A method for determining tissue sulfate

A method for the determination of the inorganic sulfate present in rat liver homogenates has been developed. In order to determine sulfate, a protein-free extract is required. The classical protein precipitation methods of preparing protein-free extracts gave 2.5–40% recovery of added ³⁵SO₄^2?. Separation of the protein by ultrafiltration gave only 29% recovery when 0.15 m KCl was the homogenizing medium. A homogenization medium containing 0.154 m NH₄OH and 20 g EDTA per liter gave 102 ± 11% recovery of added ³⁵SO₄^2? when the protein was separated by ultrafiltration.