CN103439279B - Spectrophotometry quantitative analysis method of iodine-starch color-developing system - Google Patents
Spectrophotometry quantitative analysis method of iodine-starch color-developing system Download PDFInfo
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- CN103439279B CN103439279B CN201310409134.4A CN201310409134A CN103439279B CN 103439279 B CN103439279 B CN 103439279B CN 201310409134 A CN201310409134 A CN 201310409134A CN 103439279 B CN103439279 B CN 103439279B
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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
The present invention relates to chemical and spectroscopic analysis technical field of measurement and test, be specifically related to a kind of iodine-starch color development system spectrophotometric quantitative analysis method.
Background technology
Iodine-starch chromogenic reaction is traditional very classical chemical reaction, I
-oxidized dose is oxidized to I in aqueous
2, I
2molecule penetrates in the helical structure of starch, forms I
2-starch inclusion compound, absorbs blue complementary coloured light, and solution is in blue.I
2be reversible reaction (I with the chromogenic reaction of starch
2+ starch
i
2-starch inclusion compound), reach balance under certain condition.As changed reaction conditions (concentration, temperature etc.), balance is broken, and the concentration of inclusion compound changes thereupon, and absorbance also changes thereupon.I
2the fastest in alkaline environment disproportionation, neutral secondly, acidity is slower; Even if in acid condition, still disproportionation, concentration constantly reduces, difficult maintenance equilibrium state; Iodine-starch chromogenic reaction instability, makes its color development system be difficult to meet spectrophotometric quantitative test.This chromogenic reaction is usually used in Qualitive test.
Relate to the external rare report of iodine-starch chromogenic reaction spectrophotometric method at present, domestic report is more, mainly contains: use H
2o
2, Cr
2o
7 2-, MnO
4 -, Br
2, BrO
3 -, IO
3 -, Cu (II) as oxygenant, by I
-be oxidized to I
2with use spectrophotometric quantitative test after starch coloration, such as, be oxidized I by bromine water
-generate I
2with use spectrophotometric quantitative test after starch coloration, but relevant report all fails to pay attention to and solve iodine-starch chromogenic reaction this key problem unstable, bromine water oxidation I
-generate I
2with after starch coloration with the change of spectrophotometry absorbance as Fig. 1, numerous oxygenants is used for iodine-starch colour developing identical characteristic, and therefore, adopt said method quantitative test, its analysis result degree of reliability is low.
Summary of the invention
The object of the present invention is to provide a kind of easy, accurate, micro-, quick and inexpensive iodine-starch color development system spectrophotometric quantitative analysis method.
This invention takes following technical measures, concrete steps are:
(1) in volumetric flask, get quantitative containing I
-solution, with excessive Fe Cl
3solution at room temperature fully reacts;
(2) in volumetric flask, add a certain amount of starch solution, shake up;
(3) at once add in volumetric flask distilled water diluting to volumetric flask close to neck, shake up;
(4) appropriate H is at once added
2o
2, shake up, use distilled water constant volume, shake up;
(5) FeCl is used
3make blank, make absorption curve at 400 ~ 700nm; Determine to measure wavelength;
(6) according to the method for (1) ~ (4), I is used
-the different color development system containing iodine concentration of standard solution preparation, measures absorbance with measurement wavelength
a, use I
-concentration
cwith
athe corresponding relation of value, Criterion curve, obtains equation of linear regression and related coefficient;
(7) by the method for above-mentioned (1) ~ (4), certain the unknown is measured containing I
-the color development system of solution
a, go out I in tested systems according to the regression equation calculation of (6)
-concentration.
In order to adapt with spectrophotometric sensing range and sensitivity, the present invention is by I in tested systems
-concentration guidelines be 0.02-0.10m mol/L.
The FeCl that the present invention uses
3solution is high concentration micro-volume, as used 1.5 mol/L FeCl in embodiment
3solution 50 μ L, object makes Fe in the short period
3+with I
-reaction reaches balance, and room temperature is 18 DEG C of about 30min, and room temperature can shorten this step time higher than 18 DEG C; Fe
3+with I
-the time of reaction is abundant not, can reach equilibration time (Fig. 2) by prolong color system.
The starch that the present invention uses is the pure starch of general analysis, and use 25mL volumetric flask, get 1% starch solution 2.00 more than mL, starch consumption increases on this basis, on color development system absorbance without impact.
The present invention uses appropriate H
2o
2be the important substance making color development system stable, use 25mL volumetric flask, take 1.5% H
2o
250 μ L, can make color development system in 240min stable (Fig. 3); As H
2o
2consumption reduces, color development system shortening stabilization time, H
2o
2consumption is more than more than 2 times, and color development system is collapsed at once (Fig. 4).
With the absorption curve of color development system of the present invention, determine that measuring wavelength is 600nm(Fig. 5).
