CN115963163A - Method for determining content of heavy metal elements in grain and oil based on isotope dilution inductively coupled plasma mass spectrometry - Google Patents
Method for determining content of heavy metal elements in grain and oil based on isotope dilution inductively coupled plasma mass spectrometry Download PDFInfo
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- 238000000034 method Methods 0.000 title claims abstract description 58
- 229910001385 heavy metal Inorganic materials 0.000 title claims abstract description 12
- 238000001043 isotope dilution inductively coupled plasma mass spectrometry Methods 0.000 title claims abstract description 12
- 238000012937 correction Methods 0.000 claims abstract description 54
- 239000003085 diluting agent Substances 0.000 claims description 98
- 239000000523 sample Substances 0.000 claims description 96
- 239000012086 standard solution Substances 0.000 claims description 71
- 239000000243 solution Substances 0.000 claims description 57
- 239000012488 sample solution Substances 0.000 claims description 54
- 239000000126 substance Substances 0.000 claims description 33
- 239000012490 blank solution Substances 0.000 claims description 32
- 239000000843 powder Substances 0.000 claims description 30
- 238000002156 mixing Methods 0.000 claims description 28
- GRYLNZFGIOXLOG-UHFFFAOYSA-N Nitric acid Chemical compound O[N+]([O-])=O GRYLNZFGIOXLOG-UHFFFAOYSA-N 0.000 claims description 25
- 229910052804 chromium Inorganic materials 0.000 claims description 25
- 229910017604 nitric acid Inorganic materials 0.000 claims description 25
- 238000000120 microwave digestion Methods 0.000 claims description 24
- 229910052753 mercury Inorganic materials 0.000 claims description 23
- 230000000155 isotopic effect Effects 0.000 claims description 22
- 229910021654 trace metal Inorganic materials 0.000 claims description 18
- 238000005303 weighing Methods 0.000 claims description 17
- 238000009616 inductively coupled plasma Methods 0.000 claims description 13
- 229910021642 ultra pure water Inorganic materials 0.000 claims description 12
- 239000012498 ultrapure water Substances 0.000 claims description 12
- 230000004044 response Effects 0.000 claims description 6
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- 238000011410 subtraction method Methods 0.000 claims description 3
- 238000007865 diluting Methods 0.000 claims description 2
- 238000005259 measurement Methods 0.000 claims description 2
- 239000007789 gas Substances 0.000 claims 3
- PXHVJJICTQNCMI-UHFFFAOYSA-N Nickel Chemical compound [Ni] PXHVJJICTQNCMI-UHFFFAOYSA-N 0.000 claims 2
- 229910052751 metal Inorganic materials 0.000 claims 2
- 239000002184 metal Substances 0.000 claims 2
- 239000012159 carrier gas Substances 0.000 claims 1
- 239000001307 helium Substances 0.000 claims 1
- 229910052734 helium Inorganic materials 0.000 claims 1
- SWQJXJOGLNCZEY-UHFFFAOYSA-N helium atom Chemical compound [He] SWQJXJOGLNCZEY-UHFFFAOYSA-N 0.000 claims 1
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- 238000005070 sampling Methods 0.000 claims 1
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- 239000011651 chromium Substances 0.000 description 46
- 229910052793 cadmium Inorganic materials 0.000 description 33
- BDOSMKKIYDKNTQ-UHFFFAOYSA-N cadmium atom Chemical compound [Cd] BDOSMKKIYDKNTQ-UHFFFAOYSA-N 0.000 description 33
- 235000013312 flour Nutrition 0.000 description 31
- VYZAMTAEIAYCRO-UHFFFAOYSA-N Chromium Chemical compound [Cr] VYZAMTAEIAYCRO-UHFFFAOYSA-N 0.000 description 26
- QSHDDOUJBYECFT-UHFFFAOYSA-N mercury Chemical compound [Hg] QSHDDOUJBYECFT-UHFFFAOYSA-N 0.000 description 26
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- 238000001514 detection method Methods 0.000 description 9
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- 238000010438 heat treatment Methods 0.000 description 7
- 238000004750 isotope dilution mass spectroscopy Methods 0.000 description 6
- 238000001816 cooling Methods 0.000 description 5
- 238000002360 preparation method Methods 0.000 description 5
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- 239000012535 impurity Substances 0.000 description 4
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- 239000012895 dilution Substances 0.000 description 3
- 238000001095 inductively coupled plasma mass spectrometry Methods 0.000 description 3
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- Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
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Abstract
The invention discloses a method for determining the content of heavy metal elements in grain and oil based on isotope dilution inductively coupled plasma mass spectrometry. The method has the advantages that the method introduces the correction equation and the correction factor, further accurately controls the abundance ratio range of the specific isotope and the reference isotope, realizes high test accuracy, good precision, safety, reliability and short period, can effectively avoid pollution and loss in the treatment process, and eliminates the interference influence of matrix effect and the like.
Description
Technical Field
The invention relates to the technical field of heavy metal detection. More particularly, relates to a method for determining the content of heavy metal elements in grain and oil based on isotope dilution inductively coupled plasma mass spectrometry.
Background
In the limit of pollutants in national food safety standard (GB 2762-2017), the limit of chromium, cadmium, mercury and lead in grain and oil and products thereof are definitely specified, so that the detection result of the content of heavy metals of chromium, cadmium, mercury and lead in grain and oil needs to be ensured to be accurate and reliable, the currently commonly used detection methods are Atomic Absorption Spectroscopy (AAS), atomic Fluorescence Spectroscopy (AFS), inductively coupled plasma emission spectroscopy (ICP-AES/OES), inductively coupled plasma mass spectrometry (ICP-MS) and the like, and the methods are often easily polluted by a pretreatment process in the detection process, elements to be detected are easily lost, and the detection result is easily influenced by the problems of matrix interference and the like. Isotope Dilution Mass Spectrometry (IDMS) is one of internationally recognized standard methods, the content of elements in a sample is obtained by changing the isotope abundance ratio of elements in a detected sample and adopting mathematical calculation, the content is only related to the mass of the sample and the mass of an added isotope diluent, the pollution and the loss of the elements caused in the treatment process can be well avoided, the matrix effect is eliminated by a specific correction mode, and the method has the characteristics of high accuracy and clear tracing chain. At present, no report of measuring chromium, cadmium, mercury and lead elements in grain and oil by isotope dilution inductively coupled plasma mass spectrometry is available at home and abroad.
Therefore, the isotope dilution inductively coupled plasma mass spectrometry is used for determining chromium, cadmium, mercury and lead elements in the grain and oil, so that the aim of high-efficiency and accurate detection is fulfilled, and the method is very important.
