CN103884749A - Formaldehyde electrochemical detection system and working electrode preparation method as well as formaldehyde detection method - Google Patents
Formaldehyde electrochemical detection system and working electrode preparation method as well as formaldehyde detection method Download PDFInfo
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- WSFSSNUMVMOOMR-UHFFFAOYSA-N Formaldehyde Chemical compound O=C WSFSSNUMVMOOMR-UHFFFAOYSA-N 0.000 title claims abstract description 290
- 238000000835 electrochemical detection Methods 0.000 title claims abstract description 25
- 238000001514 detection method Methods 0.000 title claims description 14
- 238000002360 preparation method Methods 0.000 title description 4
- 235000013305 food Nutrition 0.000 claims abstract description 37
- 230000003750 conditioning effect Effects 0.000 claims abstract description 32
- 238000004891 communication Methods 0.000 claims abstract description 10
- 239000002048 multi walled nanotube Substances 0.000 claims description 82
- 229910052799 carbon Inorganic materials 0.000 claims description 53
- OKTJSMMVPCPJKN-UHFFFAOYSA-N Carbon Chemical compound [C] OKTJSMMVPCPJKN-UHFFFAOYSA-N 0.000 claims description 50
- 239000011259 mixed solution Substances 0.000 claims description 35
- 238000000034 method Methods 0.000 claims description 32
- 102000004190 Enzymes Human genes 0.000 claims description 27
- 108090000790 Enzymes Proteins 0.000 claims description 27
- 239000000243 solution Substances 0.000 claims description 27
- 238000010790 dilution Methods 0.000 claims description 24
- 239000012895 dilution Substances 0.000 claims description 24
- 239000012188 paraffin wax Substances 0.000 claims description 21
- 239000006229 carbon black Substances 0.000 claims description 18
- 239000000284 extract Substances 0.000 claims description 17
- 239000000843 powder Substances 0.000 claims description 15
- 239000012086 standard solution Substances 0.000 claims description 13
- 238000001914 filtration Methods 0.000 claims description 12
- 239000000155 melt Substances 0.000 claims description 12
- BOPGDPNILDQYTO-NNYOXOHSSA-N nicotinamide-adenine dinucleotide Chemical compound C1=CCC(C(=O)N)=CN1[C@H]1[C@H](O)[C@H](O)[C@@H](COP(O)(=O)OP(O)(=O)OC[C@@H]2[C@H]([C@@H](O)[C@@H](O2)N2C3=NC=NC(N)=C3N=C2)O)O1 BOPGDPNILDQYTO-NNYOXOHSSA-N 0.000 claims description 10
- 239000008363 phosphate buffer Substances 0.000 claims description 10
- 239000011521 glass Substances 0.000 claims description 9
- 239000012456 homogeneous solution Substances 0.000 claims description 9
- 239000007787 solid Substances 0.000 claims description 9
- 238000007254 oxidation reaction Methods 0.000 claims description 8
- 238000003756 stirring Methods 0.000 claims description 7
- 102100039702 Alcohol dehydrogenase class-3 Human genes 0.000 claims description 6
- 230000003321 amplification Effects 0.000 claims description 6
- 238000001035 drying Methods 0.000 claims description 6
- 230000000694 effects Effects 0.000 claims description 6
- 108010051015 glutathione-independent formaldehyde dehydrogenase Proteins 0.000 claims description 6
- 239000012535 impurity Substances 0.000 claims description 6
- 239000011812 mixed powder Substances 0.000 claims description 6
- 239000000203 mixture Substances 0.000 claims description 6
- 238000003199 nucleic acid amplification method Methods 0.000 claims description 6
- BASFCYQUMIYNBI-UHFFFAOYSA-N platinum Chemical compound [Pt] BASFCYQUMIYNBI-UHFFFAOYSA-N 0.000 claims description 6
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Substances O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 claims description 6
- 238000006243 chemical reaction Methods 0.000 claims description 4
- 238000005498 polishing Methods 0.000 claims description 4
- SXRSQZLOMIGNAQ-UHFFFAOYSA-N Glutaraldehyde Chemical compound O=CCCCC=O SXRSQZLOMIGNAQ-UHFFFAOYSA-N 0.000 claims description 3
- 229910021607 Silver chloride Inorganic materials 0.000 claims description 3
- 239000004411 aluminium Substances 0.000 claims description 3
- XAGFODPZIPBFFR-UHFFFAOYSA-N aluminium Chemical compound [Al] XAGFODPZIPBFFR-UHFFFAOYSA-N 0.000 claims description 3
- 229910052782 aluminium Inorganic materials 0.000 claims description 3
- 230000015572 biosynthetic process Effects 0.000 claims description 3
- 150000001721 carbon Chemical class 0.000 claims description 3
- 230000015556 catabolic process Effects 0.000 claims description 3
- 238000006555 catalytic reaction Methods 0.000 claims description 3
- 238000012790 confirmation Methods 0.000 claims description 3
- 239000003431 cross linking reagent Substances 0.000 claims description 3
- 238000006731 degradation reaction Methods 0.000 claims description 3
- 239000012154 double-distilled water Substances 0.000 claims description 3
- 238000005868 electrolysis reaction Methods 0.000 claims description 3
- GPRLSGONYQIRFK-UHFFFAOYSA-N hydron Chemical compound [H+] GPRLSGONYQIRFK-UHFFFAOYSA-N 0.000 claims description 3
- 238000005259 measurement Methods 0.000 claims description 3
- 238000002844 melting Methods 0.000 claims description 3
- 230000008018 melting Effects 0.000 claims description 3
- 238000012986 modification Methods 0.000 claims description 3
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- 239000004570 mortar (masonry) Substances 0.000 claims description 3
- 229910052697 platinum Inorganic materials 0.000 claims description 3
- HKZLPVFGJNLROG-UHFFFAOYSA-M silver monochloride Chemical compound [Cl-].[Ag+] HKZLPVFGJNLROG-UHFFFAOYSA-M 0.000 claims description 3
- 230000036962 time dependent Effects 0.000 claims description 3
