Significance of the Paper
Mass spectrometry (MS), as one of the greatest analytical techniques of the 20th century, has become an indispensable analytical tool in various scientific fields such as chemistry, life sciences, biomedicine, pharmaceutical research, and disease diagnosis. Ion sources are among the most essential components of mass spectrometry (MS) and have evolved from early electron impact (EI), chemical ionization (CI), and electrospray ionization (ESI) to various types of ambient ionization technologies, providing multidimensional application scenarios for mass spectrometry analysis. Due to the large variances in the chemical characteristics of the analytes, it is difficult to cover all the analytes by a single ionization technology. An ion source with full analytical coverage is not only helpful for the analysis of complex samples, leading to the creation of more specific fingerprints, but also eliminates the need for additional mass spectrometry. Me and my co-workers belong to the College of Electronics and Information Technology and the Department of Chemistry, respectively. We hope to seek new opportunities for the advancement of mass spectrometry science through the intersection of disciplines, and to propose a new concept of digital ionization through this work.
Paper summary
Due to the limitations posed by existing ion sources utilized in ambient mass spectrometry, we propose a wide-energy programmable microwave plasma-ionization mass spectrometry (WPMPI-MS) system. The system can digitally input different function waveforms to rapidly screen plasma ionization energy, thus enabling high-coverage MS analysis of compounds with different properties. This ionization system can achieve similar ionization modes as various mainstream ion sources, including ESI, APCI, EI, and ICP. By accurately manipulating the plasma power through digital means and utilizing pneumatic nebulizer, this method can flexibly achieve soft/hard ionization, insource cleavage, and element desorption.
The WPMPI-MS system performed well in the analysis of real samples, rapidly analyzed nine toxicological standards in one drop of serum, and demonstrated good quantification and LC coupling capability. Furthermore, the capability of WPMPI to concurrently detect PFAS and heavy metal contamination was validated through spiked soil samples, while the direct analysis capacity for solid samples with complex matrices was tested using Yunnan Baiyao powder. The ability of WPMPI-MS to cope with non-targeted analysis of actual samples was also verified using landfill leachate, demonstrating the wide coverage capability of the method. The technology analyzes a much wider range of compounds than existing ion sources, and the programmable energy scanning mode leads to more flexibility and functionality during analysis.
Prospect
WPMPI-MS offers advanced coverage of analyte species compared to conventional ion sources, and is also electrically simpler than the complex combined AMS technique. Digital, fast-switching, high-coverage mass spectrometry allows for minimal sample consumption in the analysis of complex samples. Based on these advantages, we anticipate that the technology will be widely utilized in analytical chemistry and provide an alternative way to address the scalability problem in commercial mass spectrometry.
In a follow-up study, a microwave power supply with higher power could enhance the elemental analysis ability of this method. On the other hand, the method commonly uses a nebulizer to feed the sample, which can be integrated as an electrospray ion source by adding high voltage to the nebulizer selectively, thus introducing analytical capabilities for native biomolecules. In the initial submission, we used the concept of digital ionization because we wanted to make analytical chemistry more accurate and faster. The ionization process of an ion source is essentially a chemical reaction, and in the future, perhaps digitally programmable modulation of chemical reactions could lead to the development of innovative techniques and ideas.
Wide-energy programmable microwave plasma-ionization for high-coverage mass spectrometry analysis
