CN106568817B - It is a kind of for the chemically modified electrode of quantitative detection of folic acid and the preparation method of electrochemical sensor - Google Patents
It is a kind of for the chemically modified electrode of quantitative detection of folic acid and the preparation method of electrochemical sensor Download PDFInfo
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Abstract
The invention discloses the preparation methods of a kind of chemically modified electrode for quantitative detection of folic acid and electrochemical sensor.This method comprises: S11. takes multi-walled carbon nanotube, ultrasound after concentrated nitric acid and the concentrated sulfuric acid is added, obtains suspension；S12. add ethyl alcohol, centrifuge separation in above-mentioned suspension；Then plus water be centrifugated to filtrate pH value be 6~8 after, sediment is dried to obtain the multi-walled carbon nanotube of carboxylated；S13. the multi-walled carbon nanotube of carboxylated is taken, addition water ultrasonic disperse is uniform, and glucose is then added and forms solution A；S14. silver nitrate Yu Shuizhong stirring and dissolving is taken, dense NH is then added dropwise3·H2O forms solution B；S15. stirring in solution A, ageing is added in solution B, after centrifugation and washing, obtains Ag/MWCNTs composite material after dry in baking oven；S16. Ag/MWCNTs composite material is taken to disperse to obtain dispersion liquid in organic solvent；By dispersion and clean glassy carbon electrode surface is fixed on to get the electrode.The chemically modified electrode detection limit being prepared by this method is low, and selectivity is good.
Description
Technical field
The present invention relates to electrochemical sensing technical fields, and in particular to a kind of chemical modification electricity for quantitative detection of folic acid
The preparation method of pole and electrochemical sensor.
Background technique
Folic acid has important physiological function in human body, cannot directly synthesize in human body, and must lead to
Diet is crossed to obtain.In human body, folic acid can be changed into biologically active tetrahydrofolic acid after being absorbed, it participates in ribose core
The synthesis and manufacture of acid and DNA, and synthesis to intracellular purine nucleic acid and pyrimidine nucleotide and conversion play it is non-
Normal important role.The synthesis of folic acid and DNA are closely related, if there is a serious shortage of folic acid by pregnant woman, will interfere DNA in fetus body
Synthesis, and cell division can weaken, and the key position development of backbone is impaired, lead to spina bifida.Women is before pregnancy in 6 weeks
If intake folic acid is insufficient, a possibility that bearing the deformed child of anencephalus and brain spina bifida, can increase.In addition lacking folic acid can lead
Depression, cardiovascular disease, schizophrenia, senile dementia and certain cancers such as cervical carcinoma, the carcinoma of the rectum and cancer of the esophagus are suffered from cause
Risk increase.Therefore, quantitative detection is carried out for clinical treatment diagnosis and guarantee human physical and mental health etc. tool to folic acid
It is significant.
Currently, measurement folic acid method mainly has microbial method, direct colo(u)rimetry, ninhydrin colorimetry, high performance liquid chromatography
Method, thin layer chromatography, fluorimetry etc..These methods are although critically important, but have certain limitation.For example photometry is held
It is influenced vulnerable to chaff interferent；Fluorescence method needs fluorescent marker or measured object itself to have fluorescence；Chromatography not only needs to hold high
Expensive instrument and equipment also needs larger cost purchase chromatographic column and a large amount of organic solvents.Electrochemical detection method has low cost, effect
The features such as rate is high, high sensitivity and selectivity are good, and it is the biggest advantage is to can directly detect without pre-processing,
And step operation is simple, can quickly apply to on-site measurement.If the working electrode used in electrochemical determination method is without repairing
Decorations directly use, and the electrochemical response signal that lower electro catalytic activity will lead to analyte is weak, and sensitivity and detection limit reach
Less than trace detection requirement.In consideration of it, developing various nanometer material modified electrodes, the sensitive of electrochemical sensor can effectively improve
Degree and detection limit.Carbon nanotube has peculiar electric property, apparent quantum effect, big specific surface area, high stability
And strong characterization of adsorption, there is excellent catalytic effect to the oxidation of many compounds.Carbon nanotube is applied to electrochemistry
The overpotential of substrate can be reduced in sensor preparation, promoted electron transmission, increased current-responsive.It is based on multi wall carbon in the prior art
The modified electrode and its detection limit that nanotube (MWCNTs) is prepared are as follows: such as the multi-walled carbon nanotube (MWCNTs) of one pack system
The detection of the folic acid electrochemical sensor of modified electrode building is limited to 2.59 × 10-6Mol/L (Jiang Xiaoli, Li Rong, He Xiaoying, west
Magnificent normal university's journal (natural science edition), 29 (2008) 182-185), polymethine indigo plant/Multiwalled Carbon Nanotubes Modified Electrode structure
The detection for the folic acid electrochemical sensor built is limited to 1.6 × 10-6Mol/L (Du Xueping, He'nan University's master thesis, 2014)
Detection with Pt nanoparticle/Multiwalled Carbon Nanotubes Modified Electrode building folic acid electrochemical sensor is limited to 5.01 × 10- 8Mol/L (Zhao Ling, Liaoning University's master thesis, 2011).Although above-mentioned electrode obtains further the detection limit of folic acid
It reduces, but develops that a kind of detection limit is lower, the better chemically modified electrode of electro catalytic activity still has great importance.