- 238000001132 ultrasonic dispersion Methods 0.000 claims description 3
- 239000003014 ion exchange membrane Substances 0.000 abstract description 4
- 230000003647 oxidation Effects 0.000 description 5
- 238000004458 analytical method Methods 0.000 description 3
- 238000005516 engineering process Methods 0.000 description 3
- WSFSSNUMVMOOMR-NJFSPNSNSA-N methanone Chemical compound O=[14CH2] WSFSSNUMVMOOMR-NJFSPNSNSA-N 0.000 description 3
- 238000004140 cleaning Methods 0.000 description 2
- 230000003287 optical effect Effects 0.000 description 2
- 238000012360 testing method Methods 0.000 description 2
- 229930040373 Paraformaldehyde Natural products 0.000 description 1
- 230000009286 beneficial effect Effects 0.000 description 1
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- 230000003197 catalytic effect Effects 0.000 description 1
- 238000010411 cooking Methods 0.000 description 1
- 238000013461 design Methods 0.000 description 1
- 238000011161 development Methods 0.000 description 1
- 230000037213 diet Effects 0.000 description 1
- 235000005911 diet Nutrition 0.000 description 1
- 230000002255 enzymatic effect Effects 0.000 description 1
- 239000007789 gas Substances 0.000 description 1
- 238000011900 installation process Methods 0.000 description 1
- 238000002156 mixing Methods 0.000 description 1
- 239000002071 nanotube Substances 0.000 description 1
- 229920002866 paraformaldehyde Polymers 0.000 description 1
- 230000000750 progressive effect Effects 0.000 description 1
- 238000007789 sealing Methods 0.000 description 1
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Abstract
The invention discloses a formaldehyde electrochemical detection system. According to the formaldehyde electrochemical detection system, one end of a first connection channel is communicated with a first container; one end of a second connection channel is communicated with a second container; the other end of the first connection channel is communicated with the other end of the second connection channel by an ion exchange membrane; a working electrode and a reference electrode are located in the first container; a counter electrode is located in the second container; a communication port of the working electrode is connected with a current positive electrode measuring control port of a signal conditioning circuit; the commutation port of the counter electrode is connected with a current negative electrode measuring control port of the signal conditioning circuit; the commutation port of the reference electrode is connected with an electric potential state stable port of the signal conditioning circuit; the signal output end of the signal conditioning circuit is connected with the signal input end of a signal processor. According to the formaldehyde electrochemical detection system, a good linear relation between an electrolytic current signal and the concentration of formaldehyde is used so that the formaldehyde electrochemical detection system can be used for fast detecting the content of the formaldehyde in foods; the trace formaldehyde in the foods can also be detected.
Description
Technical field
The present invention relates to formaldehyde examination technical field, refer to particularly a kind of formaldehyde electrochemical detection system and working electrode preparation method and Analysis Methods for Formaldehyde.
Background technology
Along with economic society is constantly progressive, economic globalization development, the variation of people's cooking culture, but the security performance of food directly has influence on the healthy of the people, therefore the safety problem of food becomes the hot issue of World Focusing gradually, but food-safety problem is mainly derived from the safety detection of food, so the safety detection of food is also a global problem.Therefore national governments all take strong measure to guarantee the safety of food, and domestic and international market is more and more stricter to the quality requirements of food, also more and more higher to the requirement of food safety detection technology.But that present stage applies to detection method in actual testing process is all more loaded down with trivial details and expensive, be difficult to be detected fast and effectively, therefore at present food safety detection technology is proposed to new requirement.If can make various food obtain safety detection fast and effectively, can ensure the people's safe diet, also can improve the competitiveness in market.
There are optical sensor and photoproduction sensor for detection of the sensor of formaldehyde.Optical sensor price comparison is expensive, and volume is larger, is not suitable on line real time, and the popularity of its use is restricted.Although light biochemical sensor has improved selectivity, because activity and the other factors of enzyme cause sensor unstable, lack practicality, and the selling at exorbitant prices of general formaldehyde gas sensor, be difficult to popularize.
Summary of the invention
Object of the present invention will provide a kind of formaldehyde electrochemical detection system and working electrode preparation method and Analysis Methods for Formaldehyde exactly, the present invention utilizes linear relationship good between Faradaic current signal and the concentration of formaldehyde, make the present invention can detect faster the content of formaldehyde in food, also can utilize the solution of the present invention to detect even if only there is micro-formaldehyde in food.
