Search

Abstract: Objective To establish a method that combines a series of techniques including Fourier transform infrared spectrum （FTIR）, gas chromatography-mass spectrometry （GC-MS）, high resolution mass spectrometry and nuclear magnetic resonance spectroscopy （NMR） for identification of unknown substances. Methods The unknown samples （off-white powder and yellow crystal） seized in the actual cases were detected by FTIR, GC-MS （methanol as solvent）, high resolution mass spectrometry （methanol as solvent） and NMR （deuterated methanol as solvent）. Results The mass spectrum characteristic ions m/z of the main components in the samples measured by GC-MS were 219 （base peak）, 363, 307, 304, 275, 145, 131 and 213 （base peak）, 357, 301, 298, 269, 185, 171, 145 and 131, respectively. The accurate mass numbers [M+H] + measured by high resolution mass spectrometry were 364.203 61 and 358.212 34, respectively. The unknown samples were identified as synthetic cannabinoid new psychoactive substances 4F-MDMB-BUTINACA and MDMB-4en-PINACA after data consultation and database retrieval and comparison, combined with infrared analysis and mass spectrometry data analysis, and their structures were confirmed by 1 H-NMR. Conclusion The established multi-technology joint identification method can be used to identify 4F-MDMB-BUTINACA and MDMB-4en-PINACA in unknown samples. This method is fast, convenient, accurate, reliable and practical, and can provide reference for the identification of cases involving such substances in the future., Competing Interests: The authors of this article and the planning committee members and staff have no relevant financial relationships with commercial interests to disclose., (Copyright© by the Editorial Department of Journal of Forensic Medicine.)

Abstract: Objective To establish a method for determination of the azide ions in blood by gas chromatography-mass spectrometry （GC-MS） following pentafluorobenzyl derivatization. Methods A blood sample of 0.2 mL was placed into a 10 mL glass test tube, and the internal standard sodium cyanide, derivatization reagent pentafluorobenzyl bromide and catalyst tetradecyl benzyl dimethyl ammonium chloride were added in turn. After vortex mixing, the mixture was heated with low-power microwave for 3 min. After centrifugation, the organic phase was taken for GC-MS analysis. Results The azide ions in blood had a good linear relationship in the mass concentration range of 0.5 to 20 μg/mL. The lowest detection limit was 0.25 μg/mL and the relative recovery was 91.36%-94.58%. The method was successfully applied to a case of death from sodium azide poisoning. The mass concentration of azide ions in the blood of the dead was 11.11 μg/mL. Conclusion The method developed in this paper has strong specificity and is easy to operate, which is suitable for the rapid detection of azide ions in blood., Competing Interests: The authors of this article and the planning committee members and staff have no relevant financial relationships with commercial interests to disclose., (Copyright© by the Editorial Department of Journal of Forensic Medicine.)

Abstract: Objective To establish a method to identify unknown samples based on combined use of gas chromatography-mass spectrometry （GC-MS）, high resolution mass spectrometry （HRMS） and nuclear magnetic resonance spectrum （NMR） technique. Methods The unknown samples were dissolved in methanol solution containing internal standard SKF525A and detected by GC-MS and HRMS. The mixed samples were separated and purified by silica gel column chromatography, and then dissolved in methanol-d4 solution for structural analysis of 1 H nuclear magnetic resonance spectroscopy （ 1 H NMR）. Results The characteristic fragment ions （ m/z ） were 86.1 （base peak）, 71.2, 121.1, and 149.0, and the accurate mass number of molecular ion peak was measured by HRMS to be 236.128 89. By combined use of data analysis and database comparison, a new psychoactive substance of the cathinone class, Dibutylone, was detected in the sample, and the sample also contained a small amount of caffeine. The sample was purified, then identified using 1 H NMR, and was further confirmed to be Dibutylone. In addition, the GC-MS retention time and characteristic fragment ions of the main components of the sample were consistent with those of Dibutylone reference material. Conclusion The method established in this study can be used for the identification of Dibutylone in mixed samples., Competing Interests: The authors of this article and the planning committee members and staff have no relevant financial relationships with commercial interests to disclose., (Copyright© by the Editorial Department of Journal of Forensic Medicine.)

Objective: To select specific DNA aptamer for determining ketamine by FluMag-SELEX., Methods: Based on magnetic beads with tosyl surface modification as solid carrier and ketamine as target, a random ssDNA library with total length of 78 bp in vitro was compounded. After 13 rounds screening, DNA cloning and sequencing were done. Primary and secondary, structures were analyzed. The affinity, specificity and Kd values of selected aptamer were measured by monitoring the fluorescence intensity., Results: Two ssDNA aptamers (Apt#4 and Apt#8) were successfully selected with high and specific abilities to bind ketamine as target with Kd value of 0.59 and 0.66 μmol/L. The prediction of secondary structure was main stem-loop and G-tetramer. The stem was the basis of stability of aptamer's structure. And loop and G-tetramer was the key of specific binding of ketamine., Conclusion: FluMag-SELEX can greatly improve the selection efficiency of the aptamer, obtain the ketamine-binding DNA aptamer, and develop a new method for rapid detection of ketamine.

A novel assay of Norfloxacin with a sensitivity at the microgram level is proposed based on the measurement of enhanced fluorescence intensity signals by the interaction of functionalized nano-CdS with Norfloxacin. The CdS nanoparticles were synthesized by thioacetamide (TAA) and cadmium nitrate (Cd(NO3)2) in the alkaline solution, and the nanoparticles proved to be stable in the aqueous solution. At pH 7.4, the fluorescence signals of functionalized nano-CdS were greatly enhanced by Norfloxacin in the region of 300-700 nm characterized by the peak around 495 nm, and the surface defect-related emission located at 565 nm. However, the surface defect-related emission was unconspicuous, thus we concluded that the functionalized nano-CdS QDs (Quantum Dots) possessed excellent luminescence capability and favourable structure. At the same time, the absorption spectra and transmission electron microscopy (TEM) also proved this deduction. The external reaction conditions (such as effect of buffer system, pH, ionic strength, reaction time and temperature, colloid concentration) were discussed. The result showed that better fluorescence signals could be obtained in the condition of 0.10 mol x L(-1) Tris-HCl, pH 7.4, 0.1 mol x L(-1) NaCl and the reaction time 5 min. The fluorescence emission spectra of CdS QDs with increasing Norfloxacin concentration were recorded under the optimal condition. From the fluorescence intensity and peak position of nano-CdS colloidal as different concentration of Norfloxacin was added, the possible mechanism of reaction between mercapto-acetic acid capped CdS and Norfloxacin was discussed. Linear relationship can be established between the enhanced fluorescence intensity and Norfloxacin concentration in the range of 1.25-11.25 microg x mL(-1) (3.92-35.27 micromol x L(-1)) or 11.25-100.0 microg x mL(-1) (35.27-313.5 micromol x L(-1)). The limit of detection is 1.5 x 10(-3) x microg x mL(-1), which can be applied to the determination of blood serum samples. Based on this, a new direct quantitative determination method for Norfloxacin in synthetic samples without separation of foreign substances is established. At the same time, the possible enhancing mechanism is due to the formation of exciplex during reaction between nano-CdS and Norfloxacin, providing a guidance for the study of pharmacokinetics.