CN102590317A - PH composite electrode method for measuring content of nitrite ions in solution - Google Patents
PH composite electrode method for measuring content of nitrite ions in solution Download PDFInfo
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- CN102590317A CN102590317A CN2012100131475A CN201210013147A CN102590317A CN 102590317 A CN102590317 A CN 102590317A CN 2012100131475 A CN2012100131475 A CN 2012100131475A CN 201210013147 A CN201210013147 A CN 201210013147A CN 102590317 A CN102590317 A CN 102590317A
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Abstract
The invention discloses a method for measuring content of nitrite ions in a nitrogenous solution. Based on the principle that the nitrite ions and an oxidant are subjected to quantitative oxidation-reduction reaction under an acidic condition, the method adopts a potentiometric titration way to measure the content of the nitrite ions in a nitrogenous solution. The method is characterized by using a pH composite electrode as an indication electrode to indicate electrode potential change of a reaction liquid so as to determine a final point of the titration. The oxidant is ferrous sulfate, ammonium ferrous sulfate, potassium hexacyanoferrate and potassium iodide. By adopting the method for measuring content of nitrite ions in the solution, disclosed by the invention, the method has the advantages of having simple instruments and equipment, low investment, convenient and quick operation, good stability and wide detection range and being beneficial to popularization and use.
Description
Technical field
Background technology
At present; Nitrite ion Determination on content method mainly is: 1. chemical analysis method: generally adopt oxidimetry; With standard liquor potassic permanganate titration nitrite ion; But to the sample of nitrite ion content<1 μ g/mL or when having colour substance to disturb, the method is restricted.2. Optical Analysis Method: Optical Analysis Method is quick, highly sensitive, limits the quantity of at 0~41 μ g/mL but detect, and need do typical curve.Like analytic approachs commonly used such as atomic absorption spectrography (AAS), AAS, chemoluminescence methods.Wherein the used instrument of atomic absorption spectrography (AAS) is complicated, and the consumption fund is bigger; The chemoluminescence method experimental technique is comparatively complicated, and agents useful for same is more; The AAS investment is little, but experimental technique is comparatively complicated, and agents useful for same is more.3. chromatography: like chromatography commonly used such as the chromatography of ions, vapor-phase chromatography, its precision is high, but used instrument all be a large-scale instrument, and consumption raw material and fund are all more.4. electrochemical methods: like voltammetry, oscilloscopic polarography, ionic electrodes selective method etc.5. additive method: like methods such as capillary electrophoresis, gas phase flow analysis infrared detection method, catalytic kinetics methods, but because of, restrictions such as fund and technology are not widely used.
China's national standard mainly contains two methods and measures nitrite, is respectively the AAS and the chromatography of ions.From appeal is introduced, can find out that AAS fund consumption is less relatively, it is also convenient to use, and wherein Griess reagent colourimetry (hydrochloric acid-naphthalene-ethylenediamine method) is the most frequently used method.But in actual mechanical process, there are some problems: the one, when using GB/T 5009.33-1996 method, the sulfanilic acid solution of being prepared (10g/L) at room temperature is difficult to dissolving fully; The 2nd, add again after earlier two kinds of developer equal-volumes being mixed in the GB/T 5009.33-1996 method, according to the principle of this method, nitrite elder generation and sulfanilic acid diazotising are again with the hydrochloride naphthodiamide coupling, so two kinds of developers should add respectively; The 3rd, the detection limit of nitrite μ g/mL all≤4 in above-mentioned instrumental analysis; And the content of nitrite often all is>=4 μ g/mL in the actual sample test; Therefore, sample all will pass through dilution process in test process, the too small scope that will make measured value exceed typical curve of extension rate; Extension rate is excessive, the situation of having no result can occur testing.So, in test process, often all to predict extension rate earlier, the test duration also will increase.Chromatography sensitivity and accuracy are all very high but expense is also high, and operation is also complicated; And electrochemical methods sensitivity and accuracy are all higher, expense is not high, theoretical foundation is also very perfect.The content of present potentiometric determination nitrite ion; Need with nitrite ion electrode special and two electrodes of contrast electrode; And the electrode of potentiometric determination nitrite ion of the present invention only needs one, and does not see and use report and the document that pH combination electrode method is measured nitrite ion content.
Summary of the invention
The objective of the invention is the deficiency to prior art, provide that a kind of instrument and equipment is simple, small investment, easy and simple to handle, quick, good stability, sensing range are wide, the new method of utilizing the mensuration nitrogen substance Nitrite Ion Content of promoting the use of is arranged.
