Raman Spectroscopy Screening For Common Drugs And Toxicants

[BACKGROUND]The screening of drugs and toxicants refers to the rapid qualitative/quantitative detection of unknown drugs and toxicants in samples by simple,rapid and sensitive methods.At present,there are extensive demands in public security,medicine and health,environmental monitoring,pesticide residues,food and health care,and many other fields.The production and usage of pesticides are very large in our country,so the rapid inspection of pesticides in the above fields is of great significance.In acute poisoning,pesticide poisoning occupies the first place,and organophosphorus pesticide poisoning occupies the majority in pesticide poisoning.Omethoate（OMT）,also known as oxate,chemical name O,O-dimethyl-S-[2-（methylamino）-2-oxyethyl]phosphorothioate,has broad spectrum,high efficiency,high toxicity and other characteristics,is currently the largest use of a class of organophosphate pesticides.At present there are many methods for pesticide detection,such as liquid chromatography,gas chromatography,liquid chromatography-mass spectrometry,gas chromatography-mass spectrometry and spectroscopy and so on,but these methods have some limitations,such as tedious sample processing,high equipment cost,time-consuming detection and low sensitivity,which are not conducive to rapid detection at the scene.In a poisoning case/incident,it is of great significance for diagnosis,treatment and investigation of the case/incident to identify the drug and toxicant in body fluids in time.Therefore,this project plans to combine near-infrared portable laser Raman,Shell-isolated Nanoparticle-surface Enhanced Raman Spectroscopy（SHINERS）and other technologies,taking OMT as an example,to establish an economical,simple and adaptable Raman rapid detection technology for the timely identification of drugsand toxicants in poisoning case/incident.[OBJECTIVE]The Raman fast detection technology based on near infrared portable laser Raman and solid phase SHINERS was established.Combined with multi-point scanning,aachieving the economic and rapid screening of common toxicants,such as OMT.Evaluated the feasibility of spectroscopic analysis for forensic drugs and toxicants screening at the scene.[METHODS]1.Preparation of solid-phase SHINERS substrate arrays:A 15×20cm² clean aluminum foil was used,and the matte surface was coated upward on the 96-well cell culture plate.By evenly pressing the palm with clean gloves,96 slightly concave pore structures were formed on the surface of the aluminum foil,which were arranged in an array corresponding to 96 holes in the culture plate.1ml of Au@Si O₂ nano-gold colloid was centrifuged at 8000rpm for 3min.The supernatant was absorbed and discarded,leaving about 20μL of concentrated gold colloid at the bottom of the tube.Then 980μL of 10^-5mol/L Na OH was added to resuspend.0.34mol/L Na Cl was mixed with 10^-4mol/L Na OH in equal volume.Take the two reagents and mix them well in equal volume,add to the center of the round hole of aluminum foil of carrier immediately,10μL to each well.Natural evaporation at room temperature,after drying,dustproof storage at room temperature for later use.2.OMT portable solid-phase SHINERS spectroscopy collection:The micro-upgraded OMT-containing sample was dropped onto the solid-phase SHINERS substrate,remove after a few seconds,or after evaporation and concentration,the spectra were scanned using the Jianzhi SSR-200 portable near-infrared Raman spectrometer.3.Optimization of OMT solid-phase SHINERS detection conditions:The background signal intensity of solid-phase SHINERS substrate under acidic,alkaline and neutral conditions was tested,the background signal source was analyzed,and the method of background elimination or deduction was explored.Check the spectrogram effect of OMT sample by liquid drop concentration method,liquid film method,fixed point measurement,multi-point scanning,etc.Determine the effect of alkalization degree on the background signal and the pretreatment method of OMT of the sample to be tested.4.OMT solid-phase SHINERS sensitivity test:The OMT with gradient concentrations（0,3.125,6.25,12.5,25,50.Unit:ppm）was scanned by Jianzhi SSR-200 portable near-infrared Raman spectrometer to verify the sensitivity and quantitative feasibility of the method.[RESULTS]1.Using the nanoparticle deposition control technology,the nano-gold colloid was deposited on the surface of aluminum foil relatively uniformly,and the portable solid-phase SHINERS array substrate with simple,economical,stable and good enhancement effect was successfully prepared.2.The OMT Raman spectrum was obtained by scanning the 100ppm OMT evaporated and concentrated on the solid-phase SHINERS substrate using the Jianzhi SSR-200 portable laser Raman spectrometer,which is consistent with the literature,but more typical.3.The intensity of background signal of solid-phase SHINERS array substrates was different under acidic,alkaline and neutral conditions,and the signal intensity was the highest under alkaline condition,followed by pure water and the lowest under acidic condition.Different degrees of alkalization（0.05mol/L Na OH,0.075mol/L Na OH and 0.1mol/L Na OH）had different effects on the background signal,with0.1mol/L Na OH being the highest,0.075mol/L Na OH the second,and 0.05mol/L Na OH the least.The results show that the detection time of the liquid film multi-point measurement method is shorter than the liquid drop evaporation and concentration method,and the characteristic peak of OMT can be obtained in a few minutes.By cleaning and dry baking the solid-phase SHINERS array substrate and analyzing the source of the substrate background signal,it is found that the interference of background peak cannot be eliminated,but the Shell-isolation Surface-enhanced Raman technology can obtain relatively stable Raman signal,which can be deducted by software in subsequent analysis.4.The OMT with gradient concentration（0,3.125,6.25,12.5,25,50.Unit:ppm）was detected by using the solid-phase SHINERS array substrate prepared above and the optimized methods.The Raman detection results showed that OMT with 3.125ppm still had obvious characteristic peak,and the limit of detection was less than the documented 4ppm.By analyzing the Surface-enhanced Raman spectrum of gradient concentration OMT,the characteristic peak of OMT at 768cm^-1 was selected as the quantitative basis of OMT.[CONCLUSIONS]1.A method for preparing solid-phase SHINERS array substrates was established.The Surface-enhanced Raman substrates obtained are portable,economical,and can be preserved for a long time.2.Combined with the portable solid-phase SHINERS array substrate and the portable near-infrared laser Raman spectrometer,this method can be used for the economical and rapid screening of common toxicants such as OMT,etc.Combined with the multi-point scanning,the potential of this method for the rapid quantification of target molecules at the scene is initially verified.