LC-MS分析圆珠笔油墨中碱性艳蓝B染料的老化机理及色痕形成时间

Analysis of the Aging Mechanism and the Formation Time of the Victoria blue B Dye in Ballpoint Pen Ink by LC-MS

目的本实验利用液相色谱-串联质谱法,对在自然环境及紫外灯照射人工老化环境下的圆珠笔油墨进行检测分析,确定圆珠笔油墨中碱性艳蓝B染料的降解过程,从而依据色痕中染料的相对含量鉴别其相对书写时间。方法采用直径0.5 mm打孔器取样,乙腈/水(V/V,80/20)静置提取10 min,在pH值为3的乙腈/乙酸水溶液(V/V,50/50)作流动相条件下,利用液相色谱-串联质谱法对含有碱性艳蓝B染料成分的圆珠笔油墨进行检测,确定碱性艳蓝B染料定量离子对(m/z,470.44/455.38),根据碱性艳蓝B在不同时间紫外灯照射的碎片特征离子变化情况进行分析其降解过程,并依据其相对含量变化鉴别相对书写时间。结果实验确定了碱性艳蓝B特征碎片离子(m/z 470)脱掉一个甲基(—CH3+)生成新的特征碎片离子(m/z 456)的降解机理,以及碱性艳蓝B在人工老化条件下(紫外灯照射不同时间)及自然条件下(200天)的染料变化趋势图。结论碱性艳蓝B在200天的自然老化条件下,其含量变化相差近3%,可见色痕中的碱性艳蓝B在自然条件下的降解速度较慢,在司法实践中可依据其中染料的相对含量差值去评估可疑文件上字迹的书写相对时间。

Objective This experiment uses liquid chromatography-tandem mass spectrometry(LC-MS)to detect and analyze the ballpoint pen ink in the natural environment and under the artificial aging environment of ultraviolet irradiation to determine the degradation process of the Victoria blue B dye in the ballpoint pen ink,so as to identify the relative writing time based on the relative content of dye in the color trace.Methods Sampling with a 0.5 mm diameter puncher,acetonitrile/water(V/V,80/20)standing for extraction for 10 minutes,using an acetonitrile/acetic acid aqueous solution(V/V,50/50)with a pH of 3 as the mobile phase conditions,the liquid chromatography-tandem mass spectrometry use used to detect the ballpoint pen ink containing the basic the Victoria blue B dye component to determine the quantitative ion pair of the Victoria blue B dye(m/z,470.44/455.38).According to the variation of characteristic ions of the fragments irradiated by the ultraviolet lamp at different times,the degradation process of the Victoria blue B was analyzed,and the relative writing time was identified according to its relative content.Results The degradation mechanism of the characteristic fragment ions(m/z 470)of the Victoria blue B by removing a methyl group(—CH3+)to generate new characteristic fragment ions(m/z 456)was determined,and the dye variation trend chart of the Victoria blue B under artificial aging conditions(UV lamp irradiation at different times)and natural conditions(200 days)was determined.Conclusions The content of the Victoria blue B dye varies by nearly 3%,under natural aging conditions of 200 days.It can be seen that the degradation rate of the Victoria blue B dye in the visible color mark is slower under natural conditions.The relative writing time of suspicious documents can be evaluated according to the relative content difference of dyes in judicial practice.