基于FTIR光谱技术对可生物降解材料中添加PE/EVA组分的定性定量分析

以海南禁塑名录(第一批)中禁用不可降解塑料聚乙烯(PE)和乙烯-醋酸乙烯共聚物(EVA)为目标物，按不等质量梯度分别与聚己二酸/对苯二甲酸丁二醇酯(PBAT)和聚乳酸(PLA)等可生物降解聚合物熔融共混，进行复合物中PE和EVA的定性定量分析研究，以期为市场监督禁塑组分的违规添加提供数据。傅里叶变换红外光谱(FTIR)结合聚类分析，对PE-PBAT、EVA-PBAT、PE-PLA和EVA-PLA二元共混体系中的68个自制样品进行目标物鉴别及定量分析。结果表明，将所有光谱数据采用化学计量法分析研究，其聚类分析法可将样品分为3类，全波段下A=14, R2X(cum)=0.997, Q2(cum)=0.992。FTIR解析以峰形和峰位置筛选定性特征峰，以峰强变化筛选定量特征峰，其中PE-PBAT和EVA-PBAT体系有定性特征峰2 918和2 850 cm-1，定量特征峰2 918，2 850，1 714和727 cm-1；PE-PLA体系有定性特征峰2 918，2 850和718 cm-1，定量特征峰2 918，2 850和1 747 cm-1，另外1 460 cm-1谱带的强弱与组分比例不相关的特点可用于辅助定量；EVA-PLA体系包含定性特征峰2 918，2 850，1 237和718 cm-1，定量特征峰2 918，2 850和1 740 cm-1，红外定性分类结果与化学计量分析一致。进而探究峰强度比与禁塑组分含量的相关性，Spectrum Quant软件建立的定量模型表示：PBAT基共混材料的2918/727峰强度比与PE或EVA含量存在高度相关性，PE-PLA共混材料中2 918/1 460峰强比与PE含量存在高度相关性，EVA-PBAT共混材料中2 918/1 740峰强比与EVA含量有高度相关性；盲样验证显示残差值在±2.7%内。FTIR技术在禁塑组分PE和EVA定性定量分析中方法可靠，可实现简便快捷的半定量分析。

Research on Qualitative and Quantitative Analysis of PE and EVA in Biodegradable Materials by FTIR

A law on the one-time use of plastics was carried out as one measure of protecting the ecological environment in Hainan Province of China. The Hainan Forbidden Plastic List (first batch) is regulated to prohibit six non-degradable plastic compositions. The polyethylene (PE) and ethylene-vinyl acetate copolymer (EVA) were selected as detection targets in this simulating illicit-adding system. Poly(butylene adipate-co-terephthalate (PBAT) and polylactic acid (PLA) were chosen as the blend portions of simulating composites for their extensive application in bio-degradable plastics products. Then PE was blended with PBAT and PLA, respectively, according to the different mass percentages. Moreover, EVA was also blended with PBAT and PLA with the same formula, respectively. These simulating samples were provided for qualitative and quantitative testing of PE and EVA by Fourier transform infrared spectroscopy (FTIR) and cluster analysis (CLA). Their spectra screened the qualitative characteristic peaks by peak shape and wavenumbers. Furthermore, the characteristic quantitative peaks were screened for the correlation of peak-high ratios and the content of the non-degradable plastic components. Their quantitative curves were obtained and used for blind verification. The results showed that the mixture can be divided into three categories by applying all original spectral data in a chemometric method within 4 000 to 400 cm-1 and the parameter of the classification model are A=14, R2_X(cum)=0.997, Q2(cum)=0.992. The qualitative characteristic peaks of the PE-PBAT and EVA-PBAT systems were 2 918 and 2 850 cm-1, while the characteristic quantitative peaks were 2 918, 2 850, 1 714 and 727 cm-1. The characteristic qualitative peaks of the EVA-PLA system were 2 918, 2 850, 1 237 and 718 cm-1, and the characteristic quantitative peaks were 2 918, 2 850 and 1 740 cm-1. For the PE-PLA system, the characteristic qualitative peaks were 2 918, 2 850 and 718 cm-1, and the characteristic quantitative peaks were 2 918, 2 850 and 1 747 cm-1.Otherwise, the 1 460 cm-1 band intensity could be used to assist in quantification that was not related to component distribution. The qualitative classification results of ATR-FTIR were consistent with principal component analysis (PCA) classification. Furthermore, the quantitative models were established by the Spectrum Quant software. Peak-high ratios and non-degradable components had a great a high correlation. The peak-high ratio of 2 918/727 and PE or EVA content had high correlation in PBAT-base blend material. The peak-high ratio of 2 918/1 740 was determined as the dependence of the EVA content in the EVA-PBAT material. The peak-high ratio of 2 918/1 460 was defined as the dependence of the PE content in the PE-PLA material. The blind verification results indicated that the inaccuracy is within ±2.7%. Therefore, the FTIR technology showed good reliability in the qualitative and quantitative analysis of prohibited non-degradable plastic components, which could provide a scientific basis for identifying of non-biodegradable materials.