The formaldehyde electrochemical detection system that the present invention is designed, it comprises working electrode, contrast electrode, to electrode, the first container, second container, signal conditioning circuit, signal processor, the first interface channel, the second interface channel, wherein, one end of described the first interface channel is communicated with the first container, one end of the second interface channel is communicated with second container, between the other end of the other end of described the first interface channel and the second interface channel, be communicated with by amberplex, described working electrode and contrast electrode are positioned at the first container, described electrode is positioned to second container, the communication port of described working electrode connects the anodal control port of measuring of electric current of signal conditioning circuit, the described communication port to electrode connects the electric current negative pole of signal conditioning circuit and measures control port, the communication port of described contrast electrode connects the potential state of signal conditioning circuit and stablizes port, the signal output part of above-mentioned signal conditioning circuit connects the signal input part of signal processor, described working electrode is enzyme and PEM and the common carbon paste electrode of modifying of multi-walled carbon nano-tubes, contrast electrode is silver chloride contrast electrode, be platinum electrode to electrode.
Preferably, it also comprises the amberplex mounting cylinder being arranged between the other end of the first interface channel and the other end of the second interface channel, amberplex is installed in the inner side of amberplex mounting cylinder, the other end of described the first interface channel is provided with the first flange, the other end of the second interface channel is provided with the second flange, described the first interface channel, amberplex mounting cylinder is fixedly connected with the second flange by the first flange with the second interface channel, one end of described amberplex mounting cylinder offers first annular groove coaxial with amberplex mounting cylinder, the other end of the first interface channel is provided with the first annular flange flange coaxial with the first interface channel and that mate with the first annular groove, the other end of above-mentioned amberplex mounting cylinder offers second annular groove coaxial with amberplex mounting cylinder, the other end of the second interface channel is provided with the second annular flange flange coaxial with the second interface channel and that mate with the second annular groove, between described the first annular groove and the first annular flange flange, be provided with O-ring seal, between described the second annular groove and the second annular flange flange, be also provided with O-ring seal.
Preferably, it also comprises amberplex installing ring, and the inner ring of described amberplex installing ring is fixedly connected with amberplex, between the outer ring of amberplex installing ring and the inner ring of amberplex mounting cylinder, is interference fit.
A method of preparing working electrode in formaldehyde electrochemical detection system, it comprises the steps:
Step 1: be heated to 80 ℃ by water-bath in the salpeter solution that is 20～35% at mass percent concentration by the multi-walled carbon nano-tubes of 1～50 gram, and the multi-walled carbon nano-tubes of 80 ℃ is stirred 48 hours in above-mentioned salpeter solution, then the above-mentioned salpeter solution that multi-walled carbon nano-tubes is housed is carried out to centrifugal treating, impurity on multi-walled carbon nano-tubes is separated, after finishing, centrifugal treating removes the salpeter solution that contains above-mentioned multi-walled carbon nano-tubes impurity, take out multi-walled carbon nano-tubes, multi-walled carbon nano-tubes is washed till neutrality by water, then multi-walled carbon nano-tubes is dried, obtain the multi-walled carbon nano-tubes of purifying,
Step 2: carbon black and solid paraffin are ground evenly by 3 to 1 mass ratio in mortar, mixed-powder to carbon black and solid paraffin heats, make the solid paraffin powder melts in mixed-powder, carbon black powders is embedded in the paraffin of melting, this melt paraffin that is embedded with carbon black powders is packed in glass capillary, and insert aluminium wire to being embedded with in the melt paraffin of carbon black powders, the melt paraffin that is embedded with carbon black powders solidifies rear formation carbon paste electrode, and this carbon paste electrode is taken out from glass capillary;
Step 3: get ultrasonic being scattered in of the multi-walled carbon nano-tubes of purifying in the upper step 1 of 1～20mg and obtain the multi-walled carbon nano-tubes solution that concentration range is 0.1～5g/L in 1～20mL, bis-double distilled waters, getting with micro syringe multi-walled carbon nano-tubes solution that 10～100 μ L concentration ranges are 0.1～5g/L joins in the protonated ethanolic solution that 10～100 μ L mass percent concentration scopes are 0.01～1% and carries out ultrasonic dispersion treatment, form homogeneous solution, this homogeneous solution of getting 1～20 μ L is coated to described carbon paste electrode surface, place 5～10min and make above-mentioned homogeneous solution volatilization, and form film, carbon paste electrode skin drying is made to PEM and the common carbon paste electrode of modifying of multi-walled carbon nano-tubes,
Step 4: take the formaldehyde dehydrogenase of 1～3mg and the shitosan of 0.1～10mg and be dissolved in the phosphate buffer that 100～300 μ L volumetric molar concentrations are 0.01～0.5mol/L, in above-mentioned phosphate buffer, add the glutaraldehyde cross-linking agent that 5～30 μ L mass percents are 1～10% and mix, form mixed liquor, the above-mentioned mixed liquor of 5～30 μ L is coated on the PEM and the common carbon paste electrode of modifying of multi-walled carbon nano-tubes obtaining in step 3, be coated in mixed liquor on the common carbon paste electrode of modifying of PEM and multi-walled carbon nano-tubes in PEM and the common natural drying film forming in carbon paste electrode surface of modifying of multi-walled carbon nano-tubes, form the common carbon paste electrode of modifying of enzyme and PEM and multi-walled carbon nano-tubes.
Preferably, in described step 1, while carrying out centrifugal treating to the above-mentioned salpeter solution of multi-walled carbon nano-tubes is housed, the rotating speed of hydro-extractor is 3500～4500r/min.
Preferably, in described step 1, bake out temperature when multi-walled carbon nano-tubes is dried is 100 ℃.
Preferably, in described step 2, described carbon paste electrode carries out polishing after taking out from glass capillary.
