Accelerator mass spectrometry

What is AMS analysis used for?

Accelerator mass spectrometry is an ultra-sensitive analytical technique used to measure the ratio of a rare, often radioactive isotope to the total number of that element's atoms in the sample. Different isotopes of the same element have the same number of protons but different numbers of neutrons in their nuclei. Many rare isotopes, such as Be-10, C-14, Al-26, Cl-36, Ca-41, I-129, and several isotopes of uranium and plutonium can be analyzed with AMS. For the analysis of light-stable isotopes, IRMS is often a preferred method.

One of the most common applications of AMS is radiocarbon dating. The technique is widely used for determining the age of carbon-containing samples by measuring the amount of radioactive C-14 isotope in them. In addition to archaeology and historical research, AMS analysis is also commonly used to determine the bio-portion (the proportion of biobased content) of fuels, CO2 emissions gases, and other carbon-containing materials.

The isotopes analyzed with AMS have a wide range of dating applications and they are used in a variation of chronometers and tracers. Therefore, AMS is utilized in many disciplines, such as geological and planetary sciences, geomorphology, quaternary science, environmental and atmospheric research, archaeology, historical research, global climate change control, nuclear safeguards, and biomedicine.

How does accelerator mass spectrometry work? 

AMS analysis is based on the use of an ion accelerator as a powerful mass spectrometer. Ion sources, large magnets, and detectors are used together with the accelerator to separate different isotopes and count single atoms. After the ionization of the sample, the magnetic and electric fields of the accelerator system filter out additional isotopes from the ion beam by deflecting them from their original direction.

The high speed of the ion beam enables molecules to be destroyed and removed from the measurement background. Finally, the ion beam is isotopically analyzed: the magnetic and electrostatic analyzers measure the amount of the isotope of interest, and ion detectors identify selected isotopes and count them individually. As a result, even concentrations of one atom in around 1,000 atoms can be measured.

Sample requirements and preparation 

Solid, liquid, and gaseous samples can be analyzed with AMS. For example, archaeological samples (e.g. fossils, pottery), geological samples (e.g. rocks, sediments), fuels, flue gases, and natural samples like rainwater are suitable for the analysis. Because AMS is a highly sensitive method, only a small sample amount is needed. For solid materials, a few milligrams are usually enough. 

Before the AMS analysis, the element of interest (e.g. carbon, beryllium, aluminum, iodine, uranium, or plutonium) has to be isolated from the sample and purified. Chemical methods are used to separate very small amounts of the element and to prepare the appropriate target material for the measurement.

Need an AMS analysis?

Measurlabs offers high-quality AMS analyses with fast results and competitive prices for large or recurring projects. If you have any questions about your sample or its suitability for the method, our experts are always happy to help. You can contact us through the form below or at info@measurlabs.com.