Disclosure of Invention
Based on the defects, the invention aims to provide a method for determining the content of heavy metal elements in grain and oil based on isotope dilution inductively coupled plasma mass spectrometry. According to the method, a correction equation and a correction factor are introduced, the abundance ratio range of the specific isotope to the reference isotope is further accurately controlled aiming at different elements, the high test accuracy, the good precision, the safety and the reliability are realized, the test period is short, the pollution and the loss in the treatment process can be effectively avoided, and the interference influence such as the matrix effect is eliminated.
In order to achieve the purpose, the invention adopts the following technical scheme:
the invention provides a method for determining the content of heavy metal elements in grain and oil based on an isotope dilution inductively coupled plasma mass spectrometry, which comprises the following steps:
s1, preparing a plurality of parallel solutions:
sample solution to be tested: adding 5-10mL trace metal level concentrated nitric acid into 0.2-0.5g of sample powder for microwave digestion treatment, and then quantitatively accommodating the digested sample in a 25-100mL volumetric flask by using ultrapure water;
mixing sample solutions: taking 0.2-0.5g of sample powder per part, adding a diluted concentrated isotope diluent standard substance of an element to be detected by adopting a subtraction method to ensure that the isotope abundance ratio of a specific isotope to a reference isotope in a mixed sample is 0.25-1.2, adding 5-10mL of trace metal level concentrated nitric acid for microwave digestion treatment, and then fixedly containing the digested mixed sample in a 25-100mL volumetric flask by using ultrapure water;
when the element to be detected is Cr, the reference isotope and the specific isotope thereof are selected from 53 Cr or 52 Cr, and are different;
when the element to be detected is Cd, the reference isotope and the specific isotope thereof are selected from 114 Cd、 113 Cd、 112 Cd、 111 Cd or 110 Cd, and are different;
when the element to be detected is Hg, the reference isotope and the specific isotope thereof are selected from 202 Hg、 201 Hg、 200 Hg or 199 Hg, and not the same;
when the element to be detected is Pb, the reference isotope and the specific isotope thereof are selected from 208 Pb、 207 Pb or 206 Pb, and are not the same;
blank solution 1: preparing a solution which forms a blank control with the solution of the sample to be detected;
blank solution 2: preparing a solution which forms a blank control with the mixed sample solution;
s2, measuring the mass-to-charge ratio of each isotope of the element to be measured in the sample solution to be measured, the blank solution 1, the mixed sample solution and the blank solution 2 by adopting a high-resolution inductively coupled plasma mass spectrometer to obtain isotope response value data of the element to be measured; calculating the isotopic abundance ratio after correction by a correction equation;
s3, calculating the content of the element to be detected in the sample powder according to the isotope abundance ratio by a formula 1:
equation 1
In the formula,
R Y : the abundance ratio of the specific isotope of the element to be detected in the isotope diluent to the reference isotope;
R XY : mixing the abundance ratio of the specific isotope of the element to be detected in the sample solution to the reference isotope;
C Z : the concentration of the element to be detected in the standard solution is unit of mu g/g;
m X : the mass of sample powder in the sample solution to be tested, unit g;
m Y2 : mass of isotope diluent in the mixed sample solution, unit g;
C X : the content of the element to be detected in the sample powder is unit microgram/g;
k: a sample correction factor;
K 1 : and calibrating the correction factor.
The method for determining the content of the heavy metal elements in the grain and the oil is based on isotope dilution inductively coupled plasma mass spectrometry, can effectively avoid pollution introduced in the treatment process and loss of elements to be detected, is combined with a correction equation and a correction factor, accurately controls the abundance ratio range of a specific isotope and a reference isotope according to different elements, has the advantages of high test accuracy, good precision, safety, reliability, short period and the like, can be closer to the real heavy metal content value in food when being applied to the field of food detection, has real and reliable data, and provides data support for further judging the safety of the food.
Further, in step S2, different correction equations are substituted for correction according to the difference in the mass-to-charge ratio of the element to be measured, and the correction equations are shown in table 1:
TABLE 1 Mass/Charge ratio of elements to be measured and correction equation
Further, when the element to be measured is Cr, it is selected 53 Cr is used as a reference isotope and is selected 52 Cr as a specific isotope, said R XY In the range of 0.8-1.2.
Further, when the element to be detected is Cd, selecting 111 Cd as a reference isotope, selection 110 Cd as a specific isotope, said R XY In the range of 0.5-0.8; or, select 111 Cd as a reference isotope, selecting 112 Cd as a specific isotope, said R XY In the range of 0.8-1.2.
Further, when the element to be detected is Hg, the element is selected 202 Hg is selected as a reference isotope 201 Hg as the specific isotope, the R XY In the range of 0.25-0.4; or, select 202 Hg is selected as a reference isotope 200 Hg as the specific isotope, the R XY In the range of 0.3-0.6.
Further, when the element to be measured is Pb, it is selected 207 Pb as reference isotope, selection 208 Pb as the specific isotope, said R XY In the range of 0.8-1.2.
Further, the sample correction factor K is calculated as follows:
equation 2
In the formula,
k: a sample correction factor;
K 1 : and calibrating the correction factor.
Further, the calibration correction factor K 1 Obtained by the following calculation:
equation 3
In the formula,
K 1 : calibrating a correction factor;
R IUPAC : the abundance ratio of the specific isotope of the element to be detected to the reference isotope published by the international union of pure and applied chemistry;
Further, the standard solution is prepared by a standard substance by adopting a 5% trace metal level nitric acid solution weighing method; the mixed standard solution is prepared by mixing a standard substance and a concentrated isotope diluent and then diluting the mixture into a solution.
And further, preparing not less than 6 parts of parallel solution of the standard solution, the mixed standard solution, the sample solution to be detected and the mixed sample solution.
Further, the measurement conditions of the high-resolution inductively coupled plasma mass spectrometer are shown in table 2:
TABLE 2 operating reference conditions for the ICP-MS method
The invention has the following beneficial effects:
the invention discloses a method for determining the content of heavy metal elements in grain and oil based on an isotope dilution inductively coupled plasma mass spectrometry. The method is based on isotope dilution inductively coupled plasma mass spectrometry, can effectively avoid pollution introduced in the treatment process and loss of elements to be detected, combines a correction equation and a correction factor and accurately controls the abundance ratio range of a specific isotope and a reference isotope, has the advantages of high test accuracy, good precision, safety, reliability, short period and the like, and is applied to the method
Detailed Description
In order to more clearly illustrate the invention, the invention is further described below in connection with preferred embodiments. It is to be understood by persons skilled in the art that the following detailed description is illustrative and not restrictive, and is not to be taken as limiting the scope of the invention.
