CN109001130B - Inorganic selenium detection method and detection equipment - Google Patents
Inorganic selenium detection method and detection equipment Download PDFInfo
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Abstract
Discloses a detection method and a detection device of inorganic selenium, wherein the detection method comprises the following steps: respectively adding 50ml of reaction solution into a first reaction container (3) and a second reaction container (4), wherein the reaction solution comprises 0.001mol of potassium persulfate, 0.5mg of methylene blue, 2g of hexamethylenetetramine, 0.05mol of concentrated hydrochloric acid and 0.3mg of hydroxypropyl beta-cyclodextrin, 50ml of sampling solution is added into the first reaction container (3), 50ml of distilled water is added into the second reaction container (4), and the first and second reaction containers (3, 4) are cooled to room temperature after being heated for 5-7 minutes at 50 ℃; inserting the second reaction container (4) into the absorbance detection unit (5) for measurement to obtain a first absorbance, inserting the first reaction container (3) into the absorbance detection unit (5) for measurement to obtain a second absorbance, comparing the second absorbance with the first absorbance to obtain an absorbance difference value, and comparing the absorbance difference value with an inorganic selenium concentration curve based on the absorbance difference value to obtain the inorganic selenium concentration of the sample to be detected.
Description
Technical Field
The invention relates to the technical field of inorganic selenium detection, in particular to an inorganic selenium detection method and detection equipment.
Background
Selenium is a trace element necessary for human body, and is called cancer prevention king in the trace elements of human body. Scientifically found that the concentration of selenium in blood is related to the incidence rate of cancer. Because the selenium has high antioxidation, the proper selenium supplement for human bodies can play roles in preventing organ aging and pathological changes, delaying aging, enhancing immunity, resisting diseases and resisting toxic heavy metals. Selenium deficiency is the main cause of keshan disease and Kaschin-Beck disease. The world health organization recommends that 200 mug selenium be supplemented every day, and the high incidence of various diseases can be effectively prevented. A great deal of survey data show that the selenium content in food and soil in a region is directly related to the incidence of cancer, for example, the incidence and mortality of cancer are low when the selenium content in food and soil in a region is high, and conversely, the incidence and mortality of cancer are high in the region, which shows that the selenium is closely related to the incidence of cancer.
The existence of selenium in nature is divided into two categories: organic selenium and inorganic selenium. The organic selenium can eliminate free radicals in vivo, eliminate toxin in vivo, resist oxidation, effectively inhibit the generation of lipid peroxide, prevent blood clot, eliminate cholesterol, and enhance immunity. Can be used for preventing diabetes, cataract, cardiovascular and cerebrovascular diseases, keshan disease, Kashin-Beck disease, and arthritis, and has effects of removing toxic substance, preventing and treating liver diseases, and protecting liver. The organic selenium is formed by combining selenium with amino acid through biotransformation, generally exists in the form of selenomethionine, is metabolized along a methionine metabolic pathway, participates in protein synthesis, and is easy to store and absorb in tissues; can be rapidly utilized by human body after being absorbed by human body, and effectively improves the blood selenium condition in human body. Organic selenium becomes the only safe and reliable selenium source for human beings! The most easily absorbed organic selenium is selenium polysaccharide and selenium protein, and particularly, the selenium protein has the highest absorption conversion rate and is the safest in a human body, so the selenium-enriched eggs become the best choice for people to supplement selenium.
Inorganic selenium generally refers to sodium selenite and sodium selenate, and is obtained from the by-products of metal mineral deposits. The absorption and utilization of inorganic selenium fortifiers are not ideal, their biological effectiveness is low, their toxicity is high, the range between toxic quantity and required quantity is small, and they are not suitable for human and animal, so that their application quantity is strictly limited. The use of inorganic selenium such as sodium selenite in all animal feeds has been regulated by government bodies in countries such as japan.
The existing selenium content detection technology can only detect the total selenium content, and cannot detect the inorganic selenium concentration on the surface of agricultural products such as melons, fruits, vegetables, beans, grains and the like.
