International Journal of Legal Medicine

, Volume 131, Issue 3, pp 667–675 | Cite as

The effect of sodium fluoride, formaldehyde, and storage temperature on the stability of methamidophos in post-mortem blood and liver

  • Zhiwen Wei
  • Qing Niu
  • Fan Zhang
  • Kun Xiao
  • Ling Liu
  • Yujin Wang
  • Juan Jia
  • Jie Cao
  • Shanlin Fu
  • Keming YunEmail author
Original Article


Poisoning by organophosphorus insecticides such as methamidophos makes up a significant portion of forensic identification cases in China. Stability of methamidophos during specimen storage remains largely unknown. This study aimed to examine the long-term stability of methamidophos in postmortem specimens. Three experimental dogs after oral administration of methamidophos were sacrificed, and blood and liver specimens were collected and stored at various conditions. Gas chromatography-mass spectrometry (GC/MS) was used to measure the methamidophos concentrations after 0, 4, 7, 12, 16, 60, and 180 days of storage. The results showed that methamidophos was not stable and followed first-order degradation kinetics at all storage conditions investigated. The degradation half-life in blood was 12.2, 16.9, 11.0, and 1.0 days when the samples were stored at room temperature (RT, 20 °C), 4 °C, −20 °C, and at RT with 1 % sodium fluoride (NaF), respectively. The degradation half-life in liver was 4.1, 9.8, 17.8, and 2.0 days when the samples were stored at RT, 4 °C, −20 °C, and at RT with liver fixed in 10 % formaldehyde solution, respectively. These findings are significant in guiding sample storage and data interpretation. Specimens containing methamidophos should be stored at −20 °C and analyzed as early as possible. Addition of NaF in blood and fixation of liver in formaldehyde should be avoided due to the accelerated degradation of methamidophos under these conditions. The preliminary study suggests that it might be possible to calculate methamidophos concentration at the time of death based on its first-order degradation kinetic under specific storage conditions.


Methamidophos Organophosphorus insecticides Post-mortem Degradation kinetics 



This work was supported by the National Key Technology R & D Program (No. 2007BAK26B05) and NSFC (No. 81172906), the Doctoral Innovation Fund of Shanxi Province (No. 20143014), and the Science and Technology Innovation Fund of Shanxi Medical University (No. 01201121).


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Copyright information

© Springer-Verlag Berlin Heidelberg 2016

Authors and Affiliations

  1. 1.School of Forensic MedicineShanxi Medical UniversityTaiyuanPeople’s Republic of China
  2. 2.Forensic Science Centre of Jincheng Public Security BureauShanxiPeople’s Republic of China
  3. 3.Taiyuan Police Vocational AcademyTaiyuanPeople’s Republic of China
  4. 4.Shanxi Center for Disease Control and PreventionTaiyuanPeople’s Republic of China
  5. 5.Centre for Forensic ScienceUniversity of Technology SydneySydneyAustralia

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