Example 1
Step 1: preparation of Brown Rice flour sample
Selecting paddy as a raw material, and carrying out impurity removal, drying, shelling, crushing and uniform mixing treatment to obtain a coarse rice powder sample.
And 2, step: determination of the isotope to be detected
Selecting 111 Cd as a reference isotope, selecting 112 Cd as a specific isotope.
And step 3: calibration of concentrated isotope diluent solutions
(1) The following solutions were prepared
Cadmium natural abundance cadmium standard solution: selecting a cadmium standard substance with natural abundance of cadmium, and preparing 6 standard solutions with the concentration of 0.010 mu g/g by using a 5% trace metal level nitric acid solution weighing method;
mixing standard solutions: weighing 1g of cadmium standard substance diluted to 0.1 mu g/g by 5% trace metal level nitric acid solution, placing the cadmium standard substance in a centrifuge tube, weighing 0.18g of cadmium concentrated isotope diluent diluted by 100 times by a decrement method, balancing for more than 2min by using vortex mixing, and preparing 6 groups of parallel experiments under the same conditions;
standard blank solution: a5% trace metal grade nitric acid solution was taken as a blank control solution.
(2) Measuring the mass-to-charge ratio of cadmium in a cadmium standard solution, a mixed standard solution and a standard blank solution by adopting a high-resolution inductively coupled plasma mass spectrometer, scanning the mass number, correcting by a correction equation, and calculating to obtain the specific isotope 112 Cd and reference isotopes 111 Ratio R of Cd Z1 、R Z2 、…、R Z6 ，R ZY1 、R ZY2 、…、R ZY6 And arithmetic mean
And &>
The results are shown in Table 3:
table 3 isotope diluent calibration data
Note: r Z1 -R Z6 Isotopic abundance ratio data for 6 cadmium standard solutions, R ZY1 -R ZY6 Isotopic abundance ratio data for 6 mixed standard solutions.
(3) Calculation of calibration correction factor
The results obtained in Table 2
Substituting equation 3, calculate K 1 ：
(4) Concentration calculation of isotope diluents
The concentration of the isotope diluent is calculated by equation 4,
equation 4
In the formula,
C Y : the concentration of cadmium element in the isotope diluent is unit of mug/g;
C Z : the concentration of cadmium element in the standard solution is unit microgram/g;
m z : adding the cadmium standard substance in the standard solution in unit g;
m Y1 : the adding amount of the cadmium isotope diluent in the mixed standard solution is unit g;
M i : nuclear mass of isotope i;
R iZ : isotopes in standard solutions i Cd and reference isotope 111 Abundance ratio of Cd(calculated as the natural abundance ratio published by the international union of pure and applied chemistry);
R iY : isotope in concentrated isotope diluent i Cd and reference isotope 111 Abundance ratio of Cd;
Rz Y : specific isotope of cadmium in mixed standard solution of concentrated isotope diluent and cadmium standard substance 112 Cd and reference isotope 111 Abundance ratio of Cd;
R z : measuring the specific isotope of cadmium in the standard solution 112 Cd and reference isotope 111 Abundance ratio of Cd;
R Y : specific isotope of cadmium in isotope-enriched diluent 112 Cd and reference isotope 111 Abundance ratio of Cd;
K 1 : calibrating a correction factor;
substituting the concentration verification result data of the concentrated isotope diluent in the table 4 into a formula 4, and finally calculating to obtain C Y The result shows that the value of =6.31 mu g/g is consistent with the value range (6.30 +/-0.012) mu g/g calculated from the concentrated isotope diluent certificate, and the accuracy and the effectiveness of the method system are verified.
Table 4 table of concentration verification results of isotope-enriched diluent
Note: m is Y1 The actual amount of the isotope-enriched diluent is divided by 100 for the mass of the isotope diluent after 100-fold dilution.
(5) Determination of the amount of isotopically enriched diluent added to a sample
In order to further improve the sample testing accuracy, the amount of the isotope-enriched diluent added to the sample needs to be re-determined so as to reduce interference in subsequent detection.
Adding concentrated isotope diluent into selected sample, and mixing with specific isotope in solution 112 Cd and reference isotope 111 Abundance ratio of Cd R XY =1, and then C determined Y Substituting into formula 5 to obtain 0.19g of diluent with 100 times of diluted cadmium concentrated isotope;
equation 5
In the formula,
R XY ，R X ，R Y ，C Y ，m X ，m Y the meaning of (1) is the same as before;
the estimated concentration of cadmium element in the sample is unit of mug/g; a is X(111) ，a X(112) ，a Y(111) ，a Y(112) Representing specific isotopes in the sample (X) and the isotopically enriched diluent (Y) 112 Cd and reference isotopes 111 Abundance value of Cd. (references: wang Jun, zhao Motian. Thermal surface ionization isotope dilution mass spectrometry for determining trace lead in red wine [ J]Mass Spectrometry newspaper 2003 (04): 501-504)
And 4, step 4: determination of cadmium content in brown rice powder sample
(1) Preparation of Brown Rice flour sample solution
Sample solution to be tested: taking a brown rice powder sample, dividing into 6 parts and 0.25 g/part, placing the sample in a microwave digestion tank, adding 5-8mL trace metal level concentrated nitric acid, placing the sample in a microwave digestion system for digestion, taking out the sample after the digestion is finished, cooling the sample, heating the sample in an acid-dispelling sleeve at 140 ℃ for dispelling acid for 2 hours, transferring the cooled sample into a 25mL volumetric flask, and using ultrapure water to fix the volume to the scale;
mixing sample solutions: weighing 6 parts of brown rice powder samples (the adding amount is shown in table 5), respectively placing the samples in microwave digestion tanks, adding 100 times of diluted cadmium concentrated isotope diluent (the adding amount is shown in table 4) into each microwave digestion tank filled with sample powder by a decrement method, adding 5-8mL of trace metal level concentrated nitric acid solution, carrying out pre-digestion at 100 ℃ for 20min, placing the cooled sample in a microwave digestion system for digestion, taking out the cooled sample, removing acid from an acid removing sleeve at 140 ℃ for 2h, transferring the solution into a 25mL volumetric flask, and fixing the volume to scale by ultrapure water;
blank solution 1: preparing a solution which forms a blank control with the solution of the sample to be detected;
blank solution 2: preparing a solution which forms a blank control with the mixed sample solution;
(2) Measuring the mass-to-charge ratio of each isotope of cadmium element in the sample solution to be measured, the blank solution 1, the mixed sample solution and the blank solution 2 by adopting a high-resolution inductively coupled plasma mass spectrometer to obtain cadmium element isotope response value data; after being corrected by a correction equation, the isotopic abundance ratio R is calculated X1 、R X2 、…、R X6 ，R XY1 、R XY2 、…、R XY6 And arithmetic mean
The results are shown in Table 5.
