An embodiment provides a method for measuring total chlorine in a seawater sample, including: preparing a thiocarbamate-based indicator; introducing the thiocarbamate-based indicator to a seawater sample, wherein the seawater sample contains an amount of total chlorine; adding an additive to the seawater sample, wherein the additive accelerates the reaction rate between the thiocarbamate-based indicator and total chlorine and causes a change in fluorescence of the seawater sample; and measuring the amount of total chlorine in the seawater sample by measuring an intensity of the fluorescence. Other aspects are described and claimed.