Utilize above-mentioned formaldehyde electrochemical detection system to carry out a method for concentration of formaldehyde detection, it is characterized in that, it comprises the steps:
Step 100: the food that contains formaldehyde through confirmation is milled, then degradation treatment, the last food extract containing formaldehyde that therefrom extracts 1～20mL;
Step 200: getting formaldehyde standard solution that 1～10mL mass percent concentration scope is 37～40% in volumetric flask, is then 0.1 × 10 to adding the volumetric molar concentration scope of 0.1～10mL in this volumetric flask
-3～10 × 10
-3the food extract containing formaldehyde of the phosphate buffer of mol/L and 1～20mL, and the mixed solution in volumetric flask is shaken up, this mixed solution is placed after 14～16 minutes and is diluted with water to 20～50mL;
Step 300: the mixed solution after above-mentioned dilution is poured in first container and second container of above-mentioned formaldehyde electrochemical detection system, mixed solution after dilution in the first container and second container is by the first interface channel, amberplex and the second interface channel are communicated with, mixed solution after dilution in the first container is carried out to stir process, in this stir process process, under the catalysis of the formaldehyde dehydrogenase composition of the formaldehyde in mixed solution in enzyme and PEM and the common carbon paste electrode of modifying of multi-walled carbon nano-tubes, reaction generates reduced diphosphopyridine nucleotide, reduced diphosphopyridine nucleotide generation electrocatalysis oxidation reaction simultaneously, electric current produces electrolysis between to electrode and enzyme and PEM and the common carbon paste electrode of modifying of multi-walled carbon nano-tubes, simultaneously, hydrogen ion enters second container by amberplex and makes to form loop to forming voltage difference between electrode and enzyme and PEM and the common carbon paste electrode of modifying of multi-walled carbon nano-tubes, contrast electrode for playing the effect of burning voltage in the time that the carbon paste electrode of enzyme and PEM and the common modification of multi-walled carbon nano-tubes is carried out to potential measurement, the common carbon paste electrode of modifying of enzyme and PEM and multi-walled carbon nano-tubes is carried time dependent Faradaic current signal to signal conditioning circuit, signal conditioning circuit carries out filtering and amplifies and process above-mentioned Faradaic current signal, signal conditioning circuit will be transferred to signal processor with amplification Faradaic current signal after treatment after filtering, signal processor carries out computing with amplification Faradaic current signal after treatment by following algorithm after filtering to above-mentioned, obtain total concentration of formaldehyde C of the mixed solution after dilution in step 300,
Wherein, C is total concentration of formaldehyde of the mixed solution after dilution, I be above-mentioned after filtering with amplify Faradaic current signal after treatment, a is the enlargement factor of modulate circuit to current signal, t represents the common carbon paste electrode of modifying of enzyme and PEM and multi-walled carbon nano-tubes is carried T.T. from Faradaic current signal to signal conditioning circuit, and v represents the volume of the mixed solution after dilution;
Signal processor carries out computing to total concentration of formaldehyde C of the mixed solution after dilution by following algorithm again, obtains the concentration of formaldehyde C in food extract
1;
Wherein, C
1for the concentration of formaldehyde in food extract, v represents the volume of the mixed solution after dilution, V
1for the volume of formaldehyde standard solution, ρ is the density of formaldehyde standard solution.
Beneficial effect of the present invention:
1, the common carbon paste electrode of modifying of the enzyme in the present invention and PEM and multi-walled carbon nano-tubes, PARA FORMALDEHYDE PRILLS(91,95) has good catalytic oxidation effect, significantly reduce the oxidation peak current potential of formaldehyde, improve the accuracy that content of formaldehyde detects (content of formaldehyde is directly proportional to its oxidation peak current potential, only has the current potential that reduces oxidation peak just can detect the more formaldehyde of low content).
2, the present invention utilizes linear relationship good between Faradaic current signal and the concentration of formaldehyde, makes the present invention can detect faster the content of formaldehyde in food.
3, because the present invention has taked first to add formaldehyde standard solution, meet and generate the required content of formaldehyde of reduced diphosphopyridine nucleotide, and in the total concentration of formaldehyde in the end calculating, remove the content of formaldehyde standard solution, finally obtain the concentration of formaldehyde in food extract accurately, also can detect even if the concentration of formaldehyde like this in food extract is very small.The susceptibility that the present invention detects formaldehyde in food is apparently higher than existing measuring method.
4, intermediate ion exchange membrane part of the present invention has adopted detachable design, has facilitated the cleaning of amberplex, has guaranteed the accuracy of the content detection of formaldehyde in food.
5, the present invention also has advantages of that cost is low, volume is little, the real-time of testing result is good, in addition, the common carbon paste electrode of modifying of enzyme and PEM and multi-walled carbon nano-tubes has reduced the oxidation peak current potential of enzymatic product, thereby reduce the disturbing effect of other products to the pollution of electrode and other reactions, made it have good practicality and longer serviceable life.
Accompanying drawing explanation
Fig. 1 is structural representation of the present invention;
Fig. 2 is the structural representation of the first interface channel other end end face in the present invention;
Fig. 3 is the structural representation of the second interface channel other end end face in the present invention;
Fig. 4 is the structural representation of intermediate ion exchange membrane mounting cylinder of the present invention one end end face;
Fig. 5 is the structural representation of intermediate ion exchange membrane mounting cylinder other end end face of the present invention.
