I am trying to develop a method for the quantification of fosfomycin. My starting point has been the USP monograph for fosfomycin, but I am detecting nothing. We are running a 1260 Infinity II Prime with the RID detector. I am confident that I am injecting comparable amounts to the documented method. I am using a Polaris 5 NH2 250 x 4.6 mm, 5 um column. Any advice would be welcomed.