CN101893594B - Arsenic electrochemical determination method and apparatus - Google Patents
Arsenic electrochemical determination method and apparatus Download PDFInfo
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- CN101893594B CN101893594B CN201010192660.6A CN201010192660A CN101893594B CN 101893594 B CN101893594 B CN 101893594B CN 201010192660 A CN201010192660 A CN 201010192660A CN 101893594 B CN101893594 B CN 101893594B
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Abstract
Provided are a method and an apparatus for detecting arsenic or arsenic compounds and determining concentration of the arsenic or arsenic compounds with high precision and high sensitivity by simple operation and device through an electrochemical method. The method includes the following steps: adding aurum into a sample solution; changing the electric potential of a conductive diamond electrode to a negative potential to electrodeposit the arsenic and aurum on the surface of the conductive diamond electrode; and resolving the electrodeposited arsenic from the surface of the conductive diamond electrode in the sample solution by scanning the electric potential of the conductive diamond electrode to the positive potential.
Description
Technical field
The present invention relates to by electrochemical method, with easy operation and device, high precision and detect in high sensitivity arsenic or arsenic compound and measure assay method and the device thereof of its concentration.
Background technology
Arsenic (As) is that one easily enters into human body by potable water and food, in human body, after savings, causes arsenic poisoning, and a kind of extremely harmful element that can be lethal.
On arsenic minerals mountain, exploit arsenic-containing ores for the production of arsenous acid anhydride, zinc refiner produces arsine (AsH reduce recovery cadmium in the clean liquid operation of de-cadmium time
3).Also have, use the semiconductor factory of gallium arsenide (GaAs) and arsenic iridium (IrAs) to produce the discarded object of arsenical, moreover, in the manufacture process of the specific glass such as optical glass and electric glass (Electricity mood ガ ラ ス), also there is the situation of arsenous acid anhydride as clarificant that use.Therefore, in the discharge water of these facilities, probably contain arsenic.In addition, arsenic compound also had the period as wood preservative and termite repellant use.Therefore arsenic infiltrates into underground water, underground water probably can cause above-described arsenic poisoning phenomenon after being taken in by human body as potable water.
Poisonous element as arsenic, water pollution prevents that in law regulation discharge water, its content benchmark is below 0.1ppm (100ppb), in addition, in WHO potable water, its content benchmark is below 0.01ppm (10ppb).For this reason, need a kind of easy and detection method that precision is good, can detect the concentration of the compound of discharge water and Arsenic in Drinking Water and arsenic.
We know several by the method for electrochemical gaging arsenic, for example, disclosed in patent documentation 1～3.But, in the disclosed method of patent documentation 1, use gold electrode as working electrode, check in gold electrode surfaces by As (III) electro-deposition, but for electro-deposition the higher high price oxidation number As (V) of oxidation-reduction potential and additional larger negative potential, the competitive reaction that makes electrode surface that electrodeposit reaction easily occur is that the electrolytic reaction of water generates hydrogen, and is difficult for occurring the electrodeposit reaction of As (V), therefore make the method inspection become difficulty.
In addition, in the disclosed method of patent documentation 2, use has been injected the boron-doped diamond electrode of Ir ion as working electrode, and this electrode is also the concentration of measuring As (III) by the oxidation current of direct-detection As (III) → As (V).But it cannot measure the concentration of As (V).
Further, in the disclosed method of patent documentation 3, use the boron-doped diamond electrode of surface gold-plating as working electrode (hereinafter referred to as BDD-Au electrode), but its As for low concentration (V) insufficient sensitivity, the As (V) of concentration below 250ppb is difficult to be detected.In addition, every group of interelectrode difference of BDD-Au is large, all has deviation at the aspect such as semaphore and electron lifetime.Moreover BDD-Au electrode is after Reusability, the gold-plated of surface can dissolve, and causes sensitivity more to reduce, and causes the problem of poor reproducibility.
Patent documentation 1: Japanese Patent Laid-Open 2007-304081
Patent documentation 2: Japanese Patent Laid-Open 2006-98281
Patent documentation 3: Japanese Patent Laid-Open 2008-216061
Summary of the invention
Therefore the present invention makes every effort to provide a kind of electrochemical assay method and device thereof, by electrochemical method with easy operation and device, high precision and detect in high sensitivity arsenic or arsenic compound and measure its concentration.
