another?

A Crude Analysis

ASTM runs a crude oil Proficiency Testing Program (CO PTP) in which they send out samples of crude oil three times a year to be tested at independent labs and refineries around the world.³ The program then publishes statistics from the test results, including data on Ni and V by D8252 and D5708B. Since D8252 is a relatively new method, published in 2019, it has only been included in the CO PTP since 2021.

Since its inauguration, there have been 6 rounds of testing completed, and participation has nearly doubled from 6 to 11 labs (as compared to an average of 40 ICP labs). Before diving into that data, let’s look at the method scopes in more detail.

Table 1 shows the concentration ranges of the method scopes for both D5708 and D8252. Note the D5708 concentration ranges for vanadium and nickel compared to the maximum allowed concentration stated by the NYMEX specification. The NYMEX max specification (8 & 15PPM) is below the scope of D5708 for both nickel (10-100PPM) and vanadium (50-500PPM).

The D8252 range goes considerably lower than the NYMEX specs, with the lower range of 2.2 PPM and 1.9 PPM for nickel and vanadium respectively, as seen in Table 1. This begs the question; how can I certify that my crude is light sweet if the maximum acceptable value for nickel and vanadium are outside the scope of the required method?

Figure 1 - D8252 vs D5708B Nickel (PPM) CO PTP

Figure 2 - D8252 vs D5708B Vanadium (PPM) CO PTP

Crude Oil PTP Data Comparison

See Figures 1 & 2 for a comparison of average concentration and data reproducibility for the two methods. The two graphed lines on Figures 1 & 2 represent the average elemental concentration from each program cycle using D5708B or D8252. Note that D5708B (blue lines) biases low when compared to D8252 (orange lines). The primary reason for this is that D8252 will always provide results that are the TOTAL concentration of Ni/V, Whereas ICP, due to complex, multi-step sample preparation, can often provide a lower result due to incomplete sample digestion. There is a significant difference in sample preparation and measurement of the two methods. D8252 requires minimal sample prep, it’s as simple as filling a cup, applying the film, and measuring, the physical state of the sample never changes. In contrast, D5708B requires near complete consumption of the sample: decomposition with acid, drying, ashing, then digested and reconstituted with acid. Every time the sample must be handled during a measurement process, the chances for human error and incomplete recovery increase. For these reasons, ICP results tend to bias lower.

When we change our focus to reproducibility, the difference between the two methods is seen in the bar graphs in Figures 1 & 2. Reproducibility is the difference between measuring the same sample at two laboratories, using different instruments and operators. In essence, the larger the reproducibility value, the larger the variance between two laboratories measuring the same sample. D8252 consistently has better reproducibility or precision than D5708B, especially for nickel. D8252 has less variation from one lab to another due to there being much less sample preparation and handling. The more steps there are in a process, the greater variability there will be from one measurement to another.

Product Highlight: Petra MAX

Conclusion

Changes in crude specifications have resulted in an increased importance of monitoring nickel and vanadium. D8252, a much newer method, can consistently perform at lower concentrations to test light sweet crudes, instead of D5708B, which has a method precision statement that is nearly 30 years old and is used at concentrations outside of the published ranges. Even though D5708B may be considered the industry standard, new ASTM methods have grown in popularity.

The ASTM CO PTP program demonstrates that D8252 shows good correlation with ICP for nickel and vanadium in crude oil, with better precision, as well as the trend that more and more labs are using D8252 either by itself or in tandem with D5708 method B.

1 “Standard Test Methods for Determination of Nickel, Vanadium, and Iron in Crude Oils and Residual Fuels by Inductively Coupled Plasma (ICP) Atomic Emission Spectrometry.” ASTM International - Standards Worldwide, ASTM.org, 8 July 2020, https://www.astm.org/d5708-15r20e01.html.

2 “Standard Test Method for Vanadium and Nickel in Crude and Residual Oil by X-Ray Spectrometry.” ASTM International - Standards Worldwide, ASTM.org, 1 Oct. 2019, https://www.astm.org/d8252-19e01.html.

