基于顶空及表面增强拉曼散射(SERS)结合的葱属植物挥发性物质研究

为了在常温下鉴定新鲜植物样品的挥发性物质，且避免繁杂前期样品的制备过程，将新鲜样品切细后置入顶空瓶中，用注射器抽取顶空瓶上方的挥发性物质注入用微波法制备的纳米银溶胶中，用R-3000便携式拉曼光谱仪进行SERS的测量。获得了葱属植物大蒜、韭菜、葱的挥发性物质的表面增强拉曼光谱(SERS)。大蒜的SERS谱中较强的峰出现在307，399，569，711，1 182，1 287，1 397，1 622 cm-1处。韭菜的SERS谱中最强的峰出现在672 cm-1，较弱的峰出现在274，412，575，1 185，1 289，1 396，1 618 cm-1处。葱的SERS谱中最强的峰出现在693 cm-1，次强峰出现在372，888，1 023 cm-1处，较弱的峰出现在1 088，1 211，1 322 cm-1。获得二烯丙基二硫(diallyl disulfide)、烯丙基甲基硫醚(allylmethyl sulfide)、1-丙硫醇(1-Propanethiol)的液态、气态的SERS谱。经对比研究得出：吸附在银表面的大蒜、韭菜、葱的主要挥发性物质分别是二烯丙基二硫(diallyl disulfide)、烯丙基甲基硫醚(allyl methyl sulfide)、1-丙硫醇(1-Propanethiol)。同是葱属植物但不同种大蒜、韭菜、葱其吸附在银表面的主要的挥发性物质不一样，吸附在银表面的各种葱的主要挥发性物质都是1-丙硫醇。该实验结果表明顶空与SERS结合，不需要复杂的提取过程，可直接用于新鲜植物的挥发性物质快速检测。

Study of Volatile Organic Compounds of Fresh Allium Species Using Headspace Combined with Surface-Enhanced Raman Scattering

In order to identify volatile organic compounds of fresh plants at room temperature and avoid sample pretreatment and extractions which can be labor intensive, garlic, Chinese chives and scallion were chopped into pieces. Then some of them were placed in the headspace vial and sealed. The gases were drawn from the vial with a syringe and were injected very slowly into Ag colloids for test using R-3000 portable Raman spectrometer. The spectra of volatile organic compounds of allium species, fresh garlic, Chinese chive and shallot plants were successfully recorded for the first time. For garlic high intensity bands are present at 307, 399, 569, 711, 1 182, 1 287, 1 397 and 1 622 cm-1. For Chinese chives the high intensity band is present at 672 cm-1. Low intensity bands are present at 274, 412, 575, 1 185, 1 289, 1 396, 1 618 cm-1. For shallot high intensity bands are present at 693 cm-1. Lower intensity bands are present at 372, 888, 1 023 cm-1. Low intensity bands are present at 1 088, 1 211 and 1 322 cm-1. The SERS of dially1 disulfide, allyl methyl sulfide and 1-propanethiol in liquid state and gas state were also obtained. The main volatile organic compound of fresh garlic, Chinese chive and shallot are diallyl disulfide, allyl methyl sulfide and 1-propanethiol respectively, and the volatile organic compound of fresh onion, scallion, shallot and chive are all 1-propanethiol. The presented results illustrate that combining headspace and SERS is a powerful tool for volatile organic compound analysis in fresh plants. The volatile organic compound can be detected in fresh plant samples directly and quickly without extraction.