 Concentrated nitric acid and Proteinase-K, or peroxide, are added to the sample for 12 hours, centrifuged twice, rinsed with distilled water, and then mounted on a slide with Naphrax.Using this form of extraction, observers can use a light microscope when examining the results.The ‘’’Membrane Filter method’’’ is used when there is a presence of either damaged diatoms in the sample (result of pollutants) or inorganic materials.