CN101424659A - Method for testing total selenium content by employing selenium metal compound - Google Patents

Abstract

The invention relates to a method using selenium metal compound for measuring the total selenium content. The method uses one metal electrode among lead, silver, copper, zinc, iron and cadmium as a work electrode and is based on electrochemical analysisstripping voltammetry three-electrode working principle and a test system formed with an electrolytic cell; Se<+6> and Se< +4> in a measured sample of a water solution directly generate the selenium compound of Se< -2> on the metal surface of the work electrode by electrons provided by the work electrode by pouring the measured sample of the water solution selenium containing Se<+6> and Se<+4> into the electrolytic cell containing a supporting electrolyte to have the reducing reaction under a specified electrochemical condition; the solving-out current of the selenium metal compound is measured to obtain the total content of the measured sample. The method has the following advantages that no toxic substance, i.e. fluorescent substances, reducing agents and the like are used, no pollution exists, the sample loss is low, the disturbance is low, the accuracy and the sensitivity are high, the linear range is wide, the operation is simple, and the checking cost is low.

Description

Adopt the method for selenium metallic compound testing total Se content

Affiliated technical field

The present invention relates to a kind of electrochemical test method, particularly adopt the method for selenium metallic compound testing total Se content; Belong to the analytical chemistry field, particularly electrochemical analysis stripping voltammetry technical field.

Background technology

Selenium is positioned at the 34th of the periodic table of chemical element, is trace element.Data according to World Health Organization's announcement, the whole world has more than 40 country to belong to low selenium and scarce selenium area, China's investigation shows 72% low selenium of county (city) genus or scarce selenium area, and having only ground such as enshi, Ziyang, Shaanxi, Shitai County, Anhui, Guizhou Feng Gang, Fengcheng is rich selenium area.Selenium is to be found and name by Sweden scholar Bei Cailiwusi (Berzelius) that in 1817 selenium was considered to a kind of toxin at that time, and high plant causes alkali disease because some contain selenium.To mid-term the 1950's; scholar Ke Laiyida (claytan); when repeating the selenium toxicity test, find; selenium can suppress the carcinogenesis of dimethyl azobenzene; scholar's Schwarz (schwarz) finds that micro-sodium selenite can be used as the protective agent of opposing rats'liver necrosis, and confirms that selenium is a kind of protection factor.The World Health Organization (WHO) and international nutrition are organized in 1973 confirms that selenium is behaved and the interior essential trace element of animal body, antioxygen is arranged and promote the sugar metabolic function, but blood sugar lowering and glucose in urine, delay senility and prevent and treat the cardiovascular and cerebrovascular disease function, in some scarce selenium area, human body lacks selenium influences growth plate cartilage distortion trouble Kaschin-Beck disease; But point out simultaneously, selenium is the narrow range between useful content and the poisoning content in biosomes such as human body, the selenium of excess intake can be accumulated and cause selenosis in the body, cause that headache, poor appetite, dysfunction of liver, autonomic nervous dysfunction, the carious tooth incidence of disease raise, even bring out chromosome aberration and cause selenosis such as cell carcinogenesis to endanger.So absorb trace elements of selenium in right amount, prevent that selenium is excessive and selenosis is most important.

As everyone knows, selenium can be divided into two kinds of organic selenium and inorganic seleniums.Organic selenium has various ways to exist; Inorganic selenium has hexavalent selenium Se ^{+ 6}, tetravalence selenium Se ^{+ 4}, zeroth order selenium Se ⁰With negative divalence selenium Se ^-2Deng four kinds of quantivalency forms; Hexavalent selenium Se ^{+ 6}As selenic acid (H ₂SeO ₄), tetravalence selenium Se ^{+ 4}As selenous acid (H ₂SeO ₃) and sodium selenite (Na ₂SeO ₃), generally can be water-soluble, can exist with the form of aqueous solution selenium; Zeroth order selenium Se ⁰Be free state, as selenium powder (Se); Negative divalence selenium Se ^-2Two kinds of forms are arranged, and a kind of is the gaseous compound of selenium and nonmetal formation, as hydrogen selenide (H ₂Se).A kind of is the water-fast compound that selenium and metal form, and also claims the selenium metallic compound, as lead selenide (PbSe), silver selenide (Ag2Se), copper selenide (CuSe), zinc selenide (ZnSe), ferrous selenide (FeSe), cadmium selenide (CdSe) etc.

