Method for determining copper, chromium and nickel in solid mixture

Abstract

The invention relates to a method for determining copper, chromium and nickel in a solid mixture. The determination method comprises the following steps: wetting a solid mixture, and adding nitric acid, hydrochloric acid, hydrofluoric acid and perchloric acid for digestion reaction to obtain residues; dissolving the residues with a nitric acid solution to obtain a solution to be detected; and measuring the contents of copper, chromium and nickel in the solution to be measured by adopting a graphite furnace atomic absorption spectrophotometric method, namely the contents of copper, chromium and nickel in the solid mixture. The method can accurately measure the contents of copper, chromium and nickel in the solid mixture, and provides reliable data support for environmental monitoring, industrial production and scientific research.

Description

Technical Field

[0001] The invention relates to the technical field of metal element detection, and in particular to a method for determining copper, chromium and nickel in a solid mixture. Background Art

[0002] Heavy metal pollution in soil constitutes one of the major environmental problems worldwide. This pollution can be transmitted through the food chain, thereby posing a threat to human health. The characteristics of soil pollution include concealment, hysteresis, accumulation, heterogeneity and irreversibility. Heavy metals can enter the human body through three main pathways - skin contact, ingestion of contaminated water sources and consumption of contaminated crops - causing a series of health problems. Therefore, accurately analyzing the concentration of pollutants in soil is one of the key measures to ensure soil environmental safety and human health.

[0003] Among them, copper is an essential trace element for human and plant growth. Copper in soil mainly comes from crustal rocks, agricultural activities and industrial activities. The mining of copper-containing mines, the discharge of "three wastes" from smelters, and the use of copper-containing agricultural fertilizers and organic fertilizers can make the copper content in farmland soil reach several times or even dozens of times that of the original soil. Excessive copper can be toxic to plants. When the copper concentration in the soil reaches a certain threshold, the growth and development of plants will be hindered, and even cause death. When the copper content in the soil is too high, it enters the human body through the food chain, causing poisoning phenomena such as nausea, vomiting and upper abdominal pain.

[0004] Chromium is a Group VIB element. Its average content in the earth's crust is only 0.01%, but it is widely distributed. Chromium is one of the trace elements necessary for the normal metabolism of matrix proteins, lipids and carbohydrates, and has the function of regulating sugar and cholesterol metabolism in the human body. The natural source of chromium in the soil is rock weathering, and the anthropogenic source mainly comes from pollution emissions from metallurgy, leather making, electroplating and other industries involving chromium pollution. Chromium pollution may affect the chlorophyll content of plants, affect the absorption of elements such as nitrogen, phosphorus, potassium, and magnesium, and even cause plant death. Excessive intake of chromium can cause damage to the human body, including skin allergies, damage to the digestive system, damage to the respiratory system, damage to the cardiovascular system, damage to the nervous system, etc. Hexavalent chromium is also carcinogenic.

[0005] Nickel is a transition metal in the periodic table. Nickel is a relatively common metal element, and its main raw material source is nickel-rich ores. The anthropogenic source of nickel mainly comes from the discharge of nickel-containing pollutants from industrial processes such as chemical industry, smelting, and electroplating into the environment, causing nickel pollution in the soil; at the same time, in the process of agricultural production, unreasonable sewage irrigation, excessive application of fertilizers and pesticides, and large-scale consumption of plastic greenhouses and mulch, etc., also aggravate the pollution of nickel in the soil. Nickel is a potentially toxic element. Excessive nickel in the soil can hinder the growth and development of crops, and can also cause harm to plants. "Accumulation" and enter animals and humans through the food chain, causing harm to the human body, causing skin damage, digestive system damage, liver and kidney damage, etc. Summary of the invention

[0006] In view of this, the object of the present invention is to provide a method for determining copper, chromium and nickel in a solid mixture, so as to accurately determine the content of copper, chromium and nickel in the solid mixture and provide reliable data support for environmental monitoring, industrial production and scientific research.

[0007] In order to achieve the above object, the technical solution adopted by the present invention is as follows: A method for determining copper, chromium and nickel in a solid mixture comprises the following steps: S1, wetting the solid mixture, adding nitric acid, hydrochloric acid, hydrofluoric acid and perchloric acid to carry out a digestion reaction to obtain a residue; S2, dissolving the residue with nitric acid solution to obtain a solution to be tested; S3. The contents of copper, chromium and nickel in the solution to be tested are determined by graphite furnace atomic absorption spectrophotometry, that is, the contents of copper, chromium and nickel in the solid mixture.

[0008] According to the above-mentioned technical means, by using a mixed acid system of nitric acid, hydrochloric acid, hydrofluoric acid and perchloric acid to carry out digestion reaction, various compounds in the solid mixture can be effectively destroyed, ensuring that metal elements such as copper, chromium and nickel are completely converted into soluble forms, thereby improving the accuracy of the determination. By directly adding acid to digest after wetting the solid mixture, it is simple to operate, easy to grasp, and suitable for routine laboratory analysis. The metal content in the solution to be measured is determined by graphite furnace atomic absorption spectrophotometry, which has extremely high sensitivity and selectivity and can accurately determine trace metal elements. The method can simultaneously determine three metal elements of copper, chromium and nickel, saving time and improving work efficiency. Although strong acids such as hydrofluoric acid and perchloric acid are used, the whole process is carried out under laboratory conditions, and appropriate safety measures can be taken to ensure the safety of the operator. Because the digestion is thorough and the determination method is sensitive, reliable results can be obtained, which is suitable for quantitative analysis of metal elements in solid mixtures.

[0009] Preferably, the step S2 further comprises: adding a matrix modifier to the solution to be tested to eliminate Fe 3+ Mg 2+ , Ca 2+ 、Na + and K + Interference with the determination results of copper, chromium and nickel content.

[0010] Preferably, the matrix modifier is selected from at least one of diammonium hydrogen phosphate, palladium nitrate, lanthanum nitrate, magnesium sulfate and diammonium dihydrogen phosphate.

[0011] By adding matrix modifiers to change the ashing and drying temperature of the matrix, the difference between other elements and the measured elements is enlarged, thereby achieving the purpose of separating the matrix and eliminating interference, effectively eliminating Fe 3+ Mg 2+ , Ca 2+ 、Na + and K + The interference of the content of copper, chromium and nickel was reduced, thereby improving the accuracy of the determination results.

