固态复杂基体样品的直接电离一般仅发生在样品浅层表面，对固体内部深层物质的质谱分析往往需将样品破碎后才能进行。本研究以蒜瓣样品为例，无需样品预处理，带电的甲醇溶液以2μL/min持续流经蒜瓣深层组织，内部组织中的化学物质选择性地溶解到流动液中，并在蒜瓣组织的尖端形成电喷雾，产生相应气态离子供后续质谱分析。在正离子检测模式下，实验记录了两种蒜瓣样品（共24个）、经不同方式贮存加工后的同种蒜瓣样品（共36个）在m/z50-2000范围内的化学指纹谱图，并将指纹谱图数据进行主成分分析（PCA），获得了令人满意的分组结果。研究表明，电喷雾内部萃取电离质谱（iEESI-MS）可以直接获取蒜瓣内部组织生物化学信息，鉴定蒜瓣组织中重要的化学成分（如蒜氨酸、蒜素、精氨酸、多糖等），快速识别蒜瓣组织中代谢组分的变化。本方法无需样品预处理、操作简单、分析速度快（单个样品分析时间小于2min），最大程度避免了生物组织分析过程中活性物质受环境作用（如酸解、空气氧化等）的降解，有望为生物组织样品的代谢组学研究提供一种直接、快速的质谱分析方法。
Theapplicationofinternalextractiveelectrosprayionizationmassspectrometry(iEESI-MS)was extended to direct molecular analysis of garlic tissues. By obviating time-consuming sample preparations, fragile active garlic substances such as organosulfur compounds ( e. g. , alliin, allicin ) were successfully detected and identified via collision-induced dissociation ( CID) , together with amino acids ( e. g. , arginine) and saccharides ( glucose, polysaccharides) . Mass spectral fingerprints of different kinds of garlic cloves, as well as various post-treatment ones, were further processed via principal component analysis ( PCA) to better visualize the differences. Our experimental results indicated that iEESI-MS allowed rapid recognition of metabolic changes in the garlic tissue subject to various external stimuli. The merits included simplicity of analysis, high speed ( less than 2 min per sample ) , good specificity, and minimal disturbance to the bioactivity of analytes.