1) selected instruments and equipment: HPLC-HGAFS coupled system:
(1) HPLC part, using LC-10ATVP high pressure liquid phase pump; a 7725i six-way sample injection valve with 100 μ L quantitative ring; adopting a Hamilton PRP-X100, 250mm multiplied by 4.1mm i.d,10 μm anion chromatographic column, a protective column with the same material filler 25mm multiplied by 2.3mm i.d, 12-20 μm;
(2) the HGAFS-9130 atomic fluorescence spectrophotometer is provided with an excitation light source, a high-performance selenium hollow cathode lamp and morphological analysis and measurement software;
(3) cooling the circulating water;
(4) a super constant temperature blending instrument;
(5) a sand core filter;
(6) a circulating vacuum pump;
(7) a centrifuge;
(8) a numerical control ultrasonic cleaner;
(9) a 0.45 μm aqueous microporous filter membrane;
(10) the purity of argon is more than or equal to 99.99 percent;
2) preparing reagent and standard solution
(1) Reagent: a mixed solution of 7% hydrochloric acid solution, 5g/L potassium hydroxide solution and 20g/L potassium borohydride solution in volume ratio, and a diammonium hydrogen phosphate solution with pH of 6.0 and the concentration of 40mmol/L is used as a mobile phase;
(2) preparation of standard use solution for selenium form:
dissolving corresponding amounts of Se (VI), Se (IV), SeMet and SeCys to obtain a stock standard solution of each single standard solution of 1mg/L, and gradually diluting with water to obtain standard use solutions of 5.0ng/mL, 25.0ng/mL, 50.0ng/mL, 75.0ng/mL and 100.0 ng/mL;
3) and (3) carrying out a testing step:
accurately weighing dried sample which is crushed and sieved by a 40-mesh sieve, placing the dried sample into a container, adding deionized water, uniformly mixing, shaking for 1h by a super constant-temperature mixing instrument at 70 ℃ to ensure that the sample is fully extracted, taking out the sample, cooling, centrifuging, taking out supernatant, filtering the supernatant by using a 0.45-micron water-based microporous filter membrane, and measuring the selenium form value by using a machine;
4) the conditions of the apparatus used:
(1) liquid chromatography conditions: the pH value of the mobile phase is 6.040mmol/L (NH4)2HPO4, and the flow rate is 1 mL/min; the sample injection volume is 100 mu L; 46mA of auxiliary cathode; the speed of the peristaltic pump is 65 rpm;
(2) hydride generation conditions: reducing agent component: a mixed solution of a potassium hydroxide solution with a final concentration of 5g/L and a potassium borohydride solution with a final concentration of 20g/L, flow rate: 6.0 mL/min; current-carrying component: volume ratio 7% HCl, flow rate: 6.0 mL/min;
(3) atomic fluorescence spectrum conditions: the high-performance selenium hollow cathode lamp has negative high voltage of 300V and lamp current of 60 mA; the carrier gas is argon gas, and the concentration is 400 mL/min; the shielding gas is argon gas, and the concentration is 600 mL/min;
5) and (5) performing qualitative and quantitative calculation on each form of selenium according to the chromatogram. The method comprises the following steps of sequentially eluting selenocysteine (SeCys), selenite Se (IV), selenomethionine (SeMet) and selenate Se (VI) by a mobile phase through an anion chromatographic column, wherein the anion chromatographic column has different adsorption capacities, and an elution solution is subjected to hydrogenation reaction through a potassium borohydride reducing agent and hydrochloric acid to generate hydride, and the hydride enters an atomizer to be used with atomic fluorescence for analysis and determination.
Patent document 2 discloses a method for detecting selenium, which comprises the following steps: a. analytical instrument system configuration: combining a chromatographic separation system, an atomic fluorescence spectrophotometer and a selenium form pretreatment device into an HPLC-HG-AFS combined system; the chromatographic column is a C18 column or an anion exchange column which can retain SeO34+, SeO46+, selenoamino acid and derivatives thereof, dimethyl selenium and selenourea micromolecular substances; the selenium form pretreatment device is a selenium form pretreatment device which can be connected with a chromatographic separation system and converts selenium-containing components in a sample to be detected separated by the chromatographic separation system into hydride, and the instrument analysis method comprises the following steps: the mobile phase is (NH4)2HPO4 buffer solution with different concentrations or solution added with organic reagent; the elution mode adopts 30mM-150mM pH3-9 diammonium phosphate buffer solution to prepare a mobile phase for isocratic elution or gradient elution by changing the flow rate, or more than 2 mobile phases with different concentrations, and gradient elution is carried out by changing the proportion of the mobile phases; the sample introduction can adopt 2 manual or automatic modes, and the sample introduction volume is between 0.1 and 100 mu L; other parameters are recommended and set according to the instruction of the instrument and equipment; the solution added with the organic reagent is a solution added with methanol or other organic reagents; c. the detection method of the selenium form comprises the following steps: extracting with 0.1-1N HCl, HClO4, NaOH, pepsin K aqueous solution and 50-100% CH3OH solution, extracting with HCl and HClO4, and adjusting pH to 5-6 with NaOH solution; adjusting the pH value of the solution extracted by NaOH to 8-9 by hydrochloric acid; the pH value of the pepsin K water extract and 50 to 100 percent CH3OH extract is not adjusted; the shape of inorganic selenium after the extracting solution is filtered by a filter membrane of 0.45 mu m can be qualitatively and quantitatively measured for the components with the standard