Standardization Of SPME-GC-MS Technology For VOCs Detection In Exhaled Breath

In recent years,expiratory diagnosis based on volatile organic compounds(VOCs)in human exhaled breath is attracting attention of many researchers.It is reported in a large number of literatures that GC-MS has been used in the research of expiratory diagnosis,and many achievements have been made.However,these findings are difficult to be directly applied to clinical diagnosis.Especially in the screening of disease markers,the conclusions of different literatures are quite inconsistent.Through the literatures review,it is found that the current research on exhalation detection has not established a unified standard,which is the main reason for the significant difference in analysis results,and greatly restricts the application of the technology in the field of exhalation.Therefore,from the perspective of establishing expiratory detection standards,this paper analyzes the operation flow of SPME-GC-MS to explore expiratory component,and conducts in-depth research on the key factors that may affect the analysis results in each experimental procedure,aiming to explore a set of practical and standardized solution for analyzing VOCs in exhaled breath.This work is an indispensable task of applying the exhaled characteristic VOCs in early clinical screening of diseases.The main work includes the following four aspects:In this paper,based on the static volumetric method,the preparation method of self-made substitution samples for experiments is proposed,which has the characteristics of low concentration,multiple components,strong feasibility and convenient operation.The influences of storage time,temperature,oxygen content in diluent gas and relative humidity etc.on the self-made substitution samples are investigated.The experimental results show that the storage time of the sample in the dry environment can be extended to 18 hours,and it is not easily affected by the storage temperature and oxygen content.However,if the sample contains water vapor,the storage time will be greatly reduced.Therefore,this paper takes the self-made substitution samples as the sample object,and the peak area response mean and coefficient of variation of each VOC component as a measure,in order to focus on the influence of important parameters such as oven temperature program,inlet temperature,desorption time,injection mode and transmission line temperature and so on.And a GC-MS analysis method with higher accuracy and better reproducibility is established on this basis.This method has been verified to have good linearity,low detection limits,and acceptable spike recovery.The efficient enrichment of trace components based on SPME is an important pre-processing method for GC-MS analysis.In this paper,the factors including the time,the temperature,the coating type and so on in the SPME extraction process are studied.The results show that coating polarity does not show a unique adsorption effect on different kinds of VOCs in the exhalation;the extraction time has a great influence on the VOC analysis compared with the extraction temperature,and needs to be selected strictly according to the adsorption equilibrium curve.Finally,based on the above-mentioned research work,taking human exhalation as a sample,this paper focuses on the individual differences and analyses the factors including flow rate of exhalation,exhalation with or without breath holding and exhalation in single or multiple breathing.The results confirm that standardized sampling process is essential to improve the repeatability of the analytical results.In addition,the statistical results show that there are correlations between components such as acetone,ethanol and isoprene in exhalation and human physiological indicators.Grouping the samples according to the difference can improve the accuracy of the analysis results.