CN109655509A - A kind of new method of synchronous detection Pb ion and Cd ion - Google Patents
A kind of new method of synchronous detection Pb ion and Cd ion Download PDFInfo
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- 238000000034 method Methods 0.000 title claims abstract description 29
- 230000001360 synchronised effect Effects 0.000 title claims abstract description 15
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- G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
- G01N27/00—Investigating or analysing materials by the use of electric, electrochemical, or magnetic means
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- G01N27/28—Electrolytic cell components
- G01N27/30—Electrodes, e.g. test electrodes; Half-cells
- G01N27/308—Electrodes, e.g. test electrodes; Half-cells at least partially made of carbon
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- G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
- G01N27/00—Investigating or analysing materials by the use of electric, electrochemical, or magnetic means
- G01N27/26—Investigating or analysing materials by the use of electric, electrochemical, or magnetic means by investigating electrochemical variables; by using electrolysis or electrophoresis
- G01N27/28—Electrolytic cell components
- G01N27/30—Electrodes, e.g. test electrodes; Half-cells
- G01N27/333—Ion-selective electrodes or membranes
- G01N27/3335—Ion-selective electrodes or membranes the membrane containing at least one organic component
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
- G01N33/00—Investigating or analysing materials by specific methods not covered by groups G01N1/00 - G01N31/00
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- G01N33/1813—Specific cations in water, e.g. heavy metals
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Abstract
A kind of new method of synchronous detection Pb ion and Cd ion, belongs to a kind of method detected by composite film material to Pb ion in environment water and Cd ion.Obtained CNTs/poly (β-CD) electrode is first scanned in the acetate buffer solution (ABS) of pH=5 50mL using linear scan, until curve is stablized, a certain amount of Pb is added in ABS solution2+Standard solution and Cd2+Standard solution under stirring condition, stands 20 s, observation oxidation peak current value from -0.3V ~ -1V linear scan curve, recording curve in -1V preenrichment, the temperature of experiment is 25 ± 0.1 DEG C after a certain period of time.The present invention is quick, easy, and joint time current curve is applied to Pb in synchronous detection water with linear scan research CNTs/poly (β-CD) composite film material modified electrode2+And Cd2+。
Description
Technical field
The invention belongs to a kind of detection methods of heavy metal in environment water, particularly belong to a kind of by composite film material pair
The method that Pb ion and Cd ion are detected in environment water.
Background technique
In recent years, increasing to the exploitation processing of heavy metal, heavy metal element is not just discharged by processing, in turn
Cause the pollution of water body, soil property.It is well known that heavy metal can not be degraded, but can constantly be accumulated by food chain, finally
Then possibly into and poison human body.Therefore, heavy metal pollution be food, environment, the monitoring of hygiene the most important thing.Currently, micro
There are many mature analyzing detecting methods for the measurement of heavy metal.Such as ultraviolet-visible spectrophotometry (UV), atomic absorption method
(AAS), Raman spectroscopy, Inductively coupled plasma-mass spectrometry (ICP-MS), high performance liquid chromatography (HPLC), the chromatography of ions
Deng though they have the advantages that respective, also generally existing equipment price is expensive, and instrument maintenance expense is larger, and application surface is narrow etc.
Disadvantage.Interfacial electrochemistry is quickly grown in recent years, relative to the valuableness of other detection heavy metal ion methods such as photometry, operation
Complexity, electrochemical analysis method is not only sensitive, quick, efficient, and it is easy to operate, easy to carry, cost is relatively low, answered extensively
It uses among detection heavy metal ion, and the attention more and more by people.Accordingly it is desirable to can have one kind effective
The method for detecting Pb ion and Cd ion in water.
Summary of the invention
The purpose of the present invention is being directed to defect described above, the new side of a kind of synchronous detection Pb ion and Cd ion is provided
Method, this method is easy to operate, easy to carry, when detecting easy and Pb2+And Cd2+In conjunction with Pb when being easy to detect2+And Cd2+It is rich
Collection.
The purpose of the present invention is what is be achieved by the following technical programs.
A kind of new method of synchronous detection Pb ion and Cd ion, it is characterised in that: in turn include the following steps:
(1) CNTs/ poly (β-CD) combination electrode is prepared:
(1) pretreatment of glassy carbon electrode
Polishing powder (the Al of suitable 30 nm is sprinkled on chamois leather2O3), a few drop deionized waters are then added dropwise, with glass-carbon electrode side
Edge stirs evenly, and pinches glass-carbon electrode vertically afterwards, uniformly firmly, at the uniform velocity draws circle, is then cleaned with deionized water, ear washing bulb is blown
It is dry, nitric acid is dripped in glassy carbon electrode surface, is cleaned after static 10 ~ 15 s with deionized water, then in ethanol water, nitre
20 s of ultrasound are distinguished in aqueous acid, deionized water, ear washing bulb drying is spare；
The glass-carbon electrode handled well is put into 5 mM K3Fe(CN)6、0.2 M KNO3In solution, with electrochemical workstation, use
Three-electrode system, reference electrode select saturated calomel electrode (SCE), select carbon-point to electrode, working electrode selects glass-carbon electrode
(GCE) (3 mm of diameter), using cyclic voltammetry, the scanning in the scanning range of 0 ~ 0.5 V；If redox peaks potential difference
Within 64 mV or so, 80 mV, 0.2 M H is changed to2SO4It is activated in solution, the scanning in -0.2 ~ 1.4V, until circulation volt
Antu repeats；
(2) processing of carbon nanotube