As everyone knows, Zong in specimen, during Se content, must become to contain hexavalent selenium Se to the organic selenium of various forms in the sample with inorganic selenium with strong acid digestion (oxidation) exactly through the pre-treatment process ^{+ 6}With tetravalence selenium Se ^{+ 4}The form of aqueous solution selenium, just can carry out the test of next step the total Se content of sample.

According to the knowledge of the applicant, the method for testing total Se content has two kinds usually at present, and the one, fluorescence method, the 2nd, spectroscopic methodology.They all will be through an intermediate link, promptly the hexavalent selenium Se in the aqueous solution selenium ^{+ 6}With tetravalence selenium Se ^{+ 4}Transform or reduce, be transformed into another form of selenium, by testing the selenium of this a kind of form, just can be used as total Se content in the test water solution selenium by way of.Select different intermediate link, pass through by way of difference, also different as the form of selenium of test usefulness.

The principle that fluorescence method is tested total Se content is, earlier the hexavalent selenium Se in the aqueous solution selenium ^{+ 6}Be reduced into tetravalence selenium Se with hydrochloric acid ^{+ 4}, utilize 2 again, the character of 3-diaminonaphthalene in pH1.5～2.0 solution is optionally with tetravalence selenium Se ^{+ 4}Ionic reaction generates 4, and 5-benzopiaselenol green fluorescence material is extracted by thiacyclohexane, and the fluorescence intensity that is produced is directly proportional with the tetravalence Se content, and the fluorescence intensity of testing the green fluorescence material with fluorospectrophotometer or fluorophotometer draws total Se content; This method particular content can be consulted State Standard of the People's Republic of China's " mensuration 2 of water quality selenium, 3-diaminonaphthalene fluorescence method " GB 11902-1989; The intermediate link of this method testing total Se content is, by measuring the green fluorescence material---4, the 5-benzopiaselenol---as the testing total Se content by way of.

The principle of spectroscopic methodology testing total Se content is, hexavalent selenium Se ^{+ 6}With tetravalence selenium Se ^{+ 4}By hydride generator, be reduced into selenium and nonmetallic compound---hydrogen selenide (H with strong reductant (as sodium borohydride or potassium borohydride) ₂Se) gas draws total Se content with atomic absorption spectrography (AAS) or atomic fluorescence spectrometry test hydrogen selenide gas again; This method particular content can be consulted data such as People's Republic of China's health industry standard " the hydride generation-atomic absorption spectrometry of selenium in the urine " WS/T 47-1996 and State Standard of the People's Republic of China's " the hydride Generation-Atomic Fluorescence Spectrometry is measured Se content " GB/T20127.102006; The intermediate link of this method testing total Se content is, by measuring compound---the hydrogen selenide (H of selenium and nonmetal formation ₂Se) gas---as the testing total Se content by way of.

The common problem that exists of these two kinds of methods is, the intermediate link of testing total Se content will be used the bigger material of toxicity (as 2,3-diaminonaphthalene, sodium borohydride or potassium borohydride) to wait to transform or reduce, be used as testing by way of.Equipment leakproofness and ventilation condition are had relatively high expectations, and transform or have sample loss during reduction, also have in addition that testing procedure is many, complicated operation difficulty height, disturb problem such as big, cost height, make the penetration and promotion application of these two kinds of methods be subjected to certain limitation.

