CN109406612A - Use the electrolyte solution and its Cr VI detection method of mercury film electrode detection Cr VI - Google Patents

Abstract

The present invention provides a kind of new electrolytic solution and its Cr VI detection method using mercury film electrode detection Cr VI, the electrolyte component concentration are as follows: the Acetic acid-sodium acetate buffer of 0.2-2mol/L, 10-60g/LDTPA and 1-4mol/L sodium nitrate, potassium nitrate or both mixed liquor and 0.1-1mol/L sodium chloride, potassium chloride or both mixed liquor.Method are as follows: 1, by electrolyte with containing Cr VI water sample to be measured by 1:10 to 1:1 volume ratio mix；2, the glass-carbon electrode, reference electrode, platinum electrode three-electrode system of the good mercury film of preplating are connect with heavy metal detector, insertion contains Hg²⁺Plating mercury solution in, there is mercury film in processing to the glassy carbon electrode surface plated；3, three-electrode system cleaning insertion electrolyte, connect with heavy metal detector, applies different 10~120s of accumulating potential twice in succession, scan in -0.9v~-1.5v range.

Description

Use the electrolyte solution and its Cr VI detection method of mercury film electrode detection Cr VI

Technical field

The invention belongs to the analysis determining technology fields of Cr VI in water body, and it is continuous, accurate to be related to Cathodic Stripping Voltammetry The method for detecting hexavalent chromium；Specially a kind of new electrolytic solution and its sexavalence using mercury film electrode detection Cr VI Chromium detection method.

Background technique

In environment, chromium mainly exists in the form of inorganic chromium, and two kinds of common stable oxidation states chromium are trivalent chromium Cr (III) With Cr VI Cr (VI), trivalent chromium Cr (III) is that human body and animals and plants sustain life necessary microelement, but excessive concentration It can be harmful to the human body；And Cr VI Cr (VI) is in the environment mainly with CrO₄ ^2-And HCrO₄ ^-Form exist, Cr VI activity is high, There is very strong toxicity, and Cr VI Cr (VI) is easily absorbed by the body and is stored in vivo, there are potentially hazardous to biology.So six Valence chromium Cr (VI) has been put into the pollutant of priority acccess control in China's water body.Therefore hexavalent chromium content is aobvious in Accurate Determining water body It obtains particularly important.

There are many method for detecting chromium, mainly there is colorimetric method, fluorescence method, mass spectrography, atomic absorption method, chromatography, electrochemistry Analytic approach etc..These methods respectively have advantage and disadvantage, the application field for having its different in the analysis measurement of chromium.

Related voltammetry detects Cr VI, has a large amount of reports in domestic and foreign literature, but relative to other heavy metals from Son, measuring condition is complicated, and detection range is narrow, is difficult to be suitable for application of the Portable heavy metal instrument in terms of fast slowdown monitoring.It is main Wanting problem is:

1. chromium is multivalent state metal, mutually converting between different valence state ion easily occurs in reaction process；

2. preplating mercury film survey Cr VI easily occurs mercury film in measurement process and falls off, so that being needed in measurement process frequently pre- Mercury film is plated, the workload of tester is increased；

3. the content of complexing agent DTPA is less than a certain concentration, then the characteristic peak of non-hexavalent chromium occurs.And complexing agent DTPA is micro- It is dissolved in water (about 5g/L), is dissolved only in hot water and aqueous slkali.This be also why be constant temperature at 40 DEG C in many domestic and foreign literatures 30min or so is reacted in water-bath, complicated in this way, cumbersome, time-consuming reaction condition cannot obtain reality on Portable heavy metal instrument Border application.

In view of the above problems, developing suitable detection reagent is the key that solve Cr VI detection.

Summary of the invention

Technical problem to be solved by the present invention lies in the above deficiencies in the existing technologies are overcome, a kind of use is provided Mercury film electrode detects the novel detection reagent of Cr VI, using the reagent without being equipped with constant temperature water bath apparatus, in the good mercury film of preplating Afterwards, the electrolyte solution of the novel detection Cr VI of 2ml need to only be added in the water sample to be measured of 20ml, different potentials are rich twice in succession Collection, scanning, dissolution, cleaning are no more than the test that a sample can be completed in 2min in total.And it detects signal stabilization, no longer occur The phenomenon that multimodal, chromium peak disappear or mercury film falls off.