Wherein, 1-working electrode, 2-contrast electrode, 3-to electrode, the 4-the first container, 5-second container, 6-signal conditioning circuit, 7-signal processor, the 8-the first interface channel, the 9-the second interface channel, 10-amberplex, 11-amberplex mounting cylinder, the 12-the first flange, the 13-the second flange, 14-O-ring seal, the 15-the first annular groove, the 16-the first annular flange flange, the 17-the second annular groove, the 18-the second annular flange flange, 19-amberplex installing ring.
Embodiment
Below in conjunction with the drawings and specific embodiments, the present invention is described in further detail:
Formaldehyde electrochemical detection system as shown in Fig. 1～5, it comprises working electrode 1, contrast electrode 2, to electrode 3, the first container 4, second container 5, signal conditioning circuit 6, signal processor 7, the first interface channel 8, the second interface channel 9, wherein, one end of described the first interface channel 8 is communicated with the first container 4, one end of the second interface channel 9 is communicated with second container 5, between the other end of the other end of described the first interface channel 8 and the second interface channel 9, be communicated with by amberplex 10, described working electrode 1 and contrast electrode 2 are positioned at the first container 4, described electrode 3 is positioned to second container 5, the communication port of described working electrode 1 connects the anodal control port of measuring of electric current of signal conditioning circuit 6, the described communication port to electrode 3 connects the electric current negative pole of signal conditioning circuit 6 and measures control port, the communication port of described contrast electrode 2 connects the potential state of signal conditioning circuit 6 and stablizes port, the signal output part of above-mentioned signal conditioning circuit 6 connects the signal input part of signal processor 7, described working electrode 1 is enzyme and PEM and the common carbon paste electrode of modifying of multi-walled carbon nano-tubes, contrast electrode 2 is silver chloride contrast electrode, be platinum electrode to electrode 3.
In technique scheme, it also comprises the amberplex mounting cylinder 11 being arranged between the other end of the first interface channel 8 and the other end of the second interface channel 9, amberplex 10 is installed in the inner side of amberplex mounting cylinder 11, the other end of described the first interface channel 8 is provided with the first flange 12, the other end of the second interface channel 9 is provided with the second flange 13, described the first interface channel 8, amberplex mounting cylinder 11 is fixedly connected with the second flange 13 by the first flange 12 with the second interface channel 9, one end of described amberplex mounting cylinder 11 offers first annular groove 15 coaxial with amberplex mounting cylinder 11, the other end of the first interface channel 8 is provided with the first annular flange flange 16 coaxial with the first interface channel 8 and that mate with the first annular groove 15, the other end of above-mentioned amberplex mounting cylinder 11 offers second annular groove 17 coaxial with amberplex mounting cylinder 11, the other end of the second interface channel 9 is provided with the second annular flange flange 18 coaxial with the second interface channel 9 and that mate with the second annular groove 17, between described the first annular groove 15 and the first annular flange flange 16, be provided with O-ring seal 14, between described the second annular groove 17 and the second annular flange flange 18, be also provided with O-ring seal 14.The mounting structure of above-mentioned flange has been realized the dismounting of amberplex mounting cylinder 11, has facilitated the cleaning to amberplex 10, has improved the accuracy of the content detection of formaldehyde in food.
In technique scheme, it also comprises amberplex installing ring 19, and the inner ring of described amberplex installing ring 19 is fixedly connected with amberplex 10, between the outer ring of amberplex installing ring 19 and the inner ring of amberplex mounting cylinder 11, is interference fit.Amberplex installing ring 19 adopts special top cylinder to be headed in amberplex mounting cylinder 11 in installation process.
Flange, annular groove and O-ring seal 14 in technique scheme the sealing that has guaranteed detachable amberplex mounting cylinder 11 is set.
A method of preparing working electrode in formaldehyde electrochemical detection system, it comprises the steps:
Step 1: be heated to 80 ℃ by water-bath in the salpeter solution that is 20～35% at mass percent concentration by the multi-walled carbon nano-tubes of 1～50 gram, and the multi-walled carbon nano-tubes of 80 ℃ is stirred in above-mentioned salpeter solution to 48 hours (stirring by mixing plant), then the above-mentioned salpeter solution that multi-walled carbon nano-tubes is housed is carried out to centrifugal treating, impurity on multi-walled carbon nano-tubes is separated, after finishing, centrifugal treating removes the salpeter solution that contains above-mentioned multi-walled carbon nano-tubes impurity, take out multi-walled carbon nano-tubes, multi-walled carbon nano-tubes is washed till neutrality by water, then multi-walled carbon nano-tubes is dried, obtain the multi-walled carbon nano-tubes of purifying,
Step 2: carbon black and solid paraffin are ground evenly by 3 to 1 mass ratio in mortar, mixed-powder to carbon black and solid paraffin heats, make the solid paraffin powder melts in mixed-powder, carbon black powders is embedded in the paraffin of melting, this melt paraffin that is embedded with carbon black powders is packed in glass capillary, and insert aluminium wire to being embedded with in the melt paraffin of carbon black powders, the melt paraffin that is embedded with carbon black powders solidifies rear formation carbon paste electrode, and this carbon paste electrode is taken out from glass capillary;
Step 3: get ultrasonic being scattered in of the multi-walled carbon nano-tubes of purifying in the upper step 1 of 1～20mg and obtain the multi-walled carbon nano-tubes solution that concentration range is 0.1～5g/L in 1～20mL, bis-double distilled waters, getting with micro syringe multi-walled carbon nano-tubes solution that 10～100 μ L concentration ranges are 0.1～5g/L joins in the protonated ethanolic solution that 10～100 μ L mass percent concentration scopes are 0.01～1% and carries out ultrasonic dispersion treatment, form homogeneous solution, this homogeneous solution of getting 1～20 μ L is coated to described carbon paste electrode surface, place 5～10min and make above-mentioned homogeneous solution volatilization, and form film, carbon paste electrode skin drying is made to PEM and the common carbon paste electrode of modifying of multi-walled carbon nano-tubes,
Step 4: take the formaldehyde dehydrogenase of 1～3mg and the shitosan of 0.1～10mg (for serving as bonding agent) and be dissolved in the phosphate buffer that 100～300 μ L volumetric molar concentrations are 0.01～0.5mol/L, in above-mentioned phosphate buffer, add the glutaraldehyde cross-linking agent that 5～30 μ L mass percents are 1～10% and mix, form mixed liquor, the above-mentioned mixed liquor of 5～30 μ L is coated on the PEM and the common carbon paste electrode of modifying of multi-walled carbon nano-tubes obtaining in step 3, be coated in mixed liquor on the common carbon paste electrode of modifying of PEM and multi-walled carbon nano-tubes in PEM and the common natural drying film forming in carbon paste electrode surface of modifying of multi-walled carbon nano-tubes, form the common carbon paste electrode of modifying of enzyme and PEM and multi-walled carbon nano-tubes.
