CN116793971A - Method for measuring aluminum content by atomic absorption spectrometry of graphite furnace - Google Patents
Method for measuring aluminum content by atomic absorption spectrometry of graphite furnace Download PDFInfo
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- XAGFODPZIPBFFR-UHFFFAOYSA-N aluminium Chemical compound [Al] XAGFODPZIPBFFR-UHFFFAOYSA-N 0.000 title claims abstract description 123
- 229910052782 aluminium Inorganic materials 0.000 title claims abstract description 114
- 238000000034 method Methods 0.000 title claims abstract description 71
- OKTJSMMVPCPJKN-UHFFFAOYSA-N Carbon Chemical compound [C] OKTJSMMVPCPJKN-UHFFFAOYSA-N 0.000 title claims abstract description 38
- 229910002804 graphite Inorganic materials 0.000 title claims abstract description 38
- 239000010439 graphite Substances 0.000 title claims abstract description 38
- 238000001479 atomic absorption spectroscopy Methods 0.000 title claims abstract description 12
- 239000012482 calibration solution Substances 0.000 claims abstract description 50
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Substances O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 claims abstract description 49
- 238000002835 absorbance Methods 0.000 claims abstract description 45
- 229910001963 alkali metal nitrate Inorganic materials 0.000 claims abstract description 41
- AZDRQVAHHNSJOQ-UHFFFAOYSA-N alumane Chemical class [AlH3] AZDRQVAHHNSJOQ-UHFFFAOYSA-N 0.000 claims abstract description 36
- 238000000889 atomisation Methods 0.000 claims abstract description 35
- 238000005259 measurement Methods 0.000 claims abstract description 26
- 238000010521 absorption reaction Methods 0.000 claims abstract description 18
- VWDWKYIASSYTQR-UHFFFAOYSA-N sodium nitrate Chemical compound [Na+].[O-][N+]([O-])=O VWDWKYIASSYTQR-UHFFFAOYSA-N 0.000 claims description 66
- 235000010344 sodium nitrate Nutrition 0.000 claims description 33
- 239000004317 sodium nitrate Substances 0.000 claims description 33
- GRYLNZFGIOXLOG-UHFFFAOYSA-N Nitric acid Chemical compound O[N+]([O-])=O GRYLNZFGIOXLOG-UHFFFAOYSA-N 0.000 claims description 29
- 229910017604 nitric acid Inorganic materials 0.000 claims description 29
- YIXJRHPUWRPCBB-UHFFFAOYSA-N magnesium nitrate Chemical compound [Mg+2].[O-][N+]([O-])=O.[O-][N+]([O-])=O YIXJRHPUWRPCBB-UHFFFAOYSA-N 0.000 claims description 24
- 239000012086 standard solution Substances 0.000 claims description 16
- 239000011159 matrix material Substances 0.000 claims description 14
- FGIUAXJPYTZDNR-UHFFFAOYSA-N potassium nitrate Chemical compound [K+].[O-][N+]([O-])=O FGIUAXJPYTZDNR-UHFFFAOYSA-N 0.000 claims description 14
- 238000004380 ashing Methods 0.000 claims description 8
- 235000010333 potassium nitrate Nutrition 0.000 claims description 7
- 239000004323 potassium nitrate Substances 0.000 claims description 7
- 238000001514 detection method Methods 0.000 claims description 6
- 229910052783 alkali metal Inorganic materials 0.000 claims description 4
- 150000001340 alkali metals Chemical class 0.000 claims description 4
- 230000029087 digestion Effects 0.000 claims description 3
- 239000003607 modifier Substances 0.000 claims description 3
- 229910044991 metal oxide Inorganic materials 0.000 abstract description 6
- 150000004706 metal oxides Chemical class 0.000 abstract description 6
- 239000000243 solution Substances 0.000 description 52
- 230000000052 comparative effect Effects 0.000 description 22
- 238000012360 testing method Methods 0.000 description 21
- 239000012490 blank solution Substances 0.000 description 15
- 238000011084 recovery Methods 0.000 description 15
- 239000011550 stock solution Substances 0.000 description 14
- VEXZGXHMUGYJMC-UHFFFAOYSA-N Hydrochloric acid Chemical compound Cl VEXZGXHMUGYJMC-UHFFFAOYSA-N 0.000 description 12
- 238000007865 diluting Methods 0.000 description 11
- RYGMFSIKBFXOCR-UHFFFAOYSA-N Copper Chemical compound [Cu] RYGMFSIKBFXOCR-UHFFFAOYSA-N 0.000 description 10
- 239000010949 copper Substances 0.000 description 10
- 238000009835 boiling Methods 0.000 description 8
- 239000000126 substance Substances 0.000 description 8
- ZCCIPPOKBCJFDN-UHFFFAOYSA-N calcium nitrate Chemical compound [Ca+2].[O-][N+]([O-])=O.[O-][N+]([O-])=O ZCCIPPOKBCJFDN-UHFFFAOYSA-N 0.000 description 7
- 229910018072 Al 2 O 3 Inorganic materials 0.000 description 6
- BHPQYMZQTOCNFJ-UHFFFAOYSA-N Calcium cation Chemical compound [Ca+2] BHPQYMZQTOCNFJ-UHFFFAOYSA-N 0.000 description 6
- 229910001424 calcium ion Inorganic materials 0.000 description 6
- 229910001431 copper ion Inorganic materials 0.000 description 6
- 230000005284 excitation Effects 0.000 description 6
- 229910000272 alkali metal oxide Inorganic materials 0.000 description 5
- XTVVROIMIGLXTD-UHFFFAOYSA-N copper(II) nitrate Chemical compound [Cu+2].[O-][N+]([O-])=O.[O-][N+]([O-])=O XTVVROIMIGLXTD-UHFFFAOYSA-N 0.000 description 5
- 230000000694 effects Effects 0.000 description 5
- 239000000203 mixture Substances 0.000 description 5
- XKRFYHLGVUSROY-UHFFFAOYSA-N Argon Chemical compound [Ar] XKRFYHLGVUSROY-UHFFFAOYSA-N 0.000 description 4