Summary of the invention
The technical problem to be solved by the present invention is in order to overcome, there is vulnerable to chaff interferent in existing folic acid technology
Influence, sample pre-processing is complicated and the technical problems such as detection limit height, a kind of chemistry for quantitative detection of folic acid is provided and is repaired
Adorn the preparation method of electrode and electrochemical sensor.The chemically modified electrode and electrochemical sensing being prepared by this method
Device, electro-catalysis effect with selectivity it is good, detection limit is low.
Above-mentioned technical problem to be solved by this invention is achieved by the following technical programs:
A kind of preparation method of the chemical electrode for quantitative detection of folic acid, comprises the following steps:
S11. 30~50mg multi-walled carbon nanotube is taken, ultrasound 2 after 0.5~1.5mL concentrated nitric acid and 2~4mL concentrated sulfuric acid is added
~5h, obtains suspension；
S12. add ethyl alcohol to 8~15mL, centrifuge separation in above-mentioned suspension；Then plus water is centrifugated to filtrate pH
After value is 6~8, sediment is dried to obtain the multi-walled carbon nanotube of carboxylated；
S13. the multi-walled carbon nanotube of 3~6mg carboxylated is taken, addition 2~4mL water ultrasonic disperse is uniform, is then added
0.10~0.30g glucose forms solution A；
S14. 0.02~0.03g silver nitrate stirring and dissolving in 2~4mL water is taken, it is dense that 0.3~0.6mL is then added dropwise
NH3·H2O forms solution B；
S15. solution A is added in solution B and stirs 0.3~1h, after being aged 1~3h, after centrifugation and washing, in 50~80 DEG C
Dry 8 in baking oven~obtain multi-wall carbon nano-tube composite material (the nano combined material of Ag/MWCNTs that Nano silver grain loads afterwards for 24 hours
Material)；
S16. multi-wall carbon nano-tube composite material (the Ag/MWCNTs composite wood for taking 0.3~0.6mg Nano silver grain to load
Material) disperse to obtain Nano silver grain loading multi-wall carbon nanotubes composite material (Ag/MWCNTs composite wood in 1~2mL organic solvent
Material) dispersion liquid；By Nano silver grain loading multi-wall carbon nanotubes composite material (Ag/MWCNTs composite material), dispersion is simultaneously
Clean glassy carbon electrode surface is fixed on to get the complex film modified electrode (Ag/ of Nano silver grain loading multi-wall carbon nanotubes
The complex film modified electrode of MWCNTs).
For using nanocomposite preparation to measure the electrode of certain specific chemical composition content, then inventor's root is needed
Different nanocomposites is prepared according to the property of specific chemical substance to be determined.The electrode prepared is to the substance of being measured
The quality of detection limit, sensitivity, stability and anti-interference and other effects mainly determined by the preparation method of nanocomposite.
