Quality Control: Serially diluted GPx solutions with concentrations ranging from 62.5 to 3.9 mU/ml are measured with the ScienCell™ Glutathione Peroxidase Assay. The decrease in A340 nm is monitored as a function of time (Figure 1), and the resulting standard curve of ∆A340 nm/min vs. GPx concentration are plotted (Figure 2). A positive linear relationship between ΔA340 nm/min & GPx concentration can be observed.