In addition, according to the knowledge of the applicant, the main direction of studying of Applied Electrochemistry analytical approach test selenium is to use the polarography of mercury electrode as working electrode before this, the theory of institute's foundation be mercury can with hexavalent selenium Se ^{+ 6}With tetravalence selenium Se ^{+ 4}Form amalgam (amalgam also claims mercury alloy, is mercury and the formed eutectic mixture of one or more other metals), under certain scan mode, measure the current peak of stripping electric current on the peak position voltage range and finish test.Because hexavalent selenium Se ^{+ 6}With tetravalence selenium Se ^{+ 4}Two quantivalencys present two stripping current peaks on mercury electrode, bifurcated usually appears in scanning curve, or two division peaks that are superimposed appear, can't differentiate and mutual disturbing effect, bring very big difficulty to testing research, research in this respect at present is progress not, and this part content is consulted " Cathodic Stripping Voltammetry is measured trace selenium in the selenium yeast " Guangdong trace element science 11 phases of calendar year 2001.

Summary of the invention

The objective of the invention is, problem at existing fluorescence method and the existence of spectroscopic methodology testing total Se content method is improved, propose and design adopt the selenium metallic compound as the test of intermediate link by way of the method for coming the testing total Se content, it is a kind of electrochemical analysis method of testing that adopts the method for the value by measuring the selenium metallic compound to come the testing total Se content.

Technical solution of the present invention is, based on the electrochemical analysis stripping voltammetry, it is characterized in that, forms test macro by contrast electrode, auxiliary electrode with solid metal electrode as three electrodes and the electrolytic cell of working electrode; Containing hexavalent selenium Se ^{+ 6}With tetravalence selenium Se ^{+ 4}The aqueous solution sample pour in the electrolytic cell that supporting electrolyte is housed and mix, insert three electrodes and make test macro work, test process is divided into reduction reaction stage and scanning stripping stage; In the reduction reaction stage, turn on agitator is accelerated reduction reaction speed, and solution is mixed; Under the electrochemical conditions of regulation, the voltage that makes working electrode is negative value, provides reduction reaction required electronics by the electric current of working electrode, makes hexavalent selenium Se ^{+ 6}With tetravalence selenium Se ^{+ 4}Obtain different electron numbers respectively at working electrode surface, finish through reduction reaction behind the certain hour, the result is the hexavalent selenium Se in the electrolytic cell ^{+ 6}With tetravalence selenium Se ^{+ 4}Finally be reduced into negative divalence selenium Se at working electrode surface ^-2The selenium metallic compound of form; In the scanning stripping stage, stop stirrer, three electrodes of finishing the reduction reaction process are inserted in the alkaline supporting electrolyte, the selenium metallic compound of working electrode surface is carried out stripping voltammetry scan; In the scanning process, the selenium metallic compound of working electrode surface produces the stripping electric current in fixing peak position voltage range scope, value linear dependence because of the value and the selenium metallic compound of stripping electric current, relevant in finite concentration scope internal linear by the value of selenium metallic compound with total Se content in the tested aqueous sample, so it is relevant in finite concentration scope internal linear with total Se content to obtain the stripping electric current, manufacture typical curve with the selenium standard solution, get final product the testing total Se content by linear relationship; And can reach the Practical Performance requirement of testing required detectability, precision, accuracy and the range of linearity.

It is characterized in that the selenium metallic compound comprises following six kinds: lead selenide PbSe, silver selenide Ag2Se, copper selenide CuSe, zinc selenide ZnSe, ferrous selenide FeSe, cadmium selenide CdSe.

It is characterized in that, in the reduction reaction stage, the electrochemical conditions of regulation is, supporting electrolyte also is acid for acidity and with the mixed solution of sample, the pH value is 0～6, supporting electrolyte with in the nitric acid in the mineral acid, hydrochloric acid, perchloric acid, sulfuric acid, the phosphoric acid any, or the compound sour form of wherein forming more than two kinds and two kinds, concentration is 0.1%～10%; The voltage of working electrode is for negative, and voltage range is-0.1V～-0.6V; Agitator speed is 10 rev/mins～2500 rev/mins; Time in reduction reaction stage is 1～30 minute.