The arsenic electrochemical determination method the present invention relates to, is to use the working electrode forming to electrode with by conductive diamond electrode to measure the concentration of arsenic in sample solution, it is characterized in that possessing following operation: in above-mentioned sample solution, add golden operation; The current potential that makes above-mentioned conductive diamond electrode is to the variation of negative potential direction, and arsenic and golden electro-deposition are to the electro-deposition operation on above-mentioned conductive diamond electrode surface; And to the current potential of the above-mentioned conductive diamond electrode of positive potential scanning direction, make the operation of separating out that the arsenic of above-mentioned conductive diamond electrode surface electro-deposition parses in said sample solution.
So, gold is joined to sample solution, itself and arsenic are present in sample solution jointly, by making the common electro-deposition of arsenic and gold on the surface of above-mentioned conductive diamond electrode, thereby can analyze in high sensitivity the arsenic of low concentration.This method with in advance by golden electro-deposition compared with the situation of electrode surface, improved as electrode reaction active site tremendously and there is the gold of catalysis and the contact probability of arsenic, thereby having promoted significantly the generation of the electrode reaction of arsenic.Therefore, according to the present invention, can make over by BDD-Au electrode under optimum determining condition, the detection that is all difficult to the following arsenic of 250ppb concentration of measuring becomes possibility, and has improved sensitivity significantly.
In addition, according to the disclosed method of patent documentation 3, must gold be deposited on the surface of boron-doped diamond electrode in advance, and in the present invention, only gold need be joined to sample solution, operate extremely easy.Moreover, in the present invention, due to gold is joined to sample solution, therefore do not need when using BDD-Au electrode, for obtain electrode in batch between performance homogenising and carry out the control of height.
The conductive diamond electrode using in the present invention, give in the conductive diamond electrode of diamond thin electric conductivity by mixing 13 families or 15 family's elements, preferably mix the electrode of central at least one element of boron, nitrogen and phosphorus, special, the boron-doped diamond electrode that mixes boron is most suitable.
For carbon electrode, when the negative potential of additional-about 1.0V, the competitive reaction that electrodeposit reaction easily occurs is that the electrolytic reaction of water generates hydrogen, the therefore more difficult generation of electro-deposition of As (V), and cause the problem that electrode worsens.But for boron-doped diamond electrode, even if the negative potential of additional-1.0V left and right is also difficult for causing such problem.
In said sample solution, the Concentrated degree of chloride ion is 1.5～2.5M, and preferably pH value is acid.Herein, pH value more preferably 0.5～1.5.With this understanding, the electrochemical determination method to arsenic the present invention relates to, can improve the detection sensitivity of arsenic significantly.For example, the concentration of NaCl in sample solution is added to 2M, pH value is adjusted into 1.0, compares with disclosed condition in patent documentation 3 (PBS 0.1M, pH5.0), and high 50 times of left and right are wanted in its sensitivity.This can think that owing to working as chloride ion concentration be 1.5～2.5M, pH is 0.5～1.5 o'clock, arsenic ion and gold ion form stable complex compound with chloride ion respectively, the state electro-deposition disperseing with homogeneous between arsenic ion and gold ion is at electrode surface, make contact area between gold and arsenic further extended due to.
In addition, chloride ion concentration is in above-mentioned scope, and the full width at half maximum of electric current crest itself is quite little, can obtain obvious crest.This is because the complex compound of arsenic ion and gold ion and chloride ion formation has produced impact to electronics translational speed.So be also therefore subject to hardly the interference of the interfering materials such as other metals.Moreover, if chloride ion concentration is in above-mentioned scope, owing to there being excessive Cl
-ion, and then can get rid of Br
-deng the impact of negative ion.
The addition of above-mentioned gold can be greatly excessive with respect to the arsenic in sample solution, also can select rightly according to the concentration of arsenic, for example, the concentration of gold in sample solution can be added to 10～1000ppm.
