Research Progress on Estimation of Postmortem Submersion Interval / 法医学杂志

Postmortem interval （PMI） estimation is one of the most important and difficult academic tasks in forensic sciences. Due to the influence of the corpse itself and the water environment, corpses in water have unique corruption phenomenon and laws. Based on the experience of traditional PMI studies of corpses on land, forensic practitioners across the world have proposed a variety of practical methods for estimating postmortem submersion interval （PMSI）. This paper summarizes the literatures related to PMSI in recent years, and introduces methods to infer PMSI according to the phenomenon of corpses, the development of insects, the succession pattern of aquatic organisms, and the changes of other physical and chemical indexes of corpses, in order to provide some reference for the study of PMSI of corpses in water.

Rapid Determination of Ammonia in Biological Samples by GC-MS Derivatization Method / 法医学杂志

Objective To establish a qualitative and quantitative method to determine ammonia in biological samples by gas chromatography-mass spectrometry （GC-MS）. Methods A heptafluorobutyryl chloride derivatization method was used. GC-MS was used for determination. The effects of different pH conditions, derivatization temperature, time and different extraction solvents on the test results were investigated. The pretreatment conditions were optimized. Results This method could accurately detect the ammonia content in blood, and the limit of detection was determined to be 0.1 μg/mL. The target component showed good linearity in the range of 0.5-200.0 μg/mL （R2=0.987 7）. The relative standard deviation range of intra-day precision was 2.59%-3.88%. The relative standard deviation range of inter-day precision was 3.21%-3.76%. Conclusion The method showed good sensitivity, stability and specificity, therefore can be used for forensic toxicology analysis and clinical biochemical detection.

Rapid Identification of Four New Synthetic Cannabinoids in Whole Blood / 法医学杂志

Objective To establish accurate and rapid methods to identify four new synthetic cannabinoids （JWH-203, JWH-122, 5F-APINACA and AB-CHMINACA） in blood samples. Methods The whole blood samples were extracted by acetonitrile and methanol, screened by gas chromatography-mass spectrometry （GC-MS） then confirmed by liquid chromatography-tandem mass spectrometry （LC-MS/MS） method, and multiple reaction monitoring （MRM） mode was used for quantitative analysis. Results The GC-MS method needed 21 min to complete the analysis, while the LC-MS/MS method needed 5 min. The AB-CHMINACA, JWH-203, 5F-APINACA and JWH-122 all used quasi molecular ion peak as a parent ion. The precursor-product ion combinations were m/z 357.4→312.2, m/z 340.2→125.0, m/z 384.1→135.1 and m/z 356.4→169.2. The four synthetic cannabinoids in blood samples had good linearity in the 1-250 ng/mL mass concentration range （r>0.99）. The limits of detection （LODs） were in the range of 0.1-0.5 ng/mL, the recovery rate was 85.4%-95.2%, the RSD less than 10.0%, and the matrix effect was 80.3%-92.8%. Conclusion The GC-MS and LC-MS/MS chromatographic behaviors and mass spectrometry analysis information of four synthetic cannabinoids were obtained in this study, and the possible causes of differences in chromatographic behaviors were discussed preliminarily. Therefore this study has a suggestive effect on judging the development trend of synthetic cannabinoids. This method can be used for rapid identification of four synthetic cannabinoids in blood, which can provide reference for identification of new synthetic cannabinoids when they are proliferating at present.

Determination of 1-methylhydantoin Concentration in Blood by GC-MS Method and Its Application in Forensic Medicine / 法医学杂志

Objective To establish a gas chromatographic-mass spectrometric (GC-MS) analysis method for quantifying 1-methylhydantoin concentration in whole blood. To provide technical support to forensic identification related cases of 1-methylhydantoin. Methods As an internal standard, 500 ng SKF525A was added to 0.5 mL blood sample, and then 2 mL 0.01 mol/L dilute hydrochloric acid and 0.5 g ammonium carbonate were added in order to buffer the pH value to 9, and following 2 mL ethyl acetate. The organic solvent layer was obtained after centrifuge and then analysed by GC-MS after drying. Results Good linear relationship of 1-methylhydantoin in blood was obtained in the range of 0.5-50 ng/mL. The equation of linear regression was y=0.01551 x+0.00726(R2=0.9997) with 0.1 ng/mL detection limit, and the recovery was 93.02％-108.12％. The intra-day and inter-day precision were less than 6.07％ and 13.37％, respec-tively. Conclusion The results gotten by this method is accurate and reproducible, which can be used for the determination of 1-methylhydantoin concentration in blood samples.