| Objictive1. To develop decomposition kinetics model of pyrethriod insecticides in preserved specimens and buried cadaver of dogs.2. To improve a GC equipped with an ECD and a GC/MS analysis for pyrethriod insecticides determination.3. To investigate the decomposition kinetics of pyrethriod insecticides in preserved specimens and buried cadaver of dogs.Methods1.The decomposition kinetics in preserved samples1.1 Group: Eighteen dogs were allocated into three groups randomly.The first group(sixe dogs) was given an intragastric administration of fenpropathrin with a dose of 8LD50; The second group (sixe dogs) was given an intragastric administration of cypermethrin with a dose of 10LD50; The third group(sixe dogs) was given an intragastric administration of fenvalerate with a dose of 10LD50.1.2 The study on decomposition kinetics: The dogs were dissected as soon as their vital signs disappeared after intoxication. The blood and liver of every dog were divided into four parts. Three of them were preserved at -20℃, 4℃, 20℃respectively;another blood containing 1%NaF or liver fixed with 4% formaldehyde solution were preserved at 20℃. Fenpropathrin, cypermethrin and fenvalerate were determined by the GC equipped with an ECD and a GC/MS on different days after the storage. The equation and parameters of decomposition kinetics were imitated and calculated with WinNonlin program.2. Study on the decomposition kinetics of fenpropathrin cypermethrin fenvalerate in buried cadavers2.1 The effection of time to the decomposition kinetics in buried cadavers.2.1.1 Group: Ninety-nine dogs were allocated into three groups randomly.The first group (Thirty-three dogs) was given an intragastric administration of fenpropathrin with a dose of 8LD50; The second group (Thirty-three dogs) was given an intragastric administration of cyper- methrin with a dose of 10LD50; The third group(Thirty-three dogs) was given an intragastric ad- ministration of fenvalerate with a dose of 10LD50.2.1.2 Study on the decomposition kinetics of buried cadavers: The dogs were put into unsealed plastic bags after the death, buried in the hollow (100 cm 100 cm 150cm). On 0d,35d,65d,95d,125d,200d,383d and 503d after the burial ,three of the first group dogs were dugged out and dissected, the specimens were collected for fenpropathrin analysis by a GC-ECD and GC/MS. On 0d, 30d, 60d, 90d, 210d, 360d and 480d after the burial, three of the second group dogs were dugged out and dissected, the specimens were collected for cypermethrin analysis by a GC-ECD and GC/MS. On 0d, 30d, 52d, 82d, 200d, 350d and 470d, after the burial, three of the third group dogs were dugged out and dissected, the specimens were collected for fenvalerate analysis by a GC-ECD and GC/MS.2.2 The effection of doses on the decomposition kinetics in buried cadavers.2.2.1 Group: Eighteen dogs were allocated into three groups randomly. The first group(six dogs) was given an intragastric administration of fenpropathrin with the doses of 4LD50 and 8LD50; there were three dogs in each dose group. The second group (six dogs) was given an intragastric administration of cypermethrin with the doses of 2LD50 and 10LD50; there were three dogs in each dose group. The third group(six dogs) was given an intragastric administration of fenvalerate with the doses of 2LD50 and 10LD50; there were three dogs in each dose group.2.2.2 Study on the decomposition kinetics of buried cadavers: The dogs were put into semi-sealed plastic bags after the death, buried in the pits(100 cm 100 cm 150cm). On 60d after the burial, the dogs were dugged out, dissected, and the specimens were collected for fenpropathrin, cypermethrin or fenvalerate cypermethrin analysis by a GC-ECD and GC/MS.2.3 The effection of burial way on the decomposition kinetics in buried cadavers.2.3.1 Group: Twenty-seven dogs were allocated into three groups randomly. The first group (nine dogs) was given an intragastric administration of fenpropathrin with a dose of 8LD50; the second group (nine dogs) was given an intragastric administration of cypermethrin with a dose of 