Colorimetric assays have a limited H2O2 concentration regime in which they can be used (regime with linear correlation between H2O2 concentration and absorbance). Therefore, it is also useful to use semiquantitative H2O2 test strips to determine the approximate concentration of H2O2 in the samples. Based on the outcome, the dilution of the samples can be adjusted to fit into the linear regime of the chosen colorimetric assay. These considerations result in a three-step procedure for ex situ H2O2 quantification: Table Procedure for ex situ H2O2 quantification in photocatalyst dispersions