1) electronic balance weighs 5.0 g hydroxylated multi-walled carbon nanotubes, takes the HCL of 100 mL, 0.4 M with graduated cylinder, MWCNT and
HCL solution mixes, 5 h of mechanical stirring after ultrasonic oscillation；
2) in the H of 100 mL2SO4And HNO3Ultrasonic 5 hours in mixed solution (concentration ratio is 3:1), then magnetic agitation 10 are small
When；
3) carbon nanotube and mixed acid solution are filtered by vacuum, and are washed with deionized water to neutrality, and dry 24 h are placed in drying box；
4) take the processed carbon nanotube of 5 mg that deionized water is added to be settled to 10 mL, ultrasound is uniform to solution, spare；
(3) preparation of poly (β-CD) electrode
At room temperature, accurate measuring the good concentration of configured in advance be 0.1 M, pH value be 6 50 mL of phosphate buffer solution,
0.125 mM beta-cyclodextrin is added, ultrasound takes out placement after obtaining within 20 minutes uniform mixed solution after stirring to all dissolutions
It is spare；The same step of three-electrode system (1), scanning range are -1 ~ 2 V, and sweeping speed is 100 mV/s；Poly- β-is obtained after deposition
Cyclodextrin electrode is rinsed well rear spare with deionization；
(4) preparation of CNTs electrode
Taking 6 μ L concentration with liquid-transfering gun is that the MWCNTs of 0.5 mg/mL drops to the surface glass-carbon electrode (GCE), is placed under ultraviolet lamp,
It takes out to obtain CNTs electrode after drying, dries up spare after being rinsed with deionization, sample is named as CNTs electrode；
(5) preparation of CNTs/ poly (β-CD) electrode
CNTs electrode is taken to be put into the cyclodextrin PBS mixed solution prepared (concentration and step (3) are same)；Three-electrode system is same
Step (1) carries out electropolymerization using cyclic voltammetric, and scanning range is -1 ~ 2 V, and sweeping speed is 50 mV/s；After deposition
It to CNTs/poly (β-CD) electrode, is rinsed well with deionization rear spare, obtains CNTs/poly (β-CD) electrode；
(2) CNTs/ poly (β-CD) electrode is to Pb2+And Cd2+Detection:
Obtained CNTs/poly (β-CD) electrode is first used into line in the acetate buffer solution (ABS) of 50 pH=5 mL
Property scanning scanning, until curve stablize, a certain amount of Pb is added in ABS solution2+Standard solution and Cd2+Standard solution, stirring bar
Under part, 20 s are stood after a certain period of time in -1 V preenrichment, observe the linear scan curve from -0.3 V of V ~ -1, record is bent
Oxidation peak current value in line, the temperature of experiment are 25 ± 0.1 DEG C.
1891, beta-cyclodextrin (β-Cyclodextyin, abbreviation β-CD) came out, and initial stage is due to being attributed to fine chemistry
Product, it is expensive, therefore application is limited, cannot be widely applied.Later with the continuous advance of biotechnology, β-CD can be with
Large-scale production, the cheap of change obtain extensive use in fields such as industrial or agricultural, medicine also food, cosmetics quickly later.D-
Mutually with a-1,4 sugared two keys are connected glucose, cyclodextrin (CD) molecule are formed, in the tubular structure of closure.Tubular CD molecule
Center electron density is very high, and primary hydroxyl and secondary hydroxyl are protruded from both ends respectively.β-CD has the general character of cyclodextrin, and molecular structure is very
Especially, molecular center is hydrophobic, and outside is hydrophilic, and the hole at center can adsorb various guest molecules and form stable inclusion compound, keeps away
Object loses caused by exempting from because of illumination, volatilization, oxidation etc..In the application of β-CD, more be chemically modified by parent of β-CD,
It is exactly also the covalent immobilized of β-CD, it is immobilized to can solve β-CD good water solubility, it is difficult to which that the problem of recycling can also retain β-
CD cavity structure, and then retain its excellent property, the better effect if β-CD and carrier can form synergistic effect.It is immobilized
There are many type, can substantially be divided into inorganic immobilized, organic synthesis Polymer Supported and the immobilized three classes of natural polymer.β-CD is immobilized
In CNTs, nanofiber, zeolite, SiO2On the inorganic carriers such as particle, the available material that can adsorb environmental contaminants, β-
CD good water solubility itself, with possess high-specific surface area carrier between synergistic effect so that inclusion absorption property and water solubility
It improves a lot.Electropolymerization is the common preparation method of high molecular material modified electrode, one is preparation process can be controlled
System, film quality obtained is high, uniform, then secured with electrode surface, the second is method is simple, experiment condition is easy to accomplish,
Thus it is widely used.As shown in Figure 1.
The beneficial effects of the present invention are: CNTs electric conductivity that the present invention uses is high, large specific surface area, poly (β-CD) contains
Many hydroxyls, easy and Pb2+And Cd2+In conjunction with Pb when being easy to detect2+And Cd2+Enrichment, CNTs/poly (β-CD) THIN COMPOSITE membrane material
Material has both the advantages of the two.Therefore the present invention has the glass-carbon electrode of CNTs as carrier using drop coating, electropolymerization poly (β-on it
CD), CNTs/poly (β-CD) composite film material is prepared.With cyclic voltammetric study film forming procedure, joint time current curve and
Linear scan studies CNTs/poly (β-CD) composite film material modified electrode and is applied to Pb in synchronous detection water2+And Cd2+。
Detailed description of the invention
Fig. 1 is that CNTs/poly (β-CD) composite film material modified electrode detects Pb2+And Cd2+Mechanism schematic diagram.
Fig. 2 is electrodeposition process figure of the beta-cyclodextrin on glass-carbon electrode.
Fig. 3 is deposition process figure of the beta-cyclodextrin on CNTs electrode.
Fig. 4 is respectively bare glassy carbon electrode (a), poly- beta-cyclodextrin glass-carbon electrode (b), poly- beta-cyclodextrin electro-conductive glass (c) figure.
Fig. 5 is respectively poly- beta-cyclodextrin SEM figure (a), carbon nanotube SEM figure (b), carbon nano-tube/poly beta-cyclodextrin SEM figure
(c)。
Fig. 6 is respectively the infrared figure (a) of beta-cyclodextrin, the infrared figure (b) of poly- beta-cyclodextrin.