10LD50; the third group(nine dogs) was given an intragastric administration of fenvalerate with a dose of 10LD50.2.3.2 The dogs were put into semi-sealed plastic bags, woven bags and wooden cases (coffins) respectively after the death, buried in the pits(100 cm 100 cm 150cm). On 60d after the burial, the dogs were dugged out, dissected, and the specimens were collected for fenpropathrin, cypermethrin or fenvalerate cypermethrin analysis by a GC-ECD and GC/MS.2.4 The effection of temprerature on the decomposition kinetics in buried cadavers.2.4.1 Group: Eighteen dogs were allocated into three groups randomly. The first group(six dogs) was given an intragastric administration of fenpropathrin with a dose of 8LD50. The second group (six dogs) was given an intragastric administration of cypermethrin with a dose of 10LD50; the third group(six dogs) was given an intragastric administration of fenvalerate with a dose of 10LD50.2.4.2 Study on the decomposition kinetics of buried cadavers: The dogs were put into semi-sealed plastic bags after the death, buried in the pits (100 cm×100 cm×150cm). For the fir st group, three dogs were buried on 09/3/21 and dugged out on 09/6/6(75days), the other three dogs were buried on 09/8/24 and dugged out on 09/11/8. For the second group, three dogs were buried them on 09/4/11 and dugged out on 09/6/25(75days), the other three dogs were buried on 09/8/24 and dugged out on 09/11/8. For the third group, three dogs were buried on 09/4/11 and dugged out on 09/6/25(after 75days), the other three dogs were buried on 09/8/24 and dugged out on 09/11/8. The dogs were dissected, and the specimens were collected for fenpropathrin, cypermethrin or fenvalerate cypermethrin analysis by a GC-ECD and GC/MS.Results1. The decomposition kinetics of pyrethriod insecticides in preserving specimen1.1 Fenpropathrin:The decomposition kinetics of fenpropathrin in preserved blood and liver fit to the first-order kinetic process.The common equation were Ct=A*e-αt+B*e-βt and Ct=C0e-αt. Compared with the 0 d, the content of fenpropathrin in preserved blood and liver at-20℃descended significantly to 82.6±15.2% and 98.2±37.6% on 13 d. The fenpropathrin could not be detected in blood preserved at -20℃on the 215th d, but the content of fenpropathrin in liver preserved at -20℃descended to 14.7 9.2%. The decomposition half-life of fenpropathrin in blood and liver at -20℃were 18.07days and 40.57days respectively; Compared with the 0d, the content of fenpropathrin in blood and liver preserved at 4℃descended significantly to 66.326.1% and 79.1 31.2% on 13 d; the fenpropathrin could not be detected in blood preserved at 4℃on 185 d, but the content of fenpropathrin in liver preserved at 4℃descended to 0.90.9% on 345 d; the decomposition half-life of fenpropathrin in blood and liver preserved at 4℃were 15.74 d and 33.90d. Compared with the 0 d, the content of fenpropathrin in blood and liver preserved at 20℃descended significantly to 63.0±28.3% and 85.3 32.1% on 13 d. The fenpropathrincould not be detected in blood and liver preserved at 20℃on 185 d and 345 d respectively. The decomposition half-life of fenpropathrin in blood and liver preserved at 20℃were 13.99days and 23.68days respectively; Compared with the 0 d, the content of fenpropathrin in blood preserved at 20℃and containing 1%NaF descended significantly to 59.8 21.7% on 13d, it could not be detected on 155 d, the half-life of fenpropathrin in blood preserved at 20℃and containing 1%NaF was 9.94days; the content of fenpropathrin in liver stored at 20℃(fixed with 4% formaldehyde) descended to 94.5 23.9% on 13 d, the half-life was 51.97days.1.2 Cypermethrin: The decomposition kinetics of cypermethrin in preserved blood and liver fit to the first-order kinetic process.The common equation were Ct=A*e-αt+B*e-βt and Ct=C0e-αt. Compared with the 0 d, the content of cypermethrin in blood and liver preserved at-20℃descended significantly to 64.4±2.8% and 91.1±2.9% on 40d, 42.0 2.9% and 76.45.8% on 290d, the decomposition half-life were 182.83 days and 826.01days respectively; Compared with