Realize that technical scheme of the present invention is: the dual character that oxidisability and reductibility are arranged under acid condition to nitrite ion; Can with have oxidisability or have the principle of the ion generation redox reaction of reductibility, the present invention utilize nitrite ion under acid condition can with oxygenant (Fe
2+, KI) carry out the principle of quantitative redox reaction, utilize the variation of electrode potential to come method to confirm the terminal point of redox reaction.Be that nitrite ion reacts in oxygenant and the test solution; The electrode potential of indicator electrode is changed, and when titration was near stoichiometric point, the concentration of titrand matter was undergone mutation; The electrode potential of indicator electrode also is accompanied by sudden change, can confirm the terminal point of titration thus.
The oxygenant of using in the method for the present invention is divalent iron salt and potassium iodide, and reaction principle is following:
NaNO
2+Fe
2++2H
+=Fe
3++H
2O+NO↑
The Model Calculation of setting up through above-mentioned stoichiometric relationship goes out the content of nitrite ion in the test solution
, and the preferred feature oxygenant is ferrous sulphate, iron ammonium sulfate, potassium ferrocyanide and potassium iodide.The concentration of oxygenant: 0.001-0.1mol/L.
Titration end-point confirms in the inventive method; Promptly react, the electrode potential of indicator electrode is changed, when titration is near stoichiometric point through nitrite ion in oxygenant divalent iron salt or potassium iodide and the test solution; The concentration of titrand matter is undergone mutation; The electrode potential of indicator electrode also is accompanied by sudden change, and according to the accurate mathematical method of the change application of current potential, secondary difference quotient method is calculated the content of terminal point volume V end and then definite nitrite ion.Promptly occur between opposite pairing two volumes of symbol Δ being arranged in secondary difference quotient value
2E/ Δ V
2A bit of-V=0, this puts pairing volume is exactly the titration end-point volume, and pairing current potential is the terminal point current potential.The recovery of nitrite ion is 95%~105% in the mensuration, and measurement range is>1 μ g/mL.Can select the concentration of suitable oxygenant in the mensuration process according to the height of sample Nitrite Ion Content, be lower than 1 μ g/mL, also can come the test sample Nitrite Ion Content with standard addition method for the sample Nitrite Ion Content.
Method of the present invention is the mensuration of under acid condition, carrying out.Preferred feature acid is hydrochloric acid (analyzing pure), sulfuric acid (analyzing pure), phosphoric acid (analyzing pure), and employed pot is automatical potentiometric titrimeter or pH acidometer in the invention, and used indicator electrode is the pH combination electrode.
Method of the present invention, the scope of application is extensive, is mainly used in chemicals, medicine, food, the medium nitrite ion Determination on content of water, and test specification is wide in range, can directly measure the sample that nitrite ion content is 1 μ g/mL~1g/mL usually.
Embodiment
Embodiment 1:
1. the preparation of reagent
The borax of getting about 5.0g is with the saturated solution balance of white granulated sugar and salt more than 12 hours;
The preparation of 0.1% methyl red: it is that 60% ethanolic solution is to 50mL that the methyl red powder that takes by weighing 0.05g is dissolved in concentration;
0.1mol/L the preparation of hydrochloric acid: the concentrated hydrochloric acid that pipettes 8.4mL with the transfer pipet of 10mL is settled to scale with distilled water in the volumetric flask of 1000mL;
0.1mol/L the demarcation of hydrochloric acid: in electronic balance, accurately take by weighing the 0.3631g borax and put into the distilled water that the Erlenmeyer flask of 250mL adds 25mL simultaneously and drip 2 to 4 0.1% methyl reds again.The volume of supposing the hydrochloric acid that titration end-point is used is V
C=m×1000/(190.07×V)
The quality of m-borax (g)
Consume the volume (mL) of hydrochloric acid during the V-titration
Demarcate the standard solution of 0.09888mol/L hydrochloric acid; Dilute 10 times of standard solution that get 0.009888mol/L hydrochloric acid;
0.1mol/L the preparation of sodium nitrite solution: use dissolved in distilled water accurately taking by weighing on the electronic balance in the beaker of sodium nitrite solid of 6.9002g, transfer in the volumetric flask of 1000mL and be settled to scale with distilled water at 100mL;
0.01mol/L the preparation of sodium nitrite solution: the sodium nitrite solution of 0.1mol/L that accurately pipettes 10mL with the transfer pipet of 10.0mL is settled to scale with distilled water in the 100mL volumetric flask;
0.1mol/L the preparation of liquor kalii iodide: use the 0.01mol/L dissolving with hydrochloric acid accurately taking by weighing on the electronic balance in the beaker of 16.6008g potassium iodide at 100mL, transfer in the volumetric flask of 250mL and be settled to scale with 0.01mol/L hydrochloric acid;
0.01mol/L the preparation of liquor kalii iodide: the liquor kalii iodide of 0.1mol/L that accurately pipettes 10mL with the transfer pipet of 10.0mL is settled to scale with 0.01mol/L hydrochloric acid in the 100mL volumetric flask;
2. the debugging of instrument
The correction of pH meter and use: (pHS-25 acidometer, Shanghai Precision Scientific Apparatus Co., Ltd)
1. choose " pH " or " mv " shelves, power-on preheating 30 minutes.