- OYPRJOBELJOOCE-UHFFFAOYSA-N Calcium Chemical compound [Ca] OYPRJOBELJOOCE-UHFFFAOYSA-N 0.000 description 4
- 239000011575 calcium Substances 0.000 description 4
- 229910052791 calcium Inorganic materials 0.000 description 4
- 239000003153 chemical reaction reagent Substances 0.000 description 4
- 229910052802 copper Inorganic materials 0.000 description 4
- 239000000395 magnesium oxide Substances 0.000 description 4
- CPLXHLVBOLITMK-UHFFFAOYSA-N magnesium oxide Inorganic materials [Mg]=O CPLXHLVBOLITMK-UHFFFAOYSA-N 0.000 description 4
- AXZKOIWUVFPNLO-UHFFFAOYSA-N magnesium;oxygen(2-) Chemical compound [O-2].[Mg+2] AXZKOIWUVFPNLO-UHFFFAOYSA-N 0.000 description 4
- 238000002844 melting Methods 0.000 description 4
- 230000008018 melting Effects 0.000 description 4
- 229910021645 metal ion Inorganic materials 0.000 description 4
- 238000000862 absorption spectrum Methods 0.000 description 3
- 239000012530 fluid Substances 0.000 description 3
- 238000000673 graphite furnace atomic absorption spectrometry Methods 0.000 description 3
- 239000011734 sodium Substances 0.000 description 3
- 238000005303 weighing Methods 0.000 description 3
- DGAQECJNVWCQMB-PUAWFVPOSA-M Ilexoside XXIX Chemical compound C[C@@H]1CC[C@@]2(CC[C@@]3(C(=CC[C@H]4[C@]3(CC[C@@H]5[C@@]4(CC[C@@H](C5(C)C)OS(=O)(=O)[O-])C)C)[C@@H]2[C@]1(C)O)C)C(=O)O[C@H]6[C@@H]([C@H]([C@@H]([C@H](O6)CO)O)O)O.[Na+] DGAQECJNVWCQMB-PUAWFVPOSA-M 0.000 description 2
- 229910052786 argon Inorganic materials 0.000 description 2
- 239000012159 carrier gas Substances 0.000 description 2
- 150000001875 compounds Chemical class 0.000 description 2
- 238000001035 drying Methods 0.000 description 2
- 238000002474 experimental method Methods 0.000 description 2
- 238000001914 filtration Methods 0.000 description 2
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- 238000002347 injection Methods 0.000 description 2
- 239000007924 injection Substances 0.000 description 2
- 230000002452 interceptive effect Effects 0.000 description 2
- 238000002372 labelling Methods 0.000 description 2
- 229910052751 metal Inorganic materials 0.000 description 2
- 239000002184 metal Substances 0.000 description 2
- 239000011259 mixed solution Substances 0.000 description 2
- 238000000746 purification Methods 0.000 description 2
- 229910052708 sodium Inorganic materials 0.000 description 2
- KKCBUQHMOMHUOY-UHFFFAOYSA-N sodium oxide Chemical compound [O-2].[Na+].[Na+] KKCBUQHMOMHUOY-UHFFFAOYSA-N 0.000 description 2
- 229910001948 sodium oxide Inorganic materials 0.000 description 2
- 239000008247 solid mixture Substances 0.000 description 2
- ZLMJMSJWJFRBEC-UHFFFAOYSA-N Potassium Chemical compound [K] ZLMJMSJWJFRBEC-UHFFFAOYSA-N 0.000 description 1
- WNROFYMDJYEPJX-UHFFFAOYSA-K aluminium hydroxide Chemical compound [OH-].[OH-].[OH-].[Al+3] WNROFYMDJYEPJX-UHFFFAOYSA-K 0.000 description 1
- -1 aluminum ion Chemical class 0.000 description 1
- 238000003556 assay Methods 0.000 description 1
- 230000009286 beneficial effect Effects 0.000 description 1
- 239000003795 chemical substances by application Substances 0.000 description 1
- 238000011161 development Methods 0.000 description 1
- 239000003085 diluting agent Substances 0.000 description 1
- 238000005516 engineering process Methods 0.000 description 1
- 239000012467 final product Substances 0.000 description 1
- 239000007770 graphite material Substances 0.000 description 1
- 238000011835 investigation Methods 0.000 description 1
- 150000002500 ions Chemical class 0.000 description 1
- 239000007788 liquid Substances 0.000 description 1
- 239000000463 material Substances 0.000 description 1
- 150000002739 metals Chemical class 0.000 description 1
- 229910052700 potassium Inorganic materials 0.000 description 1
- 239000011591 potassium Substances 0.000 description 1
- 239000000047 product Substances 0.000 description 1
- 239000007787 solid Substances 0.000 description 1
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- Investigating Or Analysing Materials By Optical Means (AREA)
Abstract
The invention provides a method for measuring aluminum content by atomic absorption spectrometry of a graphite furnace. The method comprises the following steps: preparing an aluminum series calibration solution added with alkali metal nitrate, measuring absorbance by using a graphite furnace atomic absorption spectrometer, and drawing a standard curve by taking the measured absorbance as an ordinate and taking the aluminum content in the aluminum series calibration solution added with the alkali metal nitrate as an abscissa; adding alkali metal nitrate into a sample to be measured, measuring the absorbance by using a graphite furnace atomic absorption spectrometer, and then calculating according to a standard curve to obtain the aluminum content in the sample to be measured. The method can fully atomize the aluminum element, improves the measurement accuracy, solves the problem of different atomization rates of sample water and calibration solution, and masks the interference of other metal oxides.