the 0d, the content of cypermethrin in blood and liver preserved at 4℃ descended significantly to 54.3±1.4% and 79.4±5.8% on 40 d, 26.1 10.9% and 50.0 20.5% on 290d, the decomposition half-life were 93.76 days and 327.18 days respectively. Compared with the 0d, the content of cypermethrin in blood and liver preserved at 20℃descended significantly to 27.5±3.6% and 70.5±2.9% on 40d, the content of cypermethrin in preserved blood descended to 11.5 1.4% on 290d, the decomposition half-life of cypermethrin in blood preserved at 20℃was 10.54 days; Compared with the 0d, the content of cypermethrin in blood containing 1% NaF and liver fixed with formaldehyde preserve at 20℃descended significantly to 25.3±0.7% and 91.1±2.9% on 40d, 10.8±0.7% and 91.1±2.9% on 290d, the decomposition half-lifes were 5.11 days and 2288.49 days respectively.1.3 Fenvalerate: The decomposition kinetics of fenvalerate in preserved blood and liver fit to the first-order kinetic process.The common equation were Ct=A*e-αt+B*e-βt and Ct=C0e-αt. Compared with the 0d, the content of fenvalerate in blood and liver preserved at-20℃descended significantly to 73.6±0.5% and 95.6±8.6% on 40d, 29.6 4.0% and 50.2 4.3% on 290d, the decomposition half-lifes were 110.08 days and 347.14days; Compared with the 0d, the content of fenvalerate in blood and liver preserved at 4℃descended significantly to 26.4±6.4% and 78.3±13.0% on 40d, 6.4 0.8% and 30.4 4.3% on 290d, the decomposition half-lifes were 36.84 days and 226.42days. Compared with the 0d, the content of fenvalerate in blood and liver preserved at 20℃descended significantly to 33.7±1.1% and 47.8±4.3% on 40d; the content of fenvalerate in preserved blood descended to 6.5 0.8% on 290d; the decomposition half-lifes of fenvalerate in blood preserved at 20℃was 24.00 days; Compared with the 0d, the content of fenvalerate in blood(1% NaF) and liver(fixed with formaldehyde) preserved at 20℃descended significantly to 2.4 1.6% and 104.3 4.3% on 40d; fenvalerate could not be detected out in blood (1%NaF) preserved at 20℃on 228d, but the content of fenvalerate in liver preserved at 20℃(fixed with formaldehyde) only descended significantly to 86.9 4.3% on 290d; the decomposition half-lifes of fenvalerate in blood(1% NaF) and liver(fixed with formaldehyde) preserved at 20℃were 6.18 days and 763.75 days respectively.2.Decomposition kinetics of in pyrethriod in buried cadavers of dogs2.1 The effection of time on the decomposition kinetics in buried cadavers:Fenpropathrin group:Decomposition kinetics of fenpropathrin in buried cadavers of dogs which died from an intragastric administration of 8LD50. The fenpropathrin content in heart, spleen,lung,kidney, brain,pectoralis muscles, muscle of the right anterior limb,muscle of the right posterior limb reduced gradually to 17.6%-71.1% of the 0 d after it rised to the peak on 95 d. While the gastric wall and liver had a rise trends until the 383d. Cypermethrin group: Decomposition kinetics of in cypermethrin in buried cadavers of dogs which died from an intragastric administration of 10LD50. The cypermethrin content of heart ,spleen ,lung ,kidney ,brain ,gastric wall reduced gradually after it rised to the peak on 60d.While the pectoralis muscles and muscle of the right posterior limb rised to the peak point on 210d.Then the cypermethrin content of the samples reduced gradually. Fenvalerate group: Decomposition kinetics of in fenvalerate in buried cadavers of dogs which died from an intragastric administration of 10LD50. The fenvalerate content in heart,liver,kindy reduced gradually after it rised to the peak point on 350d. The fenvalerate content in brain and gastric wall rised to the peak point on 52 d.2.2 The effection of doses to the decomposition kinetics in buried cadavers: The results of the three experimental groups(fenpropathrin,cypermethrin,fenvalerate) showned that the drug content of the high dose group was higher than the low dose group in the heart,liver,kindy,brain and gastric wall .But the drug content in muscles had no significant difference between the two dose groups.2.3 The