2. using the concentration prepare is that the standard buffer solution solution of 4.01,6.86 pH meter is proofreaied and correct pH meter.
3. use deionized water cleaning electrode head, blot, be inserted in electrode in the detected solution liquid, after shaking or making solution evenly, treat the mV value that reading is read solution after stable with rotor with filter paper.
4. test with deionized water and obtain the ionized water cleaning electrode, blot, put into protection liquid.
3. test:
Take the potassium iodide hydrochloric acid solution of 10mL 0.01mol/L, use the sodium nitrite solution titration of concentration as 0.01mol/L, data recording is seen table 1:
Table 1
Can know through table 1: concentration is that the hop of hydrochloric acid solution of potassium iodide of sodium nitrite solution titration respective concentration of 0.01mol/L is o'clock between 4.70~4.90mL.Confirm V through secondary difference quotient method
Eventually:
V
Eventually=4.70+0.20 * 445/ (445+475)=4.80mL,
Can infer following relational expression according to as above equation again
C
1×V
1=2C
2×V
2
C
1The concentration of-hydrochloric acid (mol/L), V
1The volume of-hydrochloric acid (mL)
C
2The concentration of-sodium nitrite (mol/L), V
2The volume of-sodium nitrite (mL)
So the titration concentration of sodium nitrite should be: C
2=C
1* V
1÷ (V
2* 2)
C
2=0.009888×10÷(4.80×2)=0.0103mol/L
The recovery=C
2÷ C=103.0%
Embodiment 2:
1. the preparation of reagent
The borax of getting about 5.0g is with the saturated solution balance of white granulated sugar and salt more than 12 hours;
The preparation of 0.1% methyl red: it is that 60% ethanolic solution is to 50mL that the methyl red powder that takes by weighing 0.05g is dissolved in concentration;
0.1mol/L the preparation of hydrochloric acid: the concentrated hydrochloric acid that pipettes 8.4mL with the transfer pipet of 10mL is used the distilled water constant volume in the volumetric flask of 1000mL;
0.1mol/L the demarcation of hydrochloric acid: in electronic balance, accurately take by weighing the 0.3631g borax and put into the distilled water that the Erlenmeyer flask of 250mL adds 25mL simultaneously and drip 2 to 4 0.1% methyl reds again.The volume of supposing the hydrochloric acid that titration end-point is used is V
C=m×1000/190.07×V
The quality of m-borax (g)
Consume the volume (mL) of hydrochloric acid during the V-titration
Demarcate the standard solution of 0.09888mol/L hydrochloric acid.
0.1mol/L the preparation of sodium nitrite solution: use dissolved in distilled water accurately taking by weighing on the electronic balance in the beaker of sodium nitrite solid of 6.9002g, transfer in the volumetric flask of 1000mL and use the distilled water constant volume at 100mL.
0.01mol/L the preparation of sodium nitrite solution: accurately pipette with the transfer pipet of 10.0mL 10mL 0.1mol/L sodium nitrite solution in the 100mL volumetric flask, use the distilled water constant volume.
0.011mol/L the preparation of ferrous iron solution:
Take by weighing 2.7813g FeSO
47H
2O is dissolved in the 100mL0.01mol/L hydrochloric acid solution, moves in the 1000mL volumetric flask, is diluted to scale with the 0.01mol/L hydrochloric acid solution, mixing.
2. the debugging of instrument
The correction of potentiometric titrimeter and use: (DZ-2 type automatic potentiometric titration, last Haikang appearance Instr Ltd.)
1. positioning and demarcating: functional switch is to " pH " shelves, and the pH electrode clean washed with de-ionized water inserts in the buffer solution of pH=7.Regulate the temperature compensation knob, make its temperature indicative identical with the buffer solution temperature.Regulate positioning knob again, the pH value that instrument is shown is identical with the pH value of this buffer solution under this temperature.
