基于微液节点采样的定量质谱成像技术在包装材料中光引发剂定位与检测中的应用

Application of Liquid Microjunction Surface Sampling Based Quantitative Mass Spectrometry Imaging Technique in Localization and Determination of Photoinitiators in Packaging Materials

该文针对传统方法中光引发剂定量检测耗时长、无空间分辨信息的缺陷,开发了基于微液节点采样-质谱系统的光引发剂定量成像方法,并将其用于包装纸中光引发剂的检测。研究表明,采样探针直接与质谱连接的接口方式具有更高的检测灵敏度,最优萃取剂可在1 min内实现单点采样超过90%的回收率,使得分析物可直接通过外标法定量。将该方法应用于包装纸中光引发剂的成像分析并与传统定量检测方法进行比较。结果显示:建立的成像方法可检测到比传统方法种类更多的光引发剂,且与传统方法的定量结果基本一致。另外,成像方法提供了更多丰富的空间分布信息,这对于包装纸中光引发剂的筛查定位以及指导和改进光固化油墨的涂布配方或工艺具有重大意义。

To address the current issues of traditional methods for photoinitiators(PIs)quantitation,which are time-consuming and have no spatial resolution,a quantitative mass spectrometry imaging method was developed,based on a liquid microjunction surface sampling(LMJSS)technique which is a simple,flexible and low-cost ambient sampling method for mass spectrometry.In this technique,solid surface could be sampled in situ with liquid solvent in a confined area prior to ionization in MS,which makes it possible to achieve in situ analysis or mass spectrometry imaging.Also,it is flexible to tune the sampling selectivity by solvent compositions or add standard in sampling solvent for quanti⁃tation in LMJSS technique.In the previous study,the problem of in situ quantification on PIs in packaging paper was effectively solved by combing LMJSS technique with kinetic calibration method.In this study,LMJSS technique was applied to the mass spectrometry imaging of PIs.Results showed that higher sensitivities were obtained for PIs by directly connecting the flow probe of LMJSS system to the inlet of mass spectrometry.Using this imaging method,the kinetic curve(signal-time curve)of analytes could be obtained in each pixel.According to the kinetic curves,it was proved that the extraction efficiencies of PIs in single pixel after 1 min LMJSS were all above 90%,making the quantitation by external standard calibration possible.This new method was finally applied to the quantitative mass spectrometry imaging for PIs in packaging material.The absolute concentrations of PIs in each pixel could be obtained by scanning the sample surfaces with the LMJSS technique,and the quantitative results were compared with those by traditional PIs quantitation method using gas chromatography-mass spectrometry.From the results,it is found that more kinds of PIs could be detected by the new mass spectrometry imaging method than traditional method,and the quantitation results by two methods were mostly comparable.Moreover,the imaging method could provide the spatio-chemical information which could not be obtained by traditional method.For example,in a certain area of paper packaging material,more isopropylthioxanthone(ITX),4-benzoylbiphenyl(PBZ),2-ethylhexyl-4-dimethylamino benzoate(EHDBA)and o-methyl-benzoyl benzoate(OMBB)were found to distribute in regions of red inks,while benzophenone(BP)and 1-hydroxycyclohexyl phenyl ketone(PI184)mainly distributed in regions of green inks.This specific spatial distribution of PIs makes them difficult to be detected by the traditional quantitative method.The developed imag⁃ing method is of great significance for screening and localizing PIs in packaging materials,and for guiding and improving the coating formulation or process of UV curable ink.It can also provide a technical support for the quality control of PIs in packaging materials.