汽车罩光漆的同位素比值分析及保存条件影响研究

本文通过检验汽车油漆最外层罩光漆的同位素实现不同样品的区分，并考察保存条件对样品同位素的影响。实验共收集了10种汽车罩光漆样品，分别在室温避光、60℃高温、-20℃低温和强紫外线条件下保存6个月，然后用元素分析仪-同位素比值质谱(EA-IRMS)检测样品的碳、氢、氧同位素比值。结果表明：油漆样品在不同保存条件下发生碳、氢、氧同位素分馏，样品的δ¹³C值在高温和低温保存后向负值偏移，强紫外线照射的影响微弱；δ²H值在3种条件下均向正值偏移，受紫外线照射影响最大；δ¹⁸O值在3种条件下均向负值偏移，但不同种类树脂样品之间δ¹⁸O值的偏移幅度不同，在3类样品中，聚甲基丙烯酸甲脂类树脂样品分子中由于氧含量最少其偏移值最小。稳定同位素分析方法可为油漆样品分析提供高区分度的三维指纹，在油漆识别与区分方面具有较大的潜力，可用于油漆物证的溯源分析。

Isotope Ratio Analysis and Environmental Impact Study of Automotive Vanish

Due to the different sources of raw materials and manufacturing processes, different automotive paint samples have different isotopic signatures, which can be used as the basis for distinguishing similar paint samples. The varnish is the paint applied on the outermost layer of the car, which is easily affected by the storage conditions. Therefore, the isotope ratios of different varnish samples under different storage conditions were analyzed. Ten automotive varnish samples were collected and stored for 6 months at room temperature away from light, high temperature of 60 ℃, low temperature of -20 ℃ and strong ultraviolet light. After that, the samples were analyzed by elemental analyzer-isotope ratio mass spectrometry (EA-IRMS). The carbon, hydrogen and oxygen isotope values were determined. The results showed that the carbon, hydrogen and oxygen isotope ratios of different paint samples can be used to distinguish different samples, the potential of identification and differentiation of paint samples using stable isotopes of carbon, hydrogen and oxygen were demonstrated. The carbon, hydrogen and oxygen isotope fractionation of the paint samples occurred under different storage conditions. The δ¹³C value of the samples shifted to a negative value after storage at high temperature and low temperature, greater variation of samples occurred at high temperature, and the influence of strong ultraviolet radiation was weak, which meant that UV light had little effect on the δ¹³C value of the paint samples. The δ²H value shifted to a positive value under the three conditions, which was most affected by ultraviolet radiation, and minimal change in the condition of high temperature. The δ¹⁸O value shifted to more negative under the three conditions. But the shift amplitude of the δ¹⁸O value was different between samples of different resin types. Among the three resin types of samples, polymethyl methacrylate lipid resin samples had the smallest offset due to the least oxygen content in the molecules, the variation ranges of glyceryl elaidate and sorbitan monostearate paint samples had little difference under the three storage conditions. Stable isotope analysis method can provide high resolution three-dimensional fingerprints for paint samples, which has great potential in paint identification applications, and can be applied to traceability analysis of paint physical evidence.