The preparation method of nanocomposite mainly includes the proportion and each step reaction condition of the selection of raw material, raw material
Deng.For being used as the nanocomposite of electrode, selection, proportion and each step reaction item of preparation method chinese raw materials
The difference of part can all lead to the greatest differences of the subsequent electrode electrical property being prepared, so as to cause detection limit, sensitivity, stabilization
The greatest differences of property and anti-interference and other effects.
According to the characteristic of folic acid, to obtain the folic acid detecting electrode with low detection limits, inventor passes through a large amount of
Experiment, constantly adjust raw material composition, proportion and preparation process in technological parameter；It is 20~40nm's that partial size, which is prepared,
Ag nanoparticle simultaneously successfully by its high dispersive is supported on the multi-walled carbon nanotube of carboxylated, which will successfully increase compound
The specific surface area and catalytic activity of nano material, so that the complex film modified electrode of the Ag/MWCNTs being prepared is with excellent
The detection limit of folic acid in sample can be significantly reduced in electrochemical response performance, and improves the sensitivity of detection, stability and resist
Interference.
Preferably, 40mg multi-walled carbon nanotube is taken in step S11, and ultrasound 4h after 1mL concentrated nitric acid and the 3mL concentrated sulfuric acid is added.
Preferably, add ethyl alcohol to 10mL in above-mentioned suspension in step S12；Add water to be centrifugated to filtrate pH value to be
7。
Preferably, the multi-walled carbon nanotube of 4.5mg carboxylated is taken in step S13, addition 3mL water ultrasonic disperse is uniform, so
0.19g glucose is added afterwards and forms solution A.
Preferably, 0.026g silver nitrate stirring and dissolving in 3mL water is taken in step S14, and it is dense that 0.5mL is then added dropwise
NH3·H2O forms solution B.
Preferably, solution A is added in solution B in step S15 and stirs 0.5h, after being aged 2h, after centrifugation and washing, in 60
In DEG C baking oven after dry 12h Nano silver grain load multi-wall carbon nano-tube composite material.
Preferably, take 0.5mg Nano silver grain loading multi-wall carbon nanotubes composite material in 1mL dimethyl in step S16
Disperse to obtain Nano silver grain loading multi-wall carbon nanotubes composite material dispersion liquid in formamide；By Nano silver grain loading multi-wall carbon
Nanometer tube composite materials dispersion is negative up to Nano silver grain after drying under infrared lamp in clean glassy carbon electrode surface
Carry the complex film modified electrode of multi-walled carbon nanotube.
A kind of preparation method of the electrochemical sensor for quantitative detection of folic acid, includes the following steps: above-mentioned preparation
The obtained complex film modified electrode of Nano silver grain loading multi-wall carbon nanotubes is working electrode, and saturated calomel electrode is reference electricity
Pole, platinum electrode are auxiliary electrode, and connection electrochemical workstation must be used for leaf after assembling electrode test system using three-electrode method
The electrochemical sensor of sour quantitative detection.
A kind of method of quantitative detection of folic acid, which is characterized in that the electrochemical sensing being prepared using claim 8
Device, with the folate content in square wave voltammetry test sample.
S21. sample dissolves, and the citrate-phosphate sodium dihydrogen bottom liquid constant volume for being 2.0~7.0 with pH prepares sample solution；
S22. the electrochemical sensor being prepared using claim 8, with folic acid in square wave voltammetry test sample
Oxidation peak current value；
S23. according to equation of linear regression, the solubility of folic acid in sample solution is calculated, to converse folic acid in sample
Content.
Preferably, the citrate-phosphate sodium dihydrogen bottom liquid constant volume for being 4.0 with pH in step S21.
Inventor shows the complex film modified electrode of Ag/MWCNTs that the present invention is prepared into through lot of experiments, for pH
To test in 4.0 citrate-phosphate sodium dihydrogen bottom liquid, wherein the redox peaks sensitivity of folic acid is higher, peak current is maximum,
Peak type is preferably and the stability of electrode is preferable.
Preferably, the operating condition of square wave voltammetry described in step S22 are as follows: 0.4~1.2V of potential range, current potential increase
1~10mV, 1~50mV of potential amplitude, 5~30Hz of test frequency.