Its technical problem to be solved can be implemented by the following technical programs.

It is a kind of using mercury film electrode detection Cr VI electrolyte solution form the electrolysis relative to final mixed solution The each component concentration of matter solution are as follows:

(1), the NaAc_HAc buffer solution of 0.2-2mol/L；

(2), the DTPA of 10-60g/L；

(3), the mixed solution of the sodium nitrate of 1-4mol/L, potassium nitrate solution or both；

(4), the mixed solution of the sodium chloride of 0.1-1mol/L, Klorvess Liquid or both.

As the further improvement of the technical program, the pH value of the NaAc_HAc buffer solution is 5-7.

As the preferred embodiment of the present invention, the NaAc_HAc buffer solution is dense relative to final mixed solution Degree is 2mol/L.

The DTPA solution is 60g/L relative to the concentration of final mixed liquor.

The sodium nitrate, potassium nitrate solution or both mixed solution are 2mol/L relative to the concentration of final mixed liquor.

The sodium chloride, Klorvess Liquid or both mixed solution are 1mol/L relative to the concentration of final mixed liquor.

Another technical problem to be solved by this invention is to provide a kind of using above-mentioned electrolyte solution detection Cr VI Method.

It is adopted the following technical scheme that.

A method of Cr VI being detected using aforesaid electrolyte solution, feature is to include the following steps:

(1), the electrolyte solution is uniformly mixed with the water sample to be measured containing Cr VI by the volume ratio of 1:10 to 1:1, it is standby With；

(2), by the glass-carbon electrode of the good mercury film of prior preplating, reference electrode, platinum electrode three-electrode system and heavy metal analysis Instrument connection, insertion contain Hg²⁺In the plating mercury solution of ion, processing to the glassy carbon electrode surface plated covers one layer of uniform silver gray mercury Film；

(3), after the three-electrode system that step (2) is handled well being cleaned up, inserting step (1) resulting mixed solution In, it is connect with heavy metal detector, applies voltage twice in succession: applying (- 1.2~-1.5) v accumulating potential 1 (30~60) s；It applies Add accumulating potential 2 (10~120) s of (- 0.1~-0.8) v.

As the further improvement of this method, in step (2), Hg²⁺The plating mercury for the HCl that the plating mercury solution of ion is 0.1mol/L Liquid, processing step include the current potential 120s of application -1.0V, operation in triplicate.

Design parameter as the preferred embodiment of this method, in step (3) are as follows:

Accumulating potential 1:-1.5v；

Enrichment time: 30s；

Accumulating potential 2:-0.1v；

Enrichment time: 10s；

Quiescent time: 20s；

Scan current potential: -0.9v~-1.5v；

Clean current potential: -1.5v；

Scavenging period: 20s.

In addition, the mixed volume ratio preferred value of electrolyte solution and the water sample to be measured containing Cr VI is 1 in step (1): 10。

New electrolytic solution provided by the invention using mercury film electrode detection Cr VI, the chlorine contained in the solution from Son solves mercury film electrode and cannot be stabilized in the close neutral range of pH value, be easy to happen the drawbacks of falling off；And contain Nitrate ion, play the role of catalysis oxidation in Cathodic Stripping Voltammetry scanning process, it is suppressed that Cr VI Cr (VI) the trivalent chromium Cr (III) that reduction generates continues to be reduced to bivalent chromium Cr (II)；The increase of DTPA complexing agent solubility, so that Voltammetry detection Cr VI no longer needs to simplify operation using water bath with thermostatic control；Simultaneously to different kinds of ions contained by the electrolyte solution Concentration ratio optimizes, so that the electrolyte solution greatly improves the sensitivity of detection Cr VI, enrichment time is only needed 10s reduces trivalent chromium Cr (III) and continues the time for being reduced to bivalent chromium Cr (II), successfully solve in detection process occur it is molten The problem of peak point current becomes smaller out.

Detailed description of the invention

Attached drawing 1 is 1 series standard solution testing curve graph of embodiment；In figure: 1 is 20 μ g/L sexavalence chromium standard solution curves Figure, 2 be 40 μ g/L sexavalence chromium standard solution curve graphs, and 3 be 60 μ g/L sexavalence chromium standard solution curve graphs, and 4 be 80 μ g/L sexavalences Chromium standard solution curve graph, 5 be 100 μ g/L sexavalence chromium standard solution curve graphs.

