Development of the vibrating capillary nebulizer sample introduction system for inductively coupled plasma mass spectrometry
Date
2024-12
Authors
Taylor, Tristen Leslie
Major Professor
Advisor
Anderson, Jared
Gundlach-Graham, Alexander
Lee, Young-Jin
Anand, Robbyn
Zaikina, Yulia
Committee Member
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Abstract
This dissertation focuses on a new sample liquid introduction system for inductively coupled plasma mass spectrometry (ICP-MS) called the vibrating capillary nebulizer (VCN). The VCN operates non-pneumatically creating an aerosol using mechanical vibrations from a piezoelectric transducer. This work discusses the development and characterization of the nebulizer and then explores applications where the VCN can overcome challenges inherent to pneumatic nebulization for the specific analysis techniques. Chapter 1 presents an overview of the fundamentals of ICP and common mass analyzers utilized for ICP-MS, but is primarily focused on conventional liquid sample introduction systems and presenting the state-of-the-art in the field. This chapter serves to provide background on the technical details of liquid sample introduction as well as important literature on the subject to establish the goals of the presented work and challenges the VCN can overcome. Chapters 2-5 present research articles, which have previously been published or are in the process of being published in peer-reviewed journals.
Chapter 2 presents the first work with the VCN discussing its development and characterization. This chapter describes in detail the assembly of and operation of the VCN. Also described in this work is the associated sample introduction chamber and the use of 3D printers to create these systems. The characterization studies included are multielemental calibrations to explore the use of the VCN for routine analysis, a study of sample transport efficiency and absolute sensitivity at varying sample flow rates, a systematic study of the signal response when turning voltage and frequency inputs, and evaluation of the long-term stability of nebulization. We found that with the VCN, we achieve detection limits in the ppt range and relative sensitivities as high as 1.98×104 cts/s / ng/mL. We show the range of frequency and voltage inputs that the VCN operates at and demonstrate a sensitivity increase of two orders of magnitude in this range. Finally, we show minimal drift in signal with the VCN in a 45-minute measurement, showing the potential utility of the device for hyphenation to separation techniques which can require long analysis times.
Chapter 3 discusses the feasibility of the VCN sample introduction system for single cell inductively coupled plasma time-of-flight mass spectrometry (scICP-TOFMS). As a non-pneumatic nebulizer, the VCN provides a gentler nebulization event for delicate cell samples which could be key in preserving cell integrity for single cell analysis. In this study, we first analyze standard nanoparticles and rare earth element doped microplastic calibration beads to validate the VCN for single cell analysis and determine the most accurate calculation method for calibration. We then measure standard salinized yeast cells quantifying intracellular Se and Fe in each cell. We find that with the VCN, we can accurately quantify mass and size of standard Pt nanoparticles and when using the particle frequency method we measure accurate particle number concentrations. We measure salinized yeast with a critical value of 1 fg and show a bimodal distribution in the yeast cell population. The VCN sample introduction system proves to be feasible for single cell analysis but requires additional modifications to the sample introduction chamber to improve results.
Chapter 4 describes the use of the VCN for capillary electrophoresis (CE) ICP-MS. CE-ICP-MS is traditionally limited by self-aspiration of pneumatic nebulizers which causes band broadening in the separation profile. Being the VCN operates absent of pneumatic gas, it performs CE without the influence of self-aspiration. In this work, we describe the modifications made to the sample introduction system to perform CE. Then, complete a comparative study between the VCN and commercially available nebulizers for CE using the speciation of sulfur in river water as a model. We find that VCN performs comparably to the commercial interfaces. Peak area calibrations with the VCN show high linearity (R2=0.9956) and we find good reproducibility with an RSD of 4.1% between three replicate measurements of a standard. For the quantification of sulfate, we find no statistical difference between the results for the three CE interfaces and ion chromatography. Finally, we find lower limits of detection for the VCN versus the commercial nebulizers.
Chapter 5 explores a different line of work; the curiosity for this study was sparked while using 3D printed sample introduction chamber with the VCN and observing interferences in the mass spectra. In this work, we explore the characterization of metal containing particulate matter (PM) released by 3D printers using single particle (sp) ICP-TOFMS. We describe the development of a sampling and extraction procedure using a positive pressure acrylic chamber which allows us to limit the collection of environmental background particles as well as deposit 3D printer PM on membrane filters. We analyze commonly used thermoplastic filaments for fused deposition modeling 3D printers including acrylonitrile butadiene styrene (ABS) and polylactic acid (PLA) and a specialty filament which contains embedded stainless-steel particles. In the thermoplastic filaments, we measure single metal Fe particles as the most common particle type and single metal Al, Ti, Zr, and Bi is also commonly measured. We also measure unique multi metal particles in each filament type. Using the specialty filament, we measure characteristic stainless-steel particles in the aerosol, showing confidently that a fraction of the embedded particles are released during printing.
Chapter 6 provides general conclusions for the work described in chapter 2-5. This chapter also provided potential future work and directions for the VCN as well as for the analysis of 3D printer particulate matter using spICP-TOFMS.
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dissertation