Description
Technical Field
The invention relates to a method for measuring aluminum content by atomic absorption spectrometry of a graphite furnace, and belongs to the technical field of metal content detection.
Background
The method for measuring aluminum by using high-temperature graphite furnace to electrically heat and atomize the sample is widely applied to the technology of water quality assay and supervision. In the prior art, a method for measuring the aluminum content by using a graphite furnace atomic absorption spectrometry is to use an atomizer in the shape of a tube, a cup and the like made of a graphite material, heat a sample to 2500 ℃ by using current, measure absorbance at a wavelength of 309.3nm and calculate the aluminum content. However, when an amphoteric substance such as aluminum is measured, a problem of unstable results occurs, and the lower the aluminum content in the sample, the more remarkable the problem of instability.
The method for measuring aluminum by using the high-temperature graphite furnace to electrically and thermally atomize the sample comprises the steps of treating the calibration solution and treating the sample water. In general, the calibration fluid treatment process includes: dissolving pure aluminum in hydrochloric acid, and then diluting to a certain volume; the diluent is taken and added with nitric acid for digestion treatment to form a calibration solution, and a matrix improver (generally magnesium nitrate) is added, and then a standard curve is drawn. The final product formed after the calibration fluid and matrix modifier are fully ashed is Al 2 O 3 And magnesium oxide in Al 2 O 3 And the magnesium oxide mixture is in a final state for atomic excitation. The sample water was digested after filtration and during the test, a solid mixture was formed after ashing. Because the sample water contains even a small amount of other metal ions, other metal oxides in the mixture are relatively high in the solids formed by ashing. At this time, the final state of aluminum atom excitation is Al 2 O 3 The mixture or other aluminum mixture.
Mixtures containing other metal oxide impurities have lower melting points than pure Al according to the solid mixture melting point principle 2 O 3 And the melting point may vary greatly depending on the type of impurities. Al (Al) 2 O 3 The pure product had a melting point of 2050℃and a boiling point of 2980 ℃. The existing graphite furnace atomic absorption method needs to consider the temperature resistance and stability of a graphite tube, and an excessive test temperature is not suitable to be adopted, and the test temperature of aluminum element is generally 2500 ℃. The boiling point of magnesium oxide is 3600 ℃ and the magnesium oxide is used for Al 2 O 3 The boiling point reduction can play a small role. The higher the atomization rate of the substance, the closer the measured value of the graphite furnace atomic absorption method is to the true value, and the reaching of the boiling point of the substance is the maximum excitation factor of atomization. In the prior art, on one hand, the boiling point requirement of aluminum can not be met when the calibration solution is tested, the atomization rate is very low, the slope of a formed standard curve is very low, and under the condition of the same aluminum ion concentration, the absorbance of the standard curve and the absorbance of a sample have larger deviation, so that larger measurement error is caused. On the other hand, the atomization rate of the sample to be detected is uncertain due to the presence of interference of other ions. Therefore, the current method for measuring the aluminum content by using the atomic absorption spectrum of the graphite furnace has at least two problems: firstly, the maximum atomization rate of aluminum cannot be excited; and secondly, different atomization rates appear in the calibration solution and the detection sample. These two factors are the main causes of inaccurate measurement of aluminum in the industry.
Therefore, the development of a novel method for measuring the aluminum content by atomic absorption spectrometry of a graphite furnace becomes one of the problems to be solved urgently in the field.
Disclosure of Invention
In order to solve the technical problems, the invention aims to provide a method for measuring the aluminum content by atomic absorption spectrometry of a graphite furnace. The method can fully atomize the aluminum element, improve the measurement accuracy, solve the problem of different atomization rates of sample water and calibration solution, and mask the interference of other metal oxides.
In order to achieve the above object, the present invention provides a method for measuring aluminum content by atomic absorption spectrometry of a graphite furnace, comprising the steps of:
(1) Preparing an aluminum series calibration solution added with alkali metal nitrate, measuring the absorbance of the aluminum series calibration solution added with the alkali metal nitrate by utilizing a graphite furnace atomic absorption spectrometer, and drawing a standard curve by taking the absorbance obtained by measurement as an ordinate and the aluminum content in the aluminum series calibration solution added with the alkali metal nitrate as an abscissa;
(2) Adding alkali metal nitrate into the sample to be measured, measuring the absorbance by using a graphite furnace atomic absorption spectrometer, and then calculating according to the standard curve obtained in the step (1) to obtain the aluminum content in the sample to be measured.