The electrochemical determination method of the arsenic the present invention relates to can be implemented by the determinator that for example contains following formation.Also there is following characteristics: a kind of for measure the device that has added golden sample solution arsenic concentration with electrochemical means, comprise: groove, be inside provided with to electrode and make arsenic and golden electro-deposition at this working electrode that conductive diamond electrode of electrode surface is formed; Potential change device, it makes the current potential of above-mentioned conductive diamond electrode change to negative potential direction, provide and make arsenic and the golden electro-deposition surperficial some position at above-mentioned conductive diamond electrode, then, make the current potential of above-mentioned conductive diamond electrode to the variation of positive potential direction, the current potential that provides the arsenic that makes above-mentioned conductive diamond electrode surface substrates to parse in sample solution; Pick-up unit, the curent change that its potential change that detects above-mentioned conductive diamond electrode causes; Signal conditioning package, its curent change detecting according to above-mentioned detection device calculates arsenic concentration.The electrochemical determining device of this arsenic is also a part of the present invention.
The effect of invention
According to the present invention, while utilizing electrochemical reaction detect arsenic and measure the concentration of arsenic, by add gold in sample solution, with easy operation and device thereof, can high precision and high sensitivity, and there is good reappearance and detect arsenic and measure its concentration.
Brief description of the drawings
The concise and to the point figure of the electrochemical determining device that [Fig. 1] one embodiment of the present of invention relate to.
The chart of the result that [Fig. 2] expression use boron-doped diamond electrode electro Chemical mensuration As (V) solution obtains, (a) represents voltammogram, (b) represents As (V) concentration and detection current value correlationship figure.
[Fig. 3] represents to use BDD-Au electrode electro Chemical to measure the result that As (V) solution obtains, and (a) represents voltammogram, (b) represents As (V) concentration and detects current value correlationship figure
[Fig. 4] represents to use boron-doped diamond electrode, changes change pH values, the voltammogram of electrochemical gaging As (III) solution gained.
Embodiment
Below, with reference to accompanying drawing, a specific embodiment of the present invention is described.
That the electrochemical determining device 1 that as shown in Figure 1, present embodiment relates to uses is batch tank for electrochemical gaging (bacth cell).
The electrochemical determining device 1 that present embodiment relates to possesses boron-doped diamond electrode 2, to electrode 3 and contrast electrode 4, and in be provided with the detection groove 5 of these 3 electrodes, boron-doped diamond electrode 2, electrode 3 is connected with potentiostat 7 with contrast electrode 4, and potentiostat 7 is connected with signal conditioning package 8 again.In addition, detect groove 5 and be provided with the stirrer that stirs sample solution S.
Below each portion is described.Boron-doped diamond electrode 2 is to be originally to make it have electric conductivity gained in the adamas of insulator by boron is sneaked into, and brings into play the function of working electrode in electrochemical determining device 1.Oozing mixes has the boron-doped diamond electrode 2 of high concentration boron to have following advantageous property: have very wide electromotive force window (oxidizing potential and reduction potential are all wider), compared with other electrode materials, there is lower background current, highly sensitive to different reductant-oxidants, compare with platinum etc. with gold, because its surface is difficult for physisorption occurs, be not therefore prone to oxygen hydrogen peak value in addition.In addition, the chemical durability of boron-doped diamond electrode 2, mechanical endurance, conductivity, corrosion resistance etc. are also excellent.Further, boron-doped diamond electrode 2 is due to its hardness, and easily carries out the cleaning of chemical physics, therefore also has advantages of that electrode surface easily keeps clean state.
The addition of the boron mixing in order to make adamas obtain electric conductivity carries out suitable decision in the scope that can give adamas electric conductivity, for example, preferably gives 1 × 10
-2～10
-6the dosage of Ω cm left and right electric conductivity.
Although boron-doped diamond self also can be used as electrode without the support of base material, but preferably forms boron-doped diamond film on base material, connect wire as electrode by this film.Above-mentioned base material can be enumerated Si (for example, monocrystalline silicon), Mo, W, Nb, Ti, Fe, Au, Ni, Co, Al
2o
3, SiC, Si
3n
4, ZrO
2, MgO, graphite, single-crystal diamond, cBN, quartz glass etc., especially suitable use monocrystalline silicon, Mo, W, Nb, Ti, SiC, single-crystal diamond.
The thickness of boron-doped diamond film is not particularly limited, preferably 1～100 μ m left and right, more preferably 5～50 μ m left and right.