[0012] Among them, after many experiments and tests, it was found that Fe below 50.0 mg / L 3+ Mg 2+ , Ca 2+ 、Na + and K + It has little effect on chromium determination; Fe above 20.0 mg / L 3+ Mg 2+ , Ca 2+ 、Na + and K + Negative interference to copper determination; Fe above 10.0 mg / L 3+ Mg 2+ , Ca 2+ 、Na + and K + Negative interference is produced on the determination of nickel; soil and sediment matrix has negative interference on copper. The Zeeman method, self-absorption method and tritium lamp method are used to subtract the background, and the interference can be eliminated or reduced by adding matrix modifiers.

[0013] The matrix modifier can react with interfering elements to generate compounds with lower ashing temperature, thereby lowering the ashing temperature; it can also react with the element to be measured to increase the ashing temperature, causing the interfering elements to evaporate and be removed first, thereby reducing interference and improving sensitivity.

[0014] The principle of the testing method of the present invention is that after the soil or sediment is digested, it is injected into a graphite furnace atomizer. After drying, ashing and atomization, copper, chromium and nickel compounds form ground state atoms and selectively absorb the characteristic spectral lines emitted by the hollow cathode lamp. The absorption intensity is proportional to the concentration of the element to be tested within a certain range.

[0015] Preferably, the digestion reaction comprises a hot plate digestion method or a microwave digestion method.

[0016] Preferably, in S1, the hot plate digestion method comprises: Moisten the solid mixture with water, add nitric acid and hydrochloric acid, heat on a hot plate for preliminary digestion, evaporate and concentrate, remove and cool, add nitric acid, hydrofluoric acid and perchloric acid, heat and digest in a closed state, open to drive out the acid and remove silicon, cover when heated to emit white smoke, wait for the black organic matter to disappear, open the cover, drive out the white smoke and evaporate to a viscous state, remove and cool to obtain a residue.

[0017] This method is heated by an electric hot plate, which is simple and easy to operate and suitable for the processing of routine laboratory samples. The use of strong acids such as nitric acid, hydrochloric acid, hydrofluoric acid and perchloric acid for digestion can effectively destroy the organic and inorganic components in the sample and accelerate the digestion process. Preliminary digestion and acid removal in a closed system reduce the emission of harmful gases and reduce the risks during the experiment. Through evaporation concentration and open acid removal steps, most of the substances in the sample are completely digested, which improves the accuracy of the analysis results. It is suitable for the digestion of a variety of solid mixture samples, including soil, sediment, rock, etc., and has good versatility. Compared with other digestion methods, the electric hot plate digestion method requires simple equipment and has low operating costs, which is suitable for large-scale sample processing.

[0018] Preferably, the steps of measuring by hot plate digestion method include: Accurately weigh 0.1g~0.5g (accurate to 0.2mg) of solid mixture sample into a crucible, moisten it with a small amount of water, add 9.0 ml nitric acid and 3.0 ml hydrochloric acid respectively, and heat on a hot plate in a fume hood at 120℃ to preliminarily digest the sample. When it evaporates to 2 ml~3 ml, take it off and cool it slightly, add 5.0 ml nitric acid, 2.0 ml hydrofluoric acid and 2.0 ml perchloric acid, cover it and digest it at 160℃ for 1 hour, then open the cover to drive out the acid and continue heating to remove silicon. When it is heated to emit thick white perchloric acid smoke, cover it. After the black organic matter on the crucible disappears, open the cover, drive out the white smoke and evaporate it until it is almost dry (or in the form of liquid beads in a non-flowing state). If there is a lot of black matter, add 2.0 ml nitric acid, 1.0 ml hydrofluoric acid and 1.0 ml perchloric acid, and repeat the above digestion process until it is completely digested. When the white smoke is basically gone again and the contents are in a non-flowing viscous state, remove the crucible and cool it slightly. Rinse the inner wall of the crucible with nitric acid solution II, dissolve the residue with warm water, and transfer it to a 50 ml polyethylene volumetric flask after cooling. Use nitric acid solution II (nitric acid and experimental water are mixed in a volume ratio of 1:99) to make up to the mark, shake well, and store in a polyethylene bottle. Use graphite furnace atomic absorption spectrophotometry within 28 days to determine the content of copper, chromium and nickel in the solution to be tested, that is, analyze the content of copper, chromium and nickel in the solid mixture.

[0019] Preferably, the heating temperature of the preliminary digestion is 120°C.

[0020] Preferably, the temperature of the closed heating digestion is 160°C.

[0021] Preferably, in S1, the microwave digestion method comprises: The solid mixture is moistened with water, nitric acid, hydrochloric acid and hydrofluoric acid are added, the temperature is raised to a first temperature for microwave digestion for a first time, the temperature is raised to a second temperature for microwave digestion for a second time, the temperature is raised to a third temperature for microwave digestion for a third time, and the mixture is cooled to room temperature to obtain a digestion product; the digestion product is heated to evaporate and concentrate, removed and cooled, perchloric acid is added, and when heated to emit white smoke, a cover is added, and black organic matter disappears, and the cover is opened to drive off the white smoke and evaporate to a viscous state, removed and cooled to obtain a residue.

[0022] Microwave heating can significantly shorten the sample digestion time, usually several times faster than traditional heating methods. Microwave digestion can achieve complete digestion at a lower temperature and reduce the residual insoluble substances in the sample. Due to the high efficiency of microwave digestion, the amount of digestion reagents such as nitric acid, hydrochloric acid and hydrofluoric acid can be reduced. Microwave digestion is carried out in a closed container, which reduces the emission of harmful gases and the volatilization of samples, and improves the safety of the experiment. Microwave digestion is simple to operate, easy to automate, and reduces human operation errors. Due to the controllability of the digestion process, a more uniform and consistent digestion product can be obtained, thereby improving the accuracy of subsequent analysis. Microwave digestion reduces the use of reagents and the generation of waste, and has a relatively small impact on the environment.

