Sub-micrometer Nanosecond LA-ICP-MS Imaging at Pixel Acquisition Rates above 250 Hz via a Low-Dispersion Setup
Stijn J.M. Van Malderen, Thibaut Van Acker, Frank Vanhaecke
In this paper, the authors characterize the performance of a new low-dispersion laser ablation system, as demonstrated in ultra-fast and highest-resolution elemental imaging in combination with different ICPMS instruments, including the icpTOF 2R. Imaging rates of 300 pixels/s at 5 μm spatial resolution on a geological sample, and 100 pixels/s at 0.6 μm resolution on a biological sample are demonstrated.
The analytical figures of merit of a low-dispersion (ultrafast) ablation cell geometry within the Cobalt ablation chamber, integrated into a nanosecond laser ablation–inductively coupled plasma-mass spectrometer system, are reported. The system was investigated for its capability for fast high-resolution elemental imaging. A spot of 0.6 μm diameter was achieved on the sample surface by aperture imaging of a 10 μm pinhole. The resulting conical crater (0.6 μm ⌀ × 130 nm↓) morphology in a Au-coated glass target and carbon-coated silica wafer was characterized with atomic force microscopy. The Cobalt ablation chamber is based around a motorized height-adjustable tube cell, which allows modulating the sampling distance, i.e. the distance between the sample surface and the cell inlet, in a dynamic manner. This distance was observed to influence the single pulse response profile. The variation of the average signal intensity at multiple sample heights within a range of 0.5 mm was <3% RSD. Under optimum conditions, single pulse responses with a full width at 10% of the maximum peak intensity (FW0.1M) of ∼1 ms can be achieved for 238U upon ablation of NIST SRM612 glass, effectively opening the way to pixel acquisition rates up to 1 kHz. To demonstrate the potential of this technology, the elemental distribution of Zn in small intestine villi of mice subjected to a Zn-enriched diet was imaged using the 0.6 μm spot size, and rapid imaging of a zircon grain cross-section was performed.