Most preferably, the operating condition of square wave voltammetry described in step S22 are as follows: 0.4~1.2V of potential range, current potential
Increment 5mV, potential amplitude 25mV, test frequency 15Hz.
Preferably, equation of linear regression described in step S23 is 5.0 × 10-7~1.0 × 10-5Mol/L and 1.0 × 10-5~8.0 × 10-5Two range internal lobe acid oxidase peak currents of mol/L and its concentration are in good linear relationship, linear regression
Equation are as follows: Ip(A)=0.00577C (mol/L)+1.29498 × 10-7(R2=0.99929), Ip=0.01529C (mol/L)+
2.28819×10-7(R2=0.98232)；C is folic acid concentration, I in equationpOxidation peak current value is obtained for square wave voltammetry.
The utility model has the advantages that (1) the present invention provides a kind of completely new chemically modified electrode for quantitative detection of folic acid and
Ag nanometer particle load is prepared into Ag/ using Green Chemistry method by chemical sensor, the present invention on multi-walled carbon nanotubes
MWCNTs composite material can further increase its specific surface area and enhance its catalytic activity, using the composite nano materials to work
Electrode is modified, its electro catalytic activity and detection performance to folic acid can be greatly enhanced；(2) quantitatively being examined for folic acid described in
The chemically modified electrode or chemical sensor of survey have extremely low detection limit, and (embodiment shows that its detection is limited to 6.2nmol/L, far
Far below 2590nmol/L, 1600nmol/L and 50.1nmol/L in the prior art) and good stability, anti-interference
And reproducibility；(3) easy to operate, low in cost based on the folic acid electrochemical sensor that constructs of the present invention, drug quality control,
Food safety and clinical treatment etc. have a wide range of applications.
Detailed description of the invention
Fig. 1 is scanning electron microscope (SEM) photograph (A, B), the transmission electron microscope of MWCNTs and Ag/MWCNTs composite material of the present invention
Scheme (C, D) and energy spectrum diagram (E, F).
Fig. 2 is that MWCNTs modified electrode (a) and the complex film modified electrode (b) of Ag/MWCNTs of the present invention exist
1.0mmol/L K3[Fe(CN)6] and AC impedance (A) and cyclic voltammogram (B) in the liquid of the bottom 0.1mol/L KCl.
Fig. 3 is glass-carbon electrode (a), MWCNTs modified electrode (b) and the complex film modified electricity of Ag/MWCNTs of the present invention
Cyclic voltammogram of the pole (c) in 0.2mmol/L folic acid solution.
Fig. 4 be various concentration folic acid on the complex film modified electrode of Ag/MWCNTs between its oxidation peak current value
Linear relationship chart.
Specific embodiment
The present invention is explained further below in conjunction with specific embodiment, but embodiment does not do any type of limit to the present invention
It is fixed.
A kind of preparation of the chemical electrode for quantitative detection of folic acid of embodiment 1
S1. 40mg multi-walled carbon nanotube is taken, ultrasound 4h after 1mL concentrated nitric acid and the 3mL concentrated sulfuric acid is added, obtains suspension；
S2. add ethyl alcohol to 10mL, centrifuge separation in above-mentioned suspension；Then plus water is centrifugated to filtrate pH value and is
After neutrality, sediment is dried to obtain the multi-walled carbon nanotube (MWCNTs) of carboxylated；
S3. the multi-walled carbon nanotube of 4.5mg carboxylated is taken, addition 3mL water ultrasonic disperse is uniform, and the Portugal 0.19g is then added
Grape sugar forms solution A；
S4. 0.026g silver nitrate stirring and dissolving in 3mL water is taken, 0.5mL NH is then added dropwise3·H2O forms solution
B；
S5. solution A is added in solution B and stirs 0.5h, it is dry in 60 DEG C of baking ovens after centrifugation and washing after being aged 2h
Ag/MWCNTs composite material is obtained after 12h；
S6. glass-carbon electrode is used respectively 0.3 μm and 0.05 μm of aluminium powder to polish, then in dust technology, ethyl alcohol and pure water
Middle ultrasound 5min respectively cleans electrode, at room temperature drying for standby；Take 0.5mg Ag/MWCNTs composite material in l mL dimethyl methyl
In amide after ultrasonic disperse, takes 5 μ L dispersions in clean glassy carbon electrode surface with liquid-transfering gun, dried under infrared lamp
Obtain the complex film modified electrode of Ag/MWCNTs.
