Wen Xiujuan, Dagan Shai, Wysocki Vicki H
Department of Chemistry, University of Arizona, Tucson, Arizona 85721, USA.
Anal Chem. 2007 Jan 15;79(2):434-44. doi: 10.1021/ac061154l.
Silicon nanopowder (5-50 nm) was applied as a matrix for the analysis of small molecules in laser desorption/ionization mass spectrometry. In contrast with conventional matrix-assisted laser desorption/ionization (MALDI) time-of-flight mass spectrometry, the matrix background interference in the low mass range was significantly reduced. Effects of the particle size and sample preparation procedures on the background mass spectra and the analyte signal intensity have been investigated, and an optimized powder and sample preparation protocol was established. Several surface characterization tools have been applied as well. Both positive mode and negative mode laser desorption/ionization have been applied to different analytes including drugs, peptides, pesticides, acids, and others. Detection limits down to the low femtomole per microliter levels were achieved for propafenone and verapamil drugs. The method developed was found relatively tolerant to salt contamination, which allowed the direct analysis of morphine and propaphenone in untreated urine and triazine herbicides in a soil extract. The new silicon-nanoparticle-assisted laser desorption ionization method was found to be highly selective, which may be due to analyte-dependent precharging in solution, prior to vacuum laser desorption. Some aspects of the charge-transfer mechanism have been studied and discussed. In comparison with standard MALDI matrixes, the silicon nanopowder requires much lower laser fluence (contributing to a reduced background) has much better surface homogeneity, and is more tolerant to salt interference, which makes it an easily applicable practical tool at a potentially low cost.
硅纳米粉末（5 - 50纳米）被用作激光解吸/电离质谱中分析小分子的基质。与传统的基质辅助激光解吸/电离（MALDI）飞行时间质谱相比，低质量范围内的基质背景干扰显著降低。研究了粒径和样品制备程序对背景质谱和分析物信号强度的影响，并建立了优化的粉末和样品制备方案。还应用了几种表面表征工具。正模式和负模式激光解吸/电离均已应用于不同的分析物，包括药物、肽、农药、酸等。对于普罗帕酮和维拉帕米药物，检测限低至每微升低飞摩尔水平。所开发的方法对盐污染具有相对耐受性，这使得可以直接分析未经处理尿液中的吗啡和普罗帕酮以及土壤提取物中的三嗪类除草剂。发现新的硅纳米颗粒辅助激光解吸电离方法具有高度选择性，这可能是由于在真空激光解吸之前，溶液中分析物依赖的预充电作用。已经研究和讨论了电荷转移机制的一些方面。与标准MALDI基质相比，硅纳米粉末所需的激光能量密度低得多（有助于降低背景），具有更好的表面均匀性，并且对盐干扰更具耐受性，这使其成为一种潜在低成本且易于应用的实用工具。
