紫外-可见光谱仪在区分天然颜色和染色金珍珠的局限性

随着金珍珠饰品的流行，市场上出现越来越多的颜色处理过的金珍珠。天然颜色的金珍珠与染色金珍珠的价格相差甚远，故金珍珠的颜色检测显得尤为重要。目前，紫外一可见光谱仪（Uv-Vis）被认为是有效鉴别金珍珠颜色的测试手段之一，但在检测工作中，当利用紫外一可见光谱仪判定某些金珍珠是否染色时，发现其结论存在一定的争议性。前人的研究显示，在紫外一可见光谱中出现350-360nm处的吸收峰为天然色素的吸收所致，410-450nm出现明显吸收峰归因于有机染料所致。在实际工作中，笔者发现一些金珍珠样品不同部位的紫外一可见光谱不一样，有时测试结果还与显微镜下的特征相矛盾。因此，笔者初步分析了金珍珠的颜色成因，探讨了紫外一可见光谱仪在检测金珍珠时存在的局限性。

Limitation on Ultraviolet-Visible Spectrometer to Distinguish Golden Pearl and Dyed Golden Pearl

With the popular of golden pearl ornaments, more and more dyed golden pearls ap- pear on the market. Since the price of natural colour golden pearls and dyed golden pearls is extremely different, the colour detection is quite important. Gemmologists and detection ex- perts try to analyze the differences between golden pearls and dyed golden pearls with the help of Raman spectrometer, ultraviolet-visible spectrometer （UV-Vis）, laser ablation in- ductively coupled plasma mass spectrometry （LA-ICP-MS）, fluorescence spectrometer and cathodo luminescence （CL）. UV-Vis spectrometer is considered to be one of the effective ways to identify the colour of golden pearls, but this method is not mature and has some con- troversial opinions with testing results because of the relatively short time development. The previous studies considered that the UV-Vis spectrum peaks between 350 - 360 nm were caused by natural pigment of golden pearls and obvious peaks between 410 -450 nm were caused by the organic dye of dyed golden pearls. However, in practical work, the testing re- sults of UV-Vis spectrometer are quite different in different parts of golden pearls. Some- times it shows conflicting results between microscope observation and UV-Vis spectra, sincesome golden pearls being natural colour also have absorption peaks at 400 UV-Vis spectrometer on studying the cause of golden colour of the pearls is concluded that UV-Vis spectrum absorption peaks at 400 nm are related pearl layer. nm. Limitation of is discussed and it to the structure of