IRMS & ICPMS

IRMS (Isotope Ratio Mass Spectrometry)

Lab manager

Dr Mauro Rubino: Questo indirizzo email è protetto dagli spambots. È necessario abilitare JavaScript per vederlo.

General Overview of the methodology

Mass spectrometers can be briefly described as follows:

  • an electron impact ion source (preparation) producing positive ions which are accelerated by electric fields and separated by
  • a magnetic selection (analysis) with double focusing magnet which separate the ions with different masses that are then measured on
  • an array of Faraday Cups (detection) for simultaneous measurement of masses 1, 2 for H2 or 44, 45, 46 for CO2 or 32, 33, 34 for O2 or 28, 29 for N2 or 28, 29, 30 for CO and 64, 66 for SO2.

 IRMS

Generally, the ion source of an IRMS system accepts gaseous samples only. Therefore, the molecules whose isotopic ratio is measured (H2, CO2, N2, CO and SO2) can be produced

  • offline in external preparation lines and injected in the IRMS through a Dual Inlet system, or
  • online by means of peripherals (Elemental Analyser, Thermal Combustion, Gas Chromatography, Gas bench) and injected through a CONFLO (Continuous Flow) interface.

EA GC interface

 

 

Laboratory equipment

At the CIRCE IRMS laboratory, there are 3 (three) ThermoFisher mass spectrometers

  • 1 Thermo Quest Delta plus
  • 2 Thermo Fisher Delta V advantage

for the measurement of 2H/1H, 12C/13C, 14N/15N, 18O/16O and 34S/32S.

The following peripherals are available:

  • 2 EA (Elemental Analysers) producing CO2, N2 and SO2 through combustion of solid and liquid samples for analyses of C, N and S isotopes;
  • 2 TC/EA (Thermal Combustion/Elemental Analyser) producing CO, N2 and H2 through pyrolysis of solid and liquid samples for analyses of O, N and H isotopes;
  • 1 GC/C-TC (Gas Chromatograph/Combustion-Thermal Combustion) separating specific compounds in a mixture and then producing either CO2, N2 and SO2 through combustion or CO, N2 and H2 through pyrolysis for C, N, H, O and S isotope analyses;
  • 1 Gas bench for the analysis of H and O isotope analyses in water samples, C and O isotope analyses in Dissolved Inorganic Carbon and Carbonates, and C and O isotope analyses in ambient air CO2.

On line (continuous flow) coupling of peripherals and IRMS are performed via CONFLO interfaces (CONFLO II, III and IV) which reduce the working pressure and connect the peripherals (tipical operating pressure = 1 atm) with the IRMS source (tipical operating pressure 10-6-10-8 mbar) by means of the open split technology.

lab

Main applications carried out at the IRMS lab

Environmental pollution - Hydrology

Contamination of water resources from landfill leachate

Municipal landfills impact on ground and surface water resources. Whene they are often located in industrial areas, where there are other sources of contamination (e.g. incinerators and oil refineries), the analysis of natural isotopes of CO2, CH4 and leachate can help identify the contamination by leachate from the landfill because of the characteristic isotope signature of gas and leachate. In the IRMS laboratory at CIRCE, water samples from landfill sites (e.g. Malagrotta near Rome) have been investigated by means of dD and d18O measurements. Further work with d13C of DIC (Dissolved Inorganic Carbon) is underway.

Nitrate (NO3-) contamination of groundwater

Shallow aquifers worldwide can be contaminated by NO3- leached from soils exploited by intensive agriculture or from leaks of the sewage system in densely populated areas. The development of remediation plans for polluted areas requires the identification of the sources of NO3- in water bodies. At CIRCE IRMS lab, the apportionment of NO3- contamination sources in shallow groundwater in five regions of the Po River basin has been carried out measuring nitrogen and oxygen isotopic ratios of dissolved nitrate (d15N and d 18O).

Environmental pollution - Atmospheric Science

The identification of the sources of atmospheric pollution can be performed through measurements of isotopic composition. Particulate matter, for example, is composed of many molecules and atoms having different origins. The IRMS laboratory at CIRCE is involved in an experiment aiming to identify the sources of C and N in particulate matter samples in Naples. Dual measurements of d15N and d13C can help quantify the proportion of N and C derived from different sources of pollution (cars and bus exhausts, private houses, pizza fire oven, etc...). This is essential to develop appropriate remediation strategies.

Materials Science

Isotope methodologies guarantee high sensitivity in the quantification of tracers in the "micro" range. The technique called Isotope Dilution Mass Spectrometry (IDMS) represents the only method for the analysis of elements in concentration of a few % down to ultra trace (i.e. < ng kg-1). Basically, small quantities (traces) of an element can be quantified via measurements of isotopic ratios combined with the introduction of an isotopic spike. As an example, the IRMS lab at CIRCE is a key player in testing the detection elements of the KM3net experiment (https://www.km3net.org/) for leaks in a hyperbaric chamber.

Archaeometry

Isotopic methodologies can support archaeological sciences because they can provide information about the age and origin of ancient materials and deposits. Analyzing human remains for their C, N, O, isotopic signatures (the so-called isotopic fingerprints), one can study the dietary habits of an individual or group, determine where a person grew up or where they lived in the last years of their life. At the IRMS lab, analyses of charred grains from Turkey helped infer information about the usage of agricultural practices.