[0023] Preferably, the step of determining by microwave digestion method comprises: Accurately weigh 0.1g~0.5g (accurate to 0.1mg) of solid mixture sample and place it in a digestion tank. After moistening with a small amount of water, add 9.0ml nitric acid, 3.0ml hydrochloric acid and 2.0ml hydrofluoric acid in turn and mix thoroughly. After the reaction is stable, cover and tighten. Perform microwave digestion after program heating, and cool to room temperature after digestion. Take out the digestion tank from the microwave digestion instrument, slowly release the pressure and vent in the fume hood, open the digestion tank, transfer all the contents of the digestion tank to the crucible, wash the digestion tank and lid with a little experimental water, and transfer them to the crucible together. Place the crucible on an electric hot plate, heat at 160℃~180℃, evaporate to 2ml~3ml, remove and cool slightly, add 1.0ml perchloric acid, and cover when heated to thick white perchloric acid smoke. After the black organic matter on the crucible disappears, open the lid, drive away the white smoke and evaporate until it is almost dry (or in the form of liquid beads in a non-flowing state). If there is more black matter, add 2.0 ml nitric acid, 1.0 ml hydrofluoric acid and 1.0 ml perchloric acid, and repeat the above digestion process until all the black matter is digested. When the white smoke is basically gone again and the contents are viscous and do not flow, remove the crucible and cool it slightly. Rinse the inner wall of the crucible with nitric acid solution II (nitric acid and experimental water are mixed in a volume ratio of 1:99), dissolve the residue with warm water, and transfer it to a 50 ml polyethylene volumetric flask after cooling. Use nitric acid solution II (nitric acid and experimental water are mixed in a volume ratio of 1:99) to make up to the mark, shake well, and store in a polyethylene bottle. Use graphite furnace atomic absorption spectrophotometry within 28 days to determine the content of copper, chromium and nickel in the test solution, that is, the content of copper, chromium and nickel in the solid mixture for analysis.

[0024] Preferably, the first temperature is 120°C; the first time is 3 minutes; the second temperature is 160°C; the second time is 3 minutes; the third temperature is 180°C; and the third time is 25 minutes.

[0025] Preferably, the heating method is programmed heating, the time for heating to the first temperature is 7 minutes, the time for heating from the first temperature to the second temperature is 5 minutes, and the time for heating from the second temperature to the third temperature is 5 minutes.

[0026] Preferably, the temperature for heating the digestion product for evaporation and concentration is 160°C to 180°C.

[0027] Preferably, when the hot plate digestion method is used to digest the solid mixture, the detection limit of copper in the solid mixture is 0.3 mg / kg, the lower limit of copper determination is 1.2 mg / kg, the detection limit of chromium is 0.5 mg / kg, the lower limit of chromium determination is 2.0 mg / kg, the detection limit of nickel is 0.2 mg / kg, and the lower limit of nickel determination is 0.8 mg / kg.

[0028] Preferably, when the microwave digestion method is used to digest the solid mixture, in the solid mixture, the detection limit of copper is 0.4 mg / kg, the lower limit of copper is 1.6 mg / kg, the detection limit of chromium is 0.4 mg / kg, the lower limit of chromium is 1.6 mg / kg, the detection limit of nickel is 0.3 mg / kg, and the lower limit of nickel is 1.2 mg / kg.

[0029] Preferably, in S3, the conditions for determining the copper content in the solution to be tested by graphite furnace atomic absorption spectrophotometry are as follows: the measuring wavelength is 324.7 nm, the lamp current is 4.0 mA, the passband width is 0.7 nm, the drying method is drying at 110° C. for 30 s, drying at 130° C. for 30 s, the ashing temperature and time are 1100° C. and 20 s, the atomization temperature and time are 2000° C. and 5 s, the residue removal temperature and time are 2450° C. and 3 s, the gas is stopped during the atomization stage, the argon gas flow rate is 250 ml / min, the injection volume is 20 μl, a matrix modifier needs to be added, and the amount of matrix modifier added is 5 μl.

[0030] Preferably, in S3, the conditions for determining the chromium content in the solution to be tested by graphite furnace atomic absorption spectrophotometry are as follows: the measuring wavelength is 357.9 nm, the lamp current is 5.0 mA, the passband width is 0.7 nm, the drying method is drying at 110°C for 30 s, drying at 130°C for 30 s, the ashing temperature and time are 1500°C and 25 s, the atomization temperature and time are 2300°C and 5 s, the residue removal temperature and time are 2450°C and 3 s, the gas is stopped during the atomization stage, the argon gas flow rate is 250 ml / min, the injection volume is 20 μl, and no matrix modifier is added.

[0031] Preferably, in S3, the conditions for determining the nickel content in the test solution by graphite furnace atomic absorption spectrophotometry are as follows: the measuring wavelength is 232.0 nm, the lamp current is 4.0 mA, the passband width is 0.2 nm, the drying method is drying at 110° C. for 30 s, drying at 130° C. for 30 s, the ashing temperature and time are 1200° C. and 20 s, the atomization temperature and time are 2400° C. and 5 s, the residue removal temperature and time are 2450° C. and 3 s, the gas is stopped during the atomization stage, the argon gas flow rate is 250 ml / min, the injection volume is 20 μl, and no matrix modifier is added.

[0032] The purpose of drying is to remove moisture and acid from the solution. If the drying temperature is too low or the holding time is not enough, the moisture and acid that penetrate into the graphite tube will damage the structure of the graphite tube during the high-temperature ashing and atomization stage; if the temperature is too high or the temperature rises too quickly, the solution will boil violently, and double absorption peaks may appear during atomization. Therefore, low-temperature and long-term drying is more effective.

[0033] The purpose of ashing is to remove low-boiling point compounds before atomization, reduce matrix interference, and reduce background absorption. Under the premise of ensuring that the elements to be measured are not volatilized and lost, the ashing temperature should be increased as much as possible. If the matrix is ​​complex and the background absorption is high, the ashing time should be appropriately extended.

[0034] The purpose of atomization is to maximize the atomization degree of the element to be measured. The selection of time and temperature depends on the nature of the element to be measured: chromium and nickel are high-temperature elements, and the atomization temperature is about 2400 ℃. Too low temperature and insufficient atomization time will result in incomplete atomization, which will reduce the signal, broaden the peak shape, and produce a memory effect; too high temperature will result in too fast atomization, the detection system response cannot keep up with the atomization signal, the reproducibility and sensitivity will decrease, and the life of the graphite tube will be shortened.

[0035] The purpose of the residue removal stage is to remove the matrix and the unatomicated elements to be measured, and to remove the memory effect. The atomization temperature of chromium and nickel is high. Under the premise of the instrument allowing and ensuring the life of the graphite tube, the residue removal temperature should be increased as much as possible to ensure that all the residual substances are volatilized.