substances, and the components without the standard substances can provide a basis for further research; determining an optimal extraction method according to the separation condition and peak height of peaks in the chromatogram; d. determination of elemental selenium: dissolving a small amount of HNO3, aqua regia or HNO3+ HClO4, adjusting the pH value to 5-6 by using NaOH solution, filtering by using a 0.45 mu m filter membrane, then testing on a computer, calculating the content of SeO34+ by using an external standard method, and calculating the recovery rate of selenium so as to determine the feasibility of the method; e. and (3) determination of inorganic selenium: qualitatively and quantitatively measuring the contents of SeO34+ and SeO46+ in the sample leaching liquor, and obtaining the organic selenium content by adopting a method of reducing total selenium by inorganic selenium; f. and (3) determination of total selenium content: digesting the sample according to the GB method, reducing the sample without adding hydrochloric acid during digestion, adjusting the pH value to 5-6 by using NaOH solution, measuring the pH value on a machine after constant volume, and calculating the contents of SeO34+ and SeO46+ and the total selenium content by using an external standard method. The patent can be used as a method for detecting 5 selenium forms such as SeCYs2, SeMet, Se (IV), MeSeCys and Se (VI), and the like, and can completely separate Se (IV) and Se (VI) when used as a method for detecting inorganic selenium.
Patent document 3 discloses a method for measuring the content of inorganic selenium in selenium-enriched yeast, which comprises the following steps:
(1) weighing selenium-enriched yeast, adding strong alkali solution into the selenium-enriched yeast, performing ultrasonic treatment to dissolve the selenium-enriched yeast, and performing water bath heating; wherein the ratio of the mass of the selenium-enriched yeast to the amount of hydroxide ion substances in the strong alkaline solution is 1 g: 15-35 mmol;
(2) after heating, cooling, centrifuging again, and taking supernatant;
(3) adjusting the acidity of the supernatant obtained in the step (2) until the pH value of the supernatant is 4-5, standing, and filtering to obtain a filtrate;
(4) and (4) adding 6-12 mol/L hydrochloric acid aqueous solution into the filtrate obtained in the step (3), boiling, diluting, and measuring the content of inorganic selenium in the diluted solution by using an atomic fluorescence spectrophotometer. This patent adopts alkaline solution (for example, sodium hydroxide solution) to draw the leaching method extraction rate of inorganic selenium in the selenium-enriched yeast fast, and the time spent is short, and survey time process is no longer than 1 hour, but this patent only can detect the yeast, and the range of application is little, and detection time is long and the precision is not high, receives the interference easily, detects poor stability.
Documents of the prior art
Patent document
Patent document 1: chinese patent publication No. CN103399117A
Patent document 2: chinese patent publication No. CN103884785A
Patent document 3: chinese patent publication No. CN106841138A
The above information disclosed in this background section is only for enhancement of understanding of the background of the invention and therefore it may contain information that does not form the prior art that is already known in this country to a person of ordinary skill in the art.
Disclosure of Invention
In order to solve the defects of the prior art, the invention provides the inorganic selenium detection method and the detection equipment, which can be used for quickly detecting the surface inorganic selenium content of the samples to be detected of agricultural products such as melons, fruits, vegetables, beans, grains and the like, quickly collecting the selenium-rich agricultural products for field detection, and obtaining the detection result of the inorganic selenium on the spot.
The purpose of the invention is realized by the following technical scheme.
In one aspect of the invention, a method for detecting inorganic selenium comprises the following steps:
in the first step, a predetermined amount of sample to be tested is put into a stirring container filled with 100ml of distilled water, stirred for 4-7 minutes and then kept stand for 1-2 minutes, the liquid in the stirring container is filtered by a filtering unit with the aperture of 0.4-0.5um to obtain 50ml of sampling solution,
in the second step, 50ml of reaction solution is respectively added into a first reaction container and a second reaction container, wherein the reaction solution comprises 0.001mol of potassium persulfate, 0.5mg of methylene blue, 2g of hexamethylenetetramine, 0.05mol of concentrated hydrochloric acid and 0.3mg of hydroxypropyl beta-cyclodextrin, 50ml of sampling solution is added into the first reaction container, 50ml of distilled water is added into the second reaction container, and the first reaction container and the second reaction container are heated at 50 ℃ for 5-7 minutes and then cooled to room temperature;
in the third step, the second reaction vessel is inserted into the absorbance detection unit to obtain a first absorbance, the first reaction vessel is inserted into the absorbance detection unit to obtain a second absorbance, the second absorbance and the first absorbance are compared to obtain an absorbance difference, the absorbance difference is compared with an inorganic selenium concentration curve based on the absorbance difference to obtain the inorganic selenium concentration of the sample to be detected, wherein the inorganic selenium concentration curve based on the absorbance difference is formed by plotting a plurality of predetermined concentrations of inorganic selenium for measuring the respective absorbances.