The Ag/MWCNTs composite material that Fig. 1 shows that the MWCNTs that step S2 is prepared and step S5 are prepared exists
The transmission electron microscope picture (C, D) under scanning electron microscope (SEM) photograph (A, B) and 50000 times of magnifying powers under 20000 times of magnifying powers, as seen from the figure
MWCNTs overwhelming majority after strong acid treatment is broken, and is separated from each other, and pipe range shortens port opening, and port carbon atom is easy
It is oxidized to carboxyl, these oxygen-containing groups become the active site of carrying metal particles.It is small after metal ion in-situ reducing is added
It loads on multi-walled carbon nanotubes to the Ag nano particle high dispersive of size, entire composite material has reticular structure, load
Metal nanoparticle partial size is between 20-40nm.Nanoparticle size is small, degree of scatter is high, is conducive to improve complex film modified
The electro catalytic activity specific surface area of electrode.The energy spectrum analysis of MWCNTs and Ag/MWCNTs nanocomposite (E, F) Comparative result table
Bright, metal Ag is successfully supported on Ag/MWCNTs nanocomposite of the present invention.
A kind of electrochemical sensor for quantitative detection of folic acid of embodiment 2
The complex film modified electrode of the Ag/MWCNTs that embodiment 1 is prepared is as working electrode, with saturated calomel electrode
It is auxiliary electrode assembling into three electrode test systems for reference electrode, platinum electrode, and connect electrochemical workstation to be used for leaf
The electrochemical sensor of sour quantitative detection.
Electrical performance testing of the embodiment 3 for the electrochemical sensor of quantitative detection of folic acid
(1) the electron transmission performance comparison of Different electrodes
In the three electrode test systems that such as embodiment 2 is prepared, respectively with MWCNTs modified electrode (a) and embodiment
The 1 complex film modified electrode (b) of Ag/MWCNTs being prepared is working electrode in 1.0mmol/L K3[Fe(CN)6] be mixed with
AC impedance and cyclic voltammetry, ac impedance measurement condition are as follows: frequency range are carried out in the bottom liquid of 0.1mmol/L KCl
105~0.1HZ, amplitude 5mV, current potential 0.18V；Cyclic voltammetry condition are as follows: potential range -0.4~1.0V, scanning speed
0.1V/s, test result such as Fig. 2.Electrochemical impedance is in the complex film modified electrode of above-mentioned MWCNTs and Ag/MWCNTs as seen from Figure 2
It is respectively 60 Ω and 30 Ω on two kinds of working electrodes, oxidation peak current is respectively 50 μ A and 80 μ A, the results showed that probe ion exists
Impedance reduction, peak current on the complex film modified electrode of Ag/MWCNTs of the present invention increase, and illustrate loaded Ag on MWCNTs
Its electron transmission performance and catalytic activity are greatly enhanced after nanoparticle.
(2) Different electrodes compare the electrocatalysis characteristic of folic acid
In the three electrode test systems that such as embodiment 2 is prepared, respectively with glass-carbon electrode (a), MWCNTs modification electricity
The complex film modified electrode (c) of Ag/MWCNTs that pole (b) and embodiment 1 are prepared is that working electrode is molten in 0.2mmol/L folic acid
Carry out cyclic voltammetry in liquid, the potential range of test is 0.3~1.0V, scanning speed 0.1V/s, Fig. 3 are test knot
Fruit.Oxidation peak current of the folic acid on the complex film modified electrode of Ag/MWCNTs of the present invention is 26.75 μ as seen from the figure
A, spike potential 0.658V.Peak current of the folic acid on glass-carbon electrode and MWCNTs modified electrode is respectively 7.16 μ A and 18.20 μ
A, spike potential are respectively 0.677V and 0.691V.Oxygen of the folic acid on the complex film modified electrode of Ag/MWCNTs of the present invention
It is maximum to change peak point current, oxidation overpotential has dropped 19mV and 33mV respectively, illustrates that Ag/MWCNTs prepared by the present invention is multiple
Closing film modified electrode has preferable electro catalytic activity to folic acid, is conducive to the detection sensitivity for improving sensor.
