for sterility testing of pharma products. DILUTING FLUID D (as per USP) is used for sterility testing of pharma products. Pharmaceuticals, biological, medical devices or any material claiming to be sterile must be tested for sterility according to the procedures described in the compendia. Sterility testing is performed using the membrane filtration or direct testing methods, depending upon sample type and size. Fluid A (peptone water) is used for diluting or rinsing when performing sterility testing. These fluids aid in the complete rinsing of the membrane filter apparatus and are not toxic to microorganisms. After filtering the specified quantity of the test specimen, the membrane is rinsed with measured portions of rinsing or diluting fluid. This rinse is inoculated with known number of test bacteria and fungi as specified in pharmacopoeia. Fluid D contains Polysorbate 80, which acts as a surfactant to break down the lecithin or oils present. Peptic digest of animal tissue acts as a source of nitrogen.