内部萃取电喷雾电离质谱直接分析脐橙

在正离子模式下, 分别对不同品质脐橙的内果皮和果肉进行了内部萃取电喷雾电离质谱(iEESI-MS)分析, 在未经过预处理的前提下直接获得了72个脐橙内果皮样品和72个脐橙果肉样品在m/z 50~2000范围内的化学指纹谱图, 鉴定了脐橙组织中氨基酸、 糖类和生物碱等重要化学成分. iEESI-MS化学指纹谱图表明, 脐橙的果肉与内果皮组织中脯氨酸和糖类等成分的组成具有一定的相似性, 而其它化学组分(如水苏碱、 辛弗林等)在2类组织中的含量差异明显. 主成分分析(PCA)结果表明, 样品的iEESI-MS指纹谱图与该脐橙的品质相关, 与样品的实际品质差异一致. 因此, iEESI-MS可直接获得不同品质脐橙差异性化学成分的信息, 从分子水平上判断脐橙品质的优劣.

Direct Analysis of Navel Orange Using Internal Extractive Electrospray Ionization Mass Spectrometry†

Internal extractive electrospary ionization mass spectrometry(iEESI-MS) was applied on the assessment of navel orange quality without any sample pretreatment. Both endocarp tissues(72 samples) and flesh tissues(72 samples) of navel oranges from three habitats were interrogated directly by iEESI-MS at mass range of m/z 50—2000. A fused silicon capillary was inserted into the navel orange tissue, allowing a distance of 2 mm between the fused silicon capillary tip and the sample apex. The apex of the sample was pointed to the mass spectrometer ion inlet intentionally with a distance of 4—5 mm. Extraction solvent biased with a high voltage(4.5 kV) was injected through the fused silicon capillary into the navel orange tissue at a flow rate of 2 μL/min, producing charged fine droplets containing chemicals toward the adjacent mass spectrometer inlet. Chemical constituents such as sugars, amino acids, vitamin and alkaloids were simultaneously extracted from the navel orange tissue, and identified through collision-induced dissociation(CID) experiment. Furthermore, mass spectral fingerprints were processed by principal component analysis(PCA) to visualize the quality differences. Our experimental results indicated that iEESI-MS can directly characterize the quality differences of navel oranges by molecular analysis. The merits of iEESI-MS include simplicity, good specificity, high throughput and minimum sample pretreatment.