3 “Crude Oil Proficiency Testing Program.” ASTM International - Standards Worldwide, ASTM.org, https://www.astm.org/ptpco2023.html

4 “Chapter 200 Light Sweet Crude Oil Futures - CME Group.” NYMEX Rule Book, https://www.cmegroup.com/content/dam/cmegroup/rulebook/NYMEX/2/200.pd

Precision Comparison Between ASTM Test Methods D7039, D2622, and D5453

XOS Team — Tue, 09 Jun 2026 22:48:38 GMT

Background

For many years, professionals in the petroleum industry have faced challenges regarding compliance and quality of product. These challenges are made more difficult by the variety of regulations and specifications, and the implications they present for their refining process. Regulators across the globe are moving to even more restrictive regulations on sulfur content in a variety of fuels with many countries now requiring maximum sulfur concentration in automotive fuels of 10 to 15 parts per million (ppm).

These regulations have furthered the need for refineries to maximize the precision of their sulfur analysis methodology. Desulfurization processes are expensive utilizing catalyst, hydrogen, and heat. By using a more precise sulfur measurement technique, refiners can produce product closer to the specification maximums, reducing giveaway and saving money. This savings is illustrated in Figure 1. In addition to production efficiencies, refiners can avoid inaccurate reporting which can lead to regulatory missteps and contract disputes by using a test method with better precision.

With several different methodology options for sulfur analysis available, refineries, terminals, and test inspection certification companies must take care to select a method that produces the least amount of variability in their measurements.

Figure 1: Savings From Improved Measurement Precision

ASTM conducts Proficiency Testing Programs (PTP) several times per year. In each PTP study, ASTM sends samples of hydrocarbon products or feedstocks to various participant sites. Each participating laboratory performs analyses following ASTM methods for various test parameters, including sulfur, using the samples provided. This paper will discuss the ASTM PTP sulfur results for Reformulated Gasoline (RFG) and Ultra Low Sulfur Diesel (ULSD) programs from 2023-2025 using the most common test methods for low sulfur automotive fuels: D7039, D2622, and D5453. First, an understanding of the test methods is critical to interpreting the data presented.

ASTM Method D7039 (Monochromatic Wavelength Dispersive X-Ray Fluorescence)

Monochromatic Wavelength Dispersive X-ray Fluorescence (MWDXRF) is a subset of WDXRF that utilizes similar principles. Rather than using filters or traditional crystals that are flat or singly curved, MWDXRF incorporates doubly curved crystal (DCC) optics to provide a focused, monochromatic excitation X-ray beam to excite the sample. A second DCC optic is used to collect the sulfur signal and focus it onto the detector. This modified methodology delivers a signal-to-background ratio that is 10-times more precise than traditional WDXRF, which improves method precision and Limit of Detection (LOD).

MWDXRF Diagram

ASTM Method D2622 (Wavelength Dispersive X-ray Fluorescence)

Wavelength Dispersive X-ray Fluorescence (WDXRF) is a type of X-ray Fluorescence, or XRF, which uses high-intensity X-rays to excite elements of interest within a sample. Upon exposure, fluorescent X-rays are emitted from the sample at energy levels that are unique to each element. Additionally, the background signal, an energy region not characteristic of sulfur or other interfering elements, is collected and subtracted from the sulfur signal to improve precision and LOD. To isolate the sulfur signal and to reduce noise, WDXRF utilizes a filter and a collection crystal before the sulfur signal reaches the detector. WDXRF also differs from MWDXRF in that it doesn’t specify excitation type (i.e. monochromatic OR polychromatic excitation), whereas MWDXRF specifies monochromatic excitation.