For the shape of boron-doped diamond electrode 2, bar-shaped or planely all can.In addition, electrode surface can like this keep the growing up state of (as-grown), also can carry out hydrogen annealing to it, the physical treatment of the surface configuration of the chemical surface treatment such as electrolytic oxidation or planarization of being undertaken by various grindings etc.
, for example can select for compensating Faradaic current electrode 3, by platinum, carbon, stainless steel, gold, adamas, SnO
2at the electrode forming.
Known common electrode all can be elected to be contrast electrode 4, for example can use silver-silver chloride electrode, mercurous chloride electrode, standard hydrogen electrode, hydrogen-palladium electrode etc.
Detect in groove 5 and store sample solution S, its be configured to this sample solution S can with boron-doped diamond electrode 2, electrode 3 and contrast electrode 4 are connected.For detecting groove 5, its inside can store sample solution S, and its material is not particularly limited, the preferred resin materials such as teflon that impurity is separated out that prevent as far as possible.
Stirrer 6 is for stirring the sample solution S that detects groove 5 interior storages.Stir sample solution S by stirrer 6 and improve arsenic and the golden electro-deposition rate for boron-doped diamond electrode 2.Rotating manner for shape, material and the blade of stirrer 6 blades is all not particularly limited, preferably can fully stir sample solution S and inhibition of impurities and the generation of micro powder and the setting that inhibition electrode surface produces bubble as much as possible, for example, the cross stirrer of suitable use.
Potentiostat 7 is remaining on the current potential of boron-doped diamond electrode 2 under fixing state with respect to contrast electrode 4, detects boron-doped diamond electrode 2 and the electric current to generation between electrode 3, and this detection signal is passed to signal conditioning package 8.Potentiostat 7, except having the function of set potential of maintenance, also has with certain velocity sweeping current potential, varies to the function of selection of appointed etc. every the set time.These functions are unnecessarily loaded on 1 body machine simultaneously, and for example, current potential keeps function and electric potential scanning function can be arranged at respectively on different bodies.
Signal conditioning package 8 is that one has the input equipments such as CPU, internal memory, imput output circuit, keyboard, the general even special device of the output devices such as display and A/D converter, D/A converter etc., carry out collaborative work by above-mentioned CPU and relevant device thereof according to the program of loading in above-mentioned internal memory, resolve the detected signal of potentiostat 7, thereby arsenic is detected and measure its concentration.In addition, signal conditioning package 8 is unnecessarily all-in-one physically, by wired or be wirelessly divided into several equipment and also can.
Next, use electrochemical determining device 1 according to stripping voltammetry, the detection method of arsenic to be described.First, only the carrier solution that does not contain determination object arsenic is injected into and detects groove 5, make background current as far as possible little and stable.Then, adding HCl containing in the sample solution S of arsenic, make the content of HCl in solution become 0.1M, pH value is 1, adds NaCl, and the concentration that makes NaCl is 2M.Moreover, add AuCl
3(in hydrochloric acid with [AuCl
4]
-form exists) etc. gold compound make the concentration of gold ion become about 100ppm.By as above adjust after sample solution S inject detect groove 5.In addition, in sample solution S, add the order of HCl and NaCl and gold compound without successively.
Stir sample solution S on one side, use potentiostat 7 to make the current potential of boron-doped diamond electrode 2 to the variation of negative potential direction on one side, arsenic and gold and then electro-deposition are on the surface of boron-doped diamond electrode 2.This moment,, current potential is adjusted to-0.1V during as detected object taking As (III); During taking As (V) as detected object or taking As (III) and As (V) as common detected object, need carry out to current potential the variation in 2 stages, first under the current potential of-1.0V, reduce As (V), then again current potential is transferred to-0.1V.In any situation, after reach-0.1V of current potential, by by remain on-0.1V of the current potential of boron-doped diamond electrode 2, arsenic is concentrated and carry out fully electro-deposition within a certain period of time.
For the electrochemical reaction being occurred in the electrodeposition step that is detected object with As (V) or As (III) and As (V), be below elaborated.
The standard oxidizing potential of As (V) is as follows.