[0036] Single element hollow cathode lamps reduce spectral interference problems.

[0037] Preferably, the solid mixture is soil and / or aquatic sediment.

[0038] Among them, water system sediments include marine sediments, and marine sediments include marine fishery waters, marine nature reserves, rare and endangered species nature reserves, marine aquaculture areas, bathing beaches, marine sports or entertainment areas where the human body comes into direct contact with sediments, industrial water use areas directly related to human use, general industrial water use areas, coastal scenic tourist areas, marine port waters, and sediments generated in marine development operation areas for special purposes.

[0039] Beneficial effects of the present invention: The method for determining copper, chromium and nickel in a solid mixture of the present invention can effectively destroy various compounds in the solid mixture by using a mixed acid system of nitric acid, hydrochloric acid, hydrofluoric acid and perchloric acid to perform a digestion reaction, ensuring that copper, chromium and nickel metal elements are completely converted into soluble forms, thereby improving the accuracy of the determination. The solid mixture is directly digested by adding acid after wetting, which is simple to operate, easy to master and suitable for routine laboratory analysis. The metal content in the solution to be measured is determined by graphite furnace atomic absorption spectrophotometry, which has extremely high sensitivity and selectivity and can accurately determine trace metal elements. The method can simultaneously determine three metal elements of copper, chromium and nickel, saves time and improves work efficiency. Since the digestion is thorough and the determination method is sensitive, reliable results can be obtained, which is suitable for quantitative analysis of metal elements in solid mixtures, and has great promotion and application value in the field of metal element detection technology. DETAILED DESCRIPTION

[0040] The following will describe the embodiments of the present invention with reference to the preferred embodiments, and those skilled in the art can easily understand other advantages and effects of the present invention from the contents disclosed in this specification. The present invention can also be implemented or applied through other different specific embodiments, and the details in this specification can also be modified or changed in various ways based on different viewpoints and applications without departing from the spirit of the present invention. It should be understood that the preferred embodiments are only for illustrating the present invention, not for limiting the scope of protection of the present invention.

[0041] The present invention intends to disclose a method for determining copper, chromium and nickel in a solid mixture, so as to accurately determine the contents of copper, chromium and nickel in the solid mixture, thereby providing reliable data support for environmental monitoring, industrial production and scientific research.

[0042] Among them, a method for determining copper, chromium and nickel in a solid mixture comprises the following steps: S1, wetting the solid mixture, adding nitric acid, hydrochloric acid, hydrofluoric acid and perchloric acid to carry out a digestion reaction to obtain a residue; S2, dissolving the residue with nitric acid solution to obtain a solution to be tested; S3. The contents of copper, chromium and nickel in the solution to be tested are determined by graphite furnace atomic absorption spectrophotometry, that is, the contents of copper, chromium and nickel in the solid mixture.

[0043] In some embodiments, S2 further includes: adding a matrix modifier to the solution to be tested to eliminate Fe 3+ Mg 2+ , Ca 2+ 、Na + and K +Interference with the determination results of copper, chromium and nickel; The matrix modifier can be any one of diammonium hydrogen phosphate, palladium nitrate, lanthanum nitrate, magnesium sulfate and diammonium dihydrogen phosphate. Other matrix modifiers that can remove interference can also be used.

[0044] In some embodiments, the digestion reaction comprises hot plate digestion or microwave digestion.

[0045] In some embodiments, in S1, the hot plate digestion method comprises: Moisten the solid mixture with water, add nitric acid and hydrochloric acid, heat on a hot plate for preliminary digestion, evaporate and concentrate, remove and cool, add nitric acid, hydrofluoric acid and perchloric acid, heat and digest in a closed state, open to drive out the acid and remove silicon, cover when heated to emit white smoke, wait for the black organic matter to disappear, open the cover, drive out the white smoke and evaporate to a viscous state, remove and cool to obtain a residue.

[0046] Exemplarily, the heating temperature for the initial digestion is 120°C; Exemplarily, the temperature of the closed heating digestion is 160°C.

[0047] Exemplary, the steps of the hot plate digestion method include: Accurately weigh 0.1g~0.5g (accurate to 0.2mg) of solid mixture into a crucible, moisten it with a small amount of water, add 9.0 ml nitric acid and 3.0 ml hydrochloric acid respectively, and heat on a hot plate in a fume hood at 120℃ to preliminarily digest the sample. When it evaporates to 2 ml~3 ml, take it off and cool it slightly, add 5.0 ml nitric acid, 2.0 ml hydrofluoric acid and 2.0 ml perchloric acid, cover it and digest it at 160℃ for 1 hour, then open the cover to drive out the acid and continue heating to remove silicon. When it is heated until thick white perchloric acid smoke emerges, cover it. After the black organic matter on the crucible disappears, open the cover, drive out the white smoke and evaporate it until it is almost dry (or in the form of liquid beads in a non-flowing state). If there is a lot of black matter, add 2.0 ml nitric acid, 1.0 ml hydrofluoric acid and 1.0 ml perchloric acid, and repeat the above digestion process until it is completely digested. When the white smoke is basically gone again and the contents are in a non-flowing viscous state, remove the crucible and cool it slightly. Rinse the inner wall of the crucible with nitric acid solution II, dissolve the residue with warm water, and transfer it to a 50 ml polyethylene volumetric flask after cooling. Use nitric acid solution II (nitric acid and experimental water are mixed in a volume ratio of 1:99) to make up to the mark, shake well, and store in a polyethylene bottle. Use graphite furnace atomic absorption spectrophotometry within 28 days to determine the content of copper, chromium and nickel in the solution to be tested, that is, analyze the content of copper, chromium and nickel in the solid mixture.

[0048] In some embodiments, in S1, the microwave digestion method comprises: The solid mixture is moistened with water, nitric acid, hydrochloric acid and hydrofluoric acid are added, the temperature is raised to a first temperature for microwave digestion for a first time, the temperature is raised to a second temperature for microwave digestion for a second time, the temperature is raised to a third temperature for microwave digestion for a third time, and the mixture is cooled to room temperature to obtain a digestion product; the digestion product is heated to evaporate and concentrate, removed and cooled, perchloric acid is added, and when heated to emit white smoke, a cover is added, and black organic matter disappears, and the cover is opened to drive off the white smoke and evaporate to a viscous state, removed and cooled to obtain a residue.