In the above method, preferably, the aluminum series calibration solution to which the alkali metal nitrate is added is prepared by: respectively transferring different amounts of aluminum standard solutions, adding a proper amount of nitric acid and alkali metal nitrate, and respectively using water to fix the volume to prepare an aluminum series calibration solution with the aluminum content of 1-100 mug/L and the alkali metal nitrate. More preferably, the aluminum content in the aluminum series calibration solution added with alkali metal nitrate is 10 μg/L to 60 μg/L. It will be appreciated by those skilled in the art that the aluminum content of the alkali metal nitrate added aluminum series calibration solution is at appropriate concentration intervals. Specifically, the aluminum content in the prepared aluminum series calibration solution added with the alkali metal nitrate may be 10 μg/L, 20 μg/L, 30 μg/L, 40 μg/L, 60 μg/L, respectively.
In the above method, preferably, the alkali metal nitrate includes sodium nitrate and/or potassium nitrate, and the like.
In the method, alkali metal nitrate, in particular sodium nitrate and/or potassium nitrate, is added into a calibration solution and a sample to be measured, alkali metal oxide is formed after ashing in the process of detecting by a graphite furnace atomic absorption spectrometry, and a meta-aluminate is formed by a compound of the alkali metal oxide and aluminum at a high temperature, and is used as a final state for atomic excitation. Taking sodium nitrate as an example, sodium oxide is formed during the ashing period of sodium nitrate according to the specific embodiment of the invention, and the chemical equation is as follows: 4NaNO 3 ＝2Na 2 O+2N 2 +5O 2 Sodium oxide and amphoteric substance aluminum hydroxide react to generate sodium metaaluminate, and the chemical equation is as follows: na (Na) 2 O+2Al(OH) 3 ＝2NaAlO 2 +3H 2 O, in the final state NaAlO 2 Atomic excitation is performed. And the boiling point of meta-aluminate formed by sodium and potassium is about 2300 ℃. Therefore, the method can obviously reduce the measurement temperature of the graphite furnace, fully atomize aluminum element at 2350 ℃, excite the maximum atomization rate of aluminum, fully overlap the slope of a standard curve and a sample, improve the measurement accuracy, and obtain the standard curve with a better linear relation compared with the prior art; in addition, the method solves the problem that the sample water and the calibration solution have different atomization rates, and masks the interference of other metal oxides.
In the above method, the alkali metal nitrate is preferably added in an amount of 0.005 to 0.03mmol/L, more preferably 0.02mmol/L, based on the volume of the alkali metal nitrate-added aluminum series calibration solution. Specifically, the alkali metal nitrate may be added in the form of a solution, for example, a sodium nitrate solution, a potassium nitrate solution or a mixed solution of sodium nitrate and potassium nitrate at a concentration of 0.5 to 3mmoL/L (preferably 2 mmoL/L).
In some embodiments of the present invention, the amount of nitric acid added to the aluminum standard solution may be routinely adjusted by those skilled in the art.
In some embodiments of the invention, preferably, the concentration of aluminum in the aluminum standard solution is 1000 μg/L. Specifically, the aluminum standard solution can be prepared by the following steps: 1.000g of aluminum is dissolved in a proper amount of hydrochloric acid, and then water is used for fixing the volume to 1000mL, so as to obtain an aluminum standard stock solution I; transferring 10mL of the aluminum standard stock solution I, adding a proper amount of nitric acid, and fixing the volume to 100mL by using water to obtain an aluminum standard stock solution II; and transferring 10mL of the aluminum standard stock solution II, adding a proper amount of nitric acid, and fixing the volume to 1000mL by using water to obtain the aluminum standard solution. Wherein the hydrochloric acid employed may be a 1.16g/mL hydrochloric acid solution, and 1.000g of aluminum may be dissolved in 15mL of the hydrochloric acid solution. The nitric acid used may be 1.40g/mL nitric acid solution, and the amount of nitric acid solution added in both steps may be 1mL.
In some embodiments of the invention, preferably, the alkali metal nitrate added aluminum series calibration solution is formulated by: respectively transferring 1mL, 2mL, 3mL, 4mL and 6mL of the aluminum standard solution, adding a proper amount of nitric acid and alkali metal nitrate, and respectively using water to fix the volume to 100mL to prepare an aluminum series calibration solution with the aluminum content of 10 mug/L, 20 mug/L, 30 mug/L, 40 mug/L and 60 mug/L and added with the alkali metal nitrate; wherein the alkali metal nitrate is added in an amount of 0.005 to 0.03mmol/L, more preferably 0.02mmol/L, based on the volume of the alkali metal nitrate-added aluminum series calibration solution. Wherein, the nitric acid used may be 1.40g/mL nitric acid solution, and the addition amount of the nitric acid solution may be 1mL. The alkali metal nitrate to be used may be a sodium nitrate solution, a potassium nitrate solution or a mixed solution of sodium nitrate and potassium nitrate at a concentration of 0.5 to 3mmoL/L (preferably 2 mmoL/L), and the amount thereof added is 1mL.