2H
2AsO
4 -+6H
++4e
-＝As
2O
3+5H
2O
(E
O＝-0.036VvsAg/AgCl)
As
2O
3+H
2O＝2HAsO
2
HAsO
2+3H
++3e
-＝As+2H
2O
(E
O＝-0.036VvsAg/AgCl)
As above, until on the surface of boron-doped diamond electrode 2, there are these 2 stages of reaction of reduction reaction and electrodeposit reaction in whole process in As (V) electro-deposition (separating out).Therefore, As (V) to carry out electro-deposition, first need current potential is adjusted to-1.0V, As (V) is reduced to As (III), then current potential is adjusted to-0.1V, make the surface of As (III) electro-deposition at electrode 2.
; even if carbon electrode is at the negative potential of-1.0V; also can be because competing the water electrolysis of generation at the hydrogen of electrode surface generation with electro-deposition; so more difficult generation of electro-deposition of As (V); the electrode being simultaneously made up of vitreous carbon is under the negative potential of-1.0V left and right, and electrode self also can occur deteriorated.In contrast to this, boron-doped diamond electrode 2 is until under the current potential of-1.0V left and right, electrode surface is also difficult for producing hydrogen, and deteriorated problem more can not occur.
While using in patent documentation 3 disclosed BDD-Au electrode, the so large negative potential of additional-1.5V for electro-deposition As (V), consequent hydrogen makes the gold that is deposited in advance electrode surface become unstable.Also therefore for this reason, make to utilize BDD-Au electrode detection concentration for the arsenic below 250ppb become difficulty.
In present embodiment, first, under current potential is remained on-1.0V, then, for fear of producing hydrogen, current potential is transferred to-0.1V also keeps the regular hour (10 seconds～30 seconds).Accordingly, As (V) and As (III) together with gold common electro-deposition on the surface of boron-doped diamond electrode 2.Can think, make As (V) revert to the state of As (III) under current potential is remained on-1.0V, be in order to make As (III), under its electro-deposition current potential, electrodeposit reaction occur.
On the other hand, only using As (III) during as detected object, under current potential is remained on-0.1V, As (III) with the common electro-deposition of gold in the surface of boron-doped diamond electrode 2.
After the surperficial substrates arsenic and gold of boron-doped diamond electrode 2, stop stirrer 6, by potentiostat 7, by the current potential of boron-doped diamond electrode 2 from-0.1V is to positive potential scanning direction, arsenic separate out in sample solution S.
Arsenic separate out the generation with electric current.Now, taking As (V) and As (III) in two stages of detected object, when additional negative potential, the As (V) existing in sample solution S and the total amount of As (III) can be detected as the current peak of As (III).
The current value (electric signal) that this electrochemical reaction produces reaches potentiostat 7, and the signal again each electrode being occurred is afterwards controlled detection.The detected signal of potentiostat 7 sends to signal conditioning package 8, and it contrasts the relation curve between the current value of gained and the arsenic concentration making in advance and current value, thereby calculates the concentration of arsenic in sample solution.
Now, first, measure taking As (V) and As (III) as detected object, then, only measure taking As (III) as detected object, then the concentration that deducts As (III) from As total amount (As (III)+As (V)) concentration just can calculate the concentration of As (V).
After electric potential scanning finishes, by by remain on+1.0V of the current potential of boron-doped diamond electrode 2, gold and the residual arsenic of electro-deposition are precipitated, and make boron-doped diamond electrode 2 be returned to the state before mensuration and regenerate, and then electrode can carry out Reusability.The regeneration of boron-doped diamond electrode 2 not only, only by current potential is kept fixedly carrying out, can also scan to carry out by the current potential with wider repeatedly.
According to present embodiment, in sample solution S, add excessive gold, itself and arsenic are present in sample solution jointly, compared with using BDD-Au electrode, gold and the common electro-deposition of arsenic are in the surface of boron-doped diamond electrode 2, improve as electrode reaction active site tremendously and there is the gold of catalysis function and the contact probability of arsenic, thereby having promoted significantly the generation of the electrode reaction of arsenic, having made the arsenic of analyzing in high sensitivity low concentration become possibility.Therefore, according to present embodiment, use in the past BDD-Au electrode under optimum determining condition, the detection of the arsenic below the 250ppb concentration that is all difficult to measure becomes possibility.
