Specialty gases · Stable isotope analysis
Reference gases with defined isotopic signatures for reliable isotope ratio measurements.
CAC Gas supplies isotopic gas mixtures and pure reference gases for petroleum geochemistry, food authentication and environmental monitoring. Specify the gas composition and isotope values your analytical method requires.
Reference values selected for your analysis.
Documented values for the supplied product.
Molecular and isotopic compositions on request.
The right reference for your method
Stable isotope analysis measures the relative abundance of isotopes within a sample. These measurements can help researchers investigate gas origins, assess food authenticity and study atmospheric processes.
An isotopic reference gas has a specified isotope signature as well as a defined chemical composition. Selecting both parameters helps laboratories calibrate their analysers and check measurement performance across the range relevant to their samples.
CAC Gas can help you identify a suitable mixture, pure gas or natural air standard and discuss compatible gas handling equipment.
Applications
Match your reference gas to the sample, instrument and measurement method.
Calibrate isotope measurements used to investigate the formation, origin and evolution of natural gas accumulations.
Support isotope ratio testing used to assess authenticity and investigate adulteration in food and beverage samples.
Support atmospheric gas measurements and research into greenhouse gas sources using natural air reference standards.
Product range
Explore representative compositions below. Exact isotope values, measurement uncertainty, cylinder configuration and current availability are confirmed with your quotation and Certificate of Analysis.
Single-component and multi-component calibration mixtures with defined carbon and, where specified, hydrogen isotope values.
| Reference type | Composition (v/v) | Isotope signature | Balance |
|---|---|---|---|
| Biogenic methane | 250 ppm, 2,500 ppm or 2.5% CH4 | δ13C −69‰ VPDB δ2H −235‰ VSMOW | Air |
| Biogenic blend | 95% CH4 + 1% C2H6 | δ13C: CH4 −69‰; C2H6 −30‰ VPDB | N2 |
| Thermogenic methane | 250 ppm, 2,500 ppm or 2.5% CH4 | δ13C −45‰ / δ2H −150‰ or δ13C −25‰ / δ2H −120‰ Carbon: VPDB; hydrogen: VSMOW | Air |
| Thermogenic blend | 80% CH4 + 15% C2H6 + 5% C3H8 | δ13C: −40‰, −30‰ and −25‰ respectively, VPDB | None |
| Carbon dioxide reference | 50% CO2 | δ13C −40‰, −25‰ or +25‰ VPDB | Air |
More complex hydrocarbon mixtures can include ethane, propane, n-butane, isobutane, n-pentane and isopentane. Ask CAC Gas about your required component concentrations and individual isotope values.
Pure gases and tailored mixtures for isotope ratio measurements in food and beverage laboratories.
| Gas | Isotope parameter | Representative values / ranges | Reference scale |
|---|---|---|---|
| Carbon dioxide (CO2) | δ13C | −25, −26, −6.4 or −11‰ Additional options include −28 or −29‰ | VPDB |
| Oxygen (O2) | δ18O | −12 to −3‰ | VSMOW |
| Hydrogen (H2) | δ2H | −80 to −9‰ | VSMOW |
| Nitrogen (N2) | δ15N | Custom values on request | AIR |
Tell us your analytical method and required uncertainty so we can confirm a suitable specification. The selected reference gas does not by itself establish compliance with a food testing method.
Natural air standards and customised atmospheric mixtures for laboratory and environmental measurement programmes.
| Reference type | CO2 concentration | CO2 isotope signature |
|---|---|---|
| Natural air | 360–450 ppm | δ13C −7.5 to −9.5‰ VPDB δ18O −2 to +2‰ VPDB |
| CO2 in natural air | 250–520 ppm | δ13C −7.5 to −9.5‰ VPDB δ18O −2 to +2‰ VPDB |
| CO2-depleted natural air | <50 ppb CO2 | Not applicable |
These are reference product ranges, not present-day atmospheric background values. Additional compositions involving CH4, N2O, CO and other trace gases can be discussed on request.
Custom gas specifications
Need a specific isotopic signature or molecular composition? CAC Gas can investigate custom pure gases and mixtures to suit your application.
Provide the target concentration, isotope delta value, reference scale and required uncertainty for each relevant component. Feasibility depends on the complete gas specification.
Enquire About a Custom Gas| Gas | Isotope parameter | Delta range (‰) |
|---|---|---|
| CO2 | δ13C · VPDB | −44 to +20 |
| CO2 | δ18O · VPDB | −24 to +20 |
| CO | δ13C · VPDB | −300 to +20 |
| CO | δ18O · VSMOW | −150 to +10 |
| N2 | δ15N · AIR | −10 to +20 |
| H2 | δ2H · VSMOW | −400 to +10 |
Indicative options for enquiry; final achievable values and uncertainty are confirmed for each order. Additional hydrocarbon and sulphur isotope specifications may be available on request.
Gas supply & handling
Packaging is selected to suit the gas, quantity and analytical requirements.
Confirm cylinder capacity, fill pressure, valve connection, shelf life and lead time with CAC Gas before ordering.
Common questions
A conventional calibration mixture specifies gas concentrations. An isotopic reference also specifies isotope delta values and their reference scales for the relevant components.
Yes. Provide the required gas composition, isotope value, reference scale and uncertainty. CAC Gas will investigate feasibility and confirm the available specification.
Include your application, instrument or method, gas components and concentrations, isotope parameters and values, required uncertainty, cylinder quantity and valve connection. Add your required delivery date.
Talk to CAC Gas
Send us your specification or speak with our team about the options.
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