TABLE 5 statistical table of isotope data of samples to be tested
| Serial number | R X | m X | m Y2 | R XY |
| 1 | 1.9167 | 0.2527 | 0.1903 | 1.0141 |
| 2 | 1.8954 | 0.2511 | 0.1887 | 1.0210 |
| 3 | 1.8976 | 0.2528 | 0.1859 | 1.0270 |
| 4 | 1.9043 | 0.2518 | 0.1869 | 1.0285 |
| 5 | 1.8932 | 0.2523 | 0.1865 | 1.0213 |
| 6 | 1.9144 | 0.2505 | 0.1893 | 1.0132 |
| Mean value of | 1.9036 | 0.2519 | 0.1879 | 1.0208 |
Note: r X1 -R X6 Isotopic abundance ratio data for 6 sample solutions to be tested, R XY1 -R XY6 Isotopic abundance ratio data for 6 mixed sample solutions, m x Column number is 6 parts of brown rice powder sample addition amount, m Y2 The column is 6 parts of the added amount of the diluted cadmium concentrated isotope diluent which is 100 times, and the actual amount of the diluted cadmium concentrated isotope diluent needs to be divided by 100.
(3) Calculation of sample correction factor K
(4) Analytical calculations
(i) Calculation of cadmium content in brown rice powder:
the values of the parameters of table 6 can be obtained from table 4 and equation 1.
TABLE 6 determination of cadmium in Brown rice flour samples (μ g/g)
| Serial number | Cadmium content |
| 1 | 0.406 |
| 2 | 0.411 |
| 3 | 0.407 |
| 4 | 0.413 |
| 5 | 0.405 |
| 6 | 0.407 |
| Mean value of | 0.408 |
| Standard deviation of | 0.003 |
| Relative standard deviation (%) | 0.76 |
In this example, the result of measuring cadmium in brown rice flour and analyzing standard substance GBW (E) 100827 by IDMS method is near the median value of its assigned range of 0.408 + -0.031 μ g/g, and the relative standard deviation is 0.76%, thus proving that the method is accurate and reliable and has high precision.
Example 2
Step 1: preparation of corn flour samples
Selecting corn as a raw material, and performing impurity removal, drying, crushing and uniform mixing treatment to obtain a corn flour sample.
Step 2: determination of the isotope to be detected
Selecting 207 Pb as reference isotope, selection 208 Pb as a specific isotope.
And step 3: calibration of isotope diluent solutions
(1) The following solutions were prepared
Natural abundance lead standard solution: selecting a lead natural abundance standard substance, and preparing 6 standard solutions of 0.010 mu g/g by using a 5% trace metal level nitric acid solution weighing method;
mixing standard solutions: weighing 5g of lead standard substance diluted to 0.1 mu g/g by 5% trace metal level nitric acid solution, placing the lead standard substance in a centrifuge tube, weighing 0.3g of cadmium concentration isotope diluent diluted by 10 times by a decrement method, balancing for more than 2min by using vortex mixing, and preparing 6 groups of parallel experiments under the same conditions;
standard blank solution: a5% trace metal grade nitric acid solution was used as a blank control solution.
(2) Measuring the mass-to-charge ratio of lead in the standard solution, the mixed standard solution and the standard blank solution by adopting a high-resolution inductively coupled plasma mass spectrometer, scanning the mass number, correcting by a correction equation, and calculating to obtain the specific isotope 208 Pb and reference isotope 207 Ratio R of Pb Z1 、R Z2 、…、R Z6 ，R ZY1 、R ZY2 、…、R ZY6 And arithmetic mean
And &>
The results are shown in Table 7:
table 7 isotope diluent calibration data
Note: r Z1 -R Z6 Isotopic abundance ratio data for 6 lead standard solutions, R ZY1 -R ZY6 Isotopic abundance ratio data for 6 mixed standard solutions.
(3) Calculation of calibration correction factor
Obtained in Table 7
Substituting into equation 3, calculate K 1 ：
(4) Concentration calculation of isotope diluents
The concentration of the isotope diluent is calculated by equation 4,
equation 4
In the formula,
C Y : the concentration of lead element in isotope diluent is unit of mug/g;
C Z : the concentration of lead element in the standard solution is unit of mu g/g;
m z : adding lead standard substance in the standard solution in unit g;
m Y1 : the adding amount of the lead isotope diluent in the mixed standard solution is unit g;
mi: nuclear mass of isotope i;
R iZ : isotopes in standard solutions i Pb and reference isotope 207 The abundance ratio of Pb (calculated as the natural abundance ratio published by the international union of pure and applied chemistry);
R iY : isotope in concentrated isotope diluent i Pb and reference isotope 207 Abundance ratio of Pb;
Rz Y : specific isotope of lead in mixed standard solution of concentrated isotope diluent and lead standard substance 208 Pb and reference isotope 207 Abundance ratio of Pb;
R z : specific isotopes of lead in standard solutions 208 Pb and reference isotope 207 Abundance ratio of Pb;
R Y : specific isotopes of lead in isotope diluents 208 Pb and reference isotope 207 Abundance ratio of Pb;
K 1 : calibrating a correction factor;
substituting the concentration verification result data of the isotope diluents in Table 8 into equation 4, and finally calculating to obtain C Y And the result that the value of the (= 4.01 mu g/g) is consistent with the value range (4.01 +/-0.01) mu g/g calculated from the concentrated isotope diluent certificate verifies the accuracy and the effectiveness of the method system.
Table 8 data table of concentration verification results of isotope diluents
Note: m is Y1 The amount of the isotope diluent actually containing the enriched isotope is divided by 10, which is the mass of the isotope diluent after 10-fold dilution.
(5) Isotope diluent addition determination
To further improve the accuracy of the test, the amount of isotope diluent added needs to be re-determined in order to reduce interference in subsequent tests.
Adding concentrated isotope diluent into selected sample, and mixing with specific isotope in solution 208 Pb and reference isotope 207 Abundance ratio R of Pb XY =1, and C determined Y Substituting into formula 6 to obtain 100 times diluted lead concentrated isotope diluent with addition of 0.55g;
equation 6
In the formula,
R XY ，R X ，R Y ，C Y ，m X ，m Y the meaning of (1) is the same as that of (1);
the estimated concentration of lead element in the sample is unit of mug/g; a is X(207) ，a X(208) ，a Y(207) ，a Y(208) Representing specific isotopes in the sample (X) and the isotopically enriched diluent (Y) 208 Pb and reference isotope 207 Abundance value of Pb.