Fig. 7 be bare (a), carbon nanotube (b), poly- beta-cyclodextrin (c), carbon nano-tube/poly beta-cyclodextrin (d) modification electricity
Pole is in 5 mM Fe (CN) 63-/4-CV figure in redox couple.
Fig. 8 be bare (a), carbon nanotube (b), poly- beta-cyclodextrin (c), carbon nano-tube/poly beta-cyclodextrin (d) modification electricity
Pole is in 5 mM Fe (CN) 63-/4-Nyquist diagram in redox couple.
Fig. 9 is bare (a), CNTs(b), the glass-carbon electrode of poly- beta-cyclodextrin (d) modification of poly- beta-cyclodextrin (c), CNTs/
It is including 1 ppm Pb2+With 0.1 ppm Cd2+0.1 M acetate salt buffer molten (pH=5) in figure linear scan figure (pre- richness
- 1 V of collecting voltage, the preenrichment time 240 is s); vs SCE.
Figure 10 is respectively carbon nano tube modified glass-carbon electrode in 5 mM Fe (CN) of neutrality6 3-/4-Redox couple
It (include 5 mM K4Fe(CN)6·3H2O、5 mM K3Fe(CN)6And 0.1 M KCl) in respectively with 0.02 ~ 0.18 VS-1
Sweep the obtained cyclic voltammogram of speed and peak current (from the inside to surface) and sweep the subduplicate linear graph of speed.
Figure 11 is respectively the glass-carbon electrode of carbon nano-tube/poly beta-cyclodextrin modified in 5 mM Fe (CN) of neutrality6 3-/4-Oxidation
Reduction electricity (includes 5 mM K to solution4Fe(CN)6·3H2O、5 mM K3Fe(CN)6And 0.1 M KCl) in respectively with 0.02
~ 0.18 VS-1(from the inside to surface) cyclic voltammogram and peak current and sweep the subduplicate linear graph of speed that speed obtains are swept.
Figure 12 is the optimization figure of pH.
Figure 13 is the optimization figure of preenrichment voltage.
Figure 14 is the optimization figure of preenrichment time.
Figure 15 is carbon nanotube/beta-cyclodextrin modified glass-carbon electrode containing being 0.01 ~ 0.11 ppm Cd2+0.1
(illustration is peak current and Cd for (pH=5) linear scan response in M acetate buffer solution2+The linear graph of concentration).
Figure 16 is that carbon nanotube/beta-cyclodextrin modified glass-carbon electrode is containing 0.16 ~ 1.8 ppm Pb2+0.1M vinegar
(illustration is peak current and Pb to (pH=5) linear scan figure in hydrochlorate buffer solution2+The linear graph of concentration).
Figure 17 is carbon nanotube/beta-cyclodextrin modified glass-carbon electrode 0.01 ~ 0.09 ppm Pb of detectable concentration simultaneously2+
And Cd2+Figure is responded in the linear scan of ion, and (illustration is peak current and Cd2+Concentration (a) and Pb2+The linear graph of concentration (b)).
Figure 18 is respectively 0 ~ 5 ppmZn of CNTs/ beta-cyclodextrin electrode detection2+Concentration and 0 ~ 10 ppmCu2+It is linear
Scanning figure.
Figure 19 is that the glass-carbon electrode of CNTs/poly (β-CD) modification is including 0.02 ppm Cd2+With 0.2 ppm Pb2+
0.1M acetate buffer solution (pH=6) in -1 V, the linear scan figure (a) and+0.5 after 240 s preenrichments under stirring state
V solves the linear scan figure (b) after 240 s of chelating under stirring state.
Figure 20 is that the glass-carbon electrode of the poly- beta-cyclodextrin modified of CNTs/ is containing 0.3 ppm(a respectively), 0.6 ppm(b),
0.9 ppm(c) Pb2+With 0.1 ppmCd2+0.1 M acetate buffer solution (pH=5) in linear scan figure.
Figure 21 is that the glass-carbon electrode of the poly- beta-cyclodextrin modified of CNTs/ is containing 0.03 ppm(a respectively), 0.06 ppm(b),
0.09 ppm(c) Cd2+With 0.3 ppmPb2+0.1 M acetate buffer solution (pH=5) in linear scan figure.
Figure 22 is CNTs/ beta-cyclodextrin electrode repeatability figure.
Figure 23 is the poly- beta-cyclodextrin electrode reproducibility figure of CNTs/.
Specific embodiment
In order to further illustrate the present invention, following serial specific embodiment is provided in conjunction with attached drawing, but the present invention is not by this
The limitation of a little specific embodiments, any understanding person skilled in art will can achieve few modifications of the invention similar
As a result, these changes are also contained among the present invention.
Embodiment 1.
One, the configuration of metal ion standard solution.
The preparation method (1 mg/mL) of copper standard solution:
Weigh copper sulphate (CuSO4·5H2O) 3.9281 g, adds moderate amount of sulfuric acid, and constant volume shakes up standby in 1000 mL volumetric flasks
With.
The preparation method (0.1 mg/mL) of Zinc standard solution:
Weigh zinc sulfate (ZnSO4·7H2O) 44 mg, constant volume shake up spare in 1000 mL volumetric flasks.
The preparation method (1 mg/mL) of cadmium standard solution:
2.0311 g of caddy is weighed, constant volume shakes up spare in 1000 mL volumetric flasks.
The preparation method (0.1 mg/mL) of lead standard solution:
Weigh plumbi nitras (Pb (NO3)2) 0.160 g, add appropriate nitric acid, constant volume shakes up spare in 1000 mL measuring bottles.
Two, the preparation of CNTs/poly (β-CD) electrode.
