High-Speed, High-Resolution, Multielemental Laser Ablation-Inductively Coupled Plasma-Time-of-Flight Mass Spectrometry Imaging: Part I. Instrumentation and Two-Dimensional Imaging of Geological Samples

Abstract

Low-dispersion laser ablation (LA) has been combined with inductively coupled plasma-time-of-flight mass spectrometry (ICP-TOFMS) to provide full-spectrum elemental imaging at high lateral resolution and fast image-acquisition speeds. The low-dispersion LA cell reported here is capable of delivering 99% of the total LA signal within 9 ms, and the prototype TOFMS instrument enables simultaneous and representative determination of all elemental ions from these fast-transient ablation events. This fast ablated-aerosol transport eliminates the effects of pulse-to-pulse mixing at laser-pulse repetition rates up to 100 Hz. Additionally, by boosting the instantaneous concentration of LA aerosol into the ICP with the use of a low-dispersion ablation cell, signal-to-noise (S/N) ratios, and thus limits of detection (LODs), are improved for all measured isotopes; the lowest LODs are in the single digit parts per million for single-shot LA signal from a 10-μm diameter laser spot. Significantly, high-sensitivity, multielemental and single-shot-resolved detection enables the use of small LA spot sizes to improve lateral resolution and the development of single-shot quantitative imaging, while also maintaining fast image-acquisition speeds. Here, we demonstrate simultaneous elemental imaging of major and minor constituents in an Opalinus clay-rock sample at a 1.5 μm laser-spot diameter and quantitative imaging of a multidomain Pallasite meteorite at a 10 μm LA-spot size.

High‐resolution, Quantitative Element Imaging of an Upper Crust, Low‐angle Cataclasite (Zuccale Fault, Northern Apennines) by Laser Ablation ICP Time‐of‐Flight Mass Spectrometry

“…), only a few publications (Gundlach‐Graham et al . , Burger et al . ) report 100%‐mass‐normalised quantification across a heterogeneous material.…”

“…Elemental imaging was performed on a commercially available ICP‐ToF‐MS instrument (icp‐ToF; ToFWERK AG, Thun, Switzerland) combined with an argon fluoride (ArF) excimer LA system (193 nm, GeoLas C; Lambda Physik, Göttingen, Germany) and the low‐dispersion LA ‘tube’ cell (Gundlach‐Graham et al . ). Laser ablation was conducted in a helium atmosphere (99.999%; PanGas AG, Dagmersellen, Switzerland), and ablated aerosols were carried to the ICP‐MS in a stream of argon gas (99.996%; PanGas AG).…”

“…These gas flow rates are typical of our low‐dispersion LA system (Gundlach‐Graham et al . , Burger et al . ) and promote low‐dispersion aerosol transport to facilitate optimum pulse‐to‐pulse separation of ablated signals and thus improve lateral resolution.…”

Quantitative elemental imaging of heterogeneous catalysts using laser-induced breakdown spectroscopy

“…Acquisition rate of up to kHz has already been demonstrated [16]. Its high acquisition speed combined with its full compatibility with optical microscopy provide LIBS unique features compared to other elemental imaging methods such as laser ablation inductively coupled plasma mass spectrometry (LA-ICP-MS) [17][18][19], synchrotron radiation microanalysis (SXRF) [20][21][22][23][24], and electron probe micro-analysis (EPMA) [21,25,26]. Although these "gold standard" techniques may have a better sensitivity or spatial resolution, their relatively slow operation speed (generally limited to ∼1 Hz/pixel) makes LIBS very attractive for applications requiring fast imaging, 3D characterization and/or large-scale analysis.…”

Acquisition of fast transient signals in ICP-MS with enhanced time resolution

“…However, performing high resolution imaging within an acceptable time frame requires fast transit of the ablated material into the ICP-MS instrument. As a result, a number of rapid response interfaces have been developed, which provide baseline separated signals in less than 10 ms, [15][16][17] and are predicted to set the next paradigm in LA-ICP-MS technology. 18,19 For many years the software and hardware developed by instrument manufacturers did not evolve to meet the data acquisition requirements of the aforementioned fast transient applications.…”