It is characterized in that in the scanning stripping stage, supporting electrolyte is an alkaline solution, is NaOH or potassium hydroxide, concentration is 0.1mol/L～4mol/L, and the pH value is 8～14; Scanning voltage starting point to working electrode is-0.1V～-0.6V, require voltage with the working electrode of reduction phase on same magnitude of voltage, the scanning voltage terminating point is-1.5V; Sweep speed is 1mV/s～100mV/s; Scan mode is differentiated pulse stripping voltammetry, square wave stripping voltammetry or linear sweep stripping voltammetry; The direction of scanning is negative electrode stripping scanning; Fixing peak position voltage-0.7V～-produce the stripping electric current in the 1.1V interval range.

It is characterized in that, select as the solid metal electrode of working electrode that any is made in lead, silver, copper, zinc, iron, six kinds of solid metals of cadmium for use, shape can be ball, hemisphere, cambered surface, dish, post, silk, rod, pipe, plate, sheet and combined shaped, smooth surface, and purity is more than 98%.

Principle of work of the present invention is that the applicant finds under study for action, based on the electrochemical analysis stripping voltammetry, by measuring compound---the selenium metallic compound that selenium and metal form, as lead selenide PbSe, silver selenide Ag ₂Se, copper selenide CuSe, zinc selenide ZnSe, ferrous selenide FeSe, cadmium selenide CdSe etc., as the approach of testing total Se content, technical features such as the detectability during test, precision, accuracy and the range of linearity also can reach practical requirement.Relevant electrochemical analysis stripping voltammetry theory can be consulted " instrumental analysis " the 19 chapter voltammetry and polarography Sun Fengxia chief editor Chemical Industry Press June in 2004 the 1st edition.

The theoretical foundation that metal can generate the selenium metallic compound with selenium is, there are the mineral reserve of selenium metal compound attitude in occurring in nature, as clausthalite, naumannite, marthozite, zinc selenide, selenium copper iron ore, lehrbachite, selenium cadmium ore deposit etc., prove that on this basis redox reaction can take place for selenium and these metals, and exist with the form of compound.Related content can be consulted " mineral and rock dictionary ", chief editor Weng Runsheng, Chemical Industry Press April in 2008 the 1st edition.

The experiment proved that,, make hexavalent selenium Se by electrochemical method ^{+ 6}With tetravalence selenium Se ^{+ 4}Directly carry out reduction reaction at the surface of metal electrode electron gain, the reduction reaction process that generates the selenium metallic compound is:

Se ^{+ 6}Selenium: Se ^{+ 6}+ M+8e → MSe ... ... ... ... ... (1)

Se ^{+ 4}Selenium: Se ^{+ 4}+ M+6e → MSe ... ... ... ... ... (2)

M represents simple metal in the formula, is in six kinds of the plumbous silver-bearing copper zinc-iron cadmiums any.

Advantage of the present invention is:

(1) intermediate link of testing total Se content of the present invention is the hexavalent selenium Se that makes in the aqueous solution selenium ^{+ 6}With tetravalence selenium Se ^{+ 4}The electronics that provides by working electrode directly generates negative divalence selenium Se in the metal surface of working electrode ^-2The selenium metallic compound, reduction reaction process one step finishes, sample is loss not, thereby higher accuracy and sensitivity are arranged;

(2) testing total Se content of the present invention by way of, do not use materials such as fluorescent material or reductive agent, do not require special ventilation in the test process, supporting electrolyte is weak bronsted lowry acids and bases bronsted lowry, can not cause potential injury to operating personnel, can environment not polluted;

(3) equipment is simple, instrument cost is cheap, testing cost is little, disturbs less, simple to operate;

(4) it is wide to detect limit for width, precision height, the range of linearity.