(1) pretreatment of glassy carbon electrode
Polishing powder (the Al of suitable 30 nm is sprinkled on chamois leather2O3), a few drop deionized waters are then added dropwise, with glass-carbon electrode side
Edge stirs evenly, and pinches glass-carbon electrode vertically afterwards, uniformly firmly, at the uniform velocity draws circle, is then cleaned with deionized water, ear washing bulb is blown
It is dry, nitric acid is dripped in glassy carbon electrode surface, is cleaned after static 10 ~ 15 s with deionized water, then in ethanol water, nitre
20 s of ultrasound are distinguished in aqueous acid, deionized water, ear washing bulb drying is spare；
The glass-carbon electrode handled well is put into 5 mM K3Fe(CN)6、0.2 M KNO3In solution, with electrochemical workstation, use
Three-electrode system, reference electrode select saturated calomel electrode (SCE), select carbon-point to electrode, working electrode selects glass-carbon electrode
(GCE) (3 mm of diameter), using cyclic voltammetry, the scanning in the scanning range of 0 ~ 0.5 V；If redox peaks potential difference
Within 64 mV or so, 80 mV, 0.2 M H is changed to2SO4It is activated in solution, the scanning in -0.2 ~ 1.4V, until circulation volt
Antu repeats；
(2) processing of carbon nanotube
1) electronic balance weighs 5.0 g hydroxylated multi-walled carbon nanotubes, takes the HCL of 100 mL, 0.4 M with graduated cylinder, MWCNT and
HCL solution mixes, 5 h of mechanical stirring after ultrasonic oscillation；
2) in the H of 100 mL2SO4And HNO3Ultrasonic 5 hours in mixed solution (concentration ratio is 3:1), then magnetic agitation 10 are small
When；
3) carbon nanotube and mixed acid solution are filtered by vacuum, and are washed with deionized water to neutrality, and dry 24 h are placed in drying box；
4) take the processed carbon nanotube of 5 mg that deionized water is added to be settled to 10 mL, ultrasound is uniform to solution, spare；
(3) preparation of poly (β-CD) electrode
At room temperature, accurate measuring the good concentration of configured in advance be 0.1 M, pH value be 6 50 mL of phosphate buffer solution,
0.125 mM beta-cyclodextrin is added, ultrasound takes out placement after obtaining within 20 minutes uniform mixed solution after stirring to all dissolutions
It is spare；The same step of three-electrode system (1), scanning range are -1 ~ 2 V, and sweeping speed is 100 mV/s；Poly- β-is obtained after deposition
Cyclodextrin electrode is rinsed well rear spare with deionization；
(4) preparation of CNTs electrode
Taking 6 μ L concentration with liquid-transfering gun is that the MWCNTs of 0.5 mg/mL drops to the surface glass-carbon electrode (GCE), is placed under ultraviolet lamp,
It takes out to obtain CNTs electrode after drying, dries up spare after being rinsed with deionization, sample is named as CNTs electrode；
(5) preparation of CNTs/ poly (β-CD) electrode
CNTs electrode is taken to be put into the cyclodextrin PBS mixed solution prepared (concentration and step (3) are same)；Three-electrode system is same
Step (1) carries out electropolymerization using cyclic voltammetric, and scanning range is -1 ~ 2 V, and sweeping speed is 50 mV/s；After deposition
It to CNTs/poly (β-CD) electrode, is rinsed well with deionization rear spare, obtains CNTs/poly (β-CD) electrode.
Three, the characterization of CNTs/poly (β-CD) material.
The microstructure of material is observed using field emission scanning electron microscope (FESEM), and acceleration voltage is 15 kV.Electricity
Mirror sample preparation methods: electropolymerization obtains material on the electrode, removes electrode tip and observes directly at microscope.Material it is infrared
Infrared sample preparation methods: spectrum is obtained using measuring in Fourier Transform Infrared Spectrometer in electro-conductive glass on piece electropolymerization
Material scrapes dusty material, carries out tabletting with KBr.
Four, electro-chemical test.
The AC impedance (EIS) of material is that test is completed on CHI660C electrochemical workstation, using three electricity of standard
Polar body system, reference electrode select saturated calomel electrode (SCE), select carbon-point to electrode, working electrode selects different materials modification
Glass-carbon electrode (GCE) (3 mm of diameter), supporting electrolyte solution be include 5 mM K3[Fe(CN)6] and 5 mM K4Fe
(CN)6·3H2The 0.1 M KCl solution of O, frequency range are set as the kHz of 0.1 Hz ~ 100.
Five, modified electrode is to Pb2+And Cd2+Detection.
Different modifying electrode (CNTs electrode, p-CD electrode or CNTs/p-CD electrode) is first in the vinegar of 50 pH=5 mL
It is scanned in hydrochlorate buffer solution (ABS) using linear scan, until curve is stablized, a certain amount of Pb is added in ABS solution2+Standard
Solution and Cd2+Standard solution under stirring condition, stands 20 s in -1 V preenrichment after a certain period of time, and observation is from -0.3 V ~ -1
The linear scan curve of V, oxidation peak current value in recording curve, the temperature of experiment are 25 ± 0.1 DEG C.
Six, results and discussion.
1, the manufacturing process of sample.
In order to study beta-cyclodextrin electropolymerization on the surface that glass-carbon electrode and drop have the glass-carbon electrode of CNTs, we are used
Cyclic voltammetry, using the PBS buffer solution of pH=6 as supporting electrolyte electropolymerization beta-cyclodextrin, electropolymerization voltage scan range
For the V of -2 V ~ 2.5 (vs.SCE).Beta-cyclodextrin on glass-carbon electrode electropolymerization figure as indicated with 1, the former circles of cyclic voltammetric, with
Electropolymerization carry out, electrode surface electroactive material is increasing, and redox peak is continuously increased, with electroactive material
Increase, electrode surface electric conductivity is affected and reduces, and rear a few circle peak currents are not further added by, and are slowly tended towards stability.Fig. 3 is β-ring
Dextrin cyclic voltammetry curve when drop has the glass-carbon electrode electropolymerization of CNTs, first lap peak current is very big, is because on electrode
CNTs electric conductivity is fine, keeps peak current very high, but with the progress of electropolymerization, electrode surface constantly has polymer generation, polymerization
Object relative molecular weight is big, and electric conductivity is poor, and conductivity of composite material is caused to reduce, and peak current reduces.Later because of electric active matter
Matter increases, and peak current starts to increase by a small margin, and later as electroactive material is continuously increased, electrode surface material thickeies, and leads
Electrically reduce, peak current tends towards stability.
