Chemical sampling of 3D objects has become increasingly important, particularly in forensics and drug screening. After a proof-of-concept study using a 3D camera and robotic arm to take samples for plasma ionization (1), Facundo Fernandez and his team at Georgia Tech wanted to improve on the analysis, by combining robotic surface analysis – or RoSA – with mass spectrometry. Fernandez tells us more.
Why combine robotics and mass spec in this way?
As mass spectrometers have grown more user-friendly and powerful, the bottleneck in the analytical pipeline has become the sampling process. I feel it’s time to marry advances in automation and machine learning with mass spectrometry, opening new possibilities in analytics of complex systems. Electrospray ionization (ESI) and matrix-assisted laser desorption ionization (MALDI) can be seen as the first mass spectrometry revolution, and ambient methods, such as desorption electrospray ionization (DESI) and direct analysis in real time (DART), can be seen as the second – I foresee that the third revolution will involve the “rise of the robots!”How does RoSA-MS work?
A 3D laser scanner mounted on a robotic arm scans the object, producing a 3D representation. The user then selects points to be sampled on the surface of this representation using custom-built software. The robotic arm moves sequentially through each one of these points, “touching” the surface with a sampling probe (a spring-mounted thin needle), then placing this needle into an open sampling port that washes away the material collected. The material is dissolved by the carrier solution, and directed to an ESI ion source, where it is ionized and then mass analyzed, giving the user a mass spectrum for each point. Because ESI is such a broadband ion source, many compounds can be studied in this way – and less polar compounds can be investigated by using a different ion source, such as a photoionization or chemical ionization.What’s the potential impact?
The sky’s the limit! In the pharma industry, for example, it could detect substandard products in an assembly line by rapidly using the computer vision capabilities of the system to scan 3D objects (such as a tablet), and then probing its composition quickly without having to crush, dissolve, and analyze by HPLC. It could also be used to map tissue samples in 3D, or investigate the composition of small volumes of precious biofluids on non-planar surfaces.Any plans for further advancement?
We are planning on arming the robots with lasers! We would like to develop a next-gen system that uses a laser ablation probe for sampling the surface, which should increase our spatial resolution and generate more detailed images. We would also like to investigate its clinical applications in the fields of high throughput diagnostics and metabolomics.Newsletters
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References
- RV Bennett et al,“Robotic plasma probe ambient ionization mass spectrometry imaging of non-planar surfaces”, Analyst, 139, 2658-2662 (2014). Anyin Li et al., “Robotic surface analysis mass spectrometry (RoSA-MS) of three-dimensional objects”, Anal Chem, 20, 3981–3986 (2018).