Food traceability

Isotopic analyses of foods have become a widespread tool to evaluate the quality, authenticity and origin of labelled products. Wines, alcoholic beverages and fermented fruit juices are distilled to produce ethanol. The ethanol of a number of wine samples has been analyzed at the IRMS lab at CIRCE for O and C isotope composition in order to detect exogenous sugar added during the fermentation to increase the alcohol grade of the wine.

 

ICP-MS (Inductively Coupled Plasma Mass Spectrometry)

Lab manager

Prof Fabio Marzaioli: Questo indirizzo email è protetto dagli spambots. È necessario abilitare JavaScript per vederlo.

General Overview of the methodology

Multi-Collector High-Resolution Inductively-Coupled Plasma Mass Spectrometry (MC-HR-ICP-MS) provides the opportunity to measure the isotopic ratio of a great variety of elements. An MC-ICP-MS is generally composed of the following parts:

  • an ICP source (preparation) producing positive ions with sensible efficiencies (≥ 40%) for elements with ionization energies up to 10 eV
  • an electrostatic and magnetic sector (analysis) with Double focusing Geometry (Nier Johnson) resulting in an accurate separation of masses
  • an array (Multicollector setup) of ion detectors (detection), usually Faraday Cups or Secondary Electron Multipliers

ICPMS

Laboratory equipment

The CIRCE ICP-MS laboratory accommodates a Neptune Plus ThermoFisher MC-ICP-MS, a versatile instruments which is suitable for measurements of isotopic ratios of a wide range of elements. The Neptune Plus MC-ICP-MS is composed of the following parts:

  • A plasma interface, held at ground potential, containing a nebulizer, spray chamber and torch (the plasma)
  • A 90° ElectroStatic Analyser (ESA)
  • A 90° magnetic analyser
  • A 9 Faraday cups's adjustable array
  • Secondary Electron Multipliers (SEM)

Before being injected into the ICP ion source, a sample is generally purified (e.g. ion exchange or extraction chromatography), dissolved in HNO3 and nebulised through a pumping system. The ICP ion source extracts positive ions which are then accelerated at 10 kV. The Neptune Plus can be operated at three different resolution settings (low, medium and high) by actuating source and detector slits which cut the beam to select the isotopes of interest and reject molecular interferences. In case of low beam intensities, SEM can replace faraday cups to provide higher sensitivity.

eq icpms

Main applications carried out at the ICP-MS lab

Environmental pollution - Hydrology

Studies of source apportionment of NO3- in contaminated acquifer can be supported by measurements of the isotopic composition of Boron (d11B). Boron (B) co-migrates with NO3- from the sewage system because Sodium Perborate (NaBO3) is used as an oxidation bleaching agent in domestic and industrial cleaning products. Since d11B values of sewage are easily distinguished from uncontaminated groundwater, the d11B is useful to identify NO3- sources. At the CIRCE ICP-MS lab, measurements of d11B have helped the apportionment of NO3- contamination sources in shallow groundwater in five regions of the Po River basin.

Environmental pollution - Nuclear safeguards

Nuclear plants are a possible source of radionuclide into the enviroment. Uranium (238, 235 and 234) and Plutonium (239 and 240) isotope ratio can be utilized to trace environmental releases from nuclear plants. The ICP-LAB at CIRCE has been involved in measurements of those nuclides in soil, water and sediment samples from the Garigliano river, where the decomissioning phase of a nuclear plant is underway.

Cosmogeochemistry

Elements isotope fingerprint represents a powerful technique for examining the origins of meteorites in the Solar System. It is, for example, possible to correlate differentiated and primitive meteorite types, and study mixing processes in the early solar nebula. Nichel (Ni) is a moderately refractory and siderophile element, and also a major component of both iron and silicate meteorites. 60Ni isotope variations can therefore potentially be used to date nebula events. Similarly, 60Fe is believed to be synthesised in a high temperature stellar environment, not within the Solar System. The presence of “live” 60Fe inferred from Ni isotope compositions represents a diagnostic fingerprint of materials created in a nearby stellar explosion that was subsequently transported to the nascent solar nebula. At the ICP-MS lab, measurements of 60Ni in pallasites (a class of stony–iron meteorite) have helped infer their origin.

Archaeometry

Measurements of radiogenic Lead (208, 207, 206) and Strontium (87) isotope ratios can be utilised to reconstruct the origin of metals and organics in ancient manufacts and bones. Strontium (Sr) builds up in the bones and tooth enamel as food is digested. In contrast to the bones, Sr is no longer exchanged in tooth enamel after the age of four, allowing researchers to tell where the person lived as a child. Different isotope ratios in the bones and teeth are therefore proof of migration after the age of four. At the ICP-MS lab of CIRCE, such measurements have been used to provide important informations about commercial networks and migration pathways in ancient times.

Food traceability

Radiogenic Strontium (87) is the long-lived radiogenic daughter of ⁸⁷Rb and can be utilized to determine the provenance of animal and vegetal foods. The ⁸⁷Sr/⁸⁶Sr ratio of any geological material (i.e. minerals and rocks) on Earth depends on its time integrated ⁸⁷Rb/⁸⁶Sr ratio, and thus it is related to three main parameters: (1) the initial radiogenic isotopic abundance, (2) the age of the rock/mineral, and (3) the parent/daughter isotope ratio. The ⁸⁷Sr/⁸⁶Sr ratio is not modified during the uptake of the plant and it is transferred unchanged to all living beings of the food chain, thus remaining identical to that of the substratum from which the original plant or vegetable grew. At the ICP-MS lab at CIRCE, measurements of ⁸⁷Sr/⁸⁶Sr have provided information about the area of provenance of different Italian wines and olive oils.

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