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Home arrow Engineering arrow Manipulation and Characterization of Electrosprayed Ions Under Ambient Conditions: Methods and Instrumentation

Ion Manipulation in Air Using a System of Curved 3D Printed Plastic Electrodes

Introduction

Mass spectrometry (MS) is arguably one of the most widely used scientific tools with applications ranging from complex mixture analysis [1, 2] to molecular biology [3] and even large-scale purification and materials preparation [4, 5]. Because the fundamental basis for MS relies on a low number of collisions, the operation of a mass spectrometer requires the establishment of a low pressure environment. The first forms of mass spectrometry required that ions be produced within the vacuum system of the instrument, greatly limiting the range of compounds that could be analyzed and the throughput of analysis. This problem was largely solved with the development of atmospheric pressure interfaces (APIs), which allowed for ions to be generated at atmospheric pressure, removed from the vacuum system necessary for mass analysis. As a direct result, ambient ionization methods were born. Ambient ionization methods allowed for a sample to be directly interrogated with little-to-no sample preparation [6]. While ambient ionization provides a means of sampling, the ions produced must still undergo transfer, focusing and analysis under vacuum conditions. This is problematic as vacuum pumps are perhaps the greatest barrier to overcome in the development of miniature MS systems due to both their size and the amount of power required for their operation, which limits their practical use in a number of application areas [7].

Another method of analyzing gas-phase ions, which doesn’t necessitate the use of a vacuum system is Ion mobility spectrometry (IMS). IMS is often coupled to MS platforms as a means to achieve another dimension of separation [8]. In IMS ions are separated based on their interaction with a background gas in combination with electric fields [9]. IMS instruments are typically operated at pressures much higher than that of an MS system, including atmospheric pressure; however, in order to attain acceptable resolution it is necessary to establish laminar gas flow throughout the analysis region as well as maintain a highly uniform pressure, temperature, and gas composition.

© Springer International Publishing AG 2017 25

Z. Baird, Manipulation and Characterization of Electrosprayed Ions

Under Ambient Conditions, Springer Theses, DOI 10.1007/978-3-319-49869-0_3

In their current forms, both MS and IMS share commonalities in regards to the creation of ions in the ambient environment and their subsequent transfer into an analysis region in which pressure, temperature, and humidity are well regulated. The spatial control of ions under vacuum is a mature subject and is employed in a wide range of instruments which includes MS and IMS systems as well as electron microscopes, particle accelerators, as well as a variety of surface analysis and modification methodologies [10, 11]. Yet, the control of ions at or near atmospheric pressure is much less developed, despite the rich chemistry accessible at these more manageable conditions. In recent years there have been a number of publications highlighting the unique reactivity of gaseous ions under ambient conditions and their use in the preparation of surfaces [12-15]. The manipulation and control of these ions is crucial if they are to be utilized to full potential.

The aim of this work is to perform all of the relevant tasks required for an MS or IMS system by demonstrating the generation and transfer of ions, their subsequent focusing, ion/molecule reactions in the gas-phase, separation of ions, and finally to detect ions; all performed in the ambient environment. Furthermore, all of these demonstrations are shown using plastic electrodes produced via rapid prototyping. Of which any lab equipped with a low-cost FDM 3D printer is capable of producing. In some experiments the device is used to prepare ions for subsequent analysis by a mass spectrometer while in other cases the electrodes are operated independently as a reactor/analysis system.

 
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