Graduation Term
2024
Degree Name
Master of Science (MS)
Department
Department of Chemistry
Committee Chair
Christopher C Mulligan
Abstract
Trace metal species are relatively common in our environment, and although some are essential to sustain life, exposure to elevated levels of toxic metals can detrimentally affect both human and animal health. Correspondingly, monitoring of such contaminants in environmental systems is critical to public safety. While various methods exist for sensitive and selective metal analysis for such applications, there remains a need for a rapid, cost-effective, and, ideally, portable solution for expedited results and more impactful remediation and sustainability initiatives. Here, we investigate the use of 3D-printed cone spray ionization-mass spectrometry (3D-PCSI-MS), a newer, spray-based ambient ionization method, with specialty reagents to allow on-demand trace metal profiling in relevant samples. Here, conical vessels are mass produced via 3D-printing with conductive polymeric filament – this produces a rugged and conductive cone that can be directly filled (or used to scoop) solid samples. The addition of an appropriate spray solvent induces both analyte extraction and subsequent spray-based ionization when high voltage is applied directly to the cone. Filtration of fine solids (e.g., soils, etc.) is accomplished by an integrated filter paper stage. For priority metal pollutants, reagents are doped into the spray solvent to employ real-time chelation reactions that produce complexes more amendable to mass spectral analysis. Through Positive-ion high resolution mass spectra, it was shown that 3D-PCSI-MS readily produced highly specific and sensitive metal complexes from environmental soil samples when using such reagents, with confirmation accomplished from accurate mass data and isotopic distributions. Several priority metals were investigated in this proof-of-principle study, including lead, mercury, arsenic, nickel, cobalt, zinc, cadmium, copper, bismuth, and silver. Optimization of the method included chelator selection, metal:chelator molar ratio, and spray solvent composition, amongst others. Interestingly, certain metals demonstrated concentration-based dependence regarding the most abundant complex observed in collected spectra. Systematic studies were undertaken to determine the detection limit, robustness, and repeatability of this novel metal contaminant profiling methodology. Detection limits ranged from low part-per-million (ppm) to high part-per-trillion (ppt) in soil matrices, demonstrated trace metal profiling capability. Total analysis time (which included sampling, analysis, and interpretation) was determined to be less than 4 min./sample, and replicate measurements produced modest reproducibility and a low propensity for inter-sample carryover events. The effects of analyte concentration and pH were studied from moderate-size replicate samples which will be discussed along with other findings in this work. Representative soil samples, included lab-generated standards of exact concentration and standard reference materials, were examined to demonstrate applicability of this 3D-PCSI¬-MS methodology toward metal-contaminated soils.
Access Type
Thesis-Open Access
Recommended Citation
Chilaka, Jonathan Nzubechi, "Rapid, Direct Screening of Priority Metal Contaminants in Environmental Systems with Reactive 3 D-Printed Cone Spray Ionization-Mass Spectrometry ( 3 D- Pcsi-Ms )" (2024). Theses and Dissertations. 1969.
https://ir.library.illinoisstate.edu/etd/1969
DOI
https://doi.org/10.30707/ETD2024.20240827063556510068.999994