In addition, while using BDD-Au electrode, must in advance gold be deposited on boron-doped diamond electrode surface, and according to present embodiment, only gold need be joined to sample solution, operate extremely easy.Moreover, in present embodiment, due to gold is joined to sample solution, therefore do not need when using BDD-Au electrode, for obtain electrode in batch between performance homogenising and carry out the control of height.
Further, just at last under the negative potential lower than-1.0V, the surface of carbon electrode also can occur to produce hydrogen with the water electrolysis reaction of electro-deposition competition, make the electro-deposition of As (V) become difficulty, and boron-doped diamond electrode 2, under the negative potential of-1.0V left and right, also can be reduced to As (V) As (III), owing to being difficult for producing hydrogen under the negative potential in-1.0V left and right, so can not hinder the As that oxidation-reduction potential is large (V) to carry out electro-deposition.In addition, in present embodiment, under the negative potential of-1.0V left and right, As (V) is reduced to As (III), when using BDD-Au electrode by negative potential increase to-1.5V, just be difficult for producing hydrogen, As (V) is all improved in the lip-deep electrodeposition efficiency of boron-doped diamond electrode 2 to efficiency and the As (0) of the reduction reaction of As (III).
In addition, the NaCl concentration of sample solution S is transferred to 2M, pH value is transferred to 1.0, and arsenic ion and gold ion form stable complex compound with chloride ion respectively, thus easily generating electrodes reaction, and sensitivity increases substantially.
In addition, contain excessive chloride ion in sample solution S, the full width at half maximum of electric current crest itself is quite little, can obtain obvious crest.This is because the complex compound of arsenic ion and gold ion and chloride ion formation has produced impact to electronics translational speed.So be also therefore subject to hardly the interference of the interfering materials such as other metals.Moreover, in sample solution S, there is excessive chloride ion, can get rid of Br
-deng the impact of negative ion.
Above-mentioned embodiment of the present invention is not particularly limited.
For example, detect groove 5 and be not defined as batch-type, also can use the electrochemical determining device 1 that contains Stopped-flow (the ス ト Star プ De Off ロ same form) mensuration groove 5.
Further, the electrochemical determining device 1 that above-mentioned embodiment relates to is by possessing boron-doped diamond electrode 2, three-electrode method to electrode 3 and contrast electrode 4 carries out work, but can be also by only possessing boron-doped diamond electrode 2 and two electrode methods of electrode 3 being carried out to work for implementing the electrochemical determining device 1 of electrochemical determination method of the present invention.Three-electrode method can be controlled boron-doped diamond electrode 2 and the absolute value to impressed voltage between electrode 3, thereby can carry out high precision and highly sensitive mensuration, and two electrode methods are only used boron-doped diamond electrode 2 and to electrode 3 these two electrodes, make to detect the simple structure of groove 5, miniaturization, and then make to detect groove 5 can chip, disposable use, thus carry out easier mensuration.
To adding gold in sample solution S, adjust the concentration of pH value and chloride ion, after can get well in advance, again by sample solution S injection mensuration groove 5, also can in mensuration groove 5, carry out.In addition, electrochemical determining device 1 can be provided with before sample solution S is injected to detection groove 5, carried out golden interpolation and adjusted the adjustment tank of pH value and chloride ion concentration.
As the negative potential that makes arsenic electro-deposition on boron-doped diamond electrode 2 surfaces, be not limited to-1.0V and-0.1V, but should avoid inhaling hydrogen potential, preferably suppress the setting that hydrogen produces as far as possible, for example, for As (V), preferably-and below 0.5V, more preferably-1.0V left and right.Under electro-deposition current potential-0.1V of As (III), can not produce hydrogen.
In addition, electrochemical determining device 1 is the device that can implement the electrochemical gaging of above-mentioned arsenic, can be special purpose device, can be also that fexible unit combines, and the shape of device, capacity, the electrode size etc. of groove are all not particularly limited.
In addition, can appropriately combined above-mentioned embodiment and part or all of distortion embodiment, not departing from all distortion in aim of the present invention all likely.
Embodiment
The present invention will be described in more detail below to exemplify embodiment, but the present invention is not limited to these embodiment.