Attached drawing 2 is 32 test curve figures of continuous mark-on of embodiment；In figure: 1 is the 2 μ g/L sexavalence chromium standard solutions prepared Curve graph, the 2 sexavalence chromium standard solution to add 60 μ L 1mg/L for the first time, 3 add the sexavalence of 60 μ L 1mg/L for second Chromium standard solution.

Specific embodiment

The purpose of the present invention is overcoming problems of the prior art, provide a kind of using mercury film electrode measurement Cr VI Electrolyte solution not only ensure that mercury film electrode in pH value 5-7 model by the way that a variety of specific function ions are added in the solution It remains to be stabilized in enclosing, does not fall off phenomenon, increase the solubility of DTPA, and the special ion being added is scanned Play the role of catalysis oxidation in journey, Cr (III) is inhibited to continue the feelings being reduced to bivalent chromium Cr (II), and high in detection sensitivity Enrichment time is shortened under condition to inhibit trivalent chromium Cr (III) to be reduced to bivalent chromium Cr (II), prevents dissolution peak point current from becoming smaller, So as to guarantee hexavalent chromium in continuous, accurate detection water.

Electrolyte solution provided by the invention using mercury film electrode determination of hexavalent chromium, various groups including following concentration Point:

(1) pH value is the NaAc_HAc buffer solution of 5-7 range；

(2) DTPA of (10-60) g/L；

(3) at least one of the sodium nitrate of (1-4) mol/L, potassium nitrate solution；

(4) at least one of the sodium chloride of (0.1-1) mol/L, Klorvess Liquid.

Above-mentioned solution is mixed in a certain ratio as the electrolyte solution using mercury film electrode detection Cr VI, that is, by this Electrolyte solution with containing Cr VI water sample to be measured in 1:10 to 1:1 ratio after mixing, by the glass of the good mercury film of prior preplating Carbon electrode, reference electrode, platinum electrode three-electrode system, are inserted, and pass through application -0.1v in very short time to -0.8v range Interior voltage, Cr VI Cr (VI) are first reduced into trivalent chromium Cr (III) in the working electrode surface of preplating mercury film, while in solution Existing DTPA is adsorbed on mercury film surface, forms complex compound Cr (III)-DTPA with trivalent chromium Cr (III), when voltage is scanned to cathode When, part or all of Cr (III)-DTPA continues to be reduced into Cr (II)-DTPA, and the strong oxidizing property of nitrate anion is again by Cr (II)-at this time DTPA is oxidized to Cr (III)-DTPA, to solve the problems, such as that dissolution peak point current becomes smaller；Due to joined chlorine in mixed solution Ion not only inhibits the generation because of electrode surface calomel that mercury film is caused to fall off, and prevents the reduction of mercury membranous surface activity.

When it is implemented, using following steps:

1) it, weighs sodium acetate and pipettes the NaAc_HAc buffer solution that glacial acetic acid prepares (0.2-2) mol/L；

2) it, weighs DTPA and is configured to (10-60) g/L enveloping agent solution；

3) sodium nitrate solution that sodium nitrate is configured to (1-4) mol/L, is weighed；

4) sodium chloride solution that sodium chloride is configured to (0.1-1) mol/L, is weighed；

5), the three-electrode system handled well is connect with Portable heavy metal detector, insertion contains Hg²⁺Ion In the HCl plating mercury solution of 0.1mol/L, the current potential 120s of application -1.0V, in triplicate, the glassy carbon electrode surface plated should cover one The uniform silver gray mercury film of layer.

6) (0.2-2.0) mol/L NaAc_HAc buffer solution 2mL, is pipetted in measuring cup, by following A, B, C, D Method adds the solution of step 2) 3) 4), is added in 50 μ g/L sexavalence chromium standard solution of 20mL, after mixing for use；

Wherein, tetra- kinds of ABCD experiment be by add different proportion comparative test, come verify DTPA, nitrate ion and Chloride ion role, its purpose is to illustrate the reasonability of step 1), 2), 3) He 4) obtained concentration ratio.