Description of drawings

Scanning curve figure when Fig. 1, Fig. 2, Fig. 3, Fig. 4, Fig. 5, Fig. 6 the present invention adopt plumbous silver-bearing copper zinc-iron cadmium electrode respectively;

Fig. 7, scanning curve figure when adopting the present invention to test three kinds of quantivalency materials of selenium and stack;

The saturated upper limit synoptic diagram of Fig. 8, employing testing total Se content of the present invention;

Precision, accuracy, the range of linearity lab diagram of Fig. 9, employing testing total Se content of the present invention;

Embodiment

Below, with reference to the accompanying drawings, describe the utilization embodiments of the invention in detail.

Use instrument: the N-03 type iodine selenium tester that energy this Chinese instrument Ltd in Wuhan produces.

Instrument parameter is except that indicating, all by following setting: gain * 1, sensitivity * 2, pulse-response amplitude 50mV, burst length 40ms.

The reduction reaction stage, turn on agitator, rotating speed is 100 rev/mins; The supporting electrolyte of electrolytic cell selects nitric acid, and the concentration of nitric acid is 5%; The residing voltage of working electrode is-0.35V; Time is 25 minutes.

The scanning stripping stage stops stirrer, and alkaline supporting electrolyte is got 8ml, and selecting concentration is 2mol/L NaOH; The scanning voltage starting point is-0.35V that the scanning terminating point is-1.5V that sweep speed is 20mv/s; Scan mode is selected the differentiated pulse stripping voltammetry for use, and direction is a cathode direction, and other square wave stripping voltammetry is identical with the linear sweep stripping voltammetry.

Experiment condition: experimental water is a medical distilled water, reagent for analyze pure more than; Electronic balance weighing, precision 0.1mg; Environment temperature keeps constant temperature, humidity≤85%.

Experimental ware: 1000mL volumetric flask, 100mL volumetric flask constant volume, beaker, graduated cylinder etc.

Supporting electrolyte is got 5ml, and sample is got 10ml.

Acid supporting electrolyte compound method:

5% nitric acid (HNO ₃)---precision is measured 5mL red fuming nitric acid (RFNA) (HNO ₃), be diluted to 100mL;

Alkalescence supporting electrolyte compound method:

2mol/L NaOH---it is fixed to get the accurate title of 40 gram NaOH (NaOH), adds 500ml water, leaves in the alkaline-resisting plastic bottle.

Selenium standard solution 100mg/L (0.1mg/ml) preparation:

+ 6 valency selenium are with selenic acid (H ₂SeO ₄), get 0.1835g selenic acid (H ₂SeO ₄) accurate claim surely, pour in the 1000ml volumetric flask, be diluted with water to 1L, add the 5ml red fuming nitric acid (RFNA) and preserve stepwise dilution during use.

+ 4 valency selenium are with selenous acid (H ₂SeO ₃), get 0.1632g selenous acid (H ₂SeO ₃) accurate claim surely, pour in the 1000ml volumetric flask, be diluted with water to 1L, add the 5ml red fuming nitric acid (RFNA) and preserve stepwise dilution during use.

0 valency selenium, with selenium powder (Se), it is fixed to get the accurate title of 0.1g selenium (Se), is dissolved in 10ml red fuming nitric acid (RFNA) (HNO ₃) in, pour in the 1000ml volumetric flask, be diluted with water to 1L, stepwise dilution during use.

Embodiment 1

The present invention adopts six kinds of other scanning curves of solid metal electrode time-division such as plumbous silver-bearing copper zinc-iron cadmium, as Fig. 1, Fig. 2, Fig. 3, Fig. 4, Fig. 5, shown in Figure 6; Working electrode is Φ=4.5mm; Getting the selenium concentration of standard solution is 100 μ g/L tests.