In the detection method, in the first step, the sample to be detected with the predetermined amount of 10g is put into a stirring vessel containing 100ml of distilled water, stirred for 5 minutes and then left to stand for 1 minute.
In the detection method, the distilled water in the sample solution linearly increases with an increase of a predetermined amount, and the addition amount of the reaction solution linearly increases based on the addition amount of the sample solution.
In the detection method, in the first step, the liquid in the stirred vessel is filtered through a 0.45um pore size syringe microfiltration membrane.
According to another aspect of the present invention, a detection apparatus for implementing the detection method includes,
the stirring container for stirring the sample to be measured comprises a feed inlet arranged at the top of the stirring container and a liquid outlet arranged at the lower half part of the side wall of the stirring container, the liquid outlet is provided with a filtering unit,
the first reaction vessel comprises a first reaction vessel body with an upper opening and a first cover body capable of sealing the upper opening, the first reaction vessel body comprises a first scale mark arranged on the side wall and a first constant-temperature heating module arranged at the bottom, the first constant-temperature heating module comprises a first heating element and a constant-temperature control unit,
a second reaction vessel including a second reaction vessel body having an upper opening for receiving a reaction solution and a second lid body for sealing the upper opening, the second reaction vessel body including a second graduation mark provided at a sidewall and a second heating member provided at a bottom, the first reaction vessel and the second reaction vessel being arranged in parallel, the thermostatic control unit connecting the first heating member and the second heating member so that the first and second reaction vessels are simultaneously heated to a predetermined temperature and maintained for a predetermined time,
an absorbance detection unit inserted into the first and second reaction containers, respectively, to measure absorbance, the absorbance detection unit including,
a light source emitting light of a predetermined light intensity,
a light filter for filtering the light,
a photodetector that measures absorbance of the light filtered through the optical filter,
a display unit displaying absorbance data measured by the photodetector,
and the processing unit comprises a storage unit for storing an inorganic selenium concentration curve based on the absorbance difference and a comparison unit for obtaining the inorganic selenium concentration of the sample to be tested based on the absorbance difference.
In the detection device, the stirring container is a magnetic stirrer.
In the detection equipment, the filtering unit is an injector microfiltration membrane, and the liquid outlet is detachably connected with the injector through the injector microfiltration membrane.
In the detection device, the first reaction vessel and/or the second reaction vessel comprises a reaction tube with a cover.
In the detection device, the absorbance detection unit is a photoelectric colorimeter.
In the detection device, the light source is a light emitting diode, and the photoelectric detector is a silicon photoelectric diode.
The invention has the following beneficial effects:
compared with the prior art, in the inorganic selenium detection method, under a certain temperature condition, hydroxypropyl beta-cyclodextrin breaks through a ring-shaped hydrogen bond in a beta-cyclodextrin molecule, the defect of poor water solubility of the beta-cyclodextrin is overcome while a cyclodextrin cavity is maintained, the catalytic action of inorganic selenium is obviously improved under the action of hexamethylenetetramine and concentrated hydrochloric acid, the difference value of absorbance is obtained by measuring the absorbance after the reaction of potassium persulfate and methylene blue oxide under the same condition and the absorbance after selenium catalysis under the same condition, the concentration of the inorganic selenium can be obtained by searching a standard curve, the detection time is obviously shortened, the detection precision is superior to that of the prior art, the detection method is simple, the field in-situ rapid detection can be carried out without complex equipment, and the operation is convenient, safe and reliable.
The above description is only an overview of the technical solutions of the present invention, and in order to make the technical means of the present invention more clearly apparent, and to make the implementation of the content of the description possible for those skilled in the art, and to make the above and other objects, features and advantages of the present invention more obvious, the following description is given by way of example of the specific embodiments of the present invention.
Drawings
Various other advantages and benefits of the present invention will become apparent to those of ordinary skill in the art upon reading the following detailed description of the preferred embodiments. The drawings are only for purposes of illustrating the preferred embodiments and are not to be construed as limiting the invention. It is obvious that the drawings described below are only some embodiments of the invention, and that for a person skilled in the art, other drawings can be derived from them without inventive effort. Also, like parts are designated by like reference numerals throughout the drawings.