Then follow up the optimum proportioning of determined electrolyte solution again, arrives embodiment 3 using subsequent given embodiment 1 (error of indication experiment, repeated experiment and accuracy) verifies the effect of the electrolyte solution of invention.

Test A:

(0.2-2.0) mol/L NaAc_HAc buffer solution 2mL is pipetted in electrolysis cup by the step 6), with The sequence that (0.1-2) ml is gradually increased adds (10-60) g/L DTPA enveloping agent solution, is added to 50 μ g/L Cr VI of 20mL In standard solution, step 7) is executed after mixing, has a small peak point current to occur at about -1.164V, and with DTPA The increase of content, dissolution peak point current are increased slightly, after fall off due to non-hexavalent chromium characteristic peak because of mercury film.

Test B:

By the step 6) removing step 1) (0.2-2.0) mol/L NaAc_HAc buffer solution 2mL in electrolysis cup, The sodium chloride solution of 1ml (0.1-1) mol/L is added, by the DTPA complexing of (0.1-2) ml sequence addition step 2) gradually increased Agent solution is added in 50 μ g/L sexavalence chromium standard solution of 20mL, executes step 7) after mixing, has at about -1.172v One minor peaks occur, and with the increase of DTPA content, dissolve out peak point current and be increased slightly and be fixed on certain value, determine addition The DTPA enveloping agent solution of 0.3ml.With the addition of chloride ion, the mercury film of preplating no longer falls off, but Acetic acid-sodium acetate buffers There was only the presence of chloride ion and DTPA complexing agent in solution, relative to 50 μ g/L sexavalence chromium standard solutions, there is no apparent Cr VI characteristic peak.Increase enrichment time, dissolution peak point current is almost unchanged.

Test C:

By the step 6) removing step 1) (0.2-2.0) mol/L NaAc_HAc buffer solution 2mL in electrolysis cup, (10-60) g/L DTPA enveloping agent solution of step 2) 0.3ml is added, then the step 3) of addition certain proportion, 4) solution, It is added in 50 μ g/L sexavalence chromium standard solution of 20mL, executes step 7) after mixing, have at about -1.2V one larger molten Peak point current occurs out.With the increase of nitrate ion content in step 3), dissolves out peak point current and become larger.

Test D:

By the step 5) again preplating mercury film, by the step 6) removing step 1) (0.2-2.0) mol/L acetic acid-vinegar (10-60) g/L DTPA enveloping agent solution and step 3) of step 2) 0.3ml is added in electrolysis cup in sour sodium buffer solution 2mL The sodium nitrate solution of 0.6ml (1-4) mol/L is added to 20mL respectively to add step 4) solution and not add step 4) solution In 50 μ g/L sexavalence chromium standard solutions, step 7) is executed after mixing, and the mercury film electrode for not adding step 4) solution is often surveyed Measuring several data, i.e. there is a phenomenon where mercury films to fall off later, and after adding a certain amount of step 4) solution, it is de- no longer to there is mercury film Phenomenon is fallen, and the dissolution peak point current repeatability of the hexavalent chromium of same concentration is good.By experimental analysis, preplating mercury film is removed It can be stabilized in an acidic solution, its stability and work can be improved being added a large amount of chloride ions close in neutral environment Property.

It can be obtained by testing A-D, the addition of chloride ion, it is therefore prevented that mercury film falls off；The addition of nitrate ion, is played The effect of catalysis oxidation；And in the electrolyte solution, the solubility of DTPA is greatly increased, can be without passing through heated at constant temperature It can be detected hexavalent chromium etc. many and diverse device.The agents coordinate Portable heavy metal instrument, compared with similar products more suitable for Application in terms of fast slowdown monitoring.

7) after, the three-electrode system for handling step 5) well is rinsed well with deionized water, inserting step 6) solution in (remarks: the verifying through step 6) is the mixed solution of the four kinds of reagents 1), 2), 3) He 4) obtained used in practical operation), It is connect with heavy metal detector (Portable heavy metal detector), continuously applies voltage different twice: apply (- 1.2~- 1.5) v accumulating potential 1 (30~60) s；Accumulating potential 2 (10~120) s for applying (- 0.1~-0.8) v, in -0.9v~-1.5v Scanning in range.

Wherein, it is preferably configured by the preferred parameter in following table 1:

Table 1:

Below with reference to more specific embodiment, the present invention will be described.

