The laboratory of stable isotope

Head of the Geochemical Monitoring Functional Unit: Manfredi LONGO
E-mail: manfredi.longo@ingv.it

Referent of Stable Isotopes Laboratory: Ygor OLIVERI
E-mail: ygor.oliveri@ingv.it



Laboratory rules

The laboratory of stable isotope

The laboratory of stable isotope, started its activities in the late ’80s inside the Istituto di geochimica dei Fluidi, C.N.R. (Institute of geochemistry of fluids of the National Research Council), then merged with the INGV.
The laboratory makes determinations of isotopic ratios of light elements such as Hydrogen, Carbon, Nitrogen and Oxygen, in solid, liquid and gaseous samples. The isotopic composition of any substance (rock, water, gas but also composed of organic origin), is comparable to a “fingerprint” which then allows to identify either the process and the environmental conditions in which the substance has been produced or to evaluate qualitatively and quantitatively any secondary processes which modified the original isotopic composition.

The Laboratory has advanced and innovative analytical instrumentation based on mass spectrometry techniques IRMS (Isotope Ratio Mass Spectrometry), equipped with automated systems that helps you make isotopic analyses in many organic and inorganic substances. Currently, there are four mass spectrometers of last generation, in operation for the analysis of isotopic ratios in natural waters (meteoric, marine, surface and groundwater), in acid condensates from fumaroles, in volcanic gases, in natural and atmospheric gases, in fossils and carbonate rocks.
There are also four laser scanners, transportable equipments that enable to perform the isotopic determinations also directly in the field or in mobile laboratories.

The mass spectrometry IRMS (Isotope Ratio Mass Spectometry) was, until a few years ago, the most common analytical technique for the determination of isotope ratios in a substance. This method is based on the initial ionization and acceleration of the molecule to be analyzed which, subjected to the action of a magnetic field, separates into ion beams as a function of mass/charge ratio (m/z). The lighter ions will describe a radius of curvature smaller than the heavier ones. The simultaneous measurement of the current intensity of each ionic radius, through the “Faraday cups”, allows to determine the relative isotope abundance in a given sample.
The isotope laser analyzers are analytical tools of recent development, based on optical spectroscopy principles. The sample, in gaseous and steam form, is introduced into the measuring cell, where it interacts with a laser beam. Each of the gas molecules absorbs light at a specific wavelength and, in proportion to their relative abundance, up to molar fractions of parts per trillion (10-12). The laser analyzers are less versatile than a mass spectrometer as they can determine at most two types of isotopic ratios but, they have the great advantage of being able to make isotopic measurements at high frequency and directly in the field, otherwise impossible through the mass spectrometry.

The stable isotope geochemistry of light elements (H, C, N and O), is a scientific discipline, initially created to geochemical and cosmochemical studies, but over the years it has evolved, finding numerous applications in biology, archeology, agronomy, medicine, forensic science and not least also in the food field.
In general, in geosciences the isotopic composition represents both a genetic marker and a process indicator, as it allows to identify the origin of fluids but also to determine post-genetic processes such as interaction, mixing, or isotope exchange that have changed their original composition. In particular, it applies to the hydrogeological studies for the characterization of processes of groundwater supply and circulation; to fossils and speleothems, rainwater and ice cores for present and past climatology studies; to magmatic, hydrothermal and geothermal fluids for monitoring volcanic active areas; to analyses of the potential of natural geothermal systems and also to identify the relationships between Earth’s geodynamics and natural degassing.

In the medical field, the breath test, a non-invasive method for the diagnosis by infection with Helicobacter pylori; it is based on the simple determination of the carbon isotope ratio of carbon dioxide in human breath.
The analytical IRMS techniques are used officially by the world agency for doping (WADA) to identify phenomena of doping in sport.

In the food sector, you can identify phenomena of adulteration in many foods (wine and spirits in general, olive oil, honey, milk, juices, flours) and in natural essences (vanillin, essential oils) through the isotopic composition of carbon, hydrogen and oxygen.

In forensic science the isotopic composition can be used, as evidence, through the comparison of the sample of interest with other samples collected, during an investigation and/or the comparison with a reference database.
Finally, there are numerous studies on archeology and paleo-diet that are based on relationships among diet, geographical location and isotopic composition of human tissues.