The result shows: as seen from the figure, can obtain normal electrochemical analysis stripping voltammetry scanning curve, because the scanning peak position interval of different metal has outside little variation and the peak height difference, can prove that these six kinds of metals can use as working electrode.

Embodiment 2

Scanning result when utilization the present invention tests three kinds of quantivalency materials of selenium and stack is as Fig. 7.

Test the selenium of different price earlier respectively separately, the mixed liquor of the above-mentioned three kinds of concentration of standard solution that superpose during testing total selenium is tested again, and working electrode is the silver plate electrode, Φ=4.5mm.Test raw data such as following table, the peak height current unit is μ A.

The result shows: under variable concentrations, the electric current when measuring total selenium is to test each valency selenium (Se separately ^{+ 6}, Se ^{+ 4}, Se ⁰) time electric current stack and, proving can the testing total Se content.Situation was identical when working electrode was other several metal electrodes.

Embodiment 3,

Use the detection lower limit of testing total Se content of the present invention.

Working electrode is the silver plate electrode, diameter of phi=6.5, and instrument parameter is set: gain * 4, sensitivity * 8, pulse-response amplitude 50mV, burst length 50ms.

In the electrolytic cell of supporting electrolyte is arranged, add blank solution (deionized water).6 blank values of replication, (3) formula of pressing calculates the standard deviation S D of blank value:

Formula $\mathrm{SD}=\sqrt{\frac{\underset{i=1}{\overset{6}{\mathrm{\&Sigma;}}}{(x_i-\stackrel{\&OverBar;}{x})}^2}{6-1}}...........................\left(3\right)$

In the formula: SD---the standard deviation of blank value

x _i---measurement blank (μ A) value of i part blank solution

X---blank mean value

Get 6 parts of standard value solution respectively, concentration is selenium 1 μ g/L, with record respectively under the same terms of measuring blank solution, calculates the sensitivity H of selenium by formula (4):

Formula $H=\frac{\mathrm{\&Sigma;}{H}_i}{6}-x...........................\left(4\right)$

In the formula: H---sensitivity

H _i---measurement selenium electric current (μ A) value of i part

X---blank mean value

Criterion: H should be not less than the standard deviation S D of 10 times of blank values, i.e. H 〉=10SD.

The raw data such as the following table of test:

Blank value	0.001	0.0008	0.0009	0.0011	0.001	0.00095	SD＝0.000102
									Standard value	0.011	0.0087	0.0093	0.010	0.011	0.0095		H＝0.008959

The result shows: the requirement of H/SD=87 coincidence detection limit.So the silver plate electrode detection of Φ=6.5 limit can reach 1 μ g/L.Situation was identical when working electrode was other several metal electrodes.

Embodiment 4

Use the saturated upper limit of testing total Se content of the present invention, as Fig. 8.C is a solution concentration among the figure, and unit is μ g/L; S is the metal electrode area, and unit is (mm) ²Test data is as follows, and the peak height current unit is μ A.

The result shows: when concentration and metal electrode area ratio (C/S) when being less than or equal to 100, linear measurement range is well arranged.Ratio (C/S) saturated phenomenon occurred greater than 100 o'clock, and the stripping electric current no longer increases.Several metal electrode situations are similar.

Saturated phenomenon shows each valency selenium (Se ^{+ 6}, Se ^{+ 4}) being reduced into negative selenous selenizing metal thickness when being increased to a certain degree at the surface of metal electrode electron gain, cumulative effect hinders and continues to increase the selenium metallic compound again, and promptly measurement range has a higher limit, surpasses finite concentration and will occur saturated.

Embodiment 5

Use precision, accuracy, the range of linearity of testing total Se content of the present invention, as Fig. 9.Working electrode is the silver plate electrode, diameter of phi=4.5, and situation was identical when working electrode was other several metal electrodes.

(a) precision

With concentration is that 10 parts of 200 μ g/L selenium standard solution add respectively and have in the electrolytic cell of supporting electrolyte, measures 10 times, and by formula (5), (6) and (7) calculate coefficient of variation CV (%).

