ABSTRACT
Objective The investigation of diatom species composition and database of diatom scanning electron microscope in the Pearl River of Guangdong province. Methods Using the Lefort aqua regia digestion 19 different sampling sites (6 in the West River, 9 in the North River, and 4 in the East River) were sampled by us in June and September 2012.Water samples from each sampling site was digested and then observed by scanning electron microscopy. The diatom genera found in samples were recorded. Results 21 diatom genera, including Achnanthes, Cocconeis, Coscinodiscus, Cyclotella, Cymatopleura, Cymbella, Diatoma, Diploneis, Gomphonema, Gyrosigma, Hantzschia, Melosira, Navicula, Nitzschia, Pinnularia, Rhoicosphenia, Stauroneis, Stephanodisus, Surirella, Synedra, Tabellaria, were found in all the samples. Conclusion It is helpful to legal medical expert by using database of diatom scanning electron microscope in the Pearl River of Guangdong province. As hundreds of diatoms pictures were taken by SEM, it would be a valuable reference of diatoms identification for forensic experts as well as diagnosis of drowning place.
ABSTRACT
Objective The forensic application of Lefort aqua regia digestion method detecting diatom in rabbits’s organs. Methods Using the Lefort aqua regia digestion-membrane ifltrition-SEM observation method and the traditional acid digestion-centrifugation-light microscopy observation method to detect diatom of drowning or postmortem immersion rabbits’s organs(lung,liver,kidney), and make statistical analysis of diatom number, consuming time, digestive capability and ifne structure of diatoms. Results The diatom number of Lefort aqua regia digestion method was superior to conventional acid digestion method, with the difference being statistically signiifcant (P0.05), and have a better observation effect. Conclusion The Lefort aqua regia digestion method for diatom extraction was helpful for diatom identiifcation., and useful in drowning test by conventional and economicly.
ABSTRACT
<p><b>OBJECTIVE</b>To compare the efficacy of three methods for forensic diatom test, namely strong acid digestion-centrifuge enrichment-light microscopy (SD-CE-LM), microwave digestion-membrane filtration-automated scanning electron microscopy (MD-ME-SEM), and microwave digestion-membrane filtration-light microscopy (MD-MF-LM).</p><p><b>METHODS</b>Sixty samples were randomly divided into 3 groups for diatom test using three methods, and the sample preparation time, degree of digestion and recovery rate of diatoms were compared.</p><p><b>RESULTS</b>The sample preparation time was the shortest with MD-MF-LM and the longest with SD-CE-LM (P<0.05). MD-ME-SEM and MD-MF-LM allowed more thorough tissue digestion than SD-CE-LM. MD-ME-SEM resulted in the highest total recovery rate of diatom, followed by MD-MF-LM and then by SD-CE-LM (P<0.05); the recover rate of different diatom species was the highest with MD-ME-SEM, followed by MD-MF-LM and SD-CE-LM (P<0.05).</p><p><b>CONCLUSION</b>SD-CE-LM has a low recovery rate of diatoms especially for those with lengths shorter than 40 µm or densities less than 1/5. With a high recovery rate and accuracy in diatom test, MD-ME-SEM is suitable for diagnosis of suspected drowning cases. MD-MF-LM is highly efficient, sensitive and convenient for forensic diatom test.</p>