(3) electrochemical sensor that the present invention is prepared tests the detection performance of folic acid
The complex film modified electrode of the Ag/MWCNTs being prepared using embodiment 1 is ginseng as working electrode, saturated calomel electrode
It is auxiliary electrode than electrode and platinum electrode, assembles electrode test system using three-electrode method, and connect electrochemical workstation (structure
Construction method is as described in Example 2)；In the citrate-phosphate sodium dihydrogen bottom liquid that pH is 4.0, after stirring enrichment 60s, static 5s
Square wave voltammetry test is carried out to a series of folic acid solutions.The operating condition of square wave voltammetry setting are as follows: electric potential scanning range 0.4
~1.2V, current potential amplification 5mV, potential amplitude 25mV, test frequency 15Hz.The result shows that the oxidation peak current of (see Fig. 4) folic acid
Increase with its concentration and increase, 5.0 × 10-7~1.0 × 10-5Mol/L and 1.0 × 10-5~8.0 × 10-5Two of mol/L
Range internal lobe acid oxidase peak current and its concentration are in good linear relationship, equation of linear regression are as follows: Ip(A)=0.00577C
(mol/L)+1.29498×10-7(R2=0.99929), Ip(A)=0.01529C (mol/L)+2.28819 × 10-7(R2=
0.98232), C is folic acid concentration, I in the equationpOxidation peak current value is obtained for square wave voltammetry；Detection limit is calculated as
6.2nmol/L.Illustrate that the preparation-obtained electrode of the present invention has good linear relationship and extremely low detection limit.
(4) stability and the reproducibility test for the complex film modified electrode of Ag/MWCNTs that the present invention is prepared
According to 8 identical Ag/MWCNTs modified electrodes are prepared the step of embodiment 1, respectively using this 8 electrodes as work
Electrode, saturated calomel electrode are reference electrode and platinum electrode is auxiliary electrode, simultaneously with three-electrode method assembling electrode test system
It connects electrochemical workstation (construction method is as described in Example 2), in the citrate-phosphate sodium dihydrogen bottom liquid that pH is 4.0, stirs
Enrichment 60s, static 5s are mixed, is measured using folic acid of the square wave voltammetry to same concentration.The operation of square wave voltammetry setting
Condition are as follows: 0.4~1.2V of electric potential scanning range, current potential amplification 5mV, potential amplitude 25mV, test frequency 15Hz, measurement result
Relative standard deviation is 2.93%.To wherein an Ag/MWCNTs modified electrode be stored in 4 DEG C of refrigerators, choose 8 it is different
Period (test the 1st time before saving, then tested 1 time every 1 day), using above-mentioned similarity condition and method to same concentration
Folic acid is measured, and the relative standard deviation of measurement is 3.78%；Show the complex film modified electricity of Ag/MWCNTs provided by the invention
It is great to have preferable stability and reproducibility.
(5) anti-interference capability testing for the complex film modified electrode of Ag/MWCNTs that the present invention is prepared
The complex film modified electrode of the Ag/MWCNTs that embodiment 1 is prepared assembles electrode test body using three-electrode method
System, and connect electrochemical workstation and constitute electrochemical sensor (construction method is as described in Example 2), it is examined using square wave voltammetry
Influence of the external interfering substance to folic acid is examined.The operating condition of square wave voltammetry setting are as follows: electric potential scanning range 0.4~
1.2V, current potential amplification 5mV, potential amplitude 25mV, test frequency 15Hz.Specific test method is, in 4.5mL citrate-phosphate
The folic acid of 0.5mL1mmol/L is added in the liquid of sodium dihydrogen bottom, adjusting bottom liquid pH is 4.0, is passed through after stirring enrichment 60s, static 5s
Square wave voltammetry measures its oxidation peak current value, adds the interfering substance of 0.5mL 1mol/L, is measured by square wave voltammetry
The oxidation peak current value of folic acid.The situation of change of the oxidation peak current value of interfering substance front and back folic acid is added in comparison, if deviation
Within ± 5%, it is believed that chaff interferent is on the detection of analyte without influence.Test result shows biography prepared by the present invention
Sensor is in 10 times of caffeic acid, levodopa and 1 times of ascorbic acid, oxalic acid, VB1, the substances such as paracetamol and vanillic aldehyde
Interference under to the detected value deviation of folic acid within ± 5%, illustrate the complex film modified electrode of Ag/MWCNTs provided by the invention
With preferable anti-interference ability, testing result can be fast and effeciently provided.