Formula $\stackrel{\&OverBar;}{x}=\frac{\underset{i=1}{\overset{n}{\mathrm{\&Sigma;}}}{x}_i}{n}...........................\left(5\right)$

Formula $\mathrm{SD}=\sqrt{\frac{\mathrm{\&Sigma;}{(x_i-\stackrel{\&OverBar;}{x})}^2}{n-1}}...........................\left(6\right)$

Formula $\mathrm{CV}=\frac{\mathrm{SD}}{\stackrel{\&OverBar;}{x}}\&times;100\%...........................\left(7\right)$

In the formula: x---mean value

x _i---designated parameter is measured selenium electric current (μ A) value for the i time

N---measure number of times

SD---standard deviation

CV---the coefficient of variation

Raw data and result are as follows:

1	2	3	4	5	6	7	8	9	10	x	SD	CV％
													2.0	2.1	2.0	2.0	1.9	1.95	2.1	2.1	2.1	1.9	2.015	0.08182	4.06

Result: CV=4.06%

(b) accuracy

With three parts of standard specimens, parallel testing concentration is the calibration solution of 200 μ g/L.Calculate measurement result average (x), represent the accuracy of measurement result with relative error R, computing method as the formula (8).

Formula $R=(1-\frac{\stackrel{\&OverBar;}{x}}{\mathrm{\&mu;}})\&times;100\%...........................\left(8\right)$

In the formula: R---accuracy

X---sample measurement result average

The actual value of μ---calibration solution

Raw data and result are as follows:

The 1st part	The 2nd part	The 3rd part	x	R(％)
					190	210	215	205	2.5

Result: accuracy R=2.5%

(c) range of linearity

With concentration is the calibration solution of 5 kinds of concentration such as 100 μ g/L, 200 μ g/L, 300 μ g/L, 400 μ g/L, 500 μ g/L, and every some repeated test 3 times is by (9), (10) and (11) formula calculated line equation y=a+bx.

Formula $b=\frac{\mathrm{n\&Sigma;}{x}_i{y}_i-\mathrm{\&Sigma;}{x}_i\&CenterDot;\mathrm{\&Sigma;}{y}_i}{\mathrm{n\&Sigma;}{x}_i^2-{\left(\mathrm{\&Sigma;}{x}_i\right)}^2}.....................\left(9\right)$

Formula $\left|a\right|=\frac{|\mathrm{\&Sigma;}{y}_i-\mathrm{b\&Sigma;}{x}_i|}{n}.....................\left(10\right)$

Formula $r=\frac{\mathrm{n\&Sigma;}{x}_i{y}_i-\mathrm{\&Sigma;}{x}_i\&CenterDot;\mathrm{\&Sigma;}{y}_i}{\sqrt{[\mathrm{n\&Sigma;}{x}_i^2-{\left(\mathrm{\&Sigma;}{x}_i\right)}^2]\&CenterDot;[\mathrm{n\&Sigma;}{y}_i^2-{\left({\mathrm{\&Sigma;y}}_i\right)}^2]}}.....................\left(11\right)$

In the formula: b---the slope of the tropic

| a|---the absolute value of tropic intercept

R---regression coefficient

x _i---test solution concentration

y _i---being worth of 3 mensuration with the corresponding selenium electric current of solution concentration (μ A)

i——1，2，3，......n

N---test specimens given figure (n=5 in this example)

The result shows: under the condition of parameter setting for gain * 1, sensitivity * 2, pulse-response amplitude 50mV, burst length 40ms, scale range is 100 μ g/L～500 μ g/L, regression coefficient r=0.992.

