WHAT IT IS
An elemental analyzer (EA) is a combustion-based device coupled to an isotope ratio mass spectrometer (IRMS) for the measurement of stable isotope ratios in solid and liquid samples. It converts bulk material into simple gases such as CO₂, N₂, or SO₂, which are then introduced into the IRMS. Two main types are commonly used: the standard EA, based on oxidative combustion, and the TC/EA (high-temperature conversion/elemental analyzer), which operates at higher temperatures under pyrolytic conditions for hydrogen and oxygen isotope analysis. Together, these devices cover a wide range of applications in ecology, geology, environmental science, and food authenticity studies.
HOW IT WORKS
Samples are weighed into small tin or silver capsules and dropped into a heated reactor. In a conventional EA, combustion occurs in an oxygen-rich stream at >1000 °C, converting organic material to gases like CO₂, N₂, and H₂O, while sulfur- and halogen-containing compounds are also oxidized to simple gaseous forms. A downstream reduction column removes excess oxygen and converts nitrogen oxides to N₂.
In a TC/EA, the reactor is filled with graphite or glassy carbon and run at even higher temperatures (up to ~1450 °C) under reducing conditions. This pyrolytic process converts samples to gases such as H₂ and CO, which are then suitable for hydrogen and oxygen isotope ratio measurements.
The gas stream is dried, separated by a chromatographic column, and directed in pulses into the IRMS. This continuous-flow interface enables sequential analysis of multiple samples with minimal operator intervention, while providing both elemental content and isotopic composition.
ADVANTAGES
High throughput – automated capsule introduction and continuous-flow design allow many samples to be analyzed in sequence.
Versatile operation – EA covers C, N, S analysis, while TC/EA extends capability to H and O isotopes.
Quantitative conversion – nearly complete combustion or pyrolysis minimizes isotopic fractionation.
Dual information – yields both elemental concentrations and isotope ratios in one workflow.
Broad applicability – suitable for soils, sediments, plant and animal tissues, and diverse environmental materials.
Established technique – extensively validated across earth sciences, biology, and food testing.
CHALLENGES AND LIMITATIONS
Reactor wear – combustion and pyrolysis columns degrade quickly and must be replaced regularly.
Matrix sensitivity – saline or mineral-rich samples can damage reactors and affect yields.
Calibration needs – accuracy depends on frequent analysis of reference materials and careful normalization.
Operational costs – high-temperature furnaces, consumables, and carrier gases increase running expenses and require strict safety measures.