And 4, step 4: determination of lead content in corn flour sample
(1) Preparation of corn flour sample solution
Sample solution to be tested: taking a corn flour sample, dividing the corn flour sample into 6 parts and 0.25 g/part, placing the corn flour sample into a microwave digestion tank, adding 5-8mL trace metal-grade concentrated nitric acid, placing the corn flour sample into a microwave digestion system for digestion, taking out the corn flour sample after the digestion is finished, cooling the corn flour sample, driving the corn flour sample into an acid sleeve, heating the corn flour sample at 80-160 ℃ to completely remove brown smoke, transferring the corn flour sample into a 25mL volumetric flask, and fixing the volume to the scale by using ultrapure water;
mixing sample solutions: weighing 6 parts of corn flour samples (the adding amount is shown in table 9), respectively placing the corn flour samples into microwave digestion tanks, adding 100 times of diluted isotope diluent (the adding amount is shown in table 8) into each microwave digestion tank filled with sample powder by a decrement method, adding 5-8mL of trace metal-grade concentrated nitric acid solution, carrying out pre-digestion at 100 ℃ for 20min, placing the cooled corn flour samples into a microwave digestion system for digestion, taking out the corn flour samples for cooling after the completion, heating the corn flour samples at 80-160 ℃ in an acid sleeve to remove brown smoke completely, transferring the corn flour samples into a 25mL volumetric flask, and fixing the volume of ultrapure water to the scale;
blank solution 1: preparing a solution which forms a blank control with the solution of the sample to be detected;
blank solution 2: preparing a solution which forms a blank control with the mixed sample solution;
(2) Measuring the mass-to-charge ratio of each isotope of the element to be measured in the sample solution to be measured, the blank solution 1, the mixed sample solution and the blank solution 2 by adopting a high-resolution inductively coupled plasma mass spectrometer to obtain isotope response value data of the element to be measured; after being corrected by a correction equation, the isotopic abundance ratio R is calculated X1 、R X2 、…、R X6 ，R XY1 、R XY2 、…、R XY6 And arithmetic mean
The results are shown in Table 9.
TABLE 9 statistical table of isotope data of samples to be measured
| Serial number | R X | m X | m Y2 | R XY |
| 1 | 2.3878 | 0.2519 | 0.6762 | 0.9991 |
| 2 | 2.4186 | 0.2518 | 0.6644 | 1.0082 |
| 3 | 2.3878 | 0.2532 | 0.5543 | 1.1105 |
| 4 | 2.3902 | 0.2504 | 0.5901 | 1.0602 |
| 5 | 2.3701 | 0.2502 | 0.6346 | 1.0343 |
| 6 | 2.3946 | 0.2526 | 0.5725 | 1.0901 |
| Mean value of | 2.3915 | 0.2517 | 0.6165 | 1.0504 |
Note: r X1 -R X6 Isotopic abundance ratio data for 6 sample solutions to be tested, R XY1 -R XY6 Isotopic abundance ratio data for 6 mixed sample solutions, m x Column is 6 parts of corn flour sample addition, m Y2 The column is 6 parts of 100 times of the addition amount of the diluted lead isotope-enriched diluent, and the actual amount of the isotope-enriched diluent is divided by 100.
(3) Calculation of sample correction factor K
(4) Analytical calculations
Calculating the lead content in the corn flour:
the values of the parameters of table 10 can be obtained from the results of table 9 and equation 1,
TABLE 10 determination of lead in corn flour samples (. Mu.g/g)
| Serial number | Lead content |
| 1 | 0.238 |
| 2 | 0.238 |
| 3 | 0.240 |
| 4 | 0.235 |
| 5 | 0.241 |
| 6 | 0.239 |
| Mean value of | 0.238 |
| Standard deviation of | 0.002 |
| Relative standard deviation (%) | 0.84 |
In the embodiment, the result of measuring the lead component in the corn flour and the analysis standard substance GBW (E) 100381 by the IDMS method is near the median value of the assignment range of 0.238 +/-0.018 mu g/g, and the relative standard deviation is 0.84%, so that the method is proved to be accurate and reliable and high in precision.
Example 3
Step 1: preparation of Brown Rice flour sample
Selecting paddy as a raw material, and carrying out impurity removal, drying, shelling, crushing and uniform mixing treatment to obtain a coarse rice powder sample.
Step 2: determination of the isotope to be detected
Selecting 202 Hg is selected as a reference isotope 200 Hg as a specific isotope.
And step 3: calibration of concentrated isotope diluent solutions
(1) The following solutions were prepared
Natural abundance mercury standard solution: selecting a natural abundance mercury standard substance, and preparing 6 standard solutions with the concentration of 0.001 mu g/g by using a 5% trace metal level nitric acid solution weighing method;
mixing standard solutions: taking 5g of natural abundance mercury standard substance (0.001 mug/g), weighing 0.14g of diluent which is added with 100 times of diluted mercury concentrated isotope by a weight reduction method, placing the mixture in a centrifuge tube, and balancing for more than 2min by using vortex mixing;
standard blank solution: a5% trace metal grade nitric acid solution was taken as a blank control solution.
(2) Measuring the mass-to-charge ratio of mercury in a mercury standard solution, a mixed standard solution and a standard blank solution by adopting a high-resolution inductively coupled plasma mass spectrometer, scanning the mass number, correcting by a correction equation, and calculating to obtain the specific isotope 200 Hg and a reference isotope 202 Ratio R of Hg Z1 、R Z2 、…、R Z6 ，R ZY1 、R ZY2 、…、R ZY6 And arithmetic mean
And &>
The results are shown in Table 11:
table 11 isotope diluent calibration data
Note: r Z1 -R Z6 Isotopic abundance ratio data for 6 mercury standard solutions, R ZY1 -R ZY6 Isotopologue of 6 mixed standard solutionsAbundance ratio data of elements.
(3) Calculation of calibration correction factor
Obtained in Table 11
Substituting into equation 3, calculate K 1 ：
(4) Concentration calculation of isotope diluents
The concentration of the isotope diluent is calculated by equation 4,
equation 4
In the formula,
C Y : the concentration of mercury element in isotope diluent is unit of mug/g;
C Z : the concentration of mercury element in the standard solution is unit of mu g/g;
m z : adding mercury standard substance in the standard solution in unit g;
m Y1 : adding the mercury isotope diluent in the mixed standard solution in unit g;
M i : nuclear mass of isotope i;
R iZ : isotopes in standard solutions i Hg and reference isotope 202 The abundance ratio of Hg (calculated as the natural abundance ratio published by the international union of pure and applied chemistry);
R iY : isotope in concentrated isotope diluent i Hg and reference isotope 202 Abundance ratio of Hg;
Rz Y : specific isotope of mercury in mixed standard solution of concentrated isotope diluent and mercury standard substance 200 Hg and reference isotope 202 Abundance ratio of Hg;
R z : determination of specific isotopes of mercury in standard solutions 200 Hg and reference isotope 202 Abundance ratio of Hg;
R Y : specific isotopes of mercury in enriched isotope diluents 200 Hg and reference isotope 202 Abundance ratio of Hg;
K 1 : calibrating a correction factor;
substituting the concentration verification result data of the concentrated isotope diluents in Table 12 into equation 4, and finally calculating to obtain C Y And the value of 0.599 μ g/g is consistent with the value range (6.014 +/-0.048) μ g/g calculated by a concentrated isotope diluent certificate, so that the accuracy and the effectiveness of the method system are verified.
