i am studying the activity of laccase from fungi and I need standard curve of 2,2'-azino-bis-(3-ethylbenzthiazoline-6-sulfonic acid) to get the equation Y=aX+b. I have measured the activity of laccase using 2,2'-azino-bis-(3-ethylbenzthiazoline-6-sulfonic acid) as substrate. but I don't know how to make standard curve of 2,2'-azino-bis-(3-ethylbenzthiazoline-6-sulfonic acid).