Department of Chemistry, Open Laboratory of Chemical Biology of the Institute of Molecular Technology for Drug Discovery and Synthesis, The University of Hong Kong, Pokfulam Road, Hong Kong SAR, PR China.
Rapid Commun Mass Spectrom. 2013 Mar 30;27(6):713-21. doi: 10.1002/rcm.6497.
Despite various porous materials having been widely adopted as spraying tips for direct sample analysis using electrospray ionization mass spectrometry (ESI-MS), the effect of surface property and porosity of spraying tip materials on their analytical performances is not clear. Investigation of their relationships could provide insight into the proper choice and/or design of spraying tip materials for direct sample analysis.
The effect of spraying tip materials with different polarities, including polyester and polyethylene (hydrophobic) and wood (hydrophilic), on the detection sensitivity for a variety of compounds, and on the ESI onset voltage, were studied using ESI-MS. The porosity of each type of spraying tip was characterized by scanning electron microscopy (SEM). Factors governing the detection sensitivity were determined based on the correlation of the detection sensitivity to the ESI onset voltage, the polarity, and the porosity of the spraying tip materials.
Hydrophobic tips (i.e., polyester and polyethylene) show better detection sensitivity for polar compounds but not for non-polar compounds, while hydrophilic tips (wooden tips) show the opposite effect. This phenomenon could be due to the difference in interaction between the analytes and the tips, causing the analytes to adsorb on the tip to different extents. In addition, the micro-porous nature of the tips could facilitate solvent diffusion for transporting analytes to the tip and maintain a stable spray for recording MS data. With the proper choice of spraying tip materials, trace amount of analytes at the picomole level can be detected with minimal sample pretreatment.
Both the polarity and the porosity of the spraying tip materials could significantly affect detection sensitivity for a wide variety of analytes. With proper choice of spraying tip material, ESI on a porous spraying tip could be a sensitive method for the direct analysis of daily life samples.
尽管各种多孔材料已被广泛用作电喷雾电离质谱（ESI-MS）直接样品分析的喷雾尖端，但喷雾尖端材料的表面性质和多孔性对其分析性能的影响尚不清楚。研究它们之间的关系可以深入了解直接样品分析中喷雾尖端材料的适当选择和/或设计。
使用 ESI-MS 研究了具有不同极性的喷雾尖端材料（包括聚酯和聚乙烯（疏水性）和木材（亲水性））对各种化合物的检测灵敏度以及 ESI 起始电压的影响。通过扫描电子显微镜（SEM）对每种类型的喷雾尖端的孔隙率进行了表征。根据检测灵敏度与 ESI 起始电压、极性和喷雾尖端材料的孔隙率之间的相关性，确定了决定检测灵敏度的因素。
疏水性尖端（即聚酯和聚乙烯）对极性化合物表现出更好的检测灵敏度，但对非极性化合物则不然，而亲水性尖端（木制尖端）则相反。这种现象可能是由于分析物与尖端之间的相互作用不同，导致分析物在不同程度上吸附在尖端上。此外，尖端的微孔性质可以促进溶剂扩散，将分析物输送到尖端，并保持稳定的喷雾以记录 MS 数据。通过选择合适的喷雾尖端材料，可以在最小的样品预处理下检测到皮摩尔级别的痕量分析物。
喷雾尖端材料的极性和孔隙率都可以显著影响各种分析物的检测灵敏度。通过选择合适的喷雾尖端材料，多孔喷雾尖端上的 ESI 可以成为直接分析日常生活样品的敏感方法。