In the drawings:
fig. 1 shows a schematic step diagram of an inorganic selenium detection method according to an embodiment of the present invention.
Fig. 2 is a graph showing an inorganic selenium concentration curve based on absorbance difference of an inorganic selenium detection method according to an embodiment of the present invention.
FIG. 3 is a graph showing the comparison of the recovery of sodium selenite at different dilution factors for the inorganic selenium assay and the national standard assay of one embodiment of the present invention.
Fig. 4 shows a schematic view of the structure of a detection apparatus of an inorganic selenium detection method according to an embodiment of the present invention.
The invention is further explained below with reference to the figures and examples.
Detailed Description
Specific embodiments of the present invention will be described in more detail below with reference to the accompanying drawings. While specific embodiments of the invention are shown in the drawings, it should be understood that the invention may be embodied in various forms and should not be construed as limited to the embodiments set forth herein. Rather, these embodiments are provided so that this disclosure will be thorough and complete, and will fully convey the scope of the invention to those skilled in the art.
It should be noted that certain terms are used throughout the description and claims to refer to particular components. As one skilled in the art will appreciate, various names may be used to refer to a component. This specification and claims do not intend to distinguish between components that differ in name but not function. In the following description and in the claims, the terms "include" and "comprise" are used in an open-ended fashion, and thus should be interpreted to mean "include, but not limited to. The description which follows is a preferred embodiment of the invention, but is made for the purpose of illustrating the general principles of the invention and not for the purpose of limiting the scope of the invention. The scope of the present invention is defined by the appended claims.
For the purpose of facilitating understanding of the embodiments of the present invention, the following description will be made by taking specific embodiments as examples with reference to the accompanying drawings, and the drawings are not to be construed as limiting the embodiments of the present invention.
For a better understanding, fig. 1 shows a schematic view of the steps of an inorganic selenium detection method according to an embodiment of the present invention, as shown in fig. 1, the steps of an inorganic selenium detection method include:
in the first step S1, a predetermined amount of a sample to be tested is placed in a stirring vessel 1 containing 100ml of distilled water, stirred for 4 to 7 minutes and then left to stand for 1 to 2 minutes, the liquid in the stirring vessel 1 is filtered through a filtering unit 2 with a pore size of 0.4 to 0.5um to obtain 50ml of a sampling solution,
in a second step S2, 50ml of a reaction solution is added to each of the first reaction vessel 3 and the second reaction vessel 4, wherein the reaction solution includes 0.001mol of potassium persulfate, 0.5mg of methylene blue, 2g of hexamethylenetetramine, 0.05mol of concentrated hydrochloric acid, and 0.3mg of hydroxypropyl β -cyclodextrin, 50ml of a sampling solution is added to the first reaction vessel 3, 50ml of distilled water is added to the second reaction vessel 4, and the first and second reaction vessels 3, 4 are heated at 50 ℃ for 5 to 7 minutes and then cooled to room temperature;
in the third step S3, the second reaction container 4 is inserted into the absorbance detection unit 5 to measure a first absorbance, the first reaction container 3 is inserted into the absorbance detection unit 5 to measure a second absorbance, the second absorbance and the first absorbance are compared to obtain an absorbance difference, the absorbance difference is compared with an inorganic selenium concentration curve based on the absorbance difference to obtain an inorganic selenium concentration of the sample to be tested, wherein the inorganic selenium concentration curve based on the absorbance difference is formed by plotting a plurality of predetermined concentrations of inorganic selenium with respect to the measured absorbance.
In order to better understand the invention, in one embodiment, a small amount of samples to be measured, such as melons, fruits, vegetables or beans, grains and the like, are weighed and placed in a stirring container filled with a certain amount of purified water to be stirred and soaked for about 4min, the samples are taken out, then washing water is precipitated for about 1min, and the same volume of washing liquid and the same volume of purified water are respectively added into two same reaction tubes with covers by using a needle injector and a syringe micro-filtration membrane. The reaction tube with a cover is added with aqueous solution of potassium persulfate, methylene blue, hexamethylenetetramine, concentrated hydrochloric acid and hydroxypropyl beta-cyclodextrin with certain concentration in advance. The reaction tube with the cover is inserted into the plug hole of the temperature-controlled cast aluminum electric heating plate for reaction for a certain time, and then the reaction tube is taken out and cooled to normal temperature, the color of the reaction tube is obviously lightened in the presence of selenium, and the color is not changed greatly in the absence of selenium. The absorbance A0 and A of the two reaction tubes are respectively detected in a photoelectric colorimeter, and the difference between the absorbance A0 and the absorbance A is calculated: and delta A is A0-A, wherein A0 is the absorbance of the reaction tube with the cover added with purified water, A is the absorbance of the reaction tube with the cover added with the sample for washing and dewatering, the concentration curve of inorganic selenium based on the absorbance difference is searched, the concentration of the inorganic selenium in the eluting water is calculated, and the content of the inorganic selenium on the surface of the sample to be measured is calculated.