[0049] Exemplarily, the first temperature is 120° C.; the first time is 3 min; the second temperature is 160° C.; the second time is 3 min; the third temperature is 180° C.; and the third time is 25 min.

[0050] Exemplarily, the heating method is programmed heating, the time for heating to the first temperature is 7 minutes, the time for heating from the first temperature to the second temperature is 5 minutes, and the time for heating from the second temperature to the third temperature is 5 minutes.

[0051] Exemplary, the steps of microwave digestion determination include: Accurately weigh 0.1g~0.5g (accurate to 0.2mg) of solid mixture sample and place it in a digestion tank. After moistening with a small amount of water, add 9.0ml nitric acid, 3.0ml hydrochloric acid and 2.0ml hydrofluoric acid in turn and mix thoroughly. After the reaction is stable, cover and tighten. Refer to the heating program in Table 1 for program heating and then perform microwave digestion. After digestion, cool to room temperature. Take out the digestion tank from the microwave digestion instrument, slowly release the pressure and vent in the fume hood, open the digestion tank, transfer all the contents of the digestion tank to the crucible, wash the digestion tank and the lid with a little experimental water, and transfer them to the crucible together. Place the crucible on a hot plate and heat at 160℃~180℃. When it evaporates to 2ml~3ml, take it off and cool it slightly. Add 1.0ml perchloric acid. When it is heated to emit thick white perchloric acid smoke, cover it. After the black organic matter on the crucible disappears, open the lid, drive off the white smoke and steam until it is nearly dry (or in the form of liquid beads that do not flow). If there is a lot of black matter, add 2.0 ml nitric acid, 1.0 ml hydrofluoric acid and 1.0 ml perchloric acid, and repeat the above digestion process until it is completely digested. When the white smoke is basically gone again and the contents are viscous and do not flow, remove the crucible and cool it slightly. Rinse the inner wall of the crucible with nitric acid solution II (nitric acid and experimental water are mixed in a volume ratio of 1:99), warm and dissolve the residue, and transfer it to a 50 ml polyethylene volumetric flask after cooling. Use nitric acid solution II (nitric acid and experimental water are mixed in a volume ratio of 1:99) to make up to the mark, shake well, store in a polyethylene bottle, and complete the analysis within 28 days.

[0052] Table 1 Heating methods for microwave digestion In some embodiments, when the solid mixture is digested by a hot plate digestion method or a microwave digestion method, the detection limit and the lower limit of determination of each element in the solid mixture are shown in Table 2.

[0053] Table 2 Detection limit and determination limit In some embodiments, in S3, the conditions for determining the contents of copper, chromium and nickel in the solution to be tested by graphite furnace atomic absorption spectrophotometry are shown in Table 3.

[0054] Table 3 Determination conditions of element content by graphite furnace atomic absorption spectrophotometry The matrix modifier in Table 3 is the added amount of palladium nitrate or diammonium hydrogen phosphate.

[0055] In some embodiments, in S3, the solid mixture is soil and / or stream sediment.

[0056] In order to make the technical problems, technical solutions and beneficial effects solved by the present application clearer, the determination method of copper, chromium and nickel in the solid mixture of the present invention will be further described in detail below in conjunction with specific embodiments. Obviously, the specific embodiments described are only a part of the embodiments in the present application, rather than all the embodiments. The following description of at least one exemplary embodiment is actually only illustrative and is by no means intended to limit the present application and its application. Based on the specific embodiments in the present application, all other embodiments obtained by ordinary technicians in the art without paying creative work belong to the scope of protection of the present application.

[0057] If no specific techniques or conditions are specified in the specific embodiments, the techniques or conditions described in the literature in the field or the product instructions are used. If no manufacturer is specified for the reagents or instruments used, they are all conventional products that can be purchased commercially.

[0058] Nitric acid, hydrochloric acid, hydrofluoric acid, perchloric acid and sulfuric acid used in the experiment are all high-grade pure reagents. The experimental water is freshly prepared deionized water or water of equal purity. Hydrochloric acid: ρ(HCl)=1.19 g / ml; Nitric acid: ρ(HNO3)=1.42 g / ml; Hydrofluoric acid: ρ(HF)=1.49 g / ml; Perchloric acid: ρ(HClO4)=1.68 g / ml; Sulfuric acid: ρ(H2SO4)=1.84 g / ml; Metallic copper: spectrally pure; Potassium dichromate (K2Cr2O7): spectrally pure; Metallic nickel: spectrally pure; Palladium nitrate (Pd(NO3)2): high-grade pure; Diammonium hydrogen phosphate ((NH4)2HPO4): high-grade pure; Nitric acid solution I: Nitric acid and experimental water are mixed in a volume ratio of 1:3; Nitric acid solution II: Nitric acid and experimental water are mixed in a volume ratio of 1:99.

[0059] Copper standard stock solution: ρ(Cu)=1000 mg / L. Accurately weigh 1.0000 g (accurate to 0.2 mg) of metallic copper, dissolve it in 40 ml of nitric acid solution I, then add 100 ml of water, heat until the nitrogen oxides are completely discharged, cool, and dilute to 1 L with water. Commercially available certified standard solutions can also be used.

[0060] Chromium standard stock solution: ρ(Cr) = 1000 mg / L. Accurately weigh 2.8290 g (accurate to 0.2 mg) potassium dichromate (dried at 130 °C for 24 h) and dissolve it in 40 ml of experimental water. Add 5 ml of sulfuric acid, cool, and dilute to 1 L with water. Commercially available certified standard solutions can also be used.

[0061] Nickel standard stock solution: ρ(nickel) = 1000 mg / L. Accurately weigh 1.0000 g (accurate to 0.2 mg) of metallic nickel, dissolve it in 10 ml of hydrochloric acid and 10 ml of nitric acid solution I, then add 100 ml of water and heat until the nitrogen oxides are completely discharged. After cooling, dilute to 1 L with water. Commercially available certified standard solutions can also be used.

[0062] Copper, chromium and nickel standard working solutions, copper 100 μg / L, chromium 100 μg / L and nickel 100 μg / L: Before use, the copper, chromium and nickel standard stock solutions were prepared by stepwise dilution with nitric acid solution II.

