Effect of ammonium formate washing on the elemental composition determination in Nannochloropsis oceanica

This study investigated the effect of salt presence and removal on the integrity and elemental determination of the marine microalgae Nannochloropsis oceanica. Cells were harvested by centrifugation and washed with ammonium formate five times and subjected to mineral analysis after each washing step. Supernatants from each washing step were also analysed. Ca, Cu, Fe, Mg, Mn, Na, P, K, S, Zn were determined by inductively coupled plasma – optical emission spectrometry (ICP-OES). Results showed that washing microalgal biomass twice is sufficient to eliminate equipment oversaturation, allowing for more accurate elemental analysis, by using matrix matching. Moreover, washing the biomass did not rupture the cells, removed cell culture debris and decreased the concentration of Na, K, Ca present in the leftover growth medium. This study provides a reliable protocol for elemental determination in marine microalgae saving time in sample processing and analysis.