LA-MC-ICP-MS @ NIGL

Scientists can get often get a bit silly with acronyms. My favorite example is LA-MC-ICP-MS which stands for laser ablation multi-collector inductively coupled mass spectrometer. This instrumental method is used for in situ micro-analysis of solids. The primary application of this method is to measure the isotopic ratios of elements used in radiogenic and stable isotopic ratios. These ratios are generally applied to geochronology and using isotopic tracers wherein we can use the natural isotopic variations in radiogenic isotopes due to decay of radioactive elements to address geologic questions. In my case it is used for micro-analysis of various minerals (primarily zircon).

Let’s dissect this nasty acronym:

Laser Ablation is used to sample very small volumes of material for mass spectrum analysis. In micro-analysis, lasers come in two basic flavours: solid state and excimer. Both of these systems operate using UV lasers through two different mediums. An excimer laser uses a gas source (often argon fluoride) whereas a solid state laser uses an yttrium aluminum garnet that is doped with neodymium. Excimer lasers are used at much higher power than solid state laser generally producing more efficient and consistent ablations, however solid state laser are a fraction of the cost and do not require a gas recharge when they lose power.

Inductively Coupled Plasma is a plasma source that generated by electrical currents produced by electromagnetic induction. Lots of things to define here. Plasma is one of the four fundamental states of matter (along with solid, liquid, and gas). Just as heating a solid will change it to a liquid and then to a gas, heating a gas will often cause the gas to ionize by stripping off electrons. An ionized gas is by definition a plasma. Plasmas are generally maintained at very high energies and those used in mass spectrometry approach 10,000 degrees Kelvin (the surface of the sun is only 5800ºK). An ICP is used to ionize the ablated material sent from the laser system before it enter the mass spectrometer.

Mass Spectrometry is a deciphering the spectra of atomic masses of ionized material. This is done by bending a stream of ion with a magnet which splits the ions based on their mass-to-charge ratio. As the ions pass through the magnet, the lighter nuclei are diverted by the magnet more than heavier nuclei. These streams of nuclei now separated by their masses arrive at an electronic detector. This electronic detector is moved along a track at specified locations corresponding to specific atomic masses.

Multi-Collector is a type of mass spectrometer that has several detectors to capture multiple streams of ions of different masses simultaneously. This is especially important when you are analysing very small volumes of material and need to analyse a wide range of atomic masses because you don’t have time to slide the detector back and forth to capture the various masses.

Neptune Plus at the University of Western Australia

I have used multi-collectors of this kind in several institutions around the world although most recently at NIGL (the National Environmental Research Counsel Isotope Geoscience Laboratory) in the UK. The facility is also associated with British Geological Survey. NIGL is a world-class analytical facility with several mass spectrometers dedicated to a wide range of analyses. See their analytical facilities here.

Here is a day in the life of a LA-MC-ICP-MS.

Thanks to Camille for putting this together.

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