2. slope is demarcated: from the buffer solution of pH=7, take out electrode, clean up with ionized water, in the buffer solution of the electrode insertion pH=4 that cleans up (or pH=9 etc.).Regulate the temperature compensation knob, make its temperature indicative identical with solution temperature.Regulate the slope knob again, the pH value that instrument is shown is identical with the pH value of this solution under this temperature.
It is error free to repeat 1. 2. to be operated to instrument.
3. functional switch connects the pH combination electrode to " mV " shelves, with deionized water cleaning electrode head, blots with filter paper, is inserted in electrode in the detected solution liquid electrode potential (mV value) when instrument shows this ion concentration.
4. test with deionized water and obtain the ionized water cleaning electrode, blot, put into protection liquid.
3. test:
Get the hydrochloric acid solution of the secondary molysite of 20.0mL 0.01mol/L, use the sodium nitrite titration of concentration as 0.01mol/L, data are seen table 2:
Table 2
Can know through last table: concentration is that the hop of hydrochloric acid solution of potassium iodide of sodium nitrite solution titration respective concentration of 0.01mol/L is o'clock between 9.6~9.8mL.Confirm V through secondary difference quotient method
Eventually
V
Eventually=9.6+0.2 * 25/ (25+50)=9.67mL, again
C
1×V
1=2C
2×V
2
C
1The concentration of-hydrochloric acid (mol/L), V
1The volume of-hydrochloric acid (mL)
C
2The concentration of-sodium nitrite (mol/L), V
2The volume of-sodium nitrite (mL)
So the titration concentration of sodium nitrite should be: C
2=C
1* V
1÷ (V
2* 2)
C
2=0.009888×20÷(9.67×2)=0.0103mol/L
The recovery=C
2÷ C=103.0%.
Claims (3)
1. a solution Determination of Nitrite Ion Content method utilizes nitrite ion under acid condition, to have reductibility, can carry out the principle of quantitative redox reaction with oxygenant.With its characteristic ferrous sulphate, iron ammonium sulfate, potassium ferrocyanide and potassium iodide is oxygenant; When in oxygenant and the test solution during nitrite ion generation redox reaction, use its characteristic pH combination electrode to come the electrode potential of Indicator Reaction liquid to change as indicator electrode.According to potentiometric titration is to confirm the principle of terminal point with the hop replacement indicator change in color of electrode potential; When titration is near stoichiometric point; The concentration of titrand matter is undergone mutation, and the electrode potential of indicator electrode also is accompanied by hop, can confirm the terminal point of titration thus.Promptly occur between opposite pairing two volumes of symbol Δ being arranged in secondary difference quotient value
2E/ Δ V
2A bit of-V=0, this puts pairing volume is exactly the titration end-point volume, and pairing current potential is the terminal point current potential.Accurately calculate the content of nitrite ion through certain stoichiometric relationship.
2. according to the nitrite ion Determination on content method described in the claim 1, it is characterized in that using the pH combination electrode to come the electrode potential of Indicator Reaction liquid to change, confirm the terminal point of titration as indicator electrode.
3. according to the nitrite ion Determination on content method described in the claim 1 and 2, it is characterized in that in the redox reaction that oxygenant is ferrous sulphate, iron ammonium sulfate, potassium ferrocyanide and potassium iodide.
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Cited By (3)
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CN103616428A (en) * | 2013-12-18 | 2014-03-05 | 齐齐哈尔大学 | Potentiometric titration method for measuring concentration of Fe<2+> in solution |
CN112782252A (en) * | 2021-01-07 | 2021-05-11 | 安徽大学 | Method for quantitatively detecting potassium permanganate |
CN113702473A (en) * | 2021-08-26 | 2021-11-26 | 中国科学院青岛生物能源与过程研究所 | Method for measuring alkalinity of surfactant based on potentiometric titration method |
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Cited By (5)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
CN103616428A (en) * | 2013-12-18 | 2014-03-05 | 齐齐哈尔大学 | Potentiometric titration method for measuring concentration of Fe<2+> in solution |
CN103616428B (en) * | 2013-12-18 | 2016-02-03 | 齐齐哈尔大学 | Fe in a kind of mensuration solution 2+the potentiometric titration of concentration |
CN112782252A (en) * | 2021-01-07 | 2021-05-11 | 安徽大学 | Method for quantitatively detecting potassium permanganate |
CN112782252B (en) * | 2021-01-07 | 2022-03-25 | 安徽大学 | Method for quantitatively detecting potassium permanganate |
CN113702473A (en) * | 2021-08-26 | 2021-11-26 | 中国科学院青岛生物能源与过程研究所 | Method for measuring alkalinity of surfactant based on potentiometric titration method |
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