In one embodiment, 5g of a sample to be measured is accurately weighed by a platform balance and then placed into a 500ml stirring container 1, 200ml of purified water is poured into the stirring container 1, the sample to be measured is placed into the purified water for soaking and cleaning for 5min, the sample to be measured is taken out and deposited for about 1min, a syringe is used for filtering and cleaning water with the aperture of a microfiltration membrane of 0.45um in cooperation with the syringe, 5ml of filtered sampling solution is placed into a first reaction container such as a glass reaction tube with a cover, and the volume of the reaction tube with the cover is 25ml and is provided with scale marks. 5ml of purified water is added to a second reaction vessel such as a capped reaction tube. And (3) putting the two reaction tubes with the covers into the small holes in the temperature control heater simultaneously for reaction, setting the temperature to be 50 ℃ and the time to be 5min, and giving an alarm by the temperature control heater when the reaction is finished. Taking out the two reaction tubes with covers, cooling the reaction tubes in cold water to room temperature, and then dissolving the reaction tubes.
The method comprises the following steps of firstly, zeroing an absorbance detection unit 5 of a photoelectric colorimeter by using a standard cover-placed reaction tube special for zeroing, filling purified water in the special zeroing tube, shaking the two cooled reaction tubes with covers uniformly, sequentially inserting the two cooled reaction tubes with covers into a detection jack of the photoelectric colorimeter to measure the absorbance of the reaction tubes with covers, adding 5ml of purified water to the reaction tubes with covers to obtain A0, and adding 5ml of sample cleaning water to the reaction tubes with covers to obtain A. Then the difference in absorbance between the two is calculated: Δ a ═ a 0-a. And calculating the concentration of the inorganic selenium in the cleaning solution by utilizing the linear relation between the standard curve delta A and the concentration of the inorganic selenium, and further calculating the content of the inorganic selenium on the surface of the sample to be detected.
Determination of inorganic selenium concentration curve based on absorbance difference
Taking a reaction tube with a cover, using distilled water to fix the volume to 25ml, using sodium selenite as a standard substance, respectively adding sodium selenite solution into a series of reaction tubes with the cover, and finally fixing the volume to 25ml, so that the concentrations of the sodium selenite in the reaction tubes with the cover are respectively 0.02, 0.04, 0.06, 0.08, 0.10, 0.12, 0.14, 0.16, 0.18, 0.20, 0.22 and 0.24 mg/L. The working curve obtained according to the operation procedure of the detection method of the present invention is shown in fig. 2, and the correlation coefficient R2 of the working curve is 0.994, which is good in linearity.
The method is proved that the accuracy of the selenium concentration determined by the method completely meets the detection requirement.
Measurement of recovery rate by adding standard
Diluting a certain selenium-containing aqueous solution by 2, 4, 6, 8 and 10 times respectively, simultaneously adopting a national standard method (hydride atomic fluorescence spectrometry GB 5009.93-2010) and the method of the invention to sequentially and respectively measure the selenium concentration in the diluted solution with each dilution time, then respectively adding 0.1mL of 30mg/L sodium selenite standard solution into a reaction tube with a cover, respectively measuring the selenium concentration of each diluted water sample by two methods, paralleling each treatment for three times to obtain an average value, and obtaining the standard recovery rate of the two methods as shown in figure 3. As can be seen from the figure, the adding standard recovery rate of the two methods is within the range of 95% -105%, the adding standard recovery rate of the method is slightly smaller than that of the national standard method, and the adding standard recovery rate of the method completely meets the detection requirement, is convenient and has higher precision.
Analysis of measurement accuracy
Sodium selenite solutions with the concentration of 100 ug/L and 500ug/L are prepared, the sodium selenite solutions with the two concentrations are detected by a national standard method (hydride atomic fluorescence spectrometry GB 5009.93-2010) and the method of the invention respectively, the two solutions with the two concentrations are respectively measured by the two methods for 5 times, and the average concentration, the standard deviation and the relative standard deviation RSD (%) are obtained, and the results are shown in Table 1. As can be seen from Table 1, the parallelism of the detection results of the two methods is better, the detection average value of the method is better than that of the national standard method, and the standard deviation S and the relative standard deviation RSD are slightly smaller than that of the national standard method. When the concentration of the sodium selenite solution is 100 ug/L and 500ug/L respectively, the standard deviation S of the detection result of the method is 1.677 and 9.385 respectively, the relative standard deviation RSD is 1.655 percent and 1.877 percent respectively, and the RSD is less than 2 percent respectively.