The detection of 4 actual sample of embodiment
Certain tablet is taken into 20mg, after being pulverized in grinding, is dissolved with secondary distilled water, it is ultrasonic in supersonic wave cleaning machine
Filtered on buchner funnel is used after 30min, is transferred in volumetric flask and is settled to the citrate-phosphate sodium dihydrogen bottom liquid that pH is 4.0
50mL.A certain amount of actual sample solution is taken every time, and the complex film modified electrode of the Ag/MWCNTs that embodiment 1 is prepared utilizes
Three-electrode method assemble electrode test system, and connect electrochemical workstation constitute electrochemical sensor, using square wave voltammetry into
Then row measurement is added the folic acid standard solution matched and carries out determination of recovery rates.The operating condition of square wave voltammetry setting are as follows: electricity
0.4~1.2V of bit scan range, current potential amplification 5mV, potential amplitude 25mV, test frequency 15Hz.Specific test method is to take
Actual measurement sample 10mL is stated, standard folic acid solution 0.1mL, 0.2mL, 0.3mL of 1mmol/L are sequentially added, adjusts bottom liquid pH respectively
It is 4.0, the oxidation peak current value of folic acid is measured by square wave voltammetry after stirring enrichment 60s, static 5s, according to embodiment 3
Obtained linear relationship finds corresponding folic acid concentration value.Existed according to the relative standard deviation that the above method obtains folic acid value
Between 2.98~4.12%, the rate of recovery is between 98.11~99.82%；Illustrate chemically modified electrode provided by the invention or
Electrochemical sensor can be used for the Accurate Determining of folate content in the industries such as drug quality monitoring and clinical treatment detection.
Claims (10)
1. a kind of preparation method of the chemically modified electrode for quantitative detection of folic acid, which is characterized in that comprise the following steps:
S11. 30~50mg multi-walled carbon nanotube is taken, 2~5h of ultrasound after 0.5~1.5mL concentrated nitric acid and 2~4mL concentrated sulfuric acid is added,
Obtain suspension；
S12. add ethyl alcohol to 8~15mL, centrifuge separation in above-mentioned suspension；Then plus water is centrifugated to filtrate pH value and is
After 6~8, sediment is dried to obtain the multi-walled carbon nanotube of carboxylated；
S13. the multi-walled carbon nanotube of 3~6mg carboxylated is taken, it is uniform to be added 2~4mL water ultrasonic disperse, then it is added 0.10~
0.30g glucose forms solution A；
S14. 0.02~0.03g silver nitrate stirring and dissolving in 2~4mL water is taken, the dense NH of 0.3~0.6mL is then added dropwise3·
H2O forms solution B；
S15. solution A is added in solution B and stirs 0.3~1h, after being aged 1~3h, after centrifugation and washing, in 50~80 DEG C of baking ovens
Middle drying 8~for 24 hours afterwards Nano silver grain load multi-wall carbon nano-tube composite material；
S16. the multi-wall carbon nano-tube composite material for taking 0.3~0.6mg Nano silver grain to load divides in 1~2mL organic solvent
Dissipate Nano silver grain load multi-wall carbon nano-tube composite material dispersion liquid；Nano silver grain loading multi-wall carbon nanotubes are answered
Condensation material dispersion and to be fixed on clean glassy carbon electrode surface compound to get Nano silver grain loading multi-wall carbon nanotubes
Film modified electrode.
