Department of Chemistry and Biology, University of Siegen, Adolf-Reichwein-Str. 2, 57076, Siegen, Germany.
Research Center of Micro- and Nanochemistry and (Bio)Technology, University of Siegen, Adolf-Reichwein-Str. 2, 57076, Siegen, Germany.
Anal Bioanal Chem. 2022 Jun;414(15):4481-4495. doi: 10.1007/s00216-022-04045-z. Epub 2022 Apr 20.
Ambient desorption/ionization mass spectrometry (ADI-MS) is widely used as a rapid screening tool of samples in their native state without sample preparation. While analysis times are much less than 1 min per sample, one challenge of ADI-MS is the possibility to perform quantitative analysis of analytes in complex matrices. Typically, the goal is to probe a variety of different analytes in a complex matrix from a solid, liquid, or otherwise uncharacterized surface in the open air in front of the MS inlet. In this study, it is demonstrated that a carefully selected surface for analyte spot sampling and co-deposited isotopically labeled standards both significantly improve the capabilities of flowing atmospheric-pressure afterglow (FAPA) high-resolution (HR) MS for direct quantitative analysis. Specifically, a systematic study of different surfaces (glass, steel mesh, high-performance thin-layer chromatography (HPTLC) stationary phases including silica, reversed-phase (RP)-modified silica, and cyano (CN)-modified silica) and their suitability for spot sampling with FAPA-MS was performed. A set of different caffeine-containing standards and beverages (Red Bull, Coca-Cola, coffee, and black tea) was deposited on the surfaces and direct FAPA-HR-MS analysis of caffeine was performed using internal calibration with co-deposited C-caffeine. For TLC surfaces, it was demonstrated that quantitative results could be achieved with the matrix and concomitants present and that a preceding chromatographic separation was not mandatory for this application. In addition, the use of a CN-HPTLC surface resulted in a significantly more intense caffeine signal in the beverage samples compared to the other surfaces studied, with the highest increase compared to the silica (200-fold higher) and the lowest increase compared to the steel mesh (30-fold higher). The utilization of TLC-based surfaces as sample carriers is considered an attractive tool in the ADI-MS toolbox for fast and efficient mass spectrometric investigations of complex samples without time-consuming sample preparation.
环境解吸电离质谱（ADI-MS）被广泛用作一种快速筛选工具，可以在无需样品制备的情况下对原始状态的样品进行筛选。虽然分析时间比每个样品 1 分钟要短得多，但 ADI-MS 的一个挑战是有可能对复杂基质中的分析物进行定量分析。通常，目标是在 MS 入口前的空气中从固体、液体或其他未表征的表面上探测复杂基质中的各种不同分析物。在本研究中，证明了仔细选择的用于分析物斑点取样的表面和共沉积的同位素标记标准物都显著提高了流动大气压后流光（FAPA）高分辨率（HR）MS 进行直接定量分析的能力。具体来说，对不同表面（玻璃、钢网、高性能薄层色谱（HPTLC）固定相，包括硅胶、反相（RP）改性硅胶和氰基（CN）改性硅胶）及其在 FAPA-MS 中的斑点取样适用性进行了系统研究。将一组不同的含咖啡因标准品和饮料（红牛、可口可乐、咖啡和红茶）沉积在这些表面上，并使用共沉积的 C-咖啡因进行内部校准，对咖啡因进行直接 FAPA-HR-MS 分析。对于 TLC 表面，证明在存在基质和伴随物的情况下可以获得定量结果，并且对于这种应用，不需要进行预先的色谱分离。此外，与研究的其他表面相比，CN-HPTLC 表面导致饮料样品中的咖啡因信号强度显著增加，与硅胶相比增加最高（增加 200 倍），与钢网相比增加最低（增加 30 倍）。将 TLC 基表面用作样品载体被认为是 ADI-MS 工具包中的一种有吸引力的工具，可用于快速有效地对复杂样品进行质谱研究，而无需耗时的样品制备。
