Heide, Maximilian
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Publication Access status: Metadata only , Chemical analysis of electronic cigarette liquids (e-liquids) and direct nicotine quantitation using surface-assisted flowing atmospheric-pressure afterglow desorption/ionization mass spectrometry (SA-FAPA-MS)(2023); Surface-assisted flowing atmospheric-pressure afterglow mass spectrometry (SA-FAPA-MS) was succesfully used for direct and rapid analysis of e-liquids including qualitative screening and accurate nicotine quantification.Source Type:Article1 - Some of the metrics are blocked by yourconsent settings
Publication Access status: Metadata only , Effect of Sample Plates and Sample Matrix on the Quantification Capabilities of Surface-Assisted Flowing Atmospheric-Pressure Afterglow Mass Spectrometry (SA-FAPA-MS)(2023); Ambient desorption/ionization mass spectrometry (ADI-MS) has been broadly applied to accomplish direct analysis without sample preparation or separation. However, quantification capabilities and analytical performance are sometimes limited. Here, we report signal enhancement effects and improved quantification capabilities in plasma-based ADI-MS, when a flowing atmospheric-pressure afterglow (FAPA) source is used to probe analytes on tailored thin-layer chromatography (TLC) plates. It was found that quantitative results could be achieved when the TLC plate merely served as a sampling plate without a preceding separation step. Specifically, the dynamic response of caffeine, nicotine, acetaminophen, and progesterone was investigated with FAPA-MS on a variety of different TLC surfaces (normal-phase silica, reversed-phase-modified silica, cyano [CN]-modified silica, and dimethyl [RP2]-modified silica). All analytes were studied as single-analyte standards and in a multianalyte mixture to evaluate the effect of sample plates and sample matrix on analytical performance and competitive ionization processes. Overall, dimethyl (RP2)- and CN-modified silica resulted in superior performance compared to other TLC materials. After careful optimization and without the use of internal standards, linear ranges of five orders of magnitude were accessible for caffeine and nicotine. Limits of detection down to femtomole amounts of analyte were achieved. Quantitation limits using RP2-TLC and FAPA-MS were 0.062, 0.062l, 0.31, and 14 pmol for caffeine, nicotine, progesterone, and acetaminophen, respectively. Interestingly, the presence of nicotine at relatively high amounts reduced the signal of the other analytes, an observation that was found to correlate with the differences in the enthalpy of vaporization (Δ H vap ) and proton affinity. To prove the quantitative capabilities, nicotine quantification in a real matrix-heavy e-liquid sample was demonstrated using an isotopically labeled standard. The use of TLC-based surfaces with FAPA-MS can aid in the direct and quantitative mass spectrometric investigation of complex mixtures.Source Type:Article1 - Some of the metrics are blocked by yourconsent settings
Publication Access status: Open Access , Surface-Assisted Flowing Atmospheric-Pressure Afterglow Mass Spectrometry (SA-FAPA-MS)(2025)Analytical chemistry plays a crucial role in ensuring the safety, quality, and authenticity of products and processes, e.g. in the food and beverage industry, pharmaceutical production, but also in forensics, diagnostics, and environmental sciences. One of its most powerful tools is mass spectrometry (MS) which allows scientists to selectively detect substances even at lowest amounts. Conventional MS techniques usually require extensive and complex sample preparation and additional separation procedures which make them time-consuming, resource-intensive and therefore costly. A novel approach known as ambient desorption/ionization MS (ADI-MS), offers a faster and more sustainable alternative by allowing direct analysis of samples in their original state. This dissertation presents the development, optimization, and application of a specific ADI-MS technique termed surface-assisted flowing atmospheric-pressure afterglow MS (SA FAPA MS). This method is based on a plasma-based ionization source in combination with functionalized sample carrier surfaces and enables rapid, preparation-free detection of small molecules in matrix-containing samples, e.g. in beverages, pharmaceutical products or even body fluids. One core goal was to improve the quantitative capabilities of SA FAPA MS as ADI MS in general faces challenges regarding signal stability and overall reproducibility. A key finding was that the choice of the sampling surface dramatically influences performance. Among the surfaces tested, cyano- and dimethyl-functionalized thin-layer chromatography (TLC) plates performed better than conventional supports such as glass or metal mesh. These surfaces enabled higher ion yields, better signal stability, and broader dynamic ranges, ultimately leading to detection limits down to the femtomole (fmol) range. The method was successfully applied to accurately quantify model substances in beverages and electronic cigarette liquids even when matrix effects were expected. Precision and accuracy were further improved by isotopically labeled standards. Further, the semi-quantitative detection of benzocaine in human saliva demonstrated the potential for biomonitoring and diagnostic applications. For the applications above, SA FAPA MS proves to be a fast, sensitive, and sustainable alternative to conventional MS methods. Minimal sample pre-treatment requirements, versatility, and high throughput make it very attractive for use in quality control, toxicology, diagnostics, and environmental monitoring where accurate results are required as quickly as possible.Source Type:Doctoral Thesis11 35
