Working Standard Solution 2 - Level 3 Calibration Standard SolutionFor Brea in-house method (Study 1.1): Dilute Working Standard Solution 1, 1000x by adding 0.5 mL stock to 500 mL volumetric flask and diluting to volume with water.For Brea in-house method (Studies 1.2-1.6): Dilute Working Standard Solution 1, 2000x by adding 0.25 mL stock to 500 mL volumetric flask and diluting to volume with water.For DSM method (Study 1.1):Dilute Working Standard Solution 1 1000x by adding 0.5 mL stock to 500 mL volumetric flask and diluting to volume with diluent (1:1 ammonium acetate:acetonitrile).