Dilute test portion to ca70mL with H2Oat room temperature, and mix until all H O-soluble substances are in solution (ca 15 min). Add 6 g Cand mix thoroughly. (For products containing starch, also add 60 mL acetone to precipitate starch and to aid test portion solution.) Let stand 30 min. Filter with vacuum through 60 mL coarse fritted glass funnel containing asbestos pad. Wash flask and residue with six 25 mL portions H20 or, if acetone was added, with six 25 mL portions acetone-H20 (1 1). Collect filtrate and washings in 400 mL beaker, add2 drops HCl (1 2.5), and evaporate on steam bath to ca 40 mL. (HCl prevents conversion of glutamic acid to pyrrolidone carboxylic acid.) Quantitatively transfer to 50 mL volumetric flask, dilute to volume with H2O, and mix.