TABLE 1 determination of sodium selenite concentration by two methods and error analysis
In a preferred embodiment of the detection method of the present invention, in the first step S1, the predetermined amount of 10g of the sample to be detected is placed in the stirring vessel 1 containing 100ml of distilled water, stirred for 5 minutes, and then left to stand for 1 minute.
In a preferred embodiment of the detection method according to the present invention, the distilled water in the sample solution linearly increases with an increase in the predetermined amount, and the amount of the reaction solution added linearly increases based on the amount of the sample solution added.
In a preferred embodiment of the detection method of the present invention, in the first step S1, the liquid in the stirred vessel 1 is filtered through a 0.45um pore size syringe microfiltration membrane.
A detection device for implementing the detection method comprises,
the stirring container 1 is used for stirring a sample to be measured, the stirring container 1 comprises a feed inlet arranged at the top of the stirring container and a liquid outlet arranged at the lower half part of the side wall of the stirring container, the liquid outlet is provided with a filtering unit 2,
a first reaction vessel 3, which comprises a first reaction vessel body with an upper opening for containing reaction solution and a first cover body capable of sealing the upper opening, wherein the first reaction vessel body comprises a first scale mark arranged on the side wall and a first constant temperature heating module arranged at the bottom, the first constant temperature heating module comprises a first heating element and a constant temperature control unit,
a second reaction vessel 4 including a second reaction vessel body having an upper opening for receiving a reaction solution and a second cover body for sealing the upper opening, the second reaction vessel body including a second graduation mark provided at a sidewall and a second heating member provided at a bottom, the first reaction vessel 3 and the second reaction vessel 4 being arranged in parallel, the thermostatic control unit connecting the first heating member and the second heating member such that the first and second reaction vessels are simultaneously heated to a predetermined temperature for a predetermined time,
an absorbance detection unit 5 inserted into the first and second reaction containers 3, 4, respectively, to measure absorbance, the absorbance detection unit 5 including,
a light source emitting light of a predetermined light intensity,
a light filter for filtering the light,
a photodetector that measures absorbance of the light filtered through the optical filter,
a display unit displaying absorbance data measured by the photodetector,
and the processing unit 6 comprises a storage unit 7 for storing an inorganic selenium concentration curve based on the absorbance difference and a comparison unit 8 for obtaining the inorganic selenium concentration of the sample to be tested based on the absorbance difference.
In a preferred embodiment of the detecting apparatus of the present invention, the stirring container 1 is a magnetic stirrer.
In a preferred embodiment of the detection apparatus of the present invention, the filter unit 2 is a syringe micro-filtration membrane, and the liquid outlet is detachably connected to the syringe through the syringe micro-filtration membrane.
In a preferred embodiment of the detection apparatus of the present invention, the first reaction vessel 3 and/or the second reaction vessel 4 comprises a reaction tube with a cover.
In a preferred embodiment of the detection apparatus of the present invention, the absorbance detection unit 5 is a photoelectric colorimeter.
In a preferred embodiment of the detecting apparatus of the present invention, the light source is a light emitting diode, and the photodetector is a silicon photodiode.
In the preferred embodiment of the detection equipment, the constant temperature control unit comprises a cast aluminum porous heating plate, the temperature can be accurately controlled to be 20-180 ℃, a row of jacks are arranged on the heating plate, the reaction tube with the cover is just inserted into the jack for constant temperature reaction, the temperature control reactor can display the set temperature and the actual temperature, the reaction time can be set, and the alarm prompt can be given when the reaction time is over.
In the preferred embodiment of the detection equipment, the photoelectric colorimeter comprises a light source, an optical filter, a cuvette, a photoelectric detector, an amplifying part, a displaying part and the like, the photoelectric colorimeter can directly read, three effective digits are reserved for absorbance, data storage can be realized, and the data are output through a U disk.
Although the embodiments of the present invention have been described above with reference to the accompanying drawings, the present invention is not limited to the above-described embodiments and application fields, and the above-described embodiments are illustrative, instructive, and not restrictive. Those skilled in the art, having the benefit of this disclosure, may effect numerous modifications thereto without departing from the scope of the invention as defined by the appended claims.