In the step 1 of technique scheme, while carrying out centrifugal treating to the above-mentioned salpeter solution of multi-walled carbon nano-tubes is housed, the rotating speed of hydro-extractor is 3500～4500r/min.It is centrifugal thoroughly that rotating speed while selecting the work of above-mentioned hydro-extractor can guarantee to be equipped with the salpeter solution of multi-walled carbon nano-tubes, makes multi-wall carbon nano-tube be in control relatively good pre-service.
In the step 1 of technique scheme, bake out temperature when multi-walled carbon nano-tubes is dried is 100 ℃.This temperature can make many walls nanotube dry to be unlikely to make it to fire the ash of charring because of excess Temperature preferably.
In the step 2 of technique scheme, described carbon paste electrode carries out polishing after taking out from glass capillary.Polishing improves the reappearance of electrode.
Utilize above-mentioned formaldehyde electrochemical detection system to carry out a method for concentration of formaldehyde detection, it is characterized in that, it comprises the steps:
Step 100: the food that contains formaldehyde through confirmation is milled, then degradation treatment, the last food extract containing formaldehyde that therefrom extracts 1～20mL;
Step 200: getting formaldehyde standard solution that 1～10mL mass percent concentration scope is 37～40% in volumetric flask, is then 0.1 × 10 to adding the volumetric molar concentration scope of 0.1～10mL in this volumetric flask
-3～10 × 10
-3the food extract containing formaldehyde of the phosphate buffer (this phosphate buffer guarantees that the pH value of solution is in suitable scope) of mol/L and 1～20mL, and the mixed solution in volumetric flask is shaken up, this mixed solution is placed after 14～16 minutes and is diluted with water to 20～50mL;
Step 300: the mixed solution after above-mentioned dilution is poured in first container 4 and second container 5 of above-mentioned formaldehyde electrochemical detection system, mixed solution after dilution in the first container 4 and second container 5 is by the first interface channel 8, amberplex 10 and the second interface channel 9 are communicated with, mixed solution after dilution in the first container 4 is carried out to stir process, in this stir process process, under the catalysis of the formaldehyde dehydrogenase composition of the formaldehyde in mixed solution in enzyme and PEM and the common carbon paste electrode of modifying of multi-walled carbon nano-tubes, reaction generates reduced diphosphopyridine nucleotide, reduced diphosphopyridine nucleotide generation electrocatalysis oxidation reaction simultaneously, electric current produces electrolysis between to electrode 3 and enzyme and PEM and the common carbon paste electrode of modifying of multi-walled carbon nano-tubes, simultaneously, hydrogen ion enters second container 5 by amberplex 10 and makes to form loop to forming voltage difference between electrode 3 and enzyme and PEM and the common carbon paste electrode of modifying of multi-walled carbon nano-tubes, contrast electrode 2 (guarantees that mixed solution electric charge evenly moves for the effect of playing burning voltage in the time that the carbon paste electrode of enzyme and PEM and the common modification of multi-walled carbon nano-tubes is carried out to potential measurement, sufficient reacting carries out), the common carbon paste electrode of modifying of enzyme and PEM and multi-walled carbon nano-tubes is carried time dependent Faradaic current signal to signal conditioning circuit 6, signal conditioning circuit 6 carries out filtering and amplifies and process above-mentioned Faradaic current signal, signal conditioning circuit 6 will be transferred to signal processor 7 with amplification Faradaic current signal after treatment after filtering, signal processor 7 carries out computing with amplification Faradaic current signal after treatment by following algorithm after filtering to above-mentioned, obtain total concentration of formaldehyde C of the mixed solution after dilution in step 300,
Wherein, C is total concentration of formaldehyde of the mixed solution after dilution, I be above-mentioned after filtering with amplify Faradaic current signal after treatment, a is the enlargement factor of modulate circuit 6 to current signal, t represents the common carbon paste electrode of modifying of enzyme and PEM and multi-walled carbon nano-tubes is carried T.T. from Faradaic current signal to signal conditioning circuit 6, and v represents the volume of the mixed solution after dilution;
Right
Wherein, C
1for the concentration of formaldehyde in food extract, v represents the volume of the mixed solution after dilution, V
1for the volume of formaldehyde standard solution, ρ is the density of formaldehyde standard solution.
