Skip to main content
U.S. flag

An official website of the United States government

Official websites use .gov
A .gov website belongs to an official government organization in the United States.

Secure .gov websites use HTTPS
A lock ( ) or https:// means you’ve safely connected to the .gov website. Share sensitive information only on official, secure websites.

Reference Materials and Standards for Fossil Fuels, Electric Utility Emissions, and Coal Combustion By-Products


National Institute of Standards and Technology (NIST) fossil fuel Standard Reference Materials (SRMs) continue to be in high demand by the petroleum industry and the fossil fuel-based electric utility industries. In the past, the measurement of sulfur in fuels and combustion systems has received principal attention, but mercury emissions are now attracting regulatory interest because of the potential risk to human health. Measurements of carbon will also become more important as trading systems come into effect to combat climate change effects from the release of carbon dioxide into the atmosphere. The generation of large quantities of coal combustion by-products, having significant levels of unwanted contaminants, also represents a significant measurement challenge.


Until newer sustainable energy technologies can be deployed, fossil fuels will remain the principal source of energy for the developed world. Coal, oil, and natural gas account for over 85 % of the energy consumed by the U.S. Along with the need for more efficient utilization of these resources, there is a need for the environmental management of electric utility combustion emissions and waste products, and pollutant emissions from vehicles using liquid fuels. Sulfur, mercury, and carbon are (or will likely be) subject to environmental regulations. Management of energy production from the specification of fossil fuel raw materials to the release of environmental pollutants from combustion processes, together with risk assessment of bulk waste products, such as fly-ash and flue gas de-sulfurization (FGD) gypsum, will require accurate analytical measurements, and there will undoubtedly be increasing demand for relevant reference materials to support the emerging needs of these markets.

Major Accomplishments

  • Approximately 60 fossil fuel-related SRMs are available to support the needs of the energy, electric utility, and transportation fuel sectors.     
  • A gravimetric mixing tool for producing intermediate certified values for sulfur in fossil fuel SRMs has been developed. 
  • New high-accuracy isotope dilution mass spectrometric analytical methods have been developed for the measurement of mercury and chlorine in complex matrix materials. All of the coal SRMs are now certified for mercury, and three of them for chlorine.     
  • A certification system has been implemented to provide traceability infrastructure for electric utility mercury emissions monitoring.


The fossil fuel SRM program is now 40 years old, and the current inventory of fossil fuel reference materials includes coals, cokes, residual fuel oils, distillates and gasolines. Many of these have been certified, and will continue to be certified, using high-accuracy methods such as isotope dilution mass spectrometry. A challenge in recent years has been the assignment of accurate mercury concentrations in bituminous and sub-bituminous coals and at lower levels in unrefined crude oil and diesel fuel. This has been achieved through the development of a method using high-pressure Carius digestion coupled with isotope dilution mass spectrometry. Similarly, new methods for the determination of chlorine in coals using instrumental neutron activation and thermal ionization mass spectrometry have resulted in the provision of certified values for this element in several of the coal SRMs. In anticipation of demand for standards to support carbon accounting activities, new methods for the high-accuracy measurement of carbon in new and existing fossil fuel SRMs will be a priority in the near future. New instrumentation consisting of multi-collector inductively coupled plasma mass spectrometry has recently been acquired, and this will be assessed for the measurement of carbon in fossil fuels by isotope dilution.

Click on an SRM below to be transferred to a page from which you can access its Certificate of Analysis.

1635 Trace Elements in Coal (Sub-bituminous)
2294 Reformulated Gasoline (nominal 11 % MTBE)
2295 Reformulated Gasoline (nominal 15 % MTBE)
2296 Reformulated Gasoline (nominal 13 % ETBE)
2297 Reformulated Gasoline (nominal 10 % Ethanol)
2298 Sulfur in Gasoline (High-Octane)
2299 Sulfur in Gasoline (Reformulated
2689 Coal Fly Ash
2690 Coal Fly Ash
2691 Coal Fly Ash
2693 Bituminous Coal (Sulfur, Mercury, and Chlorine
2718 Trace Elements in Green Petroleum Coke
2719 Trace Elements in Calcined Petroleum Coke
2720 Sulfur in Di-n-Butyl-Sulfide
2721 Crude Oil (Light-Sour)
2722 Crude Oil (Heavy-Sweet)
2770 Sulfur in Diesel Fuel Oil
2771 Sulfur in Diesel Fuel Blend Stock
2775 Foundry Coke 
2776 Furnace Coke 
1616b Sulfur in Kerosene (Low Level)
1617a Sulfur in Kerosene (High Level)
1619b Sulfur in Residual Fuel Oil (0.7 %)
1620c Sulfur in Residual Fuel Oil (4 %)
1621e Sulfur in Residual Fuel Oil (1 %)
1622e Sulfur in Residual Fuel Oil (2 %)
1623c Sulfur in Residual Fuel Oil (0.3%) 
1624d Sulfur in Diesel Fuel Oil (0.4 %)
1632c Trace Elements in Coal (Bituminous)
1633b Constituent Elements in Coal Fly Ash
1634c Trace Elements in Fuel Oil
2682b Subbituminous Coal (Sulfur, Mercury, Chlorine)
2683b Bituminous Coal (Sulfur and Mercury)
2684b Bituminous Coal (Sulfur and Mercury)
2685b Bituminous Coal (Sulfur, Mercury, Chlorine)
2692b Bituminous Coal (Sulfur, Mercury, Chlorine)
2717a Sulfur in Residual Fuel Oil (3 %)
2723a Sulfur in Diesel Fuel Oil
2724b Sulfur in Diesel Fuel Oil

Created December 30, 2008, Updated September 27, 2023