A method for determination of the iodide casein in

A feed in the determination of iodide casein method, its character is that, the method of the specific steps are as follows: a. working curve drawing: first of all make concentration in 0.04 mu g/ml - 0.5 mu g/ml series of potassium iodide in the range of the standard working solution, and were moved to take 0.2 ml of potassium iodide in 10 ml of standard working solution scale colorimetric tube, and in turn add 0.01 mol/l arsenous acid 1.68 ml and 2.5 mol/l sulfuric acid 4 ml of distilled water and 4 ml, blending, At 20 ℃ to 30 ℃ temperature warm bath for 15 minutes, At the same time will be 0.002 mol/l ammonium ceric sulfate solution with your bath, after 15 minutes fast to 0.78 ml ammonium ceric sulfate solution in order to join to the colorimetric tube, add distilled water to scale blending, control water bath for 15 minutes to 20 minutes, reaction time in distilled water for reference, with 1 ml of colorimetric dish At 317 nm wavelength determination of each color in turn the absorbance of the solution in the tube, to remember the At; At the same time, determine the blank tube filled with distilled water absorbance at 317 nm wavelength, down to nought; And then map the Ln (A0 / At) - iodine ion concentration C curve, according to the curve, the curve equation can be calculated; B. feed sample preparation: feed after crushing, in anhydrous ethanol extract, until the soxhlet extractor were extracted with soxhlet extraction apparatus is colorless, liquid in the sample package and dried at 70 ℃; In a beaker, with a pH of 4.7 - acetic acid sodium acetate buffer washing sample packages, centrifugal separation, the separation of supernatant, add acetic acid, sodium acetate buffer washing, centrifugal separation, the separation of supernatant, then merge supernatant; To 1 ml supernatant to join 100 mu l concentration of 100% (W/V) of trichloroacetic acid precipitation, precipitation and merge drying; Moved to the porcelain crucible, fixed iodine in potassium carbonate, zinc sulfate to fuse to ashing sample processing and contents in the filter crucible, then washing with hot water residue, the filtrate and lotions collection into 100 ml volumetric flask, and add the capacity to scale the distilled water, shake well, the liquid under test; C. feed in the determination of iodide casein: take 0.2 ml of the solution under test in 10 ml graduated with colorimetric tube, according to the steps of a method to determine the absorbance of the solution under test ats, and absorbance blank A0, then calculate the Ln (A0 / At), the Ln (A0 / At) the curve of the values in the above equation, can work out the corresponding iodine ion concentration, according to the concentration of the iodine ion in the solution, the calculation of the amount of iodide casein in the feed.