Containing I
-liquid to be measured and I
-titer together develops the color, and together measures, precision and accuracy the best.
A kind of iodine-starch color development system spectrophotometric quantitative analysis method of the present invention, its color development system is stable in 240min, ensure that the at utmost reliable of measurement result.
A kind of iodine-starch color development system spectrophotometric quantitative analysis method of the present invention, do not use expensive instrument, various using amount of reagent is few, and analysis cost is low, inexpensive; General analysis personnel can complete fast in common lab, easy and simple to handle; Color development system is stable in 240min, favorable reproducibility, typical curve good linearity, and analysis result accuracy is high; The present invention has the advantages such as easy, accurate, micro-, quick and inexpensive, can be direct and indirect for iodometric analysis, is widely used.
Accompanying drawing explanation
Fig. 1 is the unstable schematic diagram of bromine water iodine oxide ion and starch coloration system absorbance.
Fig. 2 is 20 DEG C of Fe
3+with I
-reaction is colour developing and H not fully namely
2o
2the system of building together reaches the time longer schematic diagram of balance.
Fig. 3 is Fe
3+and H
2o
2to build together equilibrium system room-temperature stable schematic diagram with iodine-starch.
Fig. 4 is excessive H
2o
2destroy Fe
3+and H
2o
2to build together equilibrium system schematic diagram with iodine-starch.
Fig. 5 is Fe
3+and H
2o
2to build together equilibrium system absorption curve schematic diagram with iodine-starch.
Embodiment
Embodiment below describes the Fe that the present invention sets up
3+and H
2o
2to build together equilibrium system spectrophotometric quantitative analysis method with iodamylum.The important chemical equation of color development system of the present invention is as follows:
response inhabitation
reaction decomposes, reaches suppression
the disproportionation of reaction, maintains
equilibrium system long period of building together stablizes, appropriate H
2o
2make a small amount of I
2-starch inclusion compound methylates, and adds I
2the water wettability of-starch inclusion compound, does not precipitate for a long time, meets absorption photometric condition determination preferably; Use H
2o
2excessive response is pressed
carry out, I
2-starch inclusion compound disintegrates, Fe
3+and H
2o
2at once collapse (Fig. 4) with iodamylum equilibrium system of building together; A small amount of H
+also maintain stable system effect, system requires mild acid conditions.The mechanism that color development system of the present invention is stable within a period of time is very complicated, because having Fe in system
2+and H
2o
2, in acid condition, relate to free radical reaction as follows:
Fe
2++ H
2O
2=Fe
3++OH
-+·OH
Fe
3++ H
2O
2=Fe
2++HO
2·+H
+
The oxidability of these free radicals is very strong, the nonselective oxidation of organic compounds of energy and inorganics, also with regard to H in energy explanation system
2o
2amount is slightly large, the reason that color development system is collapsed at once.Do general reasoning for above-mentioned, color development system of the present invention can be stablized within a period of time, and its mechanism needs to be verified further.
Embodiment 1:Fe
3+and H
2o
2to build together the stability test of equilibrium system and the foundation of typical curve with iodine-starch, its operation steps:
(1) 0.00,0.20,0.40,0.60,0.80,1.00 mL I are pipetted respectively
-standard solution (2.50 m mol/mL) in 25 mL volumetric flasks (numbering 0 ~ 5), adds 1.5 mol/L FeCl
3solution 50 μ L, shakes up, places 30 min, adds 1% starch solution 3.00 mL, shakes up, and the nearly volumetric flask neck of adding distil water, shakes up, add 1.5% H
2o
250 μ L, shake up, and distilled water constant volume, shakes up;
(2) at room temperature, do with No. 0 bottle blank, make length scanning with No. 4 bottles at 400 ~ 700nm, draw absorption curve (Fig. 5), acquisition maximum absorption wavelength is 600nm;
(3) at room temperature, be measure wavelength with 600nm, survey the absorbance of 1 ~ kingpin; Survey once every 30min, take iodide ion concentration as horizontal ordinate, the absorbance of solution is ordinate drawing standard curve, and obtain corresponding equation of linear regression and related coefficient, determination data and result of calculation are as table 1; Result shows Fe
3+and H
2o
2to build together equilibrium system in 240min stable (Fig. 3) with iodine-starch, typical curve linear coefficient
r﹥ 0.999, the range of linearity 0.0200 ~ 0.1000m mol/L, follow langbobier law, color development system measures repeatedly in 120min, RSD between 0.6 ~ 1.5%, method favorable reproducibility, accuracy is high;
Table 1 (18 DEG C of mensuration)