Make boron-doped diamond electrode
, as substrate, substrate surface does after texture processing to use silicon plate { Si (100) }, is configured on microwave CVD film formation device (manufacture of ASTeX company) frame.Film forming stoste is ready to as the lysate of carbon source, wherein be dissolved with the B as boron source taking the potpourri of acetone and methyl alcohol (liquid of mixed volume than 9: 1)
2o
3, make its concentration taking boron/carbon (B/C) ratio as 10
4ppm.
Then, in this film forming stoste, pass into the pure H as carrier
2after gas, import in container, pass into hydrogen (532ml/min) with another pipe in advance, adjust pressure to setting (115Torr=115 × 133.322Pa).Then, inject the microwave electric power of 2.45GHz, after electric discharge, adjust electric power to 5kW, after stablizing, in film forming stoste, pass into the pure H as carrier
2gas (15ml/min), by microwave plasma assisted CVD method, with the speed film forming of 1～4 μ m/h.Finally, reaction obtains film thickness after 8 hours and is about 30 μ m (electrode area is less than 1cm
2) boron-doped diamond electrode.Substrate temperature is conventionally at 850～950 DEG C.
Make BDD-Au electrode
Use the hydrochloric acid of 0.1M by the K[Au of 1M (Cl)
4] ten times of aqueous solution dilutions, adopt chronoamperometry that this solution is reduced 1 minute under-0.4V, by the boron-doped diamond electrode surface deposited Au of above-mentioned gained is produced to BDD-Au electrode.
Measure the concentration of As (V) solution
Use Na
2hAsO
47H
2o, as As (V) source, modulates As (V) solution of variable concentrations, and it is measured.
(1) boron-doped diamond electrode
First, modulation end liquid.In end liquid, select ultrapure water as solvent, it is 2M that interpolation NaCl makes its concentration, and it is 0.1M that interpolation HCl makes its concentration.By the standard gold solution (H[AuCl with respect to this end liquid
4]) 1000ppm mixes with volume ratio with end liquid at 1: 9, is modulated into gold end liquid.Then, by NaAsO
2join in end liquid, be modulated into As (III) aqueous solution.This As (III) aqueous solution is mixed with the liquid of the golden end that is formulated to Au100ppm, as measuring.
In mensuration system, select boron-doped diamond electrode as working electrode, contrast electrode is done in the choosing of Ag/AgCl electrode, and the choosing of Pt electrode is done electrode.Then, employing can effectively detect the stripping voltammetry of micro constitutent, the originally outer negative potential that adds, As electro-deposition on electrode after, to positive potential scanning direction current potential, measure current value now.
Condition determination is as follows.
(1) electro-deposition current potential-1.0V, electrodeposition time 30S (stirring 30S)
(2) electro-deposition current potential-0.1V, electrodeposition time 30S (stirring 10S, static 20S)
(3) sweep velocity 600mV/S, sweep limit-0.1～1.0V
(4) desorb current potential 1.0V, keeps this current potential 30S
Result as shown in Figure 2.
(2) BDD-Au electrode
Select BDD-Au electrode as working electrode, contrast electrode is done in the choosing of Ag/AgCl electrode, and the choosing of Pt electrode is done electrode, respectively the solution that contains As (V) 100ppb, 300ppb, 500ppb, 800ppb, 1000ppb is analyzed by following condition.Adopt stripping voltammetry, originally to working electrode additional-negative potential of 1.5V, under the current potential of-0.4V, carry out electro-deposition immediately afterwards, then to positive potential scanning direction current potential, measure current value now.
Condition determination is as follows.
(1) electro-deposition current potential-1.5V
(2) electro-deposition current potential-0.4V, electrodeposition time 60S (stirring 30S, static 30S)
(3) sweep velocity 200mV/S, sweep limit-0.4～1.0V
(4) desorb current potential 1.0V, keeps this current potential 30S
Result as shown in Figure 3.
(3) result
Compare with the situation that As (V) concentration is 100ppb, while using BDD-Au electrode, peak point current is 0.5 μ A, and baseline tilts, and while using boron-doped diamond electrode, peak point current is 15 μ A, and baseline values.From then on result clearly can be found out, in sample solution, uses when having added golden boron-doped diamond and analyzing, can detect As (V) with quite high sensitivity (30 times).
The impact of pH value in sample solution
Use boron-doped diamond electrode as working electrode, under said determination condition, change the pH value containing the sample solution of As (III) 0.56ppm, originally additional negative potential, As electro-deposition, after electrode, then to positive potential scanning direction current potential, is measured current value now.Result as shown in Figure 4.
