Figure 5: Critical specific chlorophyll a content (β) as a function of primary particle size of TiO2 in terms of EC20 and EC50. Lines are fitted 3-parameter Gaussian equation (7) in SigmaPlot ver. 9.01 for EC20 (dotted) and EC50 (solid). Experimental conditions: initial algae concentration =  cell/mL, test duration = 4 days, and initial test volume = 200 mL.