Claims (10)
1. An inorganic selenium detection method, which is characterized by comprising the following steps:
in the first step (S1), a predetermined amount of a sample to be tested is put into a stirring container (1) filled with 100ml of distilled water, stirred for 4-7 minutes and then left for 1-2 minutes, the liquid in the stirring container (1) is filtered by a filtering unit (2) with a pore size of 0.4-0.5um to obtain 50ml of a sampling solution,
in a second step (S2), 50ml of a reaction solution including 0.001mol of potassium persulfate, 0.5mg of methylene blue, 2g of hexamethylenetetramine, 0.05mol of concentrated hydrochloric acid and 0.3mg of hydroxypropyl β -cyclodextrin is added to the first reaction vessel (3) and the second reaction vessel (4), respectively, 50ml of a sampling solution is added to the first reaction vessel (3), 50ml of distilled water is added to the second reaction vessel (4), and the first and second reaction vessels (3, 4) are heated at 50 ℃ for 5 to 7 minutes and then cooled to room temperature;
in the third step (S3), the second reaction container (4) is inserted into the absorbance detection unit (5) to measure a first absorbance, the first reaction container (3) is inserted into the absorbance detection unit (5) to measure a second absorbance, the second absorbance and the first absorbance are compared to obtain an absorbance difference, the absorbance difference is compared with an inorganic selenium concentration curve based on the absorbance difference to obtain an inorganic selenium concentration of the sample to be tested, wherein the inorganic selenium concentration curve based on the absorbance difference is formed by plotting a plurality of predetermined concentrations of inorganic selenium to measure corresponding absorbances.
2. The detection method according to claim 1, characterized in that: in the first step (S1), the predetermined amount of 10g of the sample to be tested is placed in a stirring vessel (1) containing 100ml of distilled water, stirred for 5 minutes and then left to stand for 1 minute.
3. The detection method according to claim 1, characterized in that: the distilled water in the sampling solution linearly increases with an increase of the predetermined amount, and the addition amount of the reaction solution linearly increases based on the addition amount of the sampling solution.
4. The detection method according to claim 1, characterized in that: in the first step (S1), the liquid in the stirred vessel (1) was filtered through a 0.45um pore size syringe microfiltration membrane.
5. A test apparatus for carrying out the test method according to any one of claims 1 to 4, wherein the test apparatus comprises,
the stirring container (1) for stirring the sample to be tested comprises a feed inlet arranged at the top of the stirring container and a liquid outlet arranged at the lower half part of the side wall of the stirring container, the liquid outlet is provided with a filtering unit (2),
a first reaction vessel (3) which comprises a first reaction vessel body with an upper opening and a first cover body capable of sealing the upper opening, wherein the first reaction vessel body is used for containing reaction solution and comprises a first scale mark arranged on the side wall and a first constant-temperature heating module arranged at the bottom, the first constant-temperature heating module comprises a first heating element and a constant-temperature control unit,
a second reaction vessel (4) including a second reaction vessel body having an upper opening for receiving a reaction solution and a second cover body for sealing the upper opening, the second reaction vessel body including a second graduation mark provided at a sidewall and a second heating member provided at a bottom, the first reaction vessel (3) and the second reaction vessel (4) being arranged in parallel, the thermostatic control unit connecting the first heating member and the second heating member so that the first and second reaction vessels are simultaneously heated to a predetermined temperature and maintained for a predetermined time,
an absorbance detection unit (5), the first and second reaction containers (3, 4) being inserted into the absorbance detection unit (5), respectively, to measure absorbance, the absorbance detection unit (5) comprising,
a light source emitting light of a predetermined light intensity,
a light filter for filtering the light,
a photodetector that measures absorbance of the light filtered through the optical filter,
a display unit displaying absorbance data measured by the photodetector,
and the processing unit (6) comprises a storage unit (7) for storing an inorganic selenium concentration curve based on the absorbance difference and a comparison unit (8) for obtaining the inorganic selenium concentration of the sample to be tested based on the absorbance difference.
6. Detection apparatus according to claim 5, characterized in that the stirring vessel (1) is a magnetic stirrer.
7. A detection device according to claim 5, wherein the filter unit (2) is a syringe microfiltration membrane, and the liquid outlet is detachably connected to the syringe via the syringe microfiltration membrane.
8. A test device according to claim 5, characterized in that the first reaction vessel (3) and/or the second reaction vessel (4) comprises a capped reaction tube.
9. The detection apparatus according to claim 5, wherein the absorbance detection unit (5) is a photoelectric colorimeter.
10. The detection apparatus of claim 5, wherein the light source is a light emitting diode and the photodetector is a silicon photodiode.
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