ASTM Method D5453 (Ultraviolet Fluorescence)

In Ultraviolet Fluorescence (UVF) technology, a hydrocarbon sample is either directly injected into a high temperature (1000°C) combustion furnace or placed in a sample boat that is cooled and then injected into the combustion furnace. The sample is combusted in the tube, and sulfur is oxidized to sulfur dioxide (SO₂) in the oxygen-rich atmosphere. Water produced during the sample combustion is removed by a membrane dryer and the sample combustion gasses are exposed to ultraviolet (UV) light. SO₂ is excited (SO₂*), and the resulting fluorescence that is emitted from the SO₂* as it returns to the stable state is detected by a photomultiplier tube. The resulting signal is a measure of the sulfur contained in the sample.

Precision and ILS Results

Hundreds of participants are involved in the monthly ULSD PTP program, which exclusively looks at sulfur. The monthly RFG PTP boasts over a hundred participants running a variety of test methods for differing RFG parameters. The data shown represents sulfur data collected throughout the study from January 2023 to May 2025.

Understanding the Data (Mean Concentration and Reproducibility)

Both graphs and tables shown below track average sample concentration and reproducibility (R). Reproducibility is the difference between two single and independent results obtained by different operators applying the same test method in different laboratories using different apparatus on identical test material. A lower reproducibility value correlates to a better level of precision which can minimize risks from inaccurate reporting such as regulatory fines and contract disputes.

The data presented is filtered to show all samples whose average concentration ranged between 5 and 15 ppm. These values were chosen based on the most common regulatory requirements for sulfur content in automotive fuel in Europe, United States, China, and others around the world. It is critical for an analyzer to have low reproducibility values (better precision) when measuring these types of samples. When interpreting the data, keep in mind:

Graphs 1 & 2

Both graphs are sorted by decreasing sample mean.
Each column cluster in the graphs represents reproducibility for one sample measured by multiple laboratories each using D7039, D2622, or D5453.
Within each column cluster, each color-coded bar corresponds to reproducibility for one test method. D7039 is in orange, D2622 is in gray, and D5453 is in blue.
The numerical value of each method/bar is graphed on the left axis. (remember - lower R values are indicative of better precision).
For many test methods, precision is often dependent on concentration. For context, the monthly average sulfur concentration is graphed as a red dot and its value is shown on the right axis of the graphs.

Tables 1 & 2

Both tables are sorted by decreasing sample mean.
Both tables are color-coded to indicate relative monthly performance; green represents the best method reproducibility, yellow represents the second best reproducibility, and red represents the poorest reproducibility.

The average R value across the 3 years of study data is the key performance indicator shown in both graphs and tables. A summary of the reproducibility of the RFG and ULSD PTP samples for 2023-2025 showed that ASTM D7039, using MWDXRF, had:

The best precision for RFG 53% of the time compared to D2622
The best precison for RFG 79% of the time compared to D5453
The best precision for ULSD 57% of the time when compared to D2622
The best precision for ULSD 36% of the time compared to D5453

Even though D5453 demonstrates better performance, when you look at the actual difference in reproducibility for the 5-15ppm data is only 0.3 ppm on average. This minimal variance suggests that the precision of D5453 and D7039 is fairly equivalent.

In the RFG PTP program, D7039 outperforms D2622 53% of the time, and outperforms D5453 79% of the time when evaluating samples with a mean sample concentration of 5 – 15 ppm.

In the ULSD PTP Program, D7039 out performs D2622 57% of the time, and better than D5453 36% of the time. Even though D5453 demonstrates better performance, when you look at the actual difference in reproducibility for the 5-15ppm data is only 0.3 ppm on average. This minimal variance suggests that the precision of D5453 and D7039 is fairly equivalent.

Table 1: RFG PTP Sulfur Reproducibility (5 – 15 ppm samples sorted by decreasing sample mean)

ASTM method D7039 D7039 outperforms D5453 79% of the time and outperforms method D2622 53% of the time.