2, the characterization and analysis of material.
(1) morphology analysis.
Fig. 4 is glass-carbon electrode (a), deposited the glass-carbon electrode (b) of beta-cyclodextrin and deposited the glass of beta-cyclodextrin (c)
The significant change of color proves that electro-deposition is successfully realized at piece, electrode and electro-conductive glass deposition materials.Fig. 5 is poly- beta-cyclodextrin
Electrode surface material shape appearance figure (the field emission scanning electron microscope of the poly- beta-cyclodextrin electrode (c) of electrode (a), CNTs electrode (b), CNTs/
Figure).It can significantly see, the non-uniform poly- beta-cyclodextrin material being stacked up is distributed on the poly- beta-cyclodextrin electrode of Fig. 5 a
Material, this is because the universal electric conductivity of high molecular polymer is bad, caused by causing deposition uneven.Fig. 5 b is CNTs electrode, can
Can be clearly seen that CNTs is more evenly distributed on glass-carbon electrode, CNTs tube wall is smooth smooth.Fig. 5 c can see,
After CNTs powers on β-cyclodextrin polymer, the surface CNTs is no longer smooth, has more uniformly coated layer of material, causes CNTs table
Face seems very coarse.This is because poly- beta-cyclodextrin more uniform deposition on CNTs with good conductivity, is coated on
The good electric conductivity of CNTs and biggish specific surface area are borrowed in the surface CNTs, increase entire material specific surface area, and electric conductivity mentions
Height, this be also after heavy metal preenrichment when, increase preenrichment amount provide possibility.
(2) infrared analysis.
It may determine that the functional group in material by infrared test, what (a), (b) were shown in Fig. 6 is pure beta-cyclodextrin respectively
With the infrared spectrogram of poly- beta-cyclodextrin material.Each absorption peak is respectively belonging in (b) in Fig. 6: 720,997,1220 cm-1Place
It is C-H deformation vibration C -- C single bond skeletal vibration, 1535 cm-1Place is C=O carbonylic stretching vibration (- CHO), 3220,3265,
3457、3510、3605 cm-1Place is O-H stretching vibration.
3, the electrochemical Characterization of modified electrode.
(1) impedance analysis.
It is bare, poly- beta-cyclodextrin, the poly- beta-cyclodextrin modified of CNTs, CNTs/ glass-carbon electrode in 5 mM Fe (CN) 63-/4-
Redox couple (includes 5 mM K4Fe(CN)6·3H2O、5 mM K3Fe(CN)6And 0.1 M KCl) circulation volt
Peace response is as shown in Figure 7.Compared with bare glass-carbon electrode, the glass of poly- beta-cyclodextrin, the poly- beta-cyclodextrin modified of CNTs, CNTs/
Carbon electrode peak point current has reduction, and poly (β-CD) reduces maximum.This conclusion shows the glass carbon for being attached with poly (β-CD)
Electrode surface electron transfer rate is reduced by containing, and electric conductivity reduces, and also turns out that poly (β-CD) electric conductivity is bad.It modifies
After the poly- beta-cyclodextrin of CNTs/, oxidation peak current and reduction peak current are all improved, and illustrate that electricity can be improved after having introduced CNTs
Pole surface conductive channel, because CNTs has good electric conductivity.This also can be from the glass-carbon electrode cyclic voltammogram for having modified CNTs
Middle peak current is higher, and slightly below bare glassy carbon electrode is confirmed.The glass-carbon electrode for having combined poly- beta-cyclodextrin and CNTs can be with
Better electrocatalysis characteristic is provided, the electronic transfer process of modified electrode can be promoted.
Modified electrode electrochemical properties are characterized by AC impedance simultaneously, and it is as shown in Figure 8 to obtain Nyquist diagram.Electrochemistry resistance
Anti- spectrum (EIS) is observed that the impedance variations of different modifying electrode, and interface can be modeled by equivalent circuit.The equivalent circuit
Ohmic resistance Rs, electronics transfer resistance Ret, double layer capacity Cd including electrolyte.EIS figure includes the control of interfacial charge transfer mechanics
The high frequency region of system and the low frequency range of diffusion control, high frequency region is in semi arch, and low frequency range is linear.Semi-circular portions diameter corresponds to electronics
Transfer resistance Ret, radius is bigger, and resistance is bigger, minimum 62 Ω of GCE resistance, and maximum poly- 1355 Ω of beta-cyclodextrin electrode, carbon is received
The poly- beta-cyclodextrin electrode of mitron electrode 750 Ω, CNTs/ because carbon nanotube addition, 855 Ω of resistance reduced.Such as Fig. 8
Shown, bigger according to semi-circular portions radius, the bigger conclusion of resistance is ranked up difference according to resistance sizes to it from small to large
It is: the poly- beta-cyclodextrin electrode of bare glassy carbon electrode, CNTs electrode, CNTs/, poly- beta-cyclodextrin electrode, it is consistent with fitting circuit resistance.
Prove that poly- beta-cyclodextrin reduces electron transfer rate in glassy carbon electrode surface, and resistance reduces after introducing CNTs, it is conductive
Property is significantly improved, these results are also proved by the above cyclic voltammetric data.
(2) modified electrode detects Pb2+And Cd2+When behavioural analysis.