Table 12 table of concentration verification results of isotope-enriched diluent
Note: m is Y1 The actual amount of the isotope-enriched diluent is divided by 100, which is the mass of the isotope-diluent after 100-fold dilution.
(5) Determination of the amount of isotopically enriched diluent added to a sample
In order to further improve the sample testing accuracy, the amount of the isotope-enriched diluent added to the sample needs to be re-determined so as to reduce interference in subsequent detection.
Adding concentrated isotope diluent into selected sample, and mixing with specific isotope in solution 200 Hg and reference isotope 202 Abundance ratio of Hg R XY =0.5, and C determined Y Substituting into formula 7 to obtain 100 times diluted mercury concentrated isotope diluent with addition of 0.14g;
equation 7
In the formula,
R XY ，R X ，R Y ，C Y ，m X ，m Y the meaning of (1) is the same as that of (1);
the estimated concentration of mercury element in the sample is unit of mug/g; a is a X(202) ，a X(200) ，a Y(202) ，a Y(200) Representing specific isotopes in the sample (X) and the isotopically enriched diluent (Y) 200 Hg and reference isotope 202 Abundance value of Hg.
And 4, step 4: determination of mercury content in brown rice flour sample
(1) Preparation of Brown Rice flour sample solution
Sample solution to be tested: taking a brown rice powder sample, dividing into 6 parts and 0.5 g/part, placing the sample in a microwave digestion tank, adding 5-8mL trace metal level concentrated nitric acid, placing the sample in a microwave digestion system for digestion, taking out the sample after the digestion is finished, cooling the sample, heating the sample in an acid-dispelling sleeve at 80-120 ℃ for dispelling acid for 2h, transferring the cooled sample into a 25mL volumetric flask, and using ultrapure water to fix the volume to the scale;
mixing sample solutions: weighing 6 parts of brown rice powder samples (the adding amount is shown in table 13), respectively placing the samples in microwave digestion tanks, adding a concentrated isotope diluent (the adding amount is shown in table 13) diluted by 100 times into each microwave digestion tank filled with sample powder by a decrement method, adding 5-8mL of trace metal-grade concentrated nitric acid solution, carrying out pre-digestion at 100 ℃ for 20min, placing the cooled sample in a microwave digestion system for digestion, taking out the cooled sample, heating the sample at 80-120 ℃ in an acid sleeve to remove brown tobacco completely, transferring the sample into a 25mL volumetric flask, and fixing the volume of ultrapure water to the scale;
blank solution 1: preparing a solution which is blank-compared with the sample solution to be detected;
blank solution 2: preparing a solution which forms a blank control with the mixed sample solution;
(2) Measuring the mass-to-charge ratio of each isotope of the mercury element in the sample solution to be measured, the blank solution 1, the mixed sample solution and the blank solution 2 by adopting a high-resolution inductively coupled plasma mass spectrometer to obtain mercury element isotope response value data; after being corrected by a correction equation, the isotopic abundance ratio R is calculated X1 、R X2 、…、R X6 ，R XY1 、R XY2 、…、R XY6 And arithmetic mean
The results are shown in Table 13.
TABLE 13 isotope data statistical table of samples to be measured
| Serial number | R X | m X | m Y2 | R XY |
| 1 | 0.7497 | 0.5017 | 0.3023 | 0.5430 |
| 2 | 0.7603 | 0.5011 | 0.2821 | 0.5058 |
| 3 | 0.7751 | 0.5001 | 0.2393 | 0.5829 |
| 4 | 0.7470 | 0.5008 | 0.2476 | 0.5298 |
| 5 | 0.7641 | 0.5007 | 0.2845 | 0.5301 |
| 6 | 0.7566 | 0.5011 | 0.3236 | 0.4848 |
| Mean value of | 0.7588 | 0.5009 | 0.2799 | 0.5294 |
Note: r is X1 -R X6 Isotopic abundance ratio data for 6 sample solutions to be tested, R XY1 -R XY6 Isotopic abundance ratio data for 6 mixed sample solutions, m x Column number is 6 parts of brown rice powder sample addition amount, m Y2 The column is 6 parts of the amount of the concentrated isotope diluent which is diluted by 100 times, and the actual amount of the concentrated isotope-containing diluent is divided by 100.
(3) Calculation of the sample correction factor K
(4) Analytical calculations
(i) Calculation of mercury content in brown rice flour:
the values of the parameters of table 14 can be obtained from the results of table 13 and equation 1,
TABLE 14 determination of Mercury in Brown Rice flour samples (μ g/g)
| Serial number | Mercury content |
| 1 | 0.0223 |
| 2 | 0.0221 |
| 3 | 0.0223 |
| 4 | 0.0225 |
| 5 | 0.0226 |
| 6 | 0.0224 |
| Mean value of | 0.0224 |
| Standard deviation of | 0.0002 |
| Relative standard deviation (%) | 0.72 |
In the embodiment, the result of measuring the mercury component in the brown rice powder and the standard substance GBW (E) 100828 by the IDMS method is near the median value of the evaluation range of 0.022 +/-0.002 mu g/g, and the relative standard deviation is 0.72 percent, so that the method is proved to be accurate and reliable and has high precision.
Example 4
Step 1: preparation of Brown Rice flour sample
Selecting brown rice as a raw material, and carrying out impurity removal, drying, shelling, crushing and uniformly mixing to obtain a brown rice powder sample.
Step 2: determination of the isotope to be detected
Selecting 52 Cr as a reference isotope, selecting 53 Cr as a specific isotope.
And 3, step 3: calibration of isotope diluent solutions
(1) The following solutions were prepared
Natural abundance chromium standard solution: selecting a natural abundance chromium standard substance, and preparing 6 standard solutions of 0.010 mu g/g by using a 5% trace metal level nitric acid solution weighing method;
chromium enriched isotope diluent (1 μ g/g): selecting a high-purity chromium concentrated isotope standard substance, and preparing by using a 5% nitric acid solution to obtain 1 mu g/g (calculated by chromium);
mixing standard solutions: weighing 5g of natural abundance chromium standard substance (0.1 mug/g), weighing 0.6g of chromium concentrated isotope diluent added in 1 mug/g by a subtraction method, placing the mixture in a centrifuge tube, and balancing for more than 2min by using vortex mixing;
standard blank solution: a5% trace metal grade nitric acid solution was taken as a blank control solution.
