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In this study, we report a simple and economical ballpoint electrospray ionization mass spectrometry (BP-ESI-MS) technique. This combines a small ballpoint tip with a syringe pump for the direct loading and ionization of various samples in different phases (including solution, semisolid, and solid) and allows for additional applications in surface analysis. The tiny metal ball on the ballpoint tip exhibits a larger surface for ionization than that of a conventional sharp tip end, resulting in higher ionization efficiency and less sample consumption. The adamant properties of the ballpoint tip allow sampling by simply penetrating or scraping various surfaces, such as a fruit peel, paper, or fabric. Complex samples, such as fine herbal powders and small solid samples, could be stored in the hollow space in the ballpoint socket and subsequently extracted online, which greatly facilitated MS analysis with little to no sample preparation. Positive ion mode was attempted, and various compounds, including amino acids, carbohydrates, flavonoids, and alkaloids, were detected from different types of samples. The results demonstrated that the special and excellent physical characteristics of ballpoint tips allowed for fast and convenient sampling and ionization for mass spectrometry analysis by the BP-ESI-MS method.E lectrospray ionization (ESI) is a powerful mass spectrometric (MS) technique for the analysis of various compounds. In conventional ESI, intact ions are generated from large and complex species in solution upon application of a high voltage to the capillary. The development of nanoelectrospray ionization (nano-ESI), 1,2 which utilizes capillaries of ∼5 μm inner diameter, allows for less consumption of samples. However, capillary-based ESI techniques are prone to clogging and thus usually require time-consuming sample preparation prior to ESI-MS analysis. Along with the emergence of ambient ionization techniques, e.g., desorption electrospray ionization (DESI), 3 extractive electrospray ionization (EESI), 4 and other successively invented techniques, 5−7 the development of ESI on solid substrates (solid-substrate ESI) has significantly facilitated the direct analysis of complex samples with little to no sample preparation, extending the applications of ESI-MS. In the past 2 decades, various materials such as wick element, 8 copper wire, 9 metal needle, 10−12 optical fiber wired with a metal coil, 13,14 surface-modified glass rod, 15 and nanostructured tungsten oxide 16 have been successfully developed as emitters for ESI, which have improved the sampling and ionization processes and facilitated the analysis of various types of samples. Recently, the analysis of samples on surfaces or in difficult-to-access corners was accomplished by paper spray 17,18 or wooden tip 19 ESI-MS. Currently, solidsubstrate ESI techniques have been further extended to direct mass spectrometric analysis of biological tissue. 20−23 Because the ionization conditions of noncapillary ESI, such as loading of sample solutions on...

Electrospray ionization mass spectrometry (ESI-MS) technique has limitations in analysis of compounds that are dissolved in nonpolar solvents. In this study, ambient ionization of compounds in solvents that are not "friendly" to electrospray ionization, such as n-hexane, is achieved by conductive nanomaterials spray ionization (CNMSI) on nanomaterial emitters, including carbon nanotubes paper and mesodendritic silver covered metal, which applies high voltages to emitters made of these materials without the assistance of polar solvents. Although the time intensity curves (TIC) commonly vary from 4.5% to 23.7% over analyses, protonated molecular ions were found to be the most abundant species, demonstrating good reproducibility of the technique in terms of ionized species. Higher mass spectrometric responses are observed in analyzing nonpolar systems than polar systems. 2-Methoxyacetophenone, 4-methylacetophenone, benzothiazole, quinolone, and cycloheptanone as low as 2 pg in n-hexane can be directly detected using the developed method. The developed technique expands the analysis capability of ESI-MS for direct, online analysis of nonpolar systems, such as low polarity extracts, normal phase liquid chromatography eluates, and synthetic mixtures. Graphical Abstract.