In Situ Analysis of Plant Tissue Using Arc iKnife Ionization Mass Spectrometry

Abstract

This study developed a portable arc iKnife ionization mass spectrometry (AII-MS) technique integrating a surgical knife with low-temperature arc plasma to interact with plant tissues. The thermal energy from the arc plasma induces the sputtering of water-containing plant tissues, leading to the formation of aerosols. These aerosols are then charged by plasma-generated ions, producing charged microdroplets that are ultimately detected by a mass spectrometer. AII-MS effectively mitigates the challenges of aerosol or tissue charring associated with arc ionization. Moreover, appropriate nitrogen cooling minimizes surface damage to plant samples, while the carrier gas facilitates the efficient generation and transfer of aerosols. Comparative analyses conducted before and after tissue cutting with a surgical knife revealed that this technology is well-suited for examining various fresh and dried plant tissues including seeds, fruits, leaves, roots, stems, flowers, and bark. The characteristic components were identified under both positive and negative ion modes. Notably, potassium nitrate was detected in various plant samples for the first time, which may be attributed to its extensive use as a nutrient in vegetable cultivation. In summary, the developed AII-MS can effectively be used for plant tissue analysis, demonstrating high throughput, environmental sustainability, rapid processing, and reliability.