Table 1: RFG PTP Sulfur Reproducibility (5-15ppm samples sorted by decreasing sample mean)

KEY:
Green = Best Reproducibility
Yellow = Second Best Reproducibility
Red = Poorest Reproducibility

Table 2: ULSD PTP Sulfur Reproducibility
(5 – 15 ppm samples sorted by decreasing sample mean)

ASTM method D7039 outperforms D2622 57% of the time, and better than D5453 36% of the time. Even though D5453 demonstrates better performance, when you look at the actual difference in reproducibility for the 5-15ppm data is only 0.3 ppm on average. This minimal variance suggests that the precision of D5453 and D7039 is fairly equivalent.

In both Tables 1 and 2, test method D7039 contains most of the lower or equivalent R values which indicated better or equivalent PTP precision.

When measuring for critical elements such as sulfur, a highly precise testing method is vital. Low precision methods can lead to products being off spec which can costs refineries millions of dollars in fines, or product downgrading. Reducing variability in sulfur analysis is critical to reducing sulfur giveaway, and from the data shown, MWDXRF methods offer the highest or equivalent level of precision and reliability.

Conclusion

For any refinery, a simple, streamlined elemental analysis process with high precision and reliability is critical to maximizing efficiency in every step of the refinement process. Whether monitoring ULSD or considering the refinery process strategy, refiners should take care when selecting the methodology for elemental analysis. With better or equivalent precision as identified in the ASTM PTP data above, MWDXRF analyzers utilizing ASTM D7039 methodology offer users the most reliability when evaluating sulfur in automotive fuel, while offering significant advantages in measurement time and ease of use.

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Chlorine Analysis for Corrosion Control in Refining Operations

julian.vanberkum@xos.com (Julian D. van Berkum) — Tue, 09 Jun 2026 22:20:16 GMT

Introduction

In the refining industry, managing chlorine levels is crucial for preventing corrosion, maintaining equipment integrity, and ensuring operational efficiency. Whether processing conventional crude oil or unconventional feedstocks for products such as pyrolysis oil, biofuels, or other renewable fuels, refineries face the challenge of controlling chlorine to avoid costly repairs, unplanned downtime, and potential safety hazards. XOS offers advanced chlorine analyzers that provide precise, real-time measurements, helping refineries effectively manage chlorine across various processing stages, including desalting units, feedstocks, intermediates, and final products.

XOS Technology: Precision and Reliability

XOS chlorine analyzers, such as the Clora R, Clora 2XP R, and Clora Online, leverage Monochromatic Wavelength Dispersive X-ray Fluorescence (MWDXRF) technology. This cutting-edge technology delivers accurate chlorine analysis down to sub-ppm (mg/kg) levels without the need for complex sample preparation, providing refineries with the data needed to make timely decisions.

Key Features:

Clora R: Suitable for low-level chlorine analysis in crude oil, refined products, and feedstocks for biofuels.
Clora 2XP R: Offers enhanced sensitivity for detecting ultra-low chlorine levels with automated sulfur correction.
Clora Online: Enables continuous, in-process chlorine monitoring, particularly beneficial for desalter units and real-time control.

Application in Refinery Environments

Crude Oil and Desalter Units: Refineries processing conventional crude oil rely on desalting units to remove salts—including chlorine compounds—which can lead to hydrochloric acid formation and severe corrosion. XOS chlorine analyzers ensure precise monitoring of chlorine content before and after desalting, helping refineries optimize the desalting process and protect downstream equipment.

Unconventional products: Nontypical products, such as pyrolysis oils, are derived from waste plastics or biofuels from renewable sources and often contain contaminants, including chlorine. Due to their high sensitivity, XOS analyzers are essential for detecting and managing chlorine in these feedstocks. These machines can ensure that refineries can process pyrolysis oil without compromising equipment and catalyst longevity.

Biofuels: The production of biofuels involves various feedstocks such as vegetable oils, animal fats, and waste biomass, which can introduce chlorine into the refining process. XOS chlorine analyzers provide the accuracy needed to monitor and control chlorine levels, ensuring that biofuels meet quality standards and that refinery equipment remains protected.

