三维荧光光谱在珍珠检测中的应用——以银灰色Akoya珍珠为例

Application of Three-Dimensional Fluorescence Spectroscopy in Pearl Detection:A Case Study of Gray Akoya Pearl

三维荧光光谱是一种多维度的检测手段,在环境、生物等多个领域均有应用,且在有机质类型的分类中有着成熟的体系,常常与多种他类光谱联用,共同解析物质结构特征。以三种不同颜色成因(天然呈色、γ射线辐照改色处理及染色)银灰色Akoya珍珠样品为研究对象,初探三维荧光光谱在珍珠研究中的应用。实验结果表明,天然呈色、γ射线辐照改色及染色处理的银灰色Akoya珍珠样品的三维荧光光谱特征差异明显,具有不同的发光中心位置分布组合,其中λex/λem:374 nm/(448 nm和462 nm)处有最强的荧光强度为样品经过处理的警示证据。根据发光中心对应溶解性有机物的分区,三者均有色氨酸和蛋白质类和腐殖酸类有机组分。天然呈银灰色Akoya珍珠的不同部位的三维荧光光谱测试结果发现,天然呈银灰色和白色Akoya珍珠样品的珠层均是色氨酸和蛋白质类有机组分,而有机质层主要是腐殖质组成,沾带有机质的珠层显示有腐殖质的峰,说明天然呈银灰色Akoya珍珠中有机质层中的有机质已经浸润到珠层,腐植酸是许多微量金属元素的络合剂,可促进金属离子与珍珠中蛋白质发生络合作用。γ射线辐照改色银灰色Akoya珍珠中有机组分以腐殖质为主,但整体荧光强度相对于天然银灰色者弱很多,推测可能是γ射线辐照使腐殖酸类有机组分降解所致;染色银灰色Akoya珍珠的三维荧光光谱显示有机组分中还含有芳香性蛋白,这种组分在天然和辐照致色者中都没有显示,应是染料所致。

Three-dimensional fluorescence spectroscopy is a multi-dimensional detection method in many fields such as environmental sciences and biology,especially in classifying organic matter types.It is often used in combination with other spectrometers to analyze the structural characteristics of samples.In this paper,the authors took three types of gray Akoya pearl with different cause of colour(naturally coloured,γ-ray irradiated,dyed)as the research objects to explore the application of three-dimensional fluorescence spectroscopy in the study of pearls.The results showed that these three types of gray Akoya pearls can be accurately identified by a three-dimensional fluorescence spectrum.These samples have different combinations of luminescence center distribution,and the highest intensity fluorescence center atλex/λem:374 nm/448 nm and 462 nm are the warning evidence of the treated samples.According to the division of dissolved organic matter corresponding to the fluorescence center,all the samples have naturally coloured ammonia,protein,and humic acid.The test result of naturally coloured gray Akoya pearls found that the nacre layers of both gray and white Akoya pearls were composed of tryptophan and protein components,while the organic matter layer was mainly composed of humus.The nacre layer with organic matter shows a peak of humus,indicating that some organic matter has infiltrated the nacre.Humic acid is a complexing agent of many trace metal elements,which can promote the complexation of metal ions with proteins in pearls.The three-dimensional fluorescence spectrum ofγ-ray irradiated gray Akoya pearls show that the main organic components are humus.Still,the overall fluorescence intensity of the irradiated sample is much weaker than that of naturally coloured gray Akoya pearls,which may be due to the degradation of organic components of humic acids caused byγ-ray irradiation.The three-dimensional fluorescence spectra of dyed gray Akoya pearl samples show aromatic protein,which were not showned in other types of samples,may caused by dye.