Application of Protease-Hydrogen Peroxide Digestion Method in Forensic Diatom Examination

Objectives: To propose a novel forensic diatom examination method, namely the protease-hydrogen peroxide (PHP) digestion method, and to explore its potential application in forensic practice.

Methods: The PHP digestion method was applied to process lung tissues and compared with the traditional nitric acid digestion method in terms of diatom quantity, recovery rate, proportion of diatom fragments, and recovery efficiency of different diatom genera.

Results: The PHP digestion method showed higher diatom quantity, recovery rate, and proportion of diatom fragments compared to the traditional nitric acid digestion method with statistical significance. The average diatom recovery rate was as high as 93.95%. In the lung tissues digested with nitric acid, there were 65 Achnanthes, 36 Nitzschia Ⅰ, 22 Nitzschia Ⅱ, 20 Diploneis and 8 Cymbella, showing significantly lower recovery rates compared to water samples which had 154 Achnanthes, 44 Nitzschia Ⅰ, 45 Nitzschia Ⅱ, 33 Diploneis and 23 Cymbella. However, with the PHP digestion method, only Nitzschia Ⅱ showed a lower recovery rate compared to water samples (P<0.05). At the same time, the diatom recovery stability of the PHP digestion method was higher than that of the nitric acid digestion method.

Conclusions: The PHP digestion method is superior to the traditional nitric acid digestion method in the lung tissue diatom extraction efficiency. Additionally, it holds significant advantages in safety, environmental protection, and other aspects. It is expected to be applied in forensic drowning identification.