Benefits of XOS Chlorine Analysis Solutions

Corrosion Prevention: Accurate chlorine measurements help refineries proactively address corrosion risks, extending the life of critical equipment.
Cost Savings: Reducing corrosion-related incidents leads to significant savings in maintenance, repairs, and unplanned downtime.
Enhanced Efficiency: Continuous, real-time monitoring allows for quick corrective actions, ensuring smooth refinery operations.
Regulatory Compliance: XOS analyzers support compliance with industry standards, including those governing the processing of unconventional feedstocks and biofuels.

Conclusion

XOS chlorine analyzers are indispensable tools for refineries processing a wide range of materials, from conventional crude oil to unconventional fuels and feedstocks. By leveraging advanced MWDXRF technology, these analyzers provide the precision and reliability needed to manage chlorine levels effectively, safeguard refinery infrastructure, and optimize operational efficiency. Investing in XOS solutions ensures that refineries can meet the challenges of modern fuel processing while minimizing costs and maximizing safety.

If you’d like to learn more about chlorine analysis, talk to one of our experts.

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Easier to use than ever, Clora 2XP analyzes total chlorine in liquid hydrocarbons such as aromatics, distillates, heavy fuels, and crude oils, as well as aqueous solutions, while automatically correcting for sulfur interference.

The enhanced precision and performance technology makes it the ideal choice for testing related to catalyst poisoning in reformers or for sites with fluid catalytic crackers and hydrocrackers monitoring very low chlorine levels.

Enhancing Micro XRF Analysis with Polycapillary Optics

Brendan Waffle — Mon, 08 Jun 2026 20:41:05 GMT

X-ray fluorescence (XRF) is a commonly used technique for elemental analysis. Compared to other technologies, XRF is non-destructive, easy to use, and requires minimal sample preparation. Micro-XRF applies the same principles as XRF but on a much smaller (micro) scale.

Challenge

To perform micro-XRF, a micron-sized beam of X-rays is required to hit the sample. This small beam can be achieved using a conventional pinhole aperture or X-ray optics. One challenge faced with using a conventional pinhole aperture is that it will block a large portion of the X-rays emitted from the source thereby reducing the number of X-rays hitting the sample, resulting in much lower fluorescence. Another challenge presented is that the output beam from the pinhole will be divergent, resulting in a larger excitation area on the sample. Both challenges impact the detection sensitivity and spatial resolution of micro-XRF analysis.

Solution

It has been proven that the use of polycapillary focusing optics greatly enhances micro-XRF analysis. Polycapillary optics offer many benefits; a large collection solid angle, high flux density, and a focused micron sized beam. Polycapillary optics transmit a polychromatic beam that can achieve a focused spot size as small as 5μm, FWHM at Rh Kα energy (20.2keV) with intensities greater than 107 photons/second. These performance attributes provide a great impact to micro-XRF across many different applications. Figure 1 below is an example of a mapping application.

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fleX- Beam^TM is a unique, compact X-ray generator that combines a low powered X-ray source and a precisely-aligned polycapillary optic to deliver a bright X-ray beam for advanced material analysis. fleX-Beam is available in several standard focused or collimated beam configurations and can also be customized for specific applications. This is the ideal solution for any OEM or lab-based system.

Monochromatic Wavelength Dispersive X-ray Fluorescence (MWDXRF)

XOS Team — Thu, 04 Jun 2026 22:17:46 GMT

Doubly curved crystals can be used to enhance conventional wavelength dispersive XRF instrumentation. These diffraction-based optics enable highly intense monochromatic X-ray beams using low-power, air-cooled X-ray tubes. These three dimensionally shaped optics selectively reflect a very narrow band of X-ray wavelengths for sample excitation, according to Bragg diffraction laws.