As shown in Figure 4, pH value is 1 o'clock peak point current maximum, and the shape at peak is also the most sharp-pointed.As can be known from the results, when pH value is set as to the highly acid of 1 left and right, can improve the detection sensitivity of arsenic.
Utilizability in industry
By the present invention, can be with easy operation and device, high precision and detect in high sensitivity arsenic or the arsenic compound containing in underground water etc. and measure its concentration.
Symbol description
1, electrochemical determining device
2, boron-doped diamond electrode
3, to electrode
4, contrast electrode
5, detect groove
6, stirrer
7, potentiostat
8, signal conditioning package
S, sample solution
Claims (5)
1. an electrochemical determination method for arsenic, it is the working electrode that a kind of use forms to electrode with by conductive diamond electrode, measures the method for the arsenic concentration in sample solution with electrochemical means, it is characterized in that, comprises following operation:
To the operation that adds gold compound in above-mentioned sample solution;
Electro-deposition operation, makes the current potential of above-mentioned conductive diamond electrode to the variation of negative potential direction, allows arsenic and golden electro-deposition on above-mentioned conductive diamond electrode surface; And
Separate out operation, to the current potential of the above-mentioned conductive diamond electrode of positive potential scanning direction, the arsenic of electro-deposition on above-mentioned conductive diamond electrode surface is parsed in said sample solution.
2. the electrochemical determination method of arsenic as claimed in claim 1, wherein the concentration of said sample Chlorine in Solution compound ion is 1.5～2.5M.
3. the electrochemical determination method of arsenic as claimed in claim 1, wherein the pH of said sample solution is acid.
4. the electrochemical determination method of arsenic as claimed in claim 1, makes golden concentration become 10～1000ppm to adding gold compound in above-mentioned sample solution.
5. an electrochemical determining device, it for measure the arsenic concentration of the sample solution that has added gold compound with electrochemical means, is characterized in that, comprising:
Groove, in it, be provided with to electrode and make arsenic and golden electro-deposition at this working electrode that conductive diamond electrode of electrode surface is formed;
Potential change device, it makes the current potential of above-mentioned conductive diamond electrode change to negative potential direction, provide and make arsenic and the golden electro-deposition surperficial current potential at above-mentioned conductive diamond electrode, then, make the current potential of above-mentioned conductive diamond electrode to the variation of positive potential direction, the current potential that the arsenic of electro-deposition on above-mentioned conductive diamond electrode surface is parsed in sample solution is provided;
Pick-up unit, the curent change that its potential change that detects above-mentioned conductive diamond electrode causes;
Signal conditioning package, its curent change detecting according to above-mentioned detection device calculates arsenic concentration.
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| JP2009124266A JP5281481B2 (en) | 2009-05-22 | 2009-05-22 | Method and apparatus for electrochemical measurement of arsenic ion, and reagent set |
| JP2009-124266 | 2009-05-22 |
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| JP2001091499A (en) * | 1999-07-19 | 2001-04-06 | Akira Fujishima | Solution analysis method |
| JP2006098281A (en) * | 2004-09-30 | 2006-04-13 | Keio Gijuku | Electrode for electrochemical analysis/measurement, electrochemical analysis/measurement device, and electrochemical analysis/measurement method of inspected material concentration |
| JP4583937B2 (en) * | 2005-01-07 | 2010-11-17 | 積水化学工業株式会社 | Method for electrochemical measurement of arsenic ions |
| JP4458362B2 (en) * | 2005-09-07 | 2010-04-28 | ペルメレック電極株式会社 | Arsenic detection electrode, sensor using the same, and arsenic concentration measurement method |
| JP4869849B2 (en) * | 2006-04-10 | 2012-02-08 | 北斗電工株式会社 | Solution analysis method |
| JP4215132B2 (en) * | 2007-03-05 | 2009-01-28 | 学校法人慶應義塾 | Electrochemical analysis method using boron-doped conductive diamond electrode |
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| JP特开2006-98281A 2006.04.13 |
| JP特开2007-304081A 2007.11.22 |
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| JP2010271236A (en) | 2010-12-02 |
| CN101893594A (en) | 2010-11-24 |
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