(2) Measuring the mass-to-charge ratio and scanning mass number of chromium in the chromium standard solution, mixed standard solution and standard blank solution by using a high-resolution inductively coupled plasma mass spectrometer, correcting by a correction equation, and calculating to obtain the specific isotopeVegetable oil 53 Cr and a reference isotope 52 Ratio R of Cr Z1 、R Z2 、…、R Z6 ，R ZY1 、R ZY2 、…、R ZY6 And arithmetic mean
And &>
The results are shown in Table 15:
table 15 isotope diluent calibration data
Note: r Z1 -R Z6 Isotopic abundance ratio data for 6 chromium standard solutions, R ZY1 -R ZY6 Isotopic abundance ratio data for 6 mixed standard solutions.
(3) Calculation of calibration correction factor
Obtained in Table 15
Substituting into equation 3, calculate K 1 ：
(4) Concentration calculation of isotope diluents
The concentration of the isotope diluent is calculated by equation 4,
equation 4
In the formula,
C Y : the concentration of chromium element in the isotope diluent is unit of mug/g;
C Z : chromium element in standard solutionThe unit is μ g/g;
m z : the addition amount of the chromium standard substance in the standard solution is unit g;
m Y1 : mixing the addition amount of the chromium isotope diluent in the standard solution, wherein the unit g is;
mi: nuclear mass of isotope i;
R iZ : isotopes in standard solutions i Cr and reference isotope 52 The abundance ratio of Cr (calculated as the natural abundance ratio published by the International Union of pure and applied chemistry);
R iY : isotope in concentrated isotope diluent i Cr and reference isotope 52 The abundance ratio of Cr;
Rz Y : specific isotope of chromium in mixed standard solution of concentrated isotope diluent and chromium standard substance 53 Cr and a reference isotope 52 The abundance ratio of Cr;
R z : specific isotopes of chromium in standard solutions 53 Cr and a reference isotope 52 The abundance ratio of Cr;
R Y : specific isotopes of chromium in isotopic diluents 53 Cr and a reference isotope 52 The abundance ratio of Cr;
K 1 : calibrating a correction factor;
substituting the concentration verification result data of the isotope diluents in table 16 into formula 4, and finally calculating to obtain C Y And the density of the product is 1.03 mu g/g, which is consistent with the theoretical calculation value, and the accuracy and effectiveness of the method system are verified.
Table 16 data table of concentration verification results of isotope diluents
(5) Isotope diluent addition determination
To further improve the accuracy of the test, the isotope diluent addition needs to be re-determined in order to reduce interference in subsequent testing.
Selecting a sampleAdding concentrated isotope diluent and mixing with specific isotope in solution 53 Cr and a reference isotope 52 Abundance ratio R of Cr XY =1, and C determined Y Substituting into formula 8 to obtain 1 μ g/g diluted chromium concentrated isotope diluent with 1.17g addition;
equation 8
In the formula,
R XY ，R X ，R Y ，C Y ，m X ，m Y the meaning of (1) is the same as before;
the estimated concentration of the chromium element in the sample is unit of mu g/g; a is X(52) ，a X(53) ，a Y(52) ，a Y(53) Representing specific isotopes in the sample (X) and the isotopically enriched diluent (Y) 53 Cr and a reference isotope 52 Abundance value of Cr.
And 4, step 4: determination of chromium content in brown rice flour sample
(1) Preparation of Brown Rice flour sample solution
Sample solution to be tested: taking a brown rice powder sample, dividing into 6 parts and 0.5 g/part, placing the sample into a microwave digestion tank, adding 5-8mL trace metal level concentrated nitric acid, placing the sample into a microwave digestion system for digestion, taking out the sample after the digestion is finished, cooling the sample, driving the sample into an acid sleeve, heating the sample at 80-160 ℃ to drive brown smoke completely, transferring the sample into a 50mL volumetric flask, and using ultrapure water to fix the volume to a scale;
mixing sample solutions: weighing 6 parts of brown rice powder samples (the adding amount is shown in the table 17), respectively placing the samples in microwave digestion tanks, adding 1 mu g/g of concentrated isotope diluent (the adding amount is shown in the table 17) into each microwave digestion tank filled with sample powder by adopting a decrement method, adding 5-8mL of trace metal-grade concentrated nitric acid solution, carrying out pre-digestion at 100 ℃ for 20min, placing the cooled samples in a microwave digestion system for digestion, taking out the cooled samples after the digestion is finished, heating the samples in an acid dispelling sleeve at 80-160 ℃ to remove brown tobacco completely, transferring the samples into a 25mL volumetric flask, and fixing the volume of ultrapure water to the scale;
blank solution 1: preparing a solution which forms a blank control with the solution of the sample to be detected;
blank solution 2: preparing a solution which is blank compared with the mixed sample solution;
(2) Measuring the mass-to-charge ratio of each isotope of the element to be measured in the sample solution to be measured, the blank solution 1, the mixed sample solution and the blank solution 2 by adopting a high-resolution inductively coupled plasma mass spectrometer to obtain isotope response value data of the element to be measured; after being corrected by a correction equation, the isotopic abundance ratio R is calculated X1 、R X2 、…、R X6 ，R XY1 、R XY2 、…、R XY6 And arithmetic mean
The results are shown in Table 17.
TABLE 17 statistical table of isotope data of samples to be tested
| Serial number | R X | m X | m Y2 | R XY |
| 1 | 0.1189 | 0.5039 | 1.1439 | 1.0061 |
| 2 | 0.1201 | 0.5031 | 1.3274 | 1.1319 |
| 3 | 0.1206 | 0.5043 | 1.1121 | 0.9708 |
| 4 | 0.1223 | 0.5038 | 1.1338 | 0.9936 |
| 5 | 0.1193 | 0.5092 | 1.2138 | 1.0504 |
| 6 | 0.1178 | 0.5030 | 1.4218 | 1.2175 |
| Mean value of | 0.1198 | 0.5046 | 1.2255 | 1.0617 |
Note: r X1 -R X6 Isotopic abundance ratio data for 6 sample solutions to be tested, R XY1 -R XY6 Isotopic abundance ratio data for 6 mixed sample solutions, m x Column number is 6 parts of brown rice powder sample addition amount, m Y2 The column is the amount of 6 parts of 1. Mu.g/g isotope-enriched diluent added.
