Receive regular emails from NPL to get a glimpse of our activities and see how our experts are informing and influencing scientific debate

Gas reference materials

Volatile organic compounds (VOCs)

Monitoring and improving air quality

Ozone precursors

NPL is the Central Calibration Laboratory (CCL) for non-methane hydrocarbons (NMHCs) within the World Meteorological Organisation Global Atmospheric Watch programme (WMO-GAW).

NPL provides a 30-component primary reference material (PRM) that contains all the ozone precursor hydrocarbon compounds listed in Annex X of the European Directive 2008/50/EC on Ambient Air Quality and Cleaner Air for Europe. These mixtures are typically prepared at amount fractions of 4 nmol/mol, but other amount fractions from 1 to 200 nmol/mol are also available.

Ethane 1,3-butadiene 2,2,4-trimethylpentane
Ethene (ethylene) Pentane Benzene
Ethyne (acetylene) 2-methylbutane Toluene
Propane 1-pentene Ethylbenzene
Propene trans-2-pentene m-xylene
Butane 2-methyl-1,3-butadiene (isoprene) p-xylene
2-methylpropane (i-butane) Hexane o-xylene
1-butene 2-methylpentane 1,2,3-trimethylbenzene
trans-2-butene Heptane 1,2,4-trimethylbenzene
cis-2-butene Octane 1,3,5-trimethylbenzene

BTEX mixtures

NPL provides a range of BTEX PRMs containing benzene, toluene, ethylbenzene, m-xylene, p-xylene and o-xylene at amount fractions from 1 nmol/mol to 10 µmol/mol. Mixtures containing BTEX and 1,3-butadiene are also available.

Oxygenated VOCs (OVOCs) including formaldehyde 

NPL offers a range of OVOC PRMs at amount fractions of 1 to 10 μmol/mol. One typical multi-component mixture contains the components shown below. Mixtures containing other OVOCs (e.g., acetaldehyde, acetonitrile, methyl ethyl ketone) are available on request. Binary mixtures of formaldehyde are also available on request in amount fractions of 1 to 10 μmol/mol.







Bespoke mixtures

NPL can provide, on request, bespoke PRMs containing C2 to C10 hydrocarbons, chlorinated hydrocarbons and fluorinated hydrocarbons at a range of amount fractions. For example, PRMs of perdeuterated toluene (d8-toluene) are available due to their use as an internal standard in GC-MS applications. We can provide these mixtures at a range of amount fractions but most commonly at 5 µmol/mol.

Download the User Guide for NPL VOC Standards


Multi-component terpene mixtures

NPL provides a range of terpene primary reference materials (PRMs) at amount fractions from 1 to 200 nmol/mol. One typical multi-component terpene mixture contains the components shown below.

(+/-)-α-pinene (+)-3-carene
1,8-cineole (eucalyptol) R-(+)-limonene

Mixtures containing other terpenes, such as β-pinene, myrcene, camphor, p-cymene or cis-ocimene, are available on request.

33-component ozone precursor and terpene mixture

NPL can provide a PRM containing all 30 components of the ozone precursor mixture, as well as α-pinene, β-pinene and limonene. This mixture is available at a range of amount fractions from 2 to 10 nmol/mol. Other components may be included and these terpenes can also be combined with just the BTEX components on request.

Don’t see what you are looking for? Our diverse skill set enables us to provide bespoke solutions. Please contact us to discuss your requirements.

Contact us

Work with us

Our research and measurement solutions support innovation and product development. We work with companies to deliver business advantage and commercial success.
Contact our Customer Services team on +44 20 8943 7070