[0063] 0.1% palladium nitrate solution. Weigh 0.1 g palladium nitrate and dilute to volume with 100 ml water. You can also use a commercially available certified standard solution to dilute to the corresponding concentration.

[0064] 5% diammonium hydrogen phosphate solution. Weigh 5 g diammonium hydrogen phosphate and dilute to volume with 100 ml water. You can also use a commercially available certified standard solution to dilute to the corresponding concentration.

[0065] Argon: purity ≥99.99%.

[0066] Instruments and equipment Graphite furnace atomic absorption spectrophotometer, with background correction function or continuous light source; hollow cathode lamp or continuous light source for five elements of copper, chromium and nickel; graphite tube: pyrolytic coated graphite tube; electric hot plate or graphite digester: with temperature control function, the highest temperature is not less than 200 ℃, and the temperature control accuracy is better than ±5 ℃; microwave digestion device: composed of microwave digester, microwave digestion container and rotating disk; microwave digester: with temperature control and program heating function; microwave digestion container: polytetrafluoroethylene or equivalent material; crucible: polytetrafluoroethylene material, 50 ml, with cover; nylon sieve: 0.15 mm (100 mesh); analytical balance: the graduation value is 0.1mg. Commonly used instruments and equipment in general laboratories.

[0067] Establishment of standard curve 0.00 ml, 2.50 ml, 5.00 ml, 7.50 ml, 10.00 ml, 15.00 ml, and 20.0 ml of 100 μg / L copper standard solution were respectively taken into 50 ml volumetric flasks, and the volume was fixed with 1% nitric acid solution and shaken well to obtain a copper standard series with concentrations of 0 μg / L, 5.0 μg / L, 10.0 μg / L, 15.0 μg / L, 20.0 μg / L, 25.0 μg / L, 30.0 μg / L, and 40.0 μg / L. The absorbance of the standard solution series was measured from low to high according to the instrument reference measurement conditions. The results are shown in Table 4.

[0068] Table 4 Cu calibration curve test data 0.00 ml, 1.00 ml, 3.00 ml, 6.00 ml, 10.0 ml, 12.5 ml, and 20.0 ml of 100 μg / L chromium standard solution were respectively taken into 50 ml volumetric flasks, and the volume was fixed with 1% nitric acid solution and then shaken to obtain a series of chromium standard concentrations of 0 μg / L, 2.0 μg / L, 6.0 μg / L, 12.0 μg / L, 16.0 μg / L, 20.0 μg / L, and 25.0 μg / L. The absorbance of the standard solution series was measured from low to high according to the instrument reference measurement conditions. The results are shown in Table 6.

[0069] Table 6 Cr calibration curve test data 0 ml, 2.50 ml, 5.00 ml, 7.50 ml, 10.00 ml, 15.00 ml, and 20.00 ml of 100 μg / L nickel working solution were respectively taken into 50 ml volumetric flasks, fixed to volume with 1% nitric acid solution, and shaken well to obtain a nickel standard series with concentrations of 0 μg / L, 5.0 μg / L, 10.0 μg / L, 15.0 μg / L, 20.0 μg / L, 30.0 μg / L, and 40.0 μg / L. The absorbance of the standard solution series was measured from low to high according to the instrument reference measurement conditions. The results are shown in Table 7.

[0070] Table 7 is the Ni calibration curve test data Sample measurement Measure the sample under the same instrument measurement conditions as those used to establish the standard curve. If the concentration of the element to be measured in the sample exceeds the range of the standard curve, dilute it appropriately with nitric acid solution II and re-measure.

[0071] Calculation of results for soil samples The mass fractions of copper, chromium and nickel in soil were calculated according to formula (1): (1) In formula (1): It represents the mass fraction of copper, chromium and nickel in soil, mg / kg; It indicates the mass concentration of copper, chromium and nickel in the test solution obtained from the standard curve, µg / L; Indicates the dilution multiple of the sample; It represents the mass concentration of copper, chromium and nickel in the laboratory blank sample, µg / L; It represents the fixed volume of soil sample after digestion, ml; dm represents the dry matter content of soil samples, %; Indicates the mass of the soil sample weighed, g.

[0072] Calculation of results for sediment samples The mass fractions of copper, chromium and nickel in the sediment were calculated according to formula (2): (2) In formula (2): It represents the mass fraction of copper, chromium and nickel in sediment, mg / kg; It indicates the mass concentration of copper, chromium and nickel in the test solution obtained from the standard curve, µg / L; It represents the mass concentration of copper, chromium and nickel in the laboratory blank sample, µg / L; It represents the fixed volume of sediment sample after digestion, ml; Indicates the dilution multiple of the sample; Indicates the moisture content of sediment samples, %; Indicates the mass of the sediment sample weighed, g.

[0073] A method for determining copper, chromium and nickel in a solid mixture comprises the following steps: S1. Put 0.25 g of solid mixture sample in a crucible, moisten it with a small amount of water, add 9.0 ml nitric acid and 3.0 ml hydrochloric acid respectively, and heat it on a hot plate in a fume hood at 120°C to preliminarily digest the solid mixture sample. When it evaporates to 2 ml to 3 ml, remove it and cool it slightly, add 5.0 ml nitric acid, 2.0 ml hydrofluoric acid and 2.0 ml perchloric acid, cover it and digest it at 160°C for 1 hour, then open the lid to drive out the acid and continue heating to remove silicon. When it is heated until thick white perchloric acid smoke emerges, cover it. After the black organic matter on the crucible disappears, open the lid, drive out the white smoke and evaporate it until it is almost dry (or in the form of liquid beads in a non-flowing state). If there is a lot of black matter, add 2.0 ml nitric acid, 1.0 ml hydrofluoric acid and 1.0 ml perchloric acid, and repeat the above digestion process until it is completely digested. When the white smoke is basically gone again and the contents are in a non-flowing viscous state, remove the crucible and cool it slightly to obtain a residue; S2. Rinse the inner wall of the crucible with nitric acid solution II, dissolve the residue with warm water, transfer to a 50 ml polyethylene volumetric flask after cooling, add 0.013 g diammonium hydrogen phosphate and mix evenly. Use nitric acid solution II to make up to the mark, shake well, obtain the solution to be tested, store in a polyethylene bottle, and complete the analysis within 28 days; S3, using graphite furnace atomic absorption spectrophotometry to measure the contents of copper, chromium and nickel in the solution to be tested, i.e. the contents of copper, chromium and nickel in the solid mixture; The solid mixture samples in this Example 1 include 4 certified soil standard samples (GSS-5 (red-yellow soil), GSS-7 (brick red soil), GSS-18 (saline-alkali soil), GSS-25 (loess)), 4 certified sediment standard samples (GSD-7a, GSD-15, GSD-18, GSD-19) and 5 actual soil samples (taken from Hunan, Guangdong, Guizhou, Ningxia and Jiangsu respectively, soil types include paddy soil, red soil, yellow soil, gray-calcium soil and brown soil, land use types include cultivated land and unused land) and were measured repeatedly for 6 times.