A monochromatic wavelength dispersive X-ray fluorescence (MWD XRF) analyzer uses two doubly curved crystal optics. Typical instrumentation includes a low-power X-ray tube, a point-to-point focusing optic for excitation, a sample cell, a second focusing optic for fluorescence collection, and an X-ray detector. The first focusing optic captures a narrow bandwidth of X-rays from the source and focuses this intense monochromatic beam to a small spot on the sample. The monochromatic primary beam excites the sample and secondary characteristic fluorescence X-rays are emitted. The second DCC collection optic collects only select characteristic X-ray wavelengths of interest within a narrow bandwidth.

This configuration offers several advantages over conventional WDXRF systems. The signal-to-background is improved by using the monochromatic excitation of the X-ray source characteristic line. Secondly, the focusing ability of the collection optic allows using a small-area X-ray counter detector, which results in low detector noise and enhanced reliability. Monochromatic excitation also provides simplified quantitation and matrix effect correction. This technique enables robust, low maintenance, online analyzers with dramatically lower detection limits and faster response times.

Monochromatic WDXRF using doubly curved crystal optics has the advantage of very high sensitivity for a specific sample element of interest. This technique has been successfully used for measurement of low levels of sulfur in petroleum products.

Advancing Archaeology with Micro X-ray Fluorescence (μXRF) Technology

XOS Team — Thu, 04 Jun 2026 17:53:57 GMT

Micro X-ray Fluorescence (μXRF) has emerged as a game-changing tool in archaeology, offering non-destructive analysis of artifacts and materials. By revealing the elemental composition and distribution of objects, μXRF provides invaluable insights into their origins, production techniques, and historical significance. Recent advancements, particularly the integration of polycapillary optics, have elevated the capabilities of μXRF systems, enabling faster, more precise analysis.

The role of polycapillary optics in μXRF advancements

Traditional μXRF systems relied on pinhole collimators, which limited spatial resolution and measurement speed. The introduction of polycapillary optics has revolutionized the field, allowing X-rays to be focused into fine beams. This innovation has significantly improved data quality and measurement speed, making high-resolution elemental mapping more accessible. Today, polycapillary optics are a cornerstone of modern μXRF systems.

Curved-Surface μXRF: A Breakthrough in Artifact Analysis

While most commercial μXRF instruments are limited to flat surfaces, researchers at the Institute of High-Energy Physics (IHEP) under the Chinese Academy of Sciences (CAS) have developed a groundbreaking curved-surface μXRF system. Equipped with XOS polycapillary optics, this system enables 3D analysis of irregularly shaped objects, opening new possibilities for archaeological research. Project lead, Dr. Qiong Xu, shares details in an interview with Chinese news channel CCTV-13:

“We deployed a piece of equipment called a curved surface micro-area X-ray fluorescence spectrometer, which allows us to scan the elemental distribution of curved artifacts. This helps overcome the limitations of the naked eye, especially in cases where the manufacturing techniques are difficult to discern. To my knowledge, this is the first time such a device has been used at an archaeological site.”

By integrating imaging technology, artificial intelligence, and advanced quantitative algorithms, the curved-surface μXRF system delivers unparalleled analysis of delicate artifacts. According to Xu, the system’s software can be adapted for broader applications in industries such as EV batteries, semiconductors, and pharmaceuticals.

Product Highlight:
Polycapillary Optics

Improve X-ray analysis performance and capability
A polycapillary optic captures a large solid angle of X-rays from an X-ray source and redirects them to a micron-sized focal spot or a highly collimated beam. The X-ray intensity achieved with such optics is a few orders of magnitude higher than that obtained with conventional pinhole collimators, contributing to the significantly improved X-ray analysis performance in detection sensitivity, spatial resolution, measurement speed, and precision. XOS optics are widely used in commercial instruments and customized X-ray analysis systems for various industrial and research applications in the fields such as microelectronics, semiconductor
manufacturing, pharma, and life sciences.

Applications of μXRF in Archaeology

Artifact Analysis

μXRF is widely used to study ceramics, glass, metals, and pigments, helping researchers identify raw material sources and manufacturing techniques.

