Multi-Collector - Inductively Coupled Plasma - Mass Spectrometry

MC-ICPMS NeptunePlus Thermofisher Scientific

figure 23a

figure 23b
MC-ICPMS Neptune Plus (2010)

Laser ESI –NWR 193 nm (2011)

Characteristics of Instrumentation:

The MC-ICPMS NeptunePlus is a mass spectrometer (MS) with a source of Argon plasma (ICP), a dual focusing (electrostatic field + magnetic field) and a multi-collection (MC). This mass spectrometer allows the precise measurement of stable, radiogenic or radioactive isotopes for many chemical elements of the Periodic Table in natural archives (waters, carbonates, apatites, sediments, soils, rocks, etc.). The high ionization efficiency of the Plasma source gives it a great sensitivity. Its dual focusing ensures good transmission of the ion beam and offers us the ability to work at low, medium or high resolution (suppression of some isobaric interferences). Finally, the high stability of multi-collection provides an excellent analytical accuracy on isotopic ratios (external reproducibility ranging from a few tens of ppm to sub- ‰). Another advantage is that the plasma source, opened to the atmosphere, allows us to introduce and analyze samples in liquid form after chemistry (micro-nebulizers, desolvating systems) or directly on solids (Ablation Laser coupling). Main fields of application are geochronology (U-Th dating), marine geochemistry and paleoceanography (Pa, Th, U, Ra, Nd isotopes), carbon cycle in ocean and the impact of ocean acidification (B, Th, Si isotopes), isotopic characterization of volcanic or sedimentary rocks or some developments in archeology (Nd, Sr, Pb or even Cu, Zn, Fe Isotopes).

Principle of Measurement:

In solution, the sample is aspirated and injected by a spray nebulizer into a "Plasma" source of argon at 6000-8000°K and atmospheric pressure. At this high temperature, the elements are ionized. Transferred by an interface (sampler and skimmer cones), the ions are accelerated under primary and then secondary vacuum to form an ion beam with a final energy of up to 10 keV. The beam is filtered in energy (electrostatic sector), then in mass (magnetic sector) according to the ratio m/z. The isotopes are detected by a multi-collector system with 15 detectors (9 Faraday cages, 1 SEM and 5 CDD). The isotopes and ratios are then measured and calculated at high precision simultaneously on several detectors. Obtained external reproducibilities are of a few tens of ppm for the isotopes of Sr, Nd, from 0.05 to a few 0.1 ‰ for Li, B isotopes or of the order of 1 ‰ for systems with low isotopic ratios (U and Th isotopes). The central cage ion beam can switch over to the central ion counter (SEM) if the signal is too low, making it possible, for example, to measure the isotopes 230Th and 234U, isotopes essential for U-Th dating. For few isotopic systems (Si, Fe or more generally transition metals), measurements are carried out in medium or high resolution in order to separate the analyzed isotopes from potential isobaric interferences. In such configuration, signal intensity is decreased but resolving power can be increased by 10-fold.

MC-ICPMS isotopic measurements are relative and require laboratory or international standards or reference materials whose isotopic values ​​are known and / or certified (NIST). The “bracketing” protocol is generally used to characterize precisely the isotopic composition of a studied element and to take into account the instrumental drifts. It is possible to introduce into the plasma source solutions previously purified in a clean room but also a flow of helium gas which entails aerosols. Thus, isotopic measurements of some elements such as Sr, B or U in carbonates are performed after coupling with the laser ablation system Excimer NWR193 nm.

Others information

  • Nebulizers PFA 20, 50 ou 100 µL/min & micro-cyclonic chamber (solutions)
  • Desolvating inlet system APEX Omega and Omega HF & ARIDUS II + QuickWash (2 to 10 -fold sensitivity increase, solutions)
  • Jet-Interface installed in 2014 (reinforced sensitivity: from 2 to 5-fold, solutions)
  • Ablation laser Excimer ESI – NWR 193 nm (in-situ analysis, aerosols from solid materials)

Isotopic measurements performed by MC-ICPMS:

Solutions (after chemistry)

  • U, Th, Pa, Ra: U-series Geochronology, marine or continental Geochemistry ;
  • Sr, Nd and recently Pb for various natural materials: source determination, erosion, ocean circulation and dynamics, archeological studies ;
  • B and Li for carbonates or waters: paleo-pH and ocean acidification (carbon cycle), marine biogeochemistry ;
  • Other systems: Si, Fe, Cu, Zn, etc.

Solid matrix per Ablation laser (development in progress)

  • B (δ11B), of Sr (87Sr/86Sr) and U (δ234U) in carbonates or silicates.

Contacts:

Instrumental responsible

Arnaud Dapoigny This email address is being protected from spambots. You need JavaScript enabled to view it. 01 69 08 04 70

Main Scientist responsible

Dr Eric Douville (B, Li, Sr) This email address is being protected from spambots. You need JavaScript enabled to view it. 01 69 08 22 57

Other GEOPS-LSCE scientists involved:

Dr Christophe Colin (Nd, Sr), Dr Edwige Pons-Branchu (U, Th, Ra, Sr, Pb), Claire Rollion-Bard & François Thil (Laser), William Gray (B), Damien Guinoiseau (Pb).