[Evaluation of three methods for forensic diatom test].

Area of Science:

• Forensic Science
• Microscopy
• Analytical Chemistry

Background:

• The forensic diatom test is crucial for determining drowning as a cause of death.
• Traditional methods like strong acid digestion-centrifuge enrichment-light microscopy (SD-CE-LM) have limitations in efficiency and diatom recovery.

Purpose of the Study:

• To compare the efficacy of three distinct methods for forensic diatom analysis.
• Evaluate sample preparation time, digestion effectiveness, and diatom recovery rates across different techniques.

Main Methods:

• Three methods were compared: 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).
• Sixty samples were analyzed, with preparation time, digestion degree, and diatom recovery rate as key metrics.

Main Results:

• Microwave digestion-membrane filtration-light microscopy (MD-MF-LM) demonstrated the shortest preparation time, while SD-CE-LM was the longest.
• MD-ME-SEM and MD-MF-LM provided more thorough tissue digestion compared to SD-CE-LM.
• MD-ME-SEM yielded the highest overall diatom recovery rate, followed by MD-MF-LM and then SD-CE-LM. MD-ME-SEM also showed superior recovery rates for various diatom species.

Conclusions:

• SD-CE-LM exhibits a low diatom recovery rate, particularly for smaller or less dense diatoms.
• MD-ME-SEM is highly accurate and suitable for diagnosing suspected drowning cases due to its high recovery rate.
• MD-MF-LM is an efficient, sensitive, and convenient method for forensic diatom testing.