(3) Calculation of the sample correction factor K
(4) Analytical calculations
(i) Calculation of chromium content in brown rice flour:
the values of the parameters of table 18 can be obtained from the results of table 17 and equation 1,
TABLE 18 determination of chromium in Brown Rice flour samples (μ g/g)
In the embodiment, the result of measuring the chromium component in the brown rice powder by the IDMS method and analyzing the standard substance GBW (E) 100619 is near the median value of the assignment range of 3.12 +/-0.23 mu g/g, and the relative standard deviation is 0.68 percent, which proves that the method is accurate and reliable and has high precision.
It should be understood that the above-mentioned embodiments of the present invention are only examples for clearly illustrating the present invention, and are not intended to limit the embodiments of the present invention, and it will be obvious to those skilled in the art that other variations or modifications may be made on the basis of the above description, and all embodiments may not be exhaustive, and all obvious variations or modifications may be included within the scope of the present invention.
Claims (10)
1. A method for determining the content of heavy metal elements in grain and oil based on isotope dilution inductively coupled plasma mass spectrometry is characterized by comprising the following steps:
s1, preparing a plurality of parallel solutions:
sample solution to be tested: taking 0.2-0.5g of sample powder per part, adding 5-10mL of trace metal-grade concentrated nitric acid into the sample powder per part for microwave digestion treatment, and then quantitatively accommodating the digested sample in a 25-100mL volumetric flask by using ultrapure water;
mixing sample solutions: taking 0.2-0.5g of sample powder per part, adding a diluted concentrated isotope diluent standard substance of an element to be detected by adopting a subtraction method to ensure that the isotope abundance ratio of a specific isotope to a reference isotope in a mixed sample is 0.25-1.2, adding 5-10mL of trace metal level concentrated nitric acid for microwave digestion treatment, and then fixedly containing the digested mixed sample in a 25-100mL volumetric flask by using ultrapure water;
when the element to be detected is Cr, the reference isotope and the specific isotope thereof are selected from 53 Cr or 52 Cr, and are different;
when the element to be detected is Cd, the reference isotope and the specific isotope thereof are selected from 114 Cd、 113 Cd、 112 Cd、 111 Cd or 110 Cd, and are different;
when the element to be detected is Hg, the reference isotope and the specific isotope thereof are selected from 202 Hg、 201 Hg、 200 Hg or 199 Hg, and not the same;
when the element to be detected is Pb, the reference isotope and the specific isotope are selected from 208 Pb、 207 Pb or 206 Pb, and are not the same;
blank solution 1: preparing a solution which forms a blank control with the solution of the sample to be detected;
blank solution 2: preparing a solution which forms a blank control with the mixed sample solution;
s2, measuring the mass-to-charge ratio of each isotope of the element to be measured in the sample solution to be measured, the blank solution 1, the mixed sample solution and the blank solution 2 by adopting a high-resolution inductively coupled plasma mass spectrometer to obtain isotope response value data of the element to be measured; calculating the isotopic abundance ratio after correction by a correction equation;
s3, according to the isotope abundance ratio, calculating the content of the element to be detected in the sample powder by the following formula:
in the formula,
R Y : the abundance ratio of the specific isotope of the element to be detected in the isotope diluent to the reference isotope;
R XY : mixing the abundance ratio of the specific isotope of the element to be detected in the sample solution to the reference isotope;
C Z : the concentration of the element to be detected in the standard solution is unit of mu g/g;
m X : the mass of sample powder in the sample solution to be tested, unit g;
m Y2 : mass of isotope diluent in the mixed sample solution, unit g;
C X : the content of the element to be detected in the sample powder is unit microgram/g;
k: a sample correction factor;
K 1 : and calibrating the correction factor.
2. The method according to claim 1, wherein in step S2, different correction equations are substituted for correction according to the difference in mass-to-charge ratio of the element to be measured:
when the metal to be detected is Cd,
when the measured mass-to-charge ratio is 110, the calibration equation is [110Cd ] = [110] -0.5249[105];
when the measured mass-to-charge ratio is 112, the calibration equation is [112Cd ] = [112] -0.0400[118];
when the measured mass-to-charge ratio is 113, the calibration equation is [113Cd ] = [113] -0.0448[115];
when the measured mass-to-charge ratio is 114, the calibration equation is [114Cd ] = [114] -0.0273 ];
when the metal to be measured is Pb,
when the measured mass-to-charge ratio is 208, the calibration equation is [208Pb ] = [206] + [207] + [208];
when the element to be detected is Cr or Hg, no correction is needed.
3. The method of claim 1, wherein when the element to be measured is Cr, selecting 53 Cr as a reference isotope, selecting 52 Cr as a specific isotope, said R XY In the range of 0.8-1.2.
4. The method of claim 1When the element to be measured is Cd, selecting 111 Cd as a reference isotope, selection 110 Cd as a specific isotope, said R XY In the range of 0.5-0.8;
or,
selecting 111 Cd as a reference isotope, selection 112 Cd as a specific isotope, said R XY In the range of 0.8-1.2.
5. The method according to claim 1, wherein when the element to be tested is Hg, it is selected 202 Hg is selected as a reference isotope 201 Hg as the specific isotope, the R XY In the range of 0.25-0.4;
or,
selecting 202 Hg is selected as a reference isotope 200 Hg as a specific isotope, said R XY In the range of 0.3 to 0.6.
6. The method according to claim 1, wherein when the element to be measured is Pb, selecting 207 Pb as reference isotope, selection 208 Pb as the specific isotope, said R XY In the range of 0.8-1.2.
7. The method of claim 1, wherein the sample correction factor K is calculated by:
in the formula,
k: a sample correction factor;
K 1 : and calibrating the correction factor.
8. The method of claim 7, wherein the calibration correction factor K 1 Obtained by the following calculation:
in the formula,
K 1 : calibrating a correction factor;
R IUPAC the abundance ratio of the specific isotope of the element to be detected to the reference isotope published by the international union of pure and applied chemistry;
9. The method according to claim 1, wherein the standard solution is prepared by weighing a standard substance by using a 5% trace metal-grade nitric acid solution; the mixed standard solution is prepared by mixing a standard substance and a concentrated isotope diluent and then diluting the mixture into a solution;
preferably, the standard solution, the mixed standard solution, the sample solution to be detected and the parallel solution of the mixed sample solution are prepared in not less than 6 parts.
10. The method of claim 1, wherein the measurement conditions of the high-resolution inductively coupled plasma mass spectrometer are: the radio frequency power is 1550W, the plasma gas flow is 15L/min, the carrier gas flow is 0.8-1.2L/min, the auxiliary gas flow is 0-0.5L/min, the helium gas flow is 4-6mL/min, the atomizer type is a concentric atomizer, the sampling cone/skimmer cone is a nickel cone, the temperature of the atomizing chamber is 2 ℃, and the repetition frequency is 10-100.
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