As shown in figure 9, Different electrodes are in the acetate buffer solution containing heavy metal ion, through current-time curvel
(i-t) reduction reaction occurs, preenrichment is carried out, through LSV(linear sweep voltammetry) oxidation reaction occurs, preenrichment in electricity
Heavy metal ion releasing on extremely.Observe and record bare, CNTs, the glass of the poly- beta-cyclodextrin modified of poly- beta-cyclodextrin, CNTs/
The respective peak point current of carbon electrode.The preenrichment stage be including 1 ppm Pb2+With 0.01 ppm Cd2+Concentration be 0.1
With the deposition voltage of -1 V in the acetate buffer solution of pH=5 M, the sedimentation time of 240 s, with time current curve come into
Row preenrichment.Bare glass-carbon electrode has been barely perceivable peak, CNTs modification in voltage window between the V of -1 V ~ 0.4
Glass-carbon electrode can only observe very weak peak.Because although CNTs electric conductivity is fine, for relative target heavy metal ion,
There is no good chelating to act on.The glass-carbon electrode of poly- beta-cyclodextrin modified is compared, and peak current is greatly improved, because
The glass-carbon electrode of poly- beta-cyclodextrin modified has preferable chelant ability to target heavy metal ion, but since its electric conductivity is poor,
Peak current is not still highest.The glass-carbon electrode for the composite film material modification that poly- beta-cyclodextrin and CNTs are combined is shown relatively most
High most sharp peak current (Pb2+And Cd2+Go out peak position respectively in -0.5 V and -0.8 V), this may have benefited from composite wood
Synergistic effect in material between two materials of CNTs and poly- beta-cyclodextrin.
(3) the electroactive analysis of electrode surface.
According to Randles-Sevcik equation: ip=kn3/2ACD1/2γ1/2, can be calculated the glass-carbon electrode of CNTs modification
Glass carbon electroactive area with the poly- beta-cyclodextrin modified of CNTs/ is respectively 1.15 × 10-2 cm2With 1.09 × 10-2 cm2,
Electrode active area is about the same.However, the glass-carbon electrode of the poly- beta-cyclodextrin modified of CNTs/ detects Pb2+When peak current obviously compare
Carbon nano tube modified glass-carbon electrode is big, by this results presumption, dissolve out peak current increase may be because, poly (β-CD) though
Right electric conductivity is bad, but there is stronger chelant ability with heavy metal ion, so facilitate electrode surface accumulation lead ion, this
It is consistent with testing result in Fig. 9.
4, modified electrode detects Pb2+And Cd2+Condition optimizing.
It is bigger in order to there is the glass-carbon electrode of the poly- beta-cyclodextrin composite film material modification of CNTs/ when detecting heavy metal ion
Sensitivity, contain 1 ppm Pb in 0.1 M2+ 0.1 ppm Cd2+Acetate buffer solution in, to volt-ampere parameter (pH value,
Sedimentation potential, sedimentation time) it optimizes.
(1) pH detects Pb to modified electrode2+And Cd2+Influence.
PH value can influence the response of volt-ampere analysis, this is also to select a suitable pH why.The optimization of pH value
It is studied 4 ~ 6, as a result as shown in figure 12.When pH is between 4 to 5, Pb2+And Cd2+Peak current is increasing always, in pH
Maximum value is reached at=5, peak current declines always instead later.It is effectively pre- to target heavy ion in stripping volt ampere analysis
Enrichment process is very important, therefore some volt-ampere analysis signals, for example, detection lead ion when peak current size, be electric
What the degree size that pole material can capture lead ion was controlled.By experimental result it is recognised that this ability of poly- beta-cyclodextrin exists
It is stronger when close to 5 or so, it is weaker under acidic environment, and peak current declines in high pH value, it may be with Pb2+And Cd2+
Hydrolysis it is related, it may be possible to because of Pb2+And Cd2+The chelate for generating hydroxide, prevents Pb2+And Cd2+Enrichment, because
This is further tested with the acetate buffer solution of pH=5.
(2) preenrichment voltage detects Pb to modified electrode2+And Cd2+Influence.
Detection heavy metal ion is by the first preenrichment Pb on the electrode of i-t (time current curve)2+And Cd2+, Zhi Houzai
By linear scan by Pb2+Peak current size is observed in dissolution.Therefore, in stripping analysis, deposition voltage appropriate is for obtaining
Optimal sensitivity is very important.It is deposited in 0.1 M acetate buffer solution of pH=5 after 180 s with not synsedimentary
Influence of the voltage to peak current is studied, and result as shown in figure 13 is obtained.Deposition voltage has been selected from -0.4 ~ -1.2 V,
The Pb with concentration is detected under the same terms2+And Cd2+, observation peak current variation.It is observed after mapping, after enrichment, when dissolution
Increase oxidation peak current with voltage constantly to increase, until -1 V reaches oxidation peak current maximum, then increase preenrichment voltage, molten
Oxidation current reduces instead out.This may be to generate H because having begun this when2, have the competition of evolving hydrogen reaction, Pb2 +And Cd2+It is all when preenrichment recovery voltage is -1 V, dissolution oxidation peak current reaches maximum, therefore selects preenrichment voltage
Further experiment is carried out for -1 V.
(3) the preenrichment time detects Pb to modified electrode2+And Cd2+Influence.
As shown in figure 14, because sedimentation time may will affect detection limit and sensitivity, when being directed to different preenrichments
Between carry out dissolution peak current compare.60 s, 120 s, 180 s, 240 s, 300 s are selected, the preenrichment time is more long, on electrode
The Pb being reduced out2+And Cd2+More, the peak current aoxidized in linear scan is bigger.Therefore, as the preenrichment time increases
Add, Pb2+And Cd2+Peak current all successively increases when detection.But pass through observation analysis it is recognised that enrichment time is too long, electrode
Upper heavy metal ion is blocked up, is unfavorable for dissolving out instead.As the preenrichment time increases before being enriched with 240 s, Pb2+And Cd2+Inspection
Peak current all successively increases when survey, more than after 240 s with the preenrichment time increase, Pb2+And Cd2+Peak current is instead when detection
It reduces.This may with electrode surface with concentration of metal ions constantly increase and be saturated it is related, therefore select the preenrichment time
Further experiment is carried out for 240 s.