In some embodiments of the present invention, the standard aluminum stock solution I, the standard aluminum stock solution II, and the standard aluminum solution may be prepared in advance for use, but the calibration aluminum series solution added with the alkali metal nitrate needs to be prepared on-the-fly.
In the above method, preferably, the sample to be measured comprises a water sample. More preferably, the sample to be assayed is a filtered water sample.
In the above method, the alkali metal nitrate is preferably added in an amount of 0.005 to 0.03mmol/L, more preferably 0.02mmol/L, based on the volume of the sample to be measured.
In the above method, preferably, step (2) further includes: adding nitric acid into the sample to be measured for digestion. Preferably, the content of nitric acid added in the sample to be determined is 0.15-0.2mol/L.
In the above method, preferably, the alkali metal nitrate-added aluminum series calibration solution and the sample to be measured are each further added with a matrix improver. More preferably, the matrix modifier comprises magnesium nitrate. It is further preferred that the matrix improving agent is added in an amount of 300 to 700. Mu.g/L, particularly preferably 500. Mu.g/L, based on the volume of the alkali metal nitrate added aluminum series calibration solution and the volume of the sample to be measured, respectively.
In the above method, preferably, the working conditions for measuring absorbance by using a graphite furnace atomic absorption spectrometer include: the detection wavelength is 309.3nm, the ashing temperature is 700-800 ℃ (more preferably 700 ℃), the time is 20-30s (more preferably 20 s), the atomization temperature is 2300-2400 ℃ (more preferably 2350 ℃) and the time is 4-5s (more preferably 5 s). In some embodiments of the invention, the operating conditions further comprise: the sample injection volume is 10-20 mu L, the carrier gas is argon, the flow is 200mL/min, the drying start and end temperatures are 80-140 ℃, the time is 40s, the purification temperature is 2600 ℃, and the time is 4s.
According to a specific embodiment of the present invention, preferably, the above method further comprises the steps of: zeroing by adopting a blank solution and measuring absorbance to deduct the blank; or zeroing by adopting zeroing solution, and then measuring absorbance by adopting blank solution to deduct blank. The zeroing can be performed by using a blank solution or a zeroing solution. If the aluminum content in the blank solution is low enough to be negligible, the blank solution can be used for zeroing, and if not, the zeroing solution is used for zeroing first. For the measurement of the absorbance of the aluminum series calibration solution added with the alkali metal nitrate and the measurement of the absorbance of the sample to be measured added with the alkali metal nitrate, zeroing is needed, and the blank is needed to be subtracted during calculation. Specifically, the blank solution comprises 14g/L nitric acid solution. More specifically, the blank solution may be formulated by the steps of: 1mL of 1.40g/mL nitric acid solution was removed and the volume was fixed with water to 100mL to give the blank solution. The zeroing solution is water.
The invention provides a method for measuring aluminum content by utilizing atomic absorption spectrometry of a graphite furnace compounded by alkali metal oxides. The technical scheme of the invention has at least the following beneficial effects:
in the method, alkali metal nitrate is added into a calibration solution and a sample to be measured, alkali metal oxide is formed after ashing in the process of detecting by a graphite furnace atomic absorption spectrometry, and a meta-aluminate is formed by a compound of the alkali metal oxide and aluminum at a high temperature, and is used as a final state for atomic excitation. The method can obviously reduce the measurement temperature of the graphite furnace, fully atomize aluminum element at 2350 ℃, excite the maximum atomization rate of aluminum, fully overlap the slope of a standard curve and a sample, improve the measurement accuracy, and obtain the standard curve with a better linear relation compared with the prior art; in addition, the method solves the problem that the sample water and the calibration solution have different atomization rates, and masks the interference of other metal oxides; meanwhile, the method has better standard adding recovery rate, and the recovery rate can reach 97.85% -101.55%. In conclusion, the method of the invention generates the same atomization environment and increases the atomization rate when the calibration solution and the sample are subjected to the aluminum element test, improves the accuracy of measuring the aluminum content by the atomic absorption spectrum of the graphite furnace, and has the advantages of scientific and reasonable method, high labeling recovery rate, simple and convenient operation and wide application prospect.
Drawings
FIG. 1 is a standard curve obtained in example 1 and comparative example 1.
FIG. 2 is a graph showing the absorbance of the standard sample in example 1 as a function of the atomization temperature.
FIG. 3 is a graph showing the absorbance of the standard sample in comparative example 1 as a function of the atomization temperature.
FIG. 4 is a graph showing the effect of copper and calcium ions on the results of aluminum content measurement without adding sodium nitrate.
FIG. 5 is a graph showing the effect of copper and calcium ions on the results of aluminum content measurement when sodium nitrate was added.
Detailed Description
The technical solution of the present invention will be described in detail below for a clearer understanding of technical features, objects and advantageous effects of the present invention, but should not be construed as limiting the scope of the present invention.