[0074] When using the hot plate digestion method, the relative standard deviation within the laboratory is 0.050%~16%, the relative standard deviation between laboratories is 1.8%~20%, the repeatability limit is 0.55 mg / kg~24 mg / kg, and the reproducibility limit is 0.84 mg / kg~57 mg / kg.

[0075] The precision data are shown in Table 9.

[0076] Table 9 Summary of precision data for soil and sediment methods (hot plate digestion method) When the hot plate digestion method was used, the relative error ranged from -23% to 13%, and the final relative error ranged from -24% to 17%.

[0077] The accuracy data is shown in Table 10.

[0078] Table 10 Summary of method accuracy data for soil and sediment (hot plate digestion method) A method for determining copper, chromium and nickel in a solid mixture comprises the following steps: S1. Place 0.25 g of solid mixture sample in a crucible, add 9.0 ml nitric acid, 3.0 ml hydrochloric acid and 2.0 ml hydrofluoric acid in sequence, and mix thoroughly. After the reaction is stable, cover and tighten. Refer to the program heating method in Table 1 for heating and microwave digestion, and cool to room temperature after digestion. Take out the digestion tank from the microwave digestion instrument, slowly release the pressure and vent in the fume hood, open the digestion tank, transfer all the contents of the digestion tank to the crucible, wash the digestion tank and lid with a little experimental water, and transfer them to the crucible together. Place the crucible on the hot plate, heat at 160℃~180℃, evaporate to 2 ml~3 ml, remove and cool slightly, add 1.0 ml perchloric acid, and cover when heated to thick perchloric acid white smoke. After the black organic matter on the crucible disappears, open the lid, drive away the white smoke and evaporate until it is almost dry (or in the form of liquid beads in a non-flowing state). If there is a lot of black matter, add 2.0 ml nitric acid, 1.0 ml hydrofluoric acid and 1.0 ml perchloric acid, and repeat the above digestion process until all the black matter is digested. When the white smoke is basically gone again and the contents are viscous and do not flow, remove the crucible and cool it slightly to obtain the residue; S2. Rinse the inner wall of the crucible with nitric acid solution II, dissolve the residue with warm water, transfer to a 50 ml polyethylene volumetric flask after cooling, add 0.013 g diammonium hydrogen phosphate and mix evenly. Use nitric acid solution II to make up to the mark, shake well, obtain the solution to be tested, store in a polyethylene bottle, and complete the analysis within 28 days; S3, using graphite furnace atomic absorption spectrophotometry to measure the contents of copper, chromium and nickel in the solution to be tested, i.e. the contents of copper, chromium and nickel in the solid mixture; The solid mixture samples in this Example 2 include 4 certified soil standard samples (GSS-5, GSS-7, GSS-18, GSS-25), 4 certified sediment standard samples (GSD-7a, GSD-15, GSD-18, GSD-19) and 5 actual soil samples (taken from Hunan, Guangdong, Guizhou, Ningxia and Jiangsu, respectively, the soil types include paddy soil, red soil, yellow soil, gray-calcium soil and brown soil, and the land use types include cultivated land and unused land) and the measurements were repeated 6 times.

[0079] When using the microwave digestion method, the relative standard deviation within the laboratory was 0.42%~15%, the relative standard deviation between laboratories was 1.1%~20%, the repeatability limit was 0.072 mg / kg~32 mg / kg, and the reproducibility limit was 0.097 mg / kg~51 mg / kg.

[0080] See Table 11 for precision data.

[0081] Table 11 Summary of soil and sediment measurement precision (microwave digestion method) When microwave digestion method was used, the relative error ranged from -19% to 16%, and the final relative error ranged from -19% to 25%.

[0082] See Table 12 for accuracy data.

[0083] Table 12 Summary of method accuracy data for soil and sediment (microwave digestion method) Comparative Example 1 S1. Put 0.25 g of solid mixture sample in a crucible, moisten it with a small amount of water, add 9.0 ml nitric acid and 3.0 ml hydrochloric acid respectively, and heat it on a hot plate in a fume hood at 120°C to preliminarily digest the solid mixture sample. When it evaporates to 2 ml to 3 ml, remove it and cool it slightly, add 5.0 ml nitric acid, 2.0 ml hydrofluoric acid and 2.0 ml perchloric acid, cover it and digest it at 160°C for 1 hour, then open the lid to drive out the acid and continue heating to remove silicon. When it is heated until thick white perchloric acid smoke emerges, cover it. After the black organic matter on the crucible disappears, open the lid, drive out the white smoke and evaporate it until it is almost dry (or in the form of liquid beads in a non-flowing state). If there is a lot of black matter, add 2.0 ml nitric acid, 1.0 ml hydrofluoric acid and 1.0 ml perchloric acid, and repeat the above digestion process until it is completely digested. When the white smoke is basically gone again and the contents are in a non-flowing viscous state, remove the crucible and cool it slightly to obtain a residue; S2. Rinse the inner wall of the crucible with nitric acid solution II, dissolve the residue with warm water, and transfer to a 50 ml polyethylene volumetric flask after cooling. Make up to the mark with nitric acid solution II, shake well, and obtain the solution to be tested. Store it in a polyethylene bottle and complete the analysis within 28 days. S3, using graphite furnace atomic absorption spectrophotometry to measure the contents of copper, chromium and nickel in the solution to be tested, i.e. the contents of copper, chromium and nickel in the solid mixture; The solid mixture samples in this comparative example 1 include 2 certified soil standard samples (GSS-18, GSS-25) and 2 certified sediment standard samples (GSD-18, GSD-19), and the measurement was repeated 6 times.

[0084] The measurement results are shown in Table 13.