5, modified electrode is to Pb2+And Cd2+Detection research.
(1) detection limit and the range of linearity.
The preenrichment in the case of stirring in the case where all conditions are all optimal of CNTs/ beta-cyclodextrin electrode, then
It is dissolved out again with linear scan, observes its curent change.The Pb of various concentration2+And Cd2+Different responses such as Figure 15,16,17 institute
Show, derives corresponding standard curve (illustration in figure) accordingly.CNTs/ beta-cyclodextrin electrode individually detects Cd2+When, Cd2+-
Nearby there is clear sharp peak in 0.8 V, when concentration range is for 0.01 ~ 0.11 ppm between, dissolution peak current with accordingly
Concentration of heavy metal ion is directly proportional.Its linear equation are as follows: i (μ A)=- 3.36+291.56 c (ppm), coefficient R2 =
0.991, blank solution METHOD FOR CONTINUOUS DETERMINATION 11 times current value standard deviation be 3.8 %, the ppb(3 σ of LOD=0.39 method).
There is clear sharp peak near -0.5 V in lead ion when CNTs/ beta-cyclodextrin electrode individually detects lead ion, in concentration model
When enclosing between 0.16 ~ 1.8 ppm, dissolution peak current is directly proportional to corresponding concentration of heavy metal ion.Linear equation are as follows: i (μ
A)=13.77+26.05 c (ppm), coefficient R2=0.993, blank solution METHOD FOR CONTINUOUS DETERMINATION 11 times current value mark
Quasi- deviation is 3.8 %, the ppb(3 σ of LOD=4.3 method).CNTs cyclodextrin electrode detects Pb simultaneously2+And Cd2+When, two targets
Ion can observe apparent peak, and peak position is almost the same out, Cd2+Occur clear sharp peak, Pb near -0.8 V2 +Occur clear sharp peak, Cd near -0.5 V2+And Pb2+The enough width of peak separation, therefore use CNTs/ beta-cyclodextrin electrode
To Pb2+And Cd2+Synchronous detection be feasible.It as shown in figure 17, is respectively 0.01 ~ 0.09 ppm and 0.1 in concentration range
When between ~ 0.9 ppm, Cd2+And Pb2+Dissolution peak current is directly proportional to corresponding concentration of heavy metal ion, and linear equation is respectively i
(μ A)=- 1.4+369.54 c (ppm) and i (μ A)=- 4.82+51.99 c (ppm), related coefficient is respectively R2 =
0.996 and R2=0.996, Cd2+And Pb2+Detection limit be respectively the ppb(3 σ of the ppb of LOD=0.31 and LOD=2.77 method).
(2) selectivity.
When detecting heavy metal ion, selectivity is also vital.For other heavy metal ion such as Zn2+、Cu2+Point
It is not detected, discharge standard is respectively 2 ppm, 5 ppm, respectively with Zn2+(0,1,2,5 ppm) and Cu2+(0, 1,
5,10 ppm) detection, occur without apparent oxidation peak current.Experiments have shown that in the poly- beta-cyclodextrin electrode detection of CNTs/
Pb2+And Cd2+The range of linearity in it is not detected and impacts, it is seen that CNTs/poly (β-CD) electrode possesses relatively good
Selectivity.
(3) chelating is solved.
Detect heavy metal ion Pb2+And Cd2+When, in the case of stirring through constant potential first, preenrichment is for a period of time
Afterwards with the Pb that electrode surface is enriched with Differential Pulse Voltammetry again2+And Cd2+Peak current size is observed in dissolution.It dissolves out every time simultaneously
It cannot be Pb all on electrode2+And Cd2+It can dissolve out, thus will affect electrode and detect next time, therefore solve chelating energy to it
The research of power is also meaningful.It is dissolved out again through differential pulse voltammetry voltammetric scan after preenrichment, obtains Figure 19 a.As preenrichment
Condition: the same stirring rate, the same parameter setting (in addition to voltage) are also passed through with the solution chelating voltage of 0.5 V
120 s, again to detect when parameter scanned to obtain Figure 19 b with differential pulse voltammetry, can be evident that, not observe
The oxidation peak of lead ion and cadmium ion, the Pb on electrode2+And Cd2+Taken off completely by solution.Therefore we it is concluded that,
CNTs essence cyclodextrin electrode has good solution chelant ability.
(4) the Study of Interference.
When synchronous detection contents of many kinds of heavy metal ion, it is critically important for will not interfering mutually between tested measured ion.Figure
20 show the synchronous detection Pb of the poly- beta-cyclodextrin electrode of CNTs/ with 21 respectively2+And Cd2+When the mutual mutual shadow of two ion pairs
It rings.Such as Figure 20, as fixed Cd2+Concentration, change Pb2+When concentration, it can be seen that Pb2+The linear increase of peak current, and
Cd2+Peak current it is almost unchanged.If Figure 21 is as fixed Pb2+Concentration, change Cd2+Concentration when, it can be seen that Cd2+Peak
Electric current is linearly increasing, and Pb2+Peak current it is almost unchanged.The result shows that at low concentrations, CNTs cyclodextrin electrode detects simultaneously
Pb2+And Cd2+When, it will not interfere with each other between object ion.
(6) repeated.
The poly- beta-cyclodextrin electrode of CNTs/ can effectively remove electrode surface residual after solution chelating acts on the suitable time
Pb2+And Cd2+, to restore electrode activity.The poly- beta-cyclodextrin electrode of CNTs/ is containing 0.3 ppm Pb2+With 0.03 ppm Cd2+
ABS buffer solution in measure 6 times, every time measurement terminate solution chelating all is carried out to electrode, obtain clean without Pb2+And Cd2+
The electroactive electrode of remaining recovery is measured next time.As a result as shown in figure 22,6 measurement results, Pb2+And Cd2+Relatively
Standard deviation is respectively 4.4 % and 5.3 %, shows the modified electrode to heavy metal ion Pb2+With relatively good repeatability.