Provenance Studies

By analyzing the elemental composition of materials like obsidian or pottery, archaeologists can trace ancient trade routes and cultural exchanges.

Cultural Heritage Preservation

The non-destructive nature of μXRF makes it ideal for analyzing delicate artifacts, ensuring their preservation for future generations.

Collaborations Driving Innovation: IHEP and XOS Partnership

The success of the curved-surface μXRF system is a testament to the collaboration between IHEP and the X-ray optics team at XOS. By optimizing optic design and system integration, the partnership has delivered multiple polycapillary optics to build prototype systems. These systems are now being used by major museums and archaeological research institutes in China, further advancing the field.

Conclusion: The Future of μXRF in Archaeology and Beyond

The integration of polycapillary optics and the development of the curved-surface μXRF system have revolutionized artifact analysis, enabling researchers to uncover new insights into history and culture. As this technology continues to evolve, its applications are expanding beyond archaeology into industries like microelectronics and pharmaceuticals. With ongoing innovation and collaboration, the future of μXRF technology is brighter than ever.

Knowledge Center

Sulfur in Jet Fuel by ASTM D4294

Background

Product Highlight: Petra MAX

How the Gulf War is Making Refineries Change Their Crude Feedstocks

Background

The War's Impact

Product Highlight: Clora Online

Precision Comparison Between EDXRF and ICP for Ni, Fe, and V

Background

Challenge

Solution

Testing Precision

Conclusion

Product Highlight: Petra MAX

A Unique Sample Introduction System to Eliminate Centrifuge

New Gen 4 Software Offers an Advanced Workflow

Precision Comparison Case Study — Petra MAX (EDXRF®) vs ICP (IP 501 & IP 621)

Background

Better Precision with EDXRF®

Challenge

Case Study

Testing Precision

Product Highlight: Petra MAX

Comparing Precision Between EDXRF and ICP Data from ASTM PTP Study

Did you know?

Results

ASTM Crude Oil Proficiency Testing Program: ICP (D5708B) vs. XRF (D8252) for Ni and V

Background

ASTM D5708B

ASTM D8252

A Crude Analysis

Crude Oil PTP Data Comparison

Product Highlight: Petra MAX

Conclusion

Precision Comparison Between ASTM Test Methods D7039, D2622, and D5453

Background

ASTM Method D7039 (Monochromatic Wavelength Dispersive X-Ray Fluorescence)

ASTM Method D2622 (Wavelength Dispersive X-ray Fluorescence)

ASTM Method D5453 (Ultraviolet Fluorescence)

Precision and ILS Results

Understanding the Data (Mean Concentration and Reproducibility)

Graphs 1 & 2

Tables 1 & 2

Table 1: RFG PTP Sulfur Reproducibility (5 – 15 ppm samples sorted by decreasing sample mean)

Conclusion

Product Highlight: Sindie +Cl

Chlorine Analysis for Corrosion Control in Refining Operations

Introduction

XOS Technology: Precision and Reliability

Key Features:

Application in Refinery Environments

Benefits of XOS Chlorine Analysis Solutions

Conclusion

Product Highlight: Clora 2XP R

Enhancing Micro XRF Analysis with Polycapillary Optics

Solution

Product Highlight: fleX-Beam

Monochromatic Wavelength Dispersive X-ray Fluorescence (MWDXRF)

Advancing Archaeology with Micro X-ray Fluorescence (μXRF) Technology

The role of polycapillary optics in μXRF advancements

Curved-Surface μXRF: A Breakthrough in Artifact Analysis

Product Highlight:Polycapillary Optics

Applications of μXRF in Archaeology

Artifact Analysis

Provenance Studies

Cultural Heritage Preservation

Collaborations Driving Innovation: IHEP and XOS Partnership

Conclusion: The Future of μXRF in Archaeology and Beyond

Product Highlight:
Polycapillary Optics