[0085] Table 13 Results of standard samples without matrix modifier From the analysis of Table 13, it can be seen that some test results of copper did not exceed the allowable error range of the standard sample. This proves that without adding matrix modifier, the matrix has some interference in the determination of copper, but no obvious interference in the determination of chromium and nickel.

[0086] The above embodiments are only preferred embodiments for fully illustrating the present invention, and the protection scope of the present invention is not limited thereto. Any equivalent substitution or change made by a person skilled in the art based on the present invention is within the protection scope of the present invention.

Claims

1. A method for determining copper, chromium and nickel in a solid mixture, characterized in that: The following steps are involved: S1, wetting the solid mixture, adding nitric acid, hydrochloric acid, hydrofluoric acid and perchloric acid to carry out a digestion reaction to obtain a residue; S2, dissolving the residue with nitric acid solution to obtain a solution to be tested; S3. The contents of copper, chromium and nickel in the solution to be tested are determined by graphite furnace atomic absorption spectrophotometry, that is, the contents of copper, chromium and nickel in the solid mixture.

2. The measuring method according to claim 1, characterized in that The step S2 also includes: adding a matrix modifier to the solution to be tested to eliminate Fe 3+ Mg 2+ , Ca 2+ 、Na + and K + Interference with the determination results of copper, chromium and nickel; The matrix improver is selected from at least one of diammonium hydrogen phosphate, palladium nitrate, lanthanum nitrate, magnesium sulfate and diammonium dihydrogen phosphate.

3. The measuring method according to claim 1, characterized in that The digestion reaction includes a hot plate digestion method or a microwave digestion method.

4. The measuring method according to claim 3, characterized in that In S1, the hot plate digestion method comprises: Moisten the solid mixture with water, add nitric acid and hydrochloric acid, heat on a hot plate for preliminary digestion, evaporate and concentrate, remove and cool, add nitric acid, hydrofluoric acid and perchloric acid, heat and digest in a closed state, open to drive out the acid and remove silicon, cover when heated to emit white smoke, wait for the black organic matter to disappear, open the cover, drive out the white smoke and evaporate to a viscous state, remove and cool to obtain a residue.

5. The measuring method according to claim 4, characterized in that The heating temperature of the preliminary digestion is 120°C; And / or, the temperature of the closed heating digestion is 160°C.

6. The measuring method according to claim 3, characterized in that In S1, the microwave digestion method comprises: The solid mixture is moistened with water, nitric acid, hydrochloric acid and hydrofluoric acid are added, the temperature is raised to a first temperature for microwave digestion for a first time, the temperature is raised to a second temperature for microwave digestion for a second time, the temperature is raised to a third temperature for microwave digestion for a third time, and the mixture is cooled to room temperature to obtain a digestion product; the digestion product is heated to evaporate and concentrate, removed and cooled, perchloric acid is added, and when heated to emit white smoke, a cover is added, and black organic matter disappears, and the cover is opened to drive off the white smoke and evaporate to a viscous state, removed and cooled to obtain a residue.

7. The measuring method according to claim 6, characterized in that The first temperature is 120°C; And / or, the first time is 3 minutes; and / or, the second temperature is 160° C.; And / or, the second time is 3 minutes; And / or, the third temperature is 180°C; And / or, the third time is 25 minutes; And / or, the heating method is programmed heating, the time for heating to the first temperature is 7 minutes, the time for heating from the first temperature to the second temperature is 5 minutes, and the time for heating from the second temperature to the third temperature is 5 minutes; And / or, the temperature for heating the digestion product for evaporation and concentration is 160° C. to 180° C.

8. The measuring method according to claim 3, characterized in that When the hot plate digestion method is used to digest the solid mixture, the detection limit of copper in the solid mixture is 0.3 mg / kg, the lower limit of copper determination is 1.2 mg / kg, the detection limit of chromium is 0.5 mg / kg, the lower limit of chromium determination is 2.0 mg / kg, the detection limit of nickel is 0.2 mg / kg, and the lower limit of nickel determination is 0.8 mg / kg; Alternatively, when the microwave digestion method is used to digest the solid mixture, in the solid mixture, the detection limit of copper is 0.4 mg / kg, the lower limit of copper determination is 1.6 mg / kg, the detection limit of chromium is 0.4 mg / kg, the lower limit of chromium determination is 1.6 mg / kg, the detection limit of nickel is 0.3 mg / kg, and the lower limit of nickel determination is 1.2 mg / kg.

9. The measuring method according to claim 1, characterized in that In the S3, the conditions for determining the copper content in the solution to be tested by graphite furnace atomic absorption spectrophotometry are as follows: the measuring wavelength is 324.7 nm, the lamp current is 4.0 mA, the passband width is 0.7 nm, the drying method is drying at 110° C. for 30 s, drying at 130° C. for 30 s, the ashing temperature and time are 1100° C. and 20 s, the atomization temperature and time are 2000° C. and 5 s, the residue removal temperature and time are 2450° C. and 3 s, the gas is stopped during the atomization stage, the argon gas flow rate is 250 ml / min, the injection volume is 20 μl, and a matrix modifier needs to be added, and the amount of the matrix modifier added is 5 μl; And / or, in S3, the conditions for determining the chromium content in the solution to be tested by graphite furnace atomic absorption spectrophotometry are: the measuring wavelength is 357.9 nm, the lamp current is 5.0 mA, the passband width is 0.7 nm, the drying method is drying at 110° C. for 30 s, drying at 130° C. for 30 s, the ashing temperature and time are 1500° C. and 25 s, the atomization temperature and time are 2300° C. and 5 s, the residue removal temperature and time are 2450° C. and 3 s, the gas is stopped during the atomization stage, the argon gas flow rate is 250 ml / min, the injection volume is 20 μl, and no matrix modifier is added; And / or, in S3, the determination conditions of the nickel content in the test solution by graphite furnace atomic absorption spectrophotometry are: the measurement wavelength is 232.0nm, the lamp current is 4.0mA, the passband width is 0.2nm, the drying method is drying at 110°C for 30s, drying at 130°C for 30s, the ashing temperature and time are 1200°C and 20s, the atomization temperature and time are 2400°C and 5s, the residue removal temperature and time are 2450°C and 3s, the gas is stopped during the atomization stage, the argon gas flow rate is 250ml / min, the injection volume is 20μl, and no matrix modifier is added.

10. The measuring method according to claim 1, characterized in that The solid mixture is soil and / or water sediment.

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