Method for measuring content of tri-(m-sodium sulfonate phenyl) phosphine in water-soluble phosphine ligand

The invention discloses a method for measuring a content of tri-(m-sodium sulfonate phenyl) phosphine in water-soluble phosphine ligand. The method comprises the following steps of: exactly weighing a certain amount of phosphine ligand to prepare an aqueous solution with the pH of about 6-7; adding 2 m of a 10.5% starch indicator solution; and titrating exactly calibrated iodine standard solution until steady blue keeps 30 seconds without fading. The content of the tri-(m-sodium sulfonate phenyl) phosphine in an unoxidized state can be calculated out based on the concentration of the iodine standard solution, the volume of the consumed iodine standard solution and the mass of the taken phosphine ligand sample.