In technique scheme, need more formaldehyde owing to producing reduced diphosphopyridine nucleotide, and content of formaldehyde in food is generally trace, be not enough to generate reduced diphosphopyridine nucleotide, so such scheme takes to add formaldehyde standard solution to increase the method for content of formaldehyde in volumetric flask, make mixed solution can generate reduced diphosphopyridine nucleotide, in the formaldehyde standard solution of above-mentioned increase, the content of formaldehyde is subtracted in the last computation process of step 3, obtain the content of formaldehyde in food accurately, so just can realize the detection to trace formaldehyde concentration in food.
The content that this instructions is not described in detail belongs to the known prior art of professional and technical personnel in the field.
Claims (8)
1. a formaldehyde electrochemical detection system, it is characterized in that: it comprises working electrode (1), contrast electrode (2), to electrode (3), the first container (4), second container (5), signal conditioning circuit (6), signal processor (7), the first interface channel (8), the second interface channel (9), wherein, one end of described the first interface channel (8) is communicated with the first container (4), one end of the second interface channel (9) is communicated with second container (5), between the other end of the other end of described the first interface channel (8) and the second interface channel (9), be communicated with by amberplex (10), described working electrode (1) and contrast electrode (2) are positioned at the first container (4), described electrode (3) is positioned to second container (5), the communication port of described working electrode (1) connects the anodal control port of measuring of electric current of signal conditioning circuit (6), the described communication port to electrode (3) connects the electric current negative pole of signal conditioning circuit (6) and measures control port, the communication port of described contrast electrode (2) connects the potential state of signal conditioning circuit (6) and stablizes port, the signal output part of above-mentioned signal conditioning circuit (6) connects the signal input part of signal processor (7), described working electrode (1) is enzyme and PEM and the common carbon paste electrode of modifying of multi-walled carbon nano-tubes, contrast electrode (2) is silver chloride contrast electrode, be platinum electrode to electrode (3).
2. formaldehyde electrochemical detection system according to claim 1, it is characterized in that: it also comprises the amberplex mounting cylinder (11) being arranged between the other end of the first interface channel (8) and the other end of the second interface channel (9), amberplex (10) is installed in the inner side of amberplex mounting cylinder (11), the other end of described the first interface channel (8) is provided with the first flange (12), the other end of the second interface channel (9) is provided with the second flange (13), described the first interface channel (8), amberplex mounting cylinder (11) is fixedly connected with the second flange (13) by the first flange (12) with the second interface channel (9), one end of described amberplex mounting cylinder (11) offers first annular groove (15) coaxial with amberplex mounting cylinder (11), the other end of the first interface channel (8) is provided with the first annular flange flange (16) coaxial with the first interface channel (8) and that mate with the first annular groove (15), the other end of above-mentioned amberplex mounting cylinder (11) offers second annular groove (17) coaxial with amberplex mounting cylinder (11), the other end of the second interface channel (9) is provided with the second annular flange flange (18) coaxial with the second interface channel (9) and that mate with the second annular groove (17), between described the first annular groove (15) and the first annular flange flange (16), be provided with O-ring seal (14), between described the second annular groove (17) and the second annular flange flange (18), be also provided with O-ring seal (14).
3. formaldehyde electrochemical detection system according to claim 2, it is characterized in that: it also comprises amberplex installing ring (19), the inner ring of described amberplex installing ring (19) is fixedly connected with amberplex (10), between the outer ring of amberplex installing ring (19) and the inner ring of amberplex mounting cylinder (11), is interference fit.
4. a method of preparing working electrode in formaldehyde electrochemical detection system, is characterized in that: it comprises the steps:
Step 1: be heated to 80 ℃ by water-bath in the salpeter solution that is 20～35% at mass percent concentration by the multi-walled carbon nano-tubes of 1～50 gram, and the multi-walled carbon nano-tubes of 80 ℃ is stirred 48 hours in above-mentioned salpeter solution, then the above-mentioned salpeter solution that multi-walled carbon nano-tubes is housed is carried out to centrifugal treating, impurity on multi-walled carbon nano-tubes is separated, after finishing, centrifugal treating removes the salpeter solution that contains above-mentioned multi-walled carbon nano-tubes impurity, take out multi-walled carbon nano-tubes, multi-walled carbon nano-tubes is washed till neutrality by water, then multi-walled carbon nano-tubes is dried, obtain the multi-walled carbon nano-tubes of purifying,
Step 2: carbon black and solid paraffin are ground evenly by 3 to 1 mass ratio in mortar, mixed-powder to carbon black and solid paraffin heats, make the solid paraffin powder melts in mixed-powder, carbon black powders is embedded in the paraffin of melting, this melt paraffin that is embedded with carbon black powders is packed in glass capillary, and insert aluminium wire to being embedded with in the melt paraffin of carbon black powders, the melt paraffin that is embedded with carbon black powders solidifies rear formation carbon paste electrode, and this carbon paste electrode is taken out from glass capillary;
Step 3: get ultrasonic being scattered in of the multi-walled carbon nano-tubes of purifying in the upper step 1 of 1～20mg and obtain the multi-walled carbon nano-tubes solution that concentration range is 0.1～5g/L in 1～20mL, bis-double distilled waters, getting with micro syringe multi-walled carbon nano-tubes solution that 10～100 μ L concentration ranges are 0.1～5g/L joins in the protonated ethanolic solution that 10～100 μ L mass percent concentration scopes are 0.01～1% and carries out ultrasonic dispersion treatment, form homogeneous solution, this homogeneous solution of getting 1～20 μ L is coated to described carbon paste electrode surface, place 5～10min and make above-mentioned homogeneous solution volatilization, and form film, carbon paste electrode skin drying is made to PEM and the common carbon paste electrode of modifying of multi-walled carbon nano-tubes,
Step 4: take the formaldehyde dehydrogenase of 1～3mg and the shitosan of 0.1～10mg and be dissolved in the phosphate buffer that 100～300 μ L volumetric molar concentrations are 0.01～0.5mol/L, in above-mentioned phosphate buffer, add the glutaraldehyde cross-linking agent that 5～30 μ L mass percents are 1～10% and mix, form mixed liquor, the above-mentioned mixed liquor of 5～30 μ L is coated on the PEM and the common carbon paste electrode of modifying of multi-walled carbon nano-tubes obtaining in step 3, be coated in mixed liquor on the common carbon paste electrode of modifying of PEM and multi-walled carbon nano-tubes in PEM and the common natural drying film forming in carbon paste electrode surface of modifying of multi-walled carbon nano-tubes, form the common carbon paste electrode of modifying of enzyme and PEM and multi-walled carbon nano-tubes.