(7) reproducibility.
Under conditions of the same, the glass-carbon electrode of 7 poly- beta-cyclodextrin modifieds of CNTs/ is made respectively, is containing 0.4 ppm respectively
It is measured in the ABS buffer solution of lead ion and 0.02 ppm cadmium ion, 7 times measurement result is as shown in figure 23.It is computed, 7 surveys
Determine result Pb2+And Cd2+Relative standard deviation is respectively 1.04 % and 12.4 %, shows that the composite film material has lead ion
Good reproducibility.
The poly- beta-cyclodextrin composite film material of CNTs/ by electrochemical polymerization obtain, this method quickly, efficiently, green, ring
It protects.The poly- beta-cyclodextrin of CNTs/ complex film modified glass-carbon electrode linear scan binding time current curve, first preenrichment is then
Dissolution can synchronize detection heavy metal ion Pb2+And Cd2+, high sensitivity, selectivity is good, also has good repeatability and reproduction
Property, effective candidate materials of synchronous detection heavy metal ion lead ion and insulator electrochemical sensor can be become.
Claims (4)
1. a kind of new method of synchronous detection Pb ion and Cd ion, it is characterised in that: in turn include the following steps:
(1) CNTs/ poly (β-CD) combination electrode is prepared:
(1) pretreatment of glassy carbon electrode
Then a few drop deionized waters are added dropwise in the polishing powder that suitable 30 nm is sprinkled on chamois leather, stirred with glass-carbon electrode edge equal
It is even, it pinches glass-carbon electrode vertically afterwards, uniformly firmly, at the uniform velocity draws circle, then cleaned with deionized water, ear washing bulb drying, in glass carbon
Electrode surface drips nitric acid, is cleaned after static 10 ~ 15 s with deionized water, then ethanol water, aqueous solution of nitric acid,
20 s of ultrasound are distinguished in deionized water, ear washing bulb drying is spare；
The glass-carbon electrode handled well is put into 5 mM K3Fe(CN)6、0.2 M KNO3In solution, with electrochemical workstation, use
Three-electrode system, reference electrode select saturated calomel electrode, select carbon-point to electrode, and working electrode selects glass-carbon electrode, uses
Cyclic voltammetry, the scanning in the scanning range of 0 ~ 0.5 V；If redox peaks potential difference in 64 mV or so, 80 mV with
It is interior, change to 0.2 M H2SO4It is activated in solution, the scanning in -0.2 ~ 1.4V, until cyclic voltammogram repeats；
(2) processing of carbon nanotube
1) electronic balance weighs 5.0 g hydroxylated multi-walled carbon nanotubes, takes the HCL of 100 mL, 0.4 M with graduated cylinder, MWCNT and
HCL solution mixes, 5 h of mechanical stirring after ultrasonic oscillation；
2) in the H of 100 mL2SO4And HNO3Ultrasonic 5 hours in mixed solution, then magnetic agitation 10 hours；
3) carbon nanotube and mixed acid solution are filtered by vacuum, and are washed with deionized water to neutrality, and dry 24 h are placed in drying box；
4) take the processed carbon nanotube of 5 mg that deionized water is added to be settled to 10 mL, ultrasound is uniform to solution, spare；
(3) preparation of poly (β-CD) electrode
At room temperature, accurate measuring the good concentration of configured in advance be 0.1 M, pH value be 6 50 mL of phosphate buffer solution,
0.125 mM beta-cyclodextrin is added, ultrasound takes out placement after obtaining within 20 minutes uniform mixed solution after stirring to all dissolutions
It is spare；The same step of three-electrode system (1), scanning range are -1 ~ 2 V, and sweeping speed is 100 mV/s；Poly- β-is obtained after deposition
Cyclodextrin electrode is rinsed well rear spare with deionization；
(4) preparation of CNTs electrode
Taking 6 μ L concentration with liquid-transfering gun is that the MWCNTs of 0.5 mg/mL drops to glassy carbon electrode surface, is placed under ultraviolet lamp, after dry
It takes out to obtain CNTs electrode, dries up spare after being rinsed with deionization, sample is named as CNTs electrode；
(5) preparation of CNTs/ poly (β-CD) electrode
CNTs electrode is taken to be put into the cyclodextrin PBS mixed solution prepared, concentration and step (3) are same；Three-electrode system is same
Step (1) carries out electropolymerization using cyclic voltammetric, and scanning range is -1 ~ 2 V, and sweeping speed is 50 mV/s；After deposition
It to CNTs/poly (β-CD) electrode, is rinsed well with deionization rear spare, obtains CNTs/poly (β-CD) electrode；
(2) CNTs/ poly (β-CD) electrode is to Pb2+And Cd2+Detection:
Obtained CNTs/poly (β-CD) electrode is first used into line in the acetate buffer solution (ABS) of 50 pH=5 mL
Property scanning scanning, until curve stablize, a certain amount of Pb is added in ABS solution2+Standard solution and Cd2+Standard solution, stirring bar
Under part, 20 s are stood after a certain period of time in -1 V preenrichment, observe the linear scan curve from -0.3 V of V ~ -1, record is bent
Oxidation peak current value in line, the temperature of experiment are 25 ± 0.1 DEG C.
2. the new method of a kind of synchronous detection Pb ion and Cd ion according to claim 1, it is characterised in that: the step
Suddenly in (1) working electrode select glass-carbon electrode 3 mm of diameter.
3. the new method of a kind of synchronous detection Pb ion and Cd ion according to claim 1, it is characterised in that: the step
Suddenly H in (2)2SO4And HNO3The concentration ratio of mixed solution is 3:1.
4. the new method of a kind of synchronous detection Pb ion and Cd ion according to claim 1, it is characterised in that: the step
Suddenly the preenrichment time is 240s in (two).
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