Ambient MS in motion: 3D robotic sampling, dynamic ionization, and microplasmas

FACUNDO M. FERNÁNDEZ; RACHEL V. BENNET; EZEQUIEL M. MORZAN; JACOB O. HUCKABY; MARÍA EUGENIA MONGE; ROSANA ALBERICI; PRABHA DWIVEDI; JOEL KEELOR; MARTIN PAINE; JOSHUA SYMONDS; THOMAS ORLANDO; HENRICK I. CHRISTENSEN

Ginebra

Conferencia; IMSC 2014, 20th International Mass Spectrometry Conference; 2014

Introduction In this presentation we showcase several examples of on-going efforts where we exploit the unique characteristics of ambient mass spectrometric analysis that enable open air, direct ionization of target analytes on native surfaces and complex 3D objects. In contrast to «classical» ambient analysis which is typically performed in a static fashion (i.e. placing the sample at a fixed location respect to the ion source), we demonstrate a «dynamic sampling» procedure based on programing a dynamic probe trajectory in the gap between the ion source outlet and the mass spectrometer inlet, thus exploiting the thermal and flow velocity gradients that exist in this region in space. We also present a 3D surface sampling approach that combines features of both DART and PESI for probing non-planar surfaces through a machine vision system commanding a robotic arm. A new generation of miniaturized plasma ion sources that can be used for low-power ionization in field applications via either proton transfer or VUV photoionization mechanisms is also presented. Methods A quadrupole-time-of-flight mass spectrometer (microTOF Q-II, Bruker) equipped with a gas-ion separator tube interface (GIST, IonSense); a single stage time-of-flight mass spectrometer (AccuTOF, JEOL); an Orbitrap mass spectrometer (Exactive Plus, Thermo); and a triple quadrupole mass spectrometer (G6410AA, Agilent) were used. Microplasmas were built in-house either through a microfabrication procedure or a metal-insulator-metal automated approach. Robotic Plasma Probe Ionization (ROPPI) experiments were conducted by coupling a DART ion source (IonSense) to a home built PESI-type sampling device mounted on two different robotic arms: (a) a KUKA KR5 sixx R650 robot or (b) a Universal Robots UR5 six axis arm. Results Dynamic sampling, when coupled to ambient plasma ion sources, was shown to enable differential analyte desorption. This generated a transient characteristic profile for each target compound. By comparing the profiles of ion pairs, assignments could be made between precursor and fragment ions without the need for an ion isolation step. Three dimensional objects, such as model patterned spheres, produce, and clothing were effectively investigated with ROPPI MS, leading to the first automated ambient surface analysis tool for non-planar samples. Finally, experiments with various microplasmas operated in both AC and DC modes coupled to a new type of electrothermal vaporizer and operated with various discharge gases were carried out for the detection of contaminants of importance during manned space missions. The obtained detection limits met or were lower than those required for ensuring the safety of the space crew. Conclusions Ambient MS has matured but not plateaued, with many still-unmet challenges that can gain from the same characteristics that have made this field exciting from the very beginning. Novel Aspect Ambient MS is used for probing 3D surfaces in an automated mode and in a dynamic sample introduction mode. Miniature plasma ambient ion sources are also presented.