Fig. 9
![Fig. 9](http://media.springernature.com/full/springer-static/image/art%3A10.1186%2Fs40543-019-0196-y/MediaObjects/40543_2019_196_Fig9_HTML.png)
Calibration curve of a cortisol and b cortisone standard solutions with concentrations from 0 to 50 ng ml−1. Standards plotted against the ΔRLU (relative light unit) emission response, insert in the figure a CL image of each standard cortisol solution.