The quantitative determination of biomass by gravimetric analysis is easy, cost effective, and the equipment required for this purpose is not very expensive. However, this technique determines the weight of the whole biomass and does not discriminate individual cells in the media. In general, wet or dry weights of the biomass can be measured, although wet weight determination is not very accurate. The microalgal cells are harvested by centrifugation and the pellet washed twice with isotonic ammonium formate (NH4HCO2, 2%) to remove suspended residual salts (Valenzuela-Espinoza et al., 2002). The advantage of using ammonium formate is that it does not leave any residue as it decomposes to volatile compounds during the drying process. An empty watch glass is weighed and the microalgal sample pellet transferred to the watch glass. The biomass is dried in an oven at 60°C for 12 hours. After drying, the weight of the watch glass plus the dry biomass is deter­mined, and the net dry cell weight (DCW) is calculated using Equation (4.1):

DCW (mg L-1) = [{Watch glass (mg) + Dry biomass (mg)}

— Watch glass (mg)]/Volume (L) (4.1)