effection of burial way to the decomposition kinetics in buried cadavers: The experimental group of fenpropathrin showed that the fenpropathrin content, detected in the heart, lung, brain and gastric wall, was higher in plastic bags than those in wooden box after 75 days. The fenpropathrin content, detected in the heart, liver, spleen,brain, muscle of the right anterior limb and muscle of the right posterior limb, was higher in the wooden box than those in woven bag; Cypermethrin group: the cypermethrin content, detected in the heart,liver, lung, brain and gastric wall, was higher in plastic bags than those in wooden box after 75 days. The cypermethrin content, detected in the heart, liver, lung, gastric wall, muscle of the right anterior limb and muscle of the right posterior limb,was higher in in the wooden box than those in woven bag; Fenvalerate group: The fenvalerate content, detected in the heart, brain, muscle of the right anterior limb and muscle of the right posterior limb, was higher in plastic bags than those in wooden box after 75 days. The fenvalerate content, detected in the heart, lung, brain, gastric wall and muscle of the right posterior limb, was higher in the wooden box than those in woven bag.2.4 The effection of temperature to the decomposition kinetics in buried cadavers: The fenpropathrin group: The content of fenpropathrin, detected in the liver,spleen,brain, chest muscle and muscle of the right posterior limb, was higher buried in March to June than those buried in August to November.The other samples had no significant difference. The cypermethrin group: The content of cypermethrin, detected in heart,lung,kindy,spleen,brain and muscle of the right posterior limb, was higher buried in April to July than those buried in August to November. The fenvalerate group: The content of fenvalerate, detected in heart,liver,kindy,spl- een,brain,breast muscle and muscle of the right posterior limb, was higher buried in April to July than those buried in August to November.The rot leave of the dog remains which buried in August to November was more seriously than those in April to July. The average temperature in April to July and March to June is lower than August to November. Conclusion1. The dogs decomposition kinetics model of fenpropathrin, cypermethrin and fenvalerate have been developed, which can be applied to forensic identification, study on forensic toxicokinetics.2. The improved GC-ECD and GC-MS methods can be used in the forensic identification and forensic toxic kinetics study on fenpropathrin, cypermethrin and fenvalerate poisoning death.3. Fenpropathrin, cypermethrin and fenvalerate in specimens were found to be decomposed at various kinds preserved environment. Cryopreservation and formaldehyde can slow down the decomposition of the pyrethroids insecticides; But the NaF can speed up the decomposition.We suggest that the specimens for analysis should be submitted as soon as possible, NaF should not be added into the samples.4. The decomposition kinetics of fenpropathrin, cypermethrin and fenvalerate in blood and liver fit to the first-order kinetic process. The common equation was Ct=A*e-αt+B*e-βt and Ct=C0e-αt, which could be used to conclude the concentrations of fenpropathrin, cypermethrin and fenvalerate when the specimen were collected.5. The content of fenpropathrin, cypermethrin and fenvalerate in the samples of buried dogs showed a firstly increase and a next decrease. The fenpropathrin, cypermethrin and fenvalerat could be detected on 503 days, 480 days and 470 days after the bural. The decomposition kinetics of fenpropathrin, cypermethrin and fenvalerate in buried dogs showed a dose, burial ways and temperature dependent.6. In the forensic identification of buried cadavers of fenpropathrin, cypermethrin and fenvalerate poisoning death, we shoud take the whole situations into the consideration, which include buried time, buried way and buried seasons, and so on. Cadaver-dugging and toxic analysis should be carried out as soon as possible.
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