(4) naturally (room temperature 20 DEG C) is heated up after a color development system part for kingpin being put into ice-water bath cooling, in mensuration process, the result of variations of absorbance is as table 2, Temperature fall (room temperature 20 DEG C) after another part is heated to 37 DEG C, in mensuration process, the result of variations of absorbance is as table 3, and result shows that temperature variation has appreciable impact to absorbance; Temperature, when ± 0.1 DEG C of scope fluctuation, measures absorbance, without significant change; Color development system in cuvette is meeting absorbing apparatus liberated heat in photometer, and therefore, during measurement, Fast Measurement can overcome this unfavorable factor
Table 2
Table 3
Embodiment 2: use Fe
3+and H
2o
2to build together the content of iodine of the commercially available potassium iodide of equilibrium system spectrophotometry with iodine-starch, its operation steps:
(1) commercially available KI (Chengdu Ke Long chemical reagent work) 0.1g(is accurately taken accurately to 0.0001g), dissolve with appropriate distilled water, proceed to 100mL volumetric flask constant volume, pipette this liquid 5.00mL in 50mL volumetric flask, use distilled water constant volume, obtain test liquid;
(2) 0.00,0.20,0.40,0.60,0.80,1.00 mL I are pipetted respectively
-standard solution (2.50 m mol/mL) in 25mL volumetric flask (numbering 0 ~ 5), pipette respectively test liquid 0.60mL in 25mL volumetric flask (
n=6); Add 1.5mol/L FeCl respectively
3solution 50 μ L, shakes up, and places 30 min and fully reacts, and adds 1% starch solution 3.00 mL, shakes up, and the nearly volumetric flask neck of adding distil water, shakes up, add 1.5% H
2o
250 μ L, shake up, and distilled water constant volume, shakes up;
(3) at room temperature, be measure wavelength with 600nm, No. 0 bottle is reference liquid, surveys the absorbance of standard solution and test liquid; Take iodide ion concentration as horizontal ordinate, the absorbance of solution is ordinate Criterion curve, obtains equation of linear regression
a=9.445
c-0.101,
r=0.999, the range of linearity 0.020 ~ 0.10m mol/mL, test liquid absorbance is substituted into equation of linear regression and carry out calculating and do relevant metering conversion, the content of iodine of commercially available potassium iodide is 76.4%(
n=6),
rSD﹤ 1%.
Claims (3)
1. an iodine-starch color development system spectrophotometric quantitative analysis method, its color development system is by FeCl
3solution, KI solution, starch solution and H
2o
2solution composition, containing following step:
(1) 2.50 m mol/mL I of certain volume are pipetted
-standard solution, in 25mL volumetric flask, pipettes I
-the volume range of standard solution is at 0.20 ~ 1.00mL;
(2) in volumetric flask, 1.5mol/L FeCl is added
3solution 50 μ L, shakes up, places 30 min;
(3) in volumetric flask, add 1% starch solution 3.00 mL, shake up;
(4) in volumetric flask, at once add distilled water to close to neck, shake up;
(5) 1.5% H is at once added
2o
250 μ L, distilled water constant volume, shakes up;
(6) FeCl is used
3make blank, make absorption curve at 400 ~ 700nm; Determine to measure wavelength;
(7) according to the method for (1) ~ (5), I is used
-standard solution prepares I
-concentration, in a series of color development system having concentration gradient of 0.020 ~ 0.100 m mol/L, measures absorbance with measurement wavelength
a, use I
-concentration
cwith
athe corresponding relation of value, sets up calibration curve;
(8) by the method for above-mentioned (1) ~ (5), certain the unknown is measured containing I
-the color development system of solution
a, calculate I in tested systems according to calibration curve
-concentration.
2., based on the method for claim 1, it is characterized in that I in tested systems
-concentration be 0.020 ~ 0.100 m mol/L.
3. based on the method for claim 1 or 2, it is characterized in that at room temperature, when temperature fluctuates within the scope of ± 0.1 DEG C, color development system can be stablized in 240min, and absorbance is stablized, calibration curve related coefficient
r﹥ 0.999.
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| CN104330403A (en) * | 2014-10-28 | 2015-02-04 | 四川农业大学 | Method for measuring sulphurous acid radical based on kinetic spectrophotometry |
| CN104977264A (en) * | 2015-07-15 | 2015-10-14 | 四川农业大学 | Method for measuring vitamin C via absorbance |
| CN108414459B (en) * | 2018-01-22 | 2019-11-15 | 华南理工大学 | A method of the detection crosslinked starch degree of cross linking |
| EP3561486A1 (en) | 2018-04-27 | 2019-10-30 | CERAGOS Electronics et Nature | Portative optical system for detection of chemical substances at trace levels in foods and liquids |
| CN111504984A (en) * | 2019-01-31 | 2020-08-07 | 湖南利诺生物药业有限公司 | Method for identifying seaweed iodine doped potassium iodide and application thereof |
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