Scientific Research On Paper Cultural Relics In The Ming And Qing Dynasties Based On Pyrolysis Gas Chromatography-mass Spectrometry

The embryonic form of paper was found in the Western Han Dynasty,indicating the papermaking history is more than 2000 years in China.There are many types of papermaking raw materials,which have experienced the development from hemp,textured bark,mulberry bark,rattan bark,bamboo and grass fibers.The commonly used method for the identification of paper fiber raw materials is according to the morphological characteristics of plant fibers.However,it is difficult to identify them according to fiber morphology in case of a serious agied sample.In addition,at present,scientific research on paper cultural relics with complex materials such as ink rubbings and wax paper is still very weak.Paper is mainly composed of plant fiber raw materials.Different kinds of plant raw materials have special chemical characteristics.Through the composition analysis of paper,the characteristic compounds of fiber raw materials can be determined,and then the fiber types of paper can be identified.In addition,other material information other than fiber raw materials in paper cultural relics can also be identified through component analysis,such as writing or printing ink on paper,binding media and additives in ink,wax in waxy paper cultural relics,etc.Pyrolysis gas chromatography-mass spectrometry(Py-GC/MS)is efficient method for the analysis of mixed organic compounds.It requires less samples and simple sample pretreatment,which is suitable for the analysis of cultural relics samples.In this paper,The Py-GC/MS method is applied to the research of paper cultural relics in order to achieve the purpose of scientific identification of fiber raw materials and other related materials.Firstly,this study optimized and established the best conditions of Py-GC/MS method in the analysis of paper materials,mainly including the selection of cracking temperature,heating program and split ratio,the application comparison of direct pyrolysis analysis method and on-line thermally assisted methylation pyrolysis gas chromatography-mass spectrometry,and the application of ion analysis method in data analysis.The optimized Py-GC/MS method was applied to the study of plant raw materials for papermaking(flax,jute,mulberry,bark,Green Sandalwood bark,Stellera chamaejasme,rice straw,asparagus and kudzu vine).The pyrolysis characteristic compounds of each raw material were summarized.Different kinds of raw materials could be distinguished according to their characteristic compounds and relative contents.The optimized method and the data of plant raw materials obtained by PyGC/MS analyses were applied to the scientific study of paper cultural relics in the Ming and Qing Dynasties.The plant sources and related material information of paper fibers were determined,including bamboo paper,mulberry paper,textured paper,linen paper,rice paper mixed with Green Sandalwood skin and straw,etc.The inks used are pine smoke ink and lampblack ink,while the binding media in ink include animal glue,eggs and their mixed materials.The wax used on waxy paper is beeswax.Some of the features detected in paper cultural relics are reduced and lost,which could be related to the papermaking process.In addition,the analysis of sample characteristics by Py-GC/MS can solve the problem when the fiber was seriously aged,which is impossible to identify the fiber origins based on morphology.In summary,in this study the Py-GC/MS analysis method of paper materials was optimized,and the characteristic data of raw materials for papermaking was established,which were applied to the analysis of paper cultural relics samples in the Ming and Qing Dynasties.The relevant material information of paper cultural relics such as fiber raw materials,ink,binding media and additives in ink were determined at the same time through one-time analysis of a small amount of sample.This study not only enriches people's scientific cognition of paper cultural relics,but also provides a scientific basis for the protection and restoration of paper objects.This study can also provide new methods and research ideas for the scientific analysis of paper cultural relics.