A new centrifugation/filtration technique to improve the observation of calcareous nannofossils under the scanning electron microscope

Abstract

A new sediment sample preparation procedure for observing calcareous nannofossils using a scanning electron microscope (SEM) is described. The new preparation technique is a moderately time-consuming technique that allows observation of the finest structural details of specimens in the SEM. It has two separate steps: 1) disaggregation employing H2O2 and an ultrasound bath, keeping the pH stable through the use of a NaCO3-HCO3 buffer solution; and 2) a filtration process that concentrates and cleans the nannofossils through use of a vacuum pump. To do this, previous techniques for improving the quality of SEM images were combined, aimed at avoiding dissolution in the process, for which a slow digestion of the organic matter was carried out using a buffered solution, adding centrifugation and controlled vacuum pumping in order to retain the coccoliths without affecting their preservation.