2. preparation method according to claim 1, which is characterized in that take 40mg multi-walled carbon nanotube in step S11, be added
Ultrasound 4h after 1mL concentrated nitric acid and the 3mL concentrated sulfuric acid.
3. preparation method according to claim 1, which is characterized in that add ethyl alcohol in step S12 in above-mentioned suspension
To 10mL；Adding water to be centrifugated to filtrate pH value is 7.
4. preparation method according to claim 1, which is characterized in that the multi wall carbon of 4.5mg carboxylated is taken to receive in step S13
Mitron, addition 3mL water ultrasonic disperse is uniform, and 0.19g glucose is then added and forms solution A.
5. preparation method according to claim 1, which is characterized in that take 0.026g silver nitrate in 3mL water in step S14
The dense NH of 0.5mL is then added dropwise in stirring and dissolving3·H2O forms solution B.
6. preparation method according to claim 1, which is characterized in that solution A stirring is added in solution B in step S15
0.5h, after being aged 2h, after centrifugation and washing, the multi wall carbon for obtaining Nano silver grain load after dry 12h in 60 DEG C of baking ovens is received
Mitron composite material.
7. preparation method according to claim 1, which is characterized in that 0.5mg Nano silver grain is taken to load in step S16
Multi-wall carbon nano-tube composite material disperse in 1mL dimethylformamide Nano silver grain load multi-walled carbon nanotube it is compound
Material dispersion liquid；By the multi-wall carbon nano-tube composite material dispersion of Nano silver grain load in clean glass-carbon electrode table
Face, up to the complex film modified electrode of Nano silver grain loading multi-wall carbon nanotubes after being dried under infrared lamp.
8. a kind of preparation method of the electrochemical sensor for quantitative detection of folic acid, which comprises the steps of: will
The complex film modified electrode of Nano silver grain loading multi-wall carbon nanotubes that any one of claim 1~7 is prepared is work electricity
Pole, saturated calomel electrode are reference electrode, and platinum electrode is auxiliary electrode, are connected after assembling electrode test system using three-electrode method
Connect the electrochemical sensor that electrochemical workstation must be used for quantitative detection of folic acid.
9. a kind of method of quantitative detection of folic acid, which is characterized in that the electrochemical sensor being prepared using claim 8,
With the folate content in square wave voltammetry test sample,
S21. sample dissolves, and the citrate-phosphate sodium dihydrogen bottom liquid constant volume for being 2.0~7.0 with pH prepares sample solution；
S22. the electrochemical sensor being prepared using claim 8, with the oxidation of folic acid in square wave voltammetry test sample
Peak point current；
S23. according to equation of linear regression, the solubility of folic acid in sample solution is calculated, to converse containing for folic acid in sample
Amount.
10. according to the method described in claim 9, it is characterized in that, the citrate-phosphate dihydro for being 4.0 with pH in step S21
Sodium bottom liquid constant volume；The operating condition of square wave voltammetry described in step S22 are as follows: 0.4~1.2V of potential range, current potential amplification 1
~10mV, 1~50mV of potential amplitude, 5~30Hz of test frequency；Equation of linear regression described in step S23 is 5.0 × 10-7
~1.0 × 10-5Mol/L and 1.0 × 10-5~8.0 × 10-5Two range internal lobe acid oxidase peak currents of mol/L are in its concentration
Good linear relationship, equation of linear regression are as follows: Ip=0.00577C+1.29498 × 10-7, linearly dependent coefficient R2=
0.99929；Ip=0.01529C+2.28819 × 10-7, linearly dependent coefficient R2=0.98232；C is folic acid concentration in equation,
Unit is mol/L；IpOxidation peak current value, unit A are obtained for square wave voltammetry.
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| Voltammetric Determination of Folic Acid with a Multi-Walled Carbon Nanotube-Modified Gold Electrode;Shuhong Wei et al.;《Microchim Acta》;20051216;第152卷;全文 |
| 叶酸在碳纳米管修饰电极上的循环伏安行为及电化学参数测定;蒋晓丽等;《西华师范大学学报(自然科学版)》;20080630;第29卷(第2期);全文 |
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