The Application Research Of Raman Spectrum And XRF Spectrum In The Diagnosis Of Drowning

Background and purpose:In forensic medicine,the examination of dead bodies in water is a common and important part.One of the main points is distinguishing between entering the water before death and throwing the corpse after death,which is of great significance for clarifying the method of death and the nature of the case.Diatom inspection is the"gold standard"for auxiliary inspections for confirming the death of drowning of dead bodies in the water.Diatoms are widely found in various water bodies,ranging in size from several to several hundred microns,and the main component of their shell is silica.In the process of drowning,diatoms will be inhaled into the human body and circulate to multiple organs,and because the shell contains silicon dioxide,it has the characteristics of acid and alkali resistance,high temperature,and so on.Therefore,the main diatom inspection methods used now The principle of digestion-observation is mainly based on this:from nitric acid digestion-centrifugal enrichment-light microscope observation to microwave digestion-filter enrichment-scanning electron microscope observation.However,the principles mentioned above and methods have problems such as large environmental pollution,harmful to the human body,low efficiency,and a certain false-negative rate.Raman spectroscopy and X-ray fluorescence spectrometers have been used more and more in the field of forensic medicine this year because of their fast and non-destructive advantages.This research attempts to establish a method to identify drowning by using Raman spectroscopy and X-ray fluorescence spectroscopy.Methods:The Agiltron peakseeker Raman spectrometer was used to detect SiO₂ and rats’lungs in the drowning group and the rats in the group of entering the water after death.The spectral data were analyzed by origin pro2018c and MATLAB 2014 software.A PANalytical Axios X-ray fluorescence spectrometer was used to examine c lung tissues of dead bodies in the water collected by our unit.The lung tissues of the dead bodies in the water were digested by nitric acid-vacuum filtration-filter enrichment-scanning electron microscope observation and divided into positive group and negative group.The spectral data were analyzed within SPSS 23software.Results:The Raman characteristic peak of SiO₂ is located at 462cm^-1;the rats’lung tissue data in the drowning group and the postmortem group entering the water group after baseline correction and peak searching by origin pro 2018c software did not find valid at 462cm^-1 and other positions peak.Principal component analysis was performed using MATLAB 2014software.According to principal component 1 and principal component 2,the drowning group’s data and the postmortem entering the water group could not be effectively distinguished.After the X-ray fluorescence spectrometer data were statistically analyzed by SPSS 23 software,the mass percentage values of silicon and chlorine in the positive and negative groups were statistically different.Conclusion:The low Raman intensity of the silicon-oxygen bond,the amorphous silica of the diatom shell will further suppress the characteristic peak intensity,the complex composition of the biological tissues tested,and the strong fluorescence effect.These are the reasons why the Raman spectrum was not used in this study.Distinguish the possible causes of the lung tissue of rats in the drowning group and the postmortem group.According to the difference in the mass percentage values of silicon and chlorine in the X-ray fluorescence spectrometer,the lung tissues containing diatoms and those without diatoms can be distinguished.Drowning in freshwater causes hypotonic fluid and diatoms to enter the lungs,which is the cause of the difference in the mass percentage values of the two elements in the positive and negative groups.