5. the method for preparing working electrode in formaldehyde electrochemical detection system according to claim 4, it is characterized in that: in described step 1, while carrying out centrifugal treating to the above-mentioned salpeter solution of multi-walled carbon nano-tubes is housed, the rotating speed of hydro-extractor is 3500～4500r/min.
6. the method for preparing working electrode in formaldehyde electrochemical detection system according to claim 4, is characterized in that: in described step 1, bake out temperature when multi-walled carbon nano-tubes is dried is 100 ℃.
7. the method for preparing working electrode in formaldehyde electrochemical detection system according to claim 4, is characterized in that: in described step 2, described carbon paste electrode carries out polishing after taking out from glass capillary.
8. utilize the method that formaldehyde electrochemical detection system carries out concentration of formaldehyde detection described in claim 1, it is characterized in that, it comprises the steps:
Step 100: the food that contains formaldehyde through confirmation is milled, then degradation treatment, the last food extract containing formaldehyde that therefrom extracts 1～20mL;
Step 200: getting formaldehyde standard solution that 1～10mL mass percent concentration scope is 37～40% in volumetric flask, is then 0.1 × 10 to adding the volumetric molar concentration scope of 0.1～10mL in this volumetric flask
-3～10 × 10
-3the food extract containing formaldehyde of the phosphate buffer of mol/L and 1～20mL, and the mixed solution in volumetric flask is shaken up, this mixed solution is placed after 14～16 minutes and is diluted with water to 20～50mL;
Step 300: the mixed solution after above-mentioned dilution is poured in first container (4) and second container (5) of above-mentioned formaldehyde electrochemical detection system, mixed solution after dilution in the first container (4) and second container (5) is by the first interface channel (8), amberplex (10) and the second interface channel (9) are communicated with, mixed solution after dilution in the first container (4) is carried out to stir process, in this stir process process, under the catalysis of the formaldehyde dehydrogenase composition of the formaldehyde in mixed solution in enzyme and PEM and the common carbon paste electrode of modifying of multi-walled carbon nano-tubes, reaction generates reduced diphosphopyridine nucleotide, reduced diphosphopyridine nucleotide generation electrocatalysis oxidation reaction simultaneously, electric current produces electrolysis between to electrode (3) and enzyme and PEM and the common carbon paste electrode of modifying of multi-walled carbon nano-tubes, simultaneously, hydrogen ion enters second container (5) by amberplex (10) and makes to form loop to forming voltage difference between electrode (3) and enzyme and PEM and the common carbon paste electrode of modifying of multi-walled carbon nano-tubes, contrast electrode (2) for playing the effect of burning voltage in the time that the carbon paste electrode of enzyme and PEM and the common modification of multi-walled carbon nano-tubes is carried out to potential measurement, the common carbon paste electrode of modifying of enzyme and PEM and multi-walled carbon nano-tubes is carried time dependent Faradaic current signal to signal conditioning circuit (6), signal conditioning circuit (6) carries out filtering and amplifies and process above-mentioned Faradaic current signal, signal conditioning circuit (6) will be transferred to signal processor (7) with amplification Faradaic current signal after treatment after filtering, signal processor (7) carries out computing with amplification Faradaic current signal after treatment by following algorithm after filtering to above-mentioned, obtain total concentration of formaldehyde C of the mixed solution after dilution in step 300,
Wherein, C is total concentration of formaldehyde of the mixed solution after dilution, I be above-mentioned after filtering with amplify Faradaic current signal after treatment, a is the enlargement factor of modulate circuit (6) to current signal, t represents the common carbon paste electrode of modifying of enzyme and PEM and multi-walled carbon nano-tubes is carried T.T. from Faradaic current signal to signal conditioning circuit (6), and v represents the volume of the mixed solution after dilution;
Signal processor (7) carries out computing to total concentration of formaldehyde C of the mixed solution after dilution by following algorithm again, obtains the concentration of formaldehyde C in food extract
1;
Wherein, C
1for the concentration of formaldehyde in food extract, v represents the volume of the mixed solution after dilution, V
1for the volume of formaldehyde standard solution, ρ is the density of formaldehyde standard solution.
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