Heide Maximilian, Engelhard Carsten
Department of Chemistry and Biology, University of Siegen Adolf-Reichwein-Str. 2 Siegen 57076 Germany
Research Center of Micro- and Nanochemistry and (Bio)Technology, University of Siegen Adolf-Reichwein-Str. 2 Siegen 57076 Germany.
RSC Adv. 2023 Aug 14;13(34):24150-24161. doi: 10.1039/d3ra03931e. eCollection 2023 Aug 4.
Ambient desorption/ionization mass spectrometry (ADI-MS) has been widely used for direct analysis of real samples without sample preparation or separation. Studies on the quantification of low molecular weight compounds in complex matrices with ADI-MS remain scarce. In this paper, we report the application of surface-assisted flowing atmospheric-pressure afterglow mass spectrometry (SA-FAPA-MS) for fast qualitative screening of electronic cigarette liquid (e-liquids) ingredients and direct quantification of nicotine. The quantification approach is rapid, uses a deuterated D-nicotine standard spike, and does not require a preceding chromatography step or other methods to remove the complex sample matrix. Selected e-liquids were directly applied on thin-layer chromatography (TLC) plate surfaces (normal phase (NP) silica, reversed phase (RP) modified silica, cyano (CN) modified silica, and dimethyl (RP2) modified silica) after dilution and internal standard spiking. The plates served purely as sample carriers and no analyte separation was performed. Promising qualitative results were obtained, demonstrating the ability to detect nicotine alkaloids using this approach and the ability to differentiate e-liquids based on their flavor variations. In addition, dimethyl- (RP2-) and cyano-modified (CN-) silica surfaces were selected for quantification based on performance results of previous studies. It was shown that results were in high accordance with high-performance liquid chromatography (HPLC) experiments with lowest deviations <3% on dimethyl surfaces. Additional quantitative experiments including a certified reference material achieved equally satisfying results with lowest deviations of -1.1% from the certified nicotine content. For nicotine, detection limits down to the fmol range (96 fmol on CN and 20 fmol on RP2) were obtained. A detailed comparison of glass surfaces with functionalized surfaces showed that the functionalized surfaces were superior in terms of sample application reproducibility, mass spectra quality, sensitivity, and information density. Thus, functionalized thin-layer surfaces are considered promising tools for both qualitative and quantitative ADI-MS analysis of complex samples.
常压解吸/电离质谱（ADI-MS）已被广泛用于无需样品制备或分离的实际样品直接分析。利用ADI-MS对复杂基质中低分子量化合物进行定量分析的研究仍然很少。在本文中，我们报道了表面辅助流动大气压余辉质谱（SA-FAPA-MS）在电子烟液（电子烟油）成分快速定性筛选和尼古丁直接定量分析中的应用。该定量方法快速，使用氘代D-尼古丁标准品加标，且无需预先进行色谱步骤或其他方法去除复杂的样品基质。将选定的电子烟油稀释并加入内标后，直接涂覆在薄层色谱（TLC）板表面（正相（NP）硅胶、反相（RP）改性硅胶、氰基（CN）改性硅胶和二甲基（RP2）改性硅胶）。这些板仅用作样品载体，不进行分析物分离。获得了有前景的定性结果，证明了使用该方法检测尼古丁生物碱的能力以及根据风味差异区分电子烟油的能力。此外，根据先前研究的性能结果，选择二甲基（RP2）和氰基改性（CN）硅胶表面进行定量分析。结果表明，与高效液相色谱（HPLC）实验结果高度一致，在二甲基表面的最低偏差<3%。包括有证标准物质在内的其他定量实验也取得了同样令人满意的结果，与认证的尼古丁含量的最低偏差为-1.1%。对于尼古丁，检测限低至飞摩尔范围（在CN上为96飞摩尔，在RP2上为20飞摩尔）。对玻璃表面与功能化表面的详细比较表明，功能化表面在样品涂覆重现性、质谱质量、灵敏度和信息密度方面更具优势。因此，功能化薄层表面被认为是复杂样品定性和定量ADI-MS分析中有前景的工具。