Example 1
The embodiment provides a method for measuring aluminum content by atomic absorption spectrometry of a graphite furnace, which comprises the following steps:
(1) Preparing aluminum series calibration solution added with sodium nitrate
Weighing 1.000g of aluminum, dissolving in 15mL of 1.16g/mL hydrochloric acid solution, transferring all the solution into a 1000mL volumetric flask, diluting with water, and fixing the volume to a scale to obtain an aluminum standard stock solution I, wherein the concentration of aluminum in the aluminum standard stock solution I is 1000mg/L;
transferring 10mL of aluminum standard stock solution I to a 100mL volumetric flask, adding 1mL of 1.40g/mL nitric acid solution, diluting with water, and fixing the volume to a scale to obtain aluminum standard stock solution II, wherein the concentration of aluminum in the aluminum standard stock solution II is 100mg/L;
transferring 10mL of aluminum standard stock solution II to a 1000mL volumetric flask, adding 1mL of 1.40g/mL nitric acid solution, diluting with water, and fixing the volume to a scale to obtain an aluminum standard solution, wherein the concentration of aluminum in the aluminum standard solution is 1000 mug/L;
respectively transferring 1mL, 2mL, 3mL, 4mL and 6mL of aluminum standard solution into 100mL volumetric flasks, adding 1mL of 1.40g/mL nitric acid solution, 10 mu L of magnesium nitrate solution with the concentration of 5mg/mL serving as a matrix improver, 1mL of sodium nitrate solution with the concentration of 2mmoL/L into each volumetric flask, diluting with water, fixing the volume to a scale, and shaking uniformly to prepare an aluminum series calibration solution with the aluminum content of 10 mu g/L, 20 mu g/L, 30 mu g/L, 40 mu g/L and 60 mu g/L and added with sodium nitrate; wherein, the magnesium nitrate solution with the concentration of 5mg/mL is prepared by the following steps: weighing 500mg anhydrous magnesium nitrate, dissolving with a proper amount of water, transferring all the materials into a 100mL volumetric flask, diluting with water, and fixing the volume to a scale;
the aluminum standard stock solution I, the aluminum standard stock solution II and the aluminum standard solution can be prepared in advance for standby, but the aluminum series calibration solution added with sodium nitrate needs to be prepared on the spot;
(2) Measuring the absorbance of the aluminum series calibration solution added with sodium nitrate by using a graphite furnace atomic absorption spectrometer, and drawing a standard curve by taking the measured absorbance as an ordinate and the aluminum content in the aluminum series calibration solution added with sodium nitrate as an abscissa;
(3) Filtering a water sample to be measured, taking a proper amount of the filtered water sample, adding a proper amount of 1.40g/mL nitric acid solution, a proper amount of magnesium nitrate solution with a concentration of 5mg/mL as a matrix improver, and a proper amount of sodium nitrate solution with a concentration of 2mmoL/L, and shaking uniformly to obtain a sample to be subjected to atomic absorption spectrometry of a graphite furnace; wherein the content of the added nitric acid in the filtered water sample is 0.15-0.2mol/L, and the added amount of magnesium nitrate is 500 mug/L and the added amount of sodium nitrate is 0.02mmol/L based on the volume of the filtered water sample;
(4) And (3) measuring the absorbance of the sample obtained in the step (3) by using a graphite furnace atomic absorption spectrometer, and then calculating according to the standard curve obtained in the step (2) to obtain the aluminum content in the water sample to be measured.
In a specific embodiment of the invention, the reagents used should be analytically pure reagents and water meeting the requirements for secondary water in GB/T6682. The amount of aluminum in the water and reagents used should be negligible compared to the lowest measured concentration (i.e., lower measured limit) of the method of the present invention.
The method of the present embodiment further comprises the steps of: zeroing by adopting a blank solution and measuring absorbance to deduct the blank; or zeroing by adopting zeroing solution, and then measuring absorbance by adopting blank solution to deduct blank. The zeroing can be performed by using a blank solution or a zeroing solution. If the aluminum content in the blank solution is low enough to be negligible, the blank solution can be used for zeroing, and if not, the zeroing solution is used for zeroing first. For the measurement of absorbance of the aluminum series calibration solution added with sodium nitrate and the measurement of absorbance of the sample in this example, zeroing was required, and the blank was required to be subtracted for calculation. Specifically, the blank solution was formulated by: 1mL of 1.40g/mL nitric acid solution is transferred to a 100mL volumetric flask, diluted with water and fixed to a scale to obtain a blank solution. The zeroing solution is water.
In this example, the working conditions for measuring absorbance using a graphite furnace atomic absorption spectrometer included: the aluminum hollow cathode lamp is adopted, the detection wavelength is 309.3nm, the sample injection volume is 20 mu L, the carrier gas is argon, the flow is 200mL/min, the drying start and end temperatures are 80-140 ℃, the time is 40s, the ashing temperature is 700 ℃, the time is 20s, the atomization temperature is 2350 ℃, the time is 5s, the purification temperature is 2600 ℃, and the time is 4s.
The method of the embodiment has the measurement result of 19.65-21.87 mug/L of aluminum content in the water sample, and the specific result is shown in table 1.
Comparative example 1
The comparative example provides a method for measuring the aluminum content by atomic absorption spectrometry of a graphite furnace.
The specific steps of the method are basically the same as those of example 1, except that: sodium nitrate is not added into the aluminum series calibration solution and the water sample to be measured; and the atomization temperature in the working condition of measuring absorbance by using a graphite furnace atomic absorption spectrometer is 2500 ℃.
The measurement results of the aluminum content in the water sample (the same as in example 1) by the method of this comparative example were 22.85-25.57. Mu.g/L, and the specific results are shown in Table 2.
