Spectrophotometry quantitative analysis method of iodine-starch color-developing system
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A quantitative analysis and spectrophotometric technology, which is applied in the field of chemical and spectral analysis and testing, can solve the problems of unstable iodine-starch color reaction and low reliability of analysis results, and achieve high accuracy, easy operation and maximum reliability. Effect
Inactive Publication Date: 2013-12-11
SICHUAN AGRI UNIV +1
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[0003] At present, there are few reports about the iodine-starch color reaction spectrophotometry in France and abroad, and there are many domestic reports, mainly including: using H 2 o 2 、Cr 2 o 7 2- , MnO 4 - 、Br 2 , BrO 3 - , IO 3 - , Cu(II) as an oxidizing agent, the I - Oxidized to I 2 Quantitative analysis by spectrophotometry after color development with starch, for example, oxidation of I with bromine water - Generate I 2 Spectrophotometric quantitative analysis was used after developing color with starch, but the relevant reports failed to pay attention to and solve the core problem of unstable iodine-starch color reaction, bromine water oxidation I - Generate I 2 After developing color with starch, the change of absorbance was measured by spectrophotometry as follows: figure 1 , many oxidants have the same characteristics for iodine-starch color development, therefore, the reliability of the analysis results is low if the above method is used for quantitative analysis
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Embodiment 1
[0032] Example 1: Fe 3+ and H 2 o 2 The stability test and the establishment of the standard curve of the equilibrium system co-constructed with iodine-starch, the operation steps:
[0033] (1) Pipette 0.00, 0.20, 0.40, 0.60, 0.80, 1.00 mL of I - Standard solution (2.50 mmol / mL) in 25 mL volumetric flask (number 0~5), add 1.5 mol / L FeCl 3 Solution 50 μL, shake well, let it stand for 30 min, add 3.00 mL of 1% starch solution, shake well, add distilled water near the neck of the volumetric flask, shake well, add 1.5% H 2 o 2 50 μL, shake well, make up to volume with distilled water, shake well;
[0034] (2) At room temperature, use No. 0 bottle as blank, use No. 4 bottle as wavelength scanning at 400-700nm, and draw the absorption curve ( Figure 5 ), the maximum absorption wavelength is 600nm;
[0035] (3) At room temperature, with 600nm as the measurement wavelength, measure the absorbance of bottles No. 1 to No. 5; measure once every 30 minutes, draw a standard curve ...
Embodiment 2
[0043] Embodiment 2: with Fe 3+ and H 2 o 2 Build an equilibrium system with iodine-starch to determine the iodine content of a certain commercially available potassium iodide by spectrophotometry, the operation steps:
[0044] (1) Accurately weigh 0.1g (accurate to 0.0001g) of commercially available KI (Chengdu Kelong Reagent Factory), dissolve it with an appropriate amount of distilled water, transfer to a 100mL volumetric flask to constant volume, pipette 5.00mL of the solution into a 50mL volumetric flask, Constant volume with distilled water to obtain the test solution;
[0045] (2) Pipette 0.00, 0.20, 0.40, 0.60, 0.80, 1.00 mL of I - Standard solution (2.50 mmol / mL) in 25mL volumetric flask (number 0~5), respectively pipette 0.60mL of test solution into 25mL volumetric flask ( n =6); respectively add 1.5mol / L FeCl 3 50 μL of the solution, shake well, let stand for 30 min to fully react, add 3.00 mL of 1% starch solution, shake well, add distilled water near the neck...
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Abstract
The invention belongs to the technical field of chemical and spectrum analysis and test, and particularly discloses a spectrophotometry quantitative analysis method of an iodine-starch color-developing system. The spectrophotometry quantitative analysis method specifically comprises the steps of: (1) in a volumetric flask, taking a quantitative I<->-containing solution to fully react with an excessive FeCl3 solution at room temperature; (2) adding a certain amount of starch solution in the volumetric flask, shaking up; (3) immediately adding distilled water in the volumetric flask for diluting until the solution is close to the neck part of the volumetric flask, shaking up; (4) immediately adding a defined amount of H2O2, shaking up, metering the volume by using the distilled water, shaking up; (5) measuring an absorption curve at 400-700nm by using FeCl3 as a blank control to determine a measurement wavelength; (6) preparing color-developing systems with different iodine concentrations by using an I<-> standard solution according to the method of (1)-(4), measuring absorbancy A by using the measurement wavelength, establishing a standard curve by using a correspondence between the I<-> concentration c and the A value, and obtaining an equation of linear regression and a coefficient of association; and (7) measuring the absorbancy A of a color-developing system of an unknown I<->-containing solution according to the method of (1)-(4), and calculating the concentration of I<-> in the system to be measured according to the equation of linear regression in the (6). The spectrophotometry quantitative analysis method is stable in color-developing system, can be directly and indirectly used for iodine amount analysis, has the advantages of convenience, accuracy, trace amount, rapidness, low cost and the like, and can be widely applied.
Description
technical field [0001] The invention relates to the technical field of chemical and spectral analysis testing, in particular to a spectrophotometric quantitative analysis method of an iodine-starch color development system. Background technique [0002] The iodine-starch color reaction is a traditional very classic chemical reaction, I - Oxidized by oxidizing agents in aqueous solution to I 2 , I 2 The molecule penetrates into the helical structure of the starch, forming an I 2 - Starch clathrate, absorbs blue complementary color light, the solution is blue. I 2 The color reaction with starch is reversible (I 2 +starch I 2 -starch clathrate), reach equilibrium under certain conditions. If the reaction conditions (concentration, temperature, etc.) are changed, the balance will be broken, the concentration of the inclusion compound will change accordingly, and the absorbance will also change accordingly. I 2 Disproportionation is the fastest in alkaline environment...
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