Claims (5)

1. adopt the method for selenium metallic compound testing total Se content,, it is characterized in that, form test macro as three electrodes and the electrolytic cell of working electrode by contrast electrode, auxiliary electrode with solid metal electrode based on the electrochemical analysis stripping voltammetry; Containing hexavalent selenium Se ^{+ 6}With tetravalence selenium Se ^{+ 4}The aqueous solution sample pour in the electrolytic cell that supporting electrolyte is housed and mix, insert three electrodes and make test macro work, test process is divided into reduction reaction stage and scanning stripping stage; In the reduction reaction stage, turn on agitator is accelerated reduction reaction speed, and solution is mixed; Under the electrochemical conditions of regulation, the voltage that makes working electrode is negative value, provides reduction reaction required electronics by the electric current of working electrode, makes hexavalent selenium Se ^{+ 6}With tetravalence selenium Se ^{+ 4}Obtain different electron numbers respectively at working electrode surface, finish through reduction reaction behind the certain hour, the result is the hexavalent selenium Se in the electrolytic cell ^{+ 6}With tetravalence selenium Se ^{+ 4}Finally be reduced into negative divalence selenium Se at working electrode surface ^-2The selenium metallic compound of form; In the scanning stripping stage, stop stirrer, three electrodes of finishing the reduction reaction process are inserted in the alkaline supporting electrolyte, the selenium metallic compound of working electrode surface is carried out stripping voltammetry scan; In the scanning process, the selenium metallic compound of working electrode surface produces the stripping electric current in fixing peak position voltage range scope, value linear dependence because of the value and the selenium metallic compound of stripping electric current, relevant in finite concentration scope internal linear by the value of selenium metallic compound with total Se content in the tested aqueous sample, so it is relevant in finite concentration scope internal linear with total Se content to obtain the stripping electric current, manufacture typical curve with the selenium standard solution, get final product the testing total Se content by linear relationship; And can reach the Practical Performance requirement of testing required detectability, precision, accuracy and the range of linearity.

2. the method for employing selenium metallic compound testing total Se content according to claim 1 is characterized in that the selenium metallic compound comprises following six kinds: lead selenide PbSe, silver selenide Ag ₂Se, copper selenide CuSe, zinc selenide ZnSe, ferrous selenide FeSe, cadmium selenide CdSe.

3. the method for employing selenium metallic compound testing total Se content according to claim 1, it is characterized in that, in the reduction reaction stage, the electrochemical conditions of regulation is, supporting electrolyte is for acid and also be acid with the mixed solution of sample, and pH value is 0～6, in the nitric acid in the supporting electrolyte usefulness mineral acid, hydrochloric acid, perchloric acid, sulfuric acid, the phosphoric acid any, or the compound sour form of wherein forming more than two kinds and two kinds, concentration is 0.1%～10%; The voltage of working electrode is for negative, and voltage range is-0.1V～-0.6V; Agitator speed is 10 rev/mins～2500 rev/mins; Time in reduction reaction stage is 1～30 minute.

4. the method for employing selenium metallic compound testing total Se content according to claim 1 is characterized in that, in the scanning stripping stage, supporting electrolyte is an alkaline solution, be NaOH or potassium hydroxide, concentration is 0.1mol/L～4mol/L, and the pH value is 8～14; Scanning voltage starting point to working electrode is-0.1V～-0.6V, require voltage with the working electrode of reduction phase on same magnitude of voltage, the scanning voltage terminating point is-1.5V; Sweep speed is 1mV/s～100mV/s; Scan mode is differentiated pulse stripping voltammetry, square wave stripping voltammetry or linear sweep stripping voltammetry; The direction of scanning is negative electrode stripping scanning; Fixing peak position voltage-0.7V～-produce the stripping electric current in the 1.1V interval range.

5. the method for employing selenium metallic compound testing total Se content according to claim 1, it is characterized in that, select as the solid metal electrode of working electrode that any is made in lead, silver, copper, zinc, iron, six kinds of solid metals of cadmium for use, shape can be ball, hemisphere, cambered surface, dish, post, silk, rod, pipe, plate, sheet and combined shaped, smooth surface, purity is more than 98%.

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