The standard curves (i.e., aluminum content-absorbance curves of aluminum series calibration solutions) obtained in example 1 and comparative example 1 are shown in fig. 1. As can be seen from fig. 1, the slope of the standard curve obtained after adding sodium nitrate to the aluminum series calibration solution in example 1 is significantly larger than that of the standard curve of comparative example 1 without adding sodium nitrate, and the linear relationship is also better than that of the standard curve of comparative example 1 without adding sodium nitrate.
Test example 1 absorbance of a Standard sample was measured as a function of the atomization temperature
In this test example, the temperatures at which aluminum was sufficiently atomized were examined by measuring the absorbance at different atomization temperatures and observing the high point of absorbance using aluminum calibration solutions (i.e., the standard samples in this test example) containing 30. Mu.g/L of aluminum in example 1 and comparative example 1 and no sodium nitrate added.
(1) Example 1 absorbance versus atomization temperature curve for a standard
Al 2 O 3 High-temperature boiling point substances are difficult to be atomized. Other conditions of example 1 were fixed, and the absorbance was measured at different atomization temperatures using an aluminum calibration solution with added sodium nitrate at an aluminum content of 30. Mu.g/L, the atomization temperature being increased by 100 ℃. The results are shown in FIG. 2. As can be seen from FIG. 2, the high absorbance point of the standard sample appears between 2300 and 2400 ℃, which proves that the method of the invention realizes the full atomization of aluminum element at the lower atomization temperature of 2300 to 2400 ℃, so that 2350 ℃ is selected as the optimal atomization temperature.
(2) Comparative example 1 absorbance versus atomization temperature curve for a standard
Al 2 O 3 High-temperature boiling point substances are difficult to be atomized. Other conditions of comparative example 1 were fixed, and the absorbance was measured at different atomization temperatures using an aluminum calibration solution with an aluminum content of 30. Mu.g/L without sodium nitrate added, the atomization temperatures being increased by 100 ℃. The results are shown in FIG. 3. As can be seen from fig. 3, the high point of absorbance of the standard sample appears between 2700 ℃ and 2800 ℃, demonstrating that the method of comparative example 1 can achieve sufficient atomization of aluminum element at the atomization temperature of 2700 ℃ to 2800 ℃.
Test example 2 influence of interfering Metal ions on measurement results
This test example analyzes the effect of interfering metal ions on the measurement results of the methods of example 1 and comparative example 1.
The reagents used in this test example included:
copper nitrate interference liquid is prepared by the following steps: weighing 100mg of anhydrous copper nitrate, dissolving the anhydrous copper nitrate with a proper amount of water, transferring the solution to a 100mL volumetric flask, diluting the solution with water, and fixing the volume to a scale;
a calcium nitrate interference fluid formulated by: 100mg of anhydrous calcium nitrate is weighed and dissolved with a proper amount of water, all are transferred into a 100mL volumetric flask, and diluted with water and fixed to a scale.
The test case comprises the following steps:
(1) Investigation of the influence of copper and calcium ions on the measurement result of the aluminum content without adding sodium nitrate
3mL of the aluminum standard solution (the concentration of aluminum is 1000 mug/L) in the example 1 is removed to a 100mL volumetric flask, 1mL of 1.40g/mL nitric acid solution, 10 mug of 5mg/mL magnesium nitrate solution serving as a matrix improver and 1mL of the copper nitrate interference solution are added, and the copper interference sample is obtained by diluting with water, fixing the volume to a scale and shaking; measuring the absorbance by using a graphite furnace atomic absorption spectrometer, wherein the working condition is the same as that of comparative example 1;
3mL of the aluminum standard solution (the concentration of aluminum is 1000 mug/L) in the example 1 is removed to a 100mL volumetric flask, 1mL of 1.40g/mL nitric acid solution, 10 mug of 5mg/mL magnesium nitrate solution serving as a matrix improver and 1mL of the calcium nitrate interference solution are added, and the calcium interference sample is obtained by diluting with water, fixing the volume to a scale and shaking; measuring the absorbance by using a graphite furnace atomic absorption spectrometer, wherein the working condition is the same as that of comparative example 1;
combining the standard curve in the comparative example 1, and examining the influence of copper and calcium ions on the aluminum content measurement result under the condition of not adding sodium nitrate;
(2) Under the condition of examining the influence of copper and calcium ions on the aluminum content measurement result when sodium nitrate is added
3mL of the aluminum standard solution (the concentration of aluminum is 1000 mug/L) in the example 1 is removed to a 100mL volumetric flask, 1mL of 1.40g/mL nitric acid solution, 10 mug of 5mg/mL magnesium nitrate solution serving as a matrix improver, 1mL of 2mmoL/L sodium nitrate solution and 1mL of the copper nitrate interference solution are added, and the copper interference sample is obtained by diluting with water, fixing the volume to a scale and shaking uniformly; the absorbance was measured by using a graphite furnace atomic absorption spectrometer, and the working conditions were the same as in example 1;
3mL of the aluminum standard solution (the concentration of aluminum is 1000 mug/L) in the example 1 is removed to a 100mL volumetric flask, 1mL of 1.40g/mL nitric acid solution, 10 mug of 5mg/mL magnesium nitrate solution serving as a matrix improver, 1mL of 2mmoL/L sodium nitrate solution and 1mL of the calcium nitrate interference solution are added, and the calcium interference sample is obtained by diluting with water, fixing the volume to a scale and shaking uniformly; the absorbance was measured by using a graphite furnace atomic absorption spectrometer, and the working conditions were the same as in example 1;
the effect of copper and calcium ions on the results of the aluminum content measurement when sodium nitrate was added was examined in combination with the standard curve in example 1.