Signified electrolyte solution preparation method of the invention is as follows:

109.2g sodium acetate, the DTPA of (10-30) g, the sodium nitrate of (42.5-170) g, (2.93-29.3) g are weighed respectively Sodium chloride pipettes 2.4mL glacial acetic acid, is diluted with water to 500mL, is uniformly mixed spare.The solution in sealed states can be at least It saves more than half a year.

Sampling method using Cr VI in solution detection water sample is as follows:

It pipettes 20mL water sample to be added in measuring cup, the above-mentioned electrolyte solution of 2mL is added, after mixing, insertion is pre- in advance The glass-carbon electrode, reference electrode, platinum electrode three-electrode system of mercury film are plated, connection heavy metal detector can divide water sample Analysis test.

Embodiment 1:

1) 5 clean 100mL volumetric flasks, are taken, it is each that the above-mentioned electrolyte solution of 10mL is added, pipette respectively 20 μ L, 40 μ L, The sexavalence chromium standard solution of the 100mg/L of 60 μ L, 80 μ L, 100 μ L are diluted to scale into 5 volumetric flasks, are configured to 20 μ g/ L, 40 μ g/L, 60 μ g/L, 80 μ g/L, 100 μ g/L series standard solution, pipette 20mL in measuring cup respectively.

2) three-electrode system being made of mercury film electrode, reference electrode, platinum electrode, is connected to Portable heavy metal instrument On.

3), three-electrode system is sequentially placed into and fills 20 μ g/L, 40 μ g/L, 60 μ g/L, 80 μ g/L, 100 μ g/L series marks In the electrolysis cup of quasi- solution." calibration " key is selected, each point is successively demarcated, saves nominal data after 5 points of calibration.

Attached drawing 1 is that the peak type figure of 1 series standard solution of embodiment is superimposed, and the curve graph of various concentration shows to use in figure The electrolyte solution test Cr VI has good linear in (0-100) μ g/L.

Embodiment 2:

1) 1 clean 200mL volumetric flask, is taken, the above-mentioned electrolyte solution of 20mL is added, pipettes the 100mg/L's of 100 μ L Sexavalence chromium standard solution is diluted to scale into volumetric flask, is configured to the sexavalence chromium standard solution of 50 μ g/L, pipettes 20mL in survey In measuring cup.

2), the three-electrode system in example 1 is put into the sexavalence chromium standard solution of 50 μ g/L, selection " measurement " key, continuous 6 It is secondary that the solution is measured.6 measurement results are respectively as follows: 48.5 μ g/L, 50.4 μ g/L, 49.0 μ g/L, 49.0 μ g/L, 50.9 μ g/L, 49.3 μ g/L, relative standard deviation 1.87%.

Embodiment 3:

1) 1 clean 100mL volumetric flask, is taken, the above-mentioned electrolyte solution of 10mL is added, is diluted to scale, is uniformly mixed, It pipettes spare in 20mL addition measuring cup.

2) the sexavalence chromium standard solution of 40 μ L1mg/L, is accurately pipetted into measuring cup 1), and theoretical value is 2 μ g/L.

3), three-electrode system is put into the measuring cup, starts to carry out mark-on test, with distinguishing twice in succession in cup solution The sexavalence chromium standard solution of the 1mg/L of 60 μ L is added, measurement terminates instrument to directly read result to be 2.58 μ g/L, with 2 μ of theoretical value G/L is close.

As can be seen from the above embodiments, Cr VI Cr (VI) is first reduced into trivalent chromium Cr in the working electrode surface of preplating mercury film (III), while DTPA present in solution is adsorbed on mercury film surface, forms complex compound Cr (III)-DTPA with trivalent chromium Cr (III), When voltage is scanned to cathode, part or all of Cr (III)-DTPA continues to be reduced into Cr (II)-DTPA, and nitrate anion is strong at this time Cr (II)-DTPA is oxidized to Cr (III)-DTPA again by oxidisability, to solve the problems, such as that dissolution peak point current becomes smaller；Due to It joined chloride ion in mixed solution, not only inhibit the generation because of electrode surface calomel that mercury film is caused to fall off, and prevent mercury Membranous surface activity reduces.

