Determination of phosphorus content

Determination of phosphorus content and DS (degree of substitution) of starch monosodium phosphate ester and distarch phosphate. Dissolved 2.2275 g of NaH2PO4.H2O in distilled water then made up the solution into 100 ml in volumetric flask, then it was made into serial dilutions. Add 2 ml of 25% conc.HCI into serial solutions and adjust their volume to 10 ml by adding distilled water, and then mixed 2 ml of vanadate-molybdate reagent, left the solution at room temperature for 45 min. Measure the absorbance of the solutions at 435 nm. Standard curve obtained by plotting absorbance against the phosphorus content.