In step (1) of the present test example, the results of comparing the absorbance measured by the copper interference sample, the calcium interference sample, and the aluminum content thereof with the standard curve of comparative example 1 are shown in fig. 4. As can be seen from FIG. 4, the method of comparative example 1 has a large influence on the measurement result of the aluminum content by other metal ions, and the difference between the measurement value of the aluminum content and the true value is large.
In step (2) of this test example, the results of comparing the absorbance measured for the copper interference sample, the calcium interference sample, and the aluminum content thereof with the standard curve of example 1 are shown in fig. 5. As can be seen from fig. 5, the interference of other metals is masked by adopting the method of example 1, and the accuracy and stability of the detection result are high.
Test example 3 recovery rate by adding standard
This test example provides a standard recovery test for the methods of example 1 and comparative example 1.
(1) Example 1 labeled recovery test
The clean water sample was taken and subjected to a standard recovery test, the results of which are shown in Table 1 below. As can be seen from Table 1, the recovery rate of the method of example 1 is between 97.85% and 101.55%, and it is clear that the method of example 1 has a better recovery rate and can be practically used.
TABLE 1 results of recovery experiments for example 1
(2) Standard recovery test of comparative example 1
The clean water sample was taken and subjected to a standard recovery test, the results of which are shown in Table 2 below. As can be seen from table 2, the recovery of the process of comparative example 1 is between 105.50% and 127.65% and the lower the aluminum content the greater the deviation from the actual value.
TABLE 2 results of recovery experiments for comparative example 1
In conclusion, the method of the invention generates the same atomization environment and increases the atomization rate when the calibration solution and the sample are subjected to the aluminum element test, improves the accuracy of measuring the aluminum content by the atomic absorption spectrum of the graphite furnace, and has the advantages of scientific and reasonable method, high labeling recovery rate, simple and convenient operation and wide application prospect.
Claims (15)
1. A method for measuring aluminum content by atomic absorption spectrometry of a graphite furnace, which comprises the following steps:
(1) Preparing an aluminum series calibration solution added with alkali metal nitrate, measuring the absorbance of the aluminum series calibration solution added with the alkali metal nitrate by utilizing a graphite furnace atomic absorption spectrometer, and drawing a standard curve by taking the absorbance obtained by measurement as an ordinate and the aluminum content in the aluminum series calibration solution added with the alkali metal nitrate as an abscissa;
(2) Adding alkali metal nitrate into the sample to be measured, measuring the absorbance by using a graphite furnace atomic absorption spectrometer, and then calculating according to the standard curve obtained in the step (1) to obtain the aluminum content in the sample to be measured.
2. The method of claim 1, wherein the alkali metal nitrate added aluminum series calibration solution is formulated by: respectively transferring different amounts of aluminum standard solutions, adding a proper amount of nitric acid and alkali metal nitrate, and respectively using water to fix the volume to prepare an aluminum series calibration solution with the aluminum content of 1-100 mug/L and the alkali metal nitrate.
3. The method according to claim 2, wherein the aluminum content in the alkali metal nitrate added aluminum series calibration solution is 10 μg/L to 60 μg/L.
4. A method according to any one of claims 1-3, wherein the alkali metal nitrate comprises sodium nitrate and/or potassium nitrate.
5. A method according to any one of claims 1 to 3, wherein the alkali metal nitrate is added in an amount of 0.005-0.03mmol/L based on the volume of the alkali metal nitrate added aluminum series calibration solution.
6. The method of claim 2, wherein the concentration of aluminum in the aluminum standard solution is 1000 μg/L.
7. The method of claim 1, wherein the sample to be assayed comprises a water sample.
8. The method of claim 7, wherein the sample to be assayed is a filtered water sample.
9. The method according to claim 1, wherein the alkali metal nitrate is added in an amount of 0.005-0.03mmol/L based on the volume of the sample to be assayed.
10. The method of claim 1, wherein step (2) further comprises: adding nitric acid into the sample to be measured for digestion.
11. The method according to claim 10, wherein the added nitric acid is present in the sample to be assayed in an amount of 0.15-0.2mol/L.
12. The method according to claim 1, wherein a matrix improver is further added to each of the alkali metal nitrate-added aluminum series calibration solution and the sample to be measured.
13. The method of claim 12, wherein the matrix modifier comprises magnesium nitrate.
14. The method according to claim 12, wherein the matrix improver is added in an amount of 300 to 700 μg/L based on the volume of the alkali metal nitrate added aluminum series calibration solution and the volume of the sample to be measured, respectively.
15. The method of claim 1, wherein the operating conditions for measuring absorbance using a graphite furnace atomic absorption spectrometer comprise: the detection wavelength is 309.3nm, the ashing temperature is 700-800 ℃, the time is 20-30s, the atomization temperature is 2300-2400 ℃, and the time is 4-5s.
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