Electrolyte solution provided by the invention using preplating mercury film detection Cr VI has the following beneficial effects:

(1), the chloride ion being added prevents mercury film to fall off, and prevents the reduction of mercury membranous surface activity；

(2), the trivalent chromium that the nitrate ion being added prevents reduction to generate continues to be reduced into bivalent chromium；

(3), the solubility of DTPA improves complexing by being dissolved only in the 5g/L of the water at least 60g/L into the electrolyte solution Effect no longer needs to the operation that voltammetry detection Cr VI is simplified using thermostat；

(4), the different ratio of various composition substantially increases the sensitivity that voltammetry surveys Cr VI in electrolyte solution, rich The collection time only needs 10s, reduces trivalent chromium Cr (III) and continues the time for being reduced to bivalent chromium Cr (II).

The above beneficial effect compared with similar products quickly supervising more suitable for Portable heavy metal instrument by function and adaptability Survey the application of aspect.

Claims (10)

1. a kind of electrolyte solution using mercury film electrode detection Cr VI, which is characterized in that relative to final mixed solution, group At each component concentration of the electrolyte solution are as follows:

(1), the NaAc_HAc buffer solution of 0.2-2mol/L；

(2), the DTPA of 10-60g/L；

(3), the mixed solution of the sodium nitrate of 1-4mol/L, potassium nitrate solution or both；

(4), the mixed solution of the sodium chloride of 0.1-1mol/L, Klorvess Liquid or both.

2. according to claim 1 using the electrolyte solution of mercury film electrode detection Cr VI, which is characterized in that the vinegar Acid-sodium acetate buffer pH value is 5-7.

3. according to claim 1 using the electrolyte solution of mercury film electrode detection Cr VI, which is characterized in that the vinegar Acid-sodium acetate buffer is 2mol/L relative to the concentration of final mixed solution in final mixed solution.

4. according to claim 1 using the electrolyte solution of mercury film electrode detection Cr VI, which is characterized in that described DTPA enveloping agent solution is 60g/L relative to the concentration of final mixed solution in final mixed solution.

5. according to claim 1 using the electrolyte solution of mercury film electrode detection Cr VI, which is characterized in that the nitre The concentration relative to final mixed solution of the final mixed solution of the mixed solution of sour sodium, potassium nitrate solution or both is 2mol/ L。

6. according to claim 1 using the electrolyte solution of mercury film electrode detection Cr VI, which is characterized in that the chlorine Changing concentration of the mixed solution of sodium, Klorvess Liquid or both in final mixed solution relative to final mixed solution is 1mol/L。

7. a kind of method using the detection Cr VI of electrolyte solution described in any claim in claim 1-6, feature It is, includes the following steps:

(1), the electrolyte solution is uniformly mixed with the water sample to be measured containing Cr VI by the volume ratio of 1:10 to 1:1, it is spare；

(2), the glass-carbon electrode of the good mercury film of prior preplating, reference electrode, platinum electrode three-electrode system and heavy metal detector are connected It connects, insertion contains Hg²⁺In the plating mercury solution of ion, processing to the glassy carbon electrode surface plated covers one layer of uniform silver gray mercury film；

(3), after the three-electrode system that step (2) is handled well being cleaned up, in inserting step (1) resulting mixed solution, with Heavy metal detector connection, applies voltage twice in succession: applying accumulating potential 1 (30~60) s of (- 1.2~-1.5) v；Apply Accumulating potential 2 (10~120) s of (- 0.1~-0.8) v.

8. the method for electrolyte solution detection Cr VI according to claim 7, which is characterized in that in step (2), Hg²⁺From The plating mercury solution for the HCl that the plating mercury solution of son is 0.1mol/L, processing step includes the current potential 120s of application -1.0V, in triplicate Operation.

9. the method for electrolyte solution detection Cr VI according to claim 7, which is characterized in that specific in step (3) Parameter are as follows:

Accumulating potential 1:-1.5v；

Enrichment time: 30s；

Accumulating potential 2:-0.1v；

Enrichment time: 10s；

Quiescent time: 20s；

Scan current potential: -0.9v~-1.5v；

Clean current potential: -1.5v；

Scavenging period: 20s.

10. the method for electrolyte solution detection Cr VI according to claim 9, which is characterized in that in step (1), electrolysis The mixed volume ratio of matter solution and the water sample to be measured containing Cr VI is 1:10.