Method for measuring various elements in atmospheric particulates by taking actual sample as standard sample
阅读说明：本技术 基于实际样品为标样测定大气颗粒物中多种元素的方法 (Method for measuring various elements in atmospheric particulates by taking actual sample as standard sample ) 是由 王烨 曹珊 朱津蕊 于 2020-11-18 设计创作，主要内容包括：本发明属于能量色散X射线荧光分析技术领域,公开了一种基于实际样品为标样测定大气颗粒物中多种元素的方法,选择实际样品做标样材料；选择实际样品做标样时,根据曲线的梯度,选择标样；建立的条件的选择；干扰校正；实验室内部方法验证实验结果,检出限,准确度,精密度；实际样品分析。本发明利用实际样品代替价格昂贵的单元素微孔滤膜标准样品为基础,建立能量色散X射线荧光分析测定大气颗粒物PM-(2.5)中35元素的方法,解决了建立能量色散X射线荧光分析测定大气颗粒物方法。本发明利用实际样品代替价格昂贵的单元素微孔滤膜标准样品,然后建立测试方法,解决了单元素微孔滤膜标准样品的问题。(The invention belongs to the technical field of energy dispersion X-ray fluorescence analysis, and discloses a method for measuring various elements in atmospheric particulates by taking an actual sample as a standard sample, wherein the actual sample is selected as a standard sample material; selecting a standard sample according to the gradient of the curve when selecting the actual sample as the standard sample; selection of established conditions; correcting interference; the laboratory internal method verifies the experimental result, detection limit, accuracy and precision; and (4) analyzing an actual sample. The invention utilizes the actual sample to replace the expensive single element microporous filter membrane standard sample as the basis to establish the energy dispersion X-ray fluorescence analysis for measuring the PM of the atmospheric particulate matters 2.5 The method of medium 35 elements solves the problem of establishing a method for measuring atmospheric particulates by energy dispersion X-ray fluorescence analysis. The invention replaces the expensive standard sample of the single-element microporous filter membrane with the actual sample, and then establishes the testing method, thereby solving the problem of the standard sample of the single-element microporous filter membrane.)
1. A method for measuring multiple elements in atmospheric particulates by taking an actual sample as a standard sample is characterized by comprising the following steps of:
correcting the matrix effect of the prepared sample by adopting an empirical coefficient and a scattered ray internal standard method, and solving the intercept, the slope, the matrix effect and the spectral line overlapping interference factor of the calibration curve by using a comprehensive mathematical correction formula and multiple regression;
the corrected sample components and detection limits for the content were tested using repeated assays.
2. The method for measuring multiple elements in atmospheric particulates based on actual samples as standard samples as claimed in claim 1, wherein a standard curve for the XRF measurement method of inorganic elements in atmospheric particulates is established, and the actual samples with different contents form a standard series, and the uncertainty of a nominal value is 5%; the standard series was constructed with 11-12 different amounts of standards and a blank film.
3. The method for measuring various elements in atmospheric particulates based on actual samples as standard samples according to claim 2, wherein the spectrum is resolved by fitting with a nonlinear least square method under the method of using energy dispersive X-ray fluorescence, fitting and analyzing adjacent overlapped spectral peaks by using a spectrogram fitting method, and deducting the influence of interference peaks to obtain the peak intensity of a target element characteristic spectrum;
establishing a standard curve for an XRF (X-ray fluorescence) method for measuring inorganic elements in atmospheric particulates, and forming a standard series by using actual samples with different contents; a series of calibration samples with appropriate gradients was prepared as a calibration curve for each element content.
4. The method for measuring various elements in atmospheric particulates based on actual samples as standard samples according to claim 1, wherein the preparation method of the samples comprises the following steps:
the filter membranes before and after sampling are respectively weighed for 2 times, the filter membranes are placed in a thermostat with the temperature of 20-23 ℃ and the RH & lt 35-45% for more than 24 hours to constant weight before each weighing, then the filter membranes are weighed, stored in a polystyrene petri dish, sealed by a polyethylene sealing bag and refrigerated at 4 ℃.
5. The method for determining multiple elements in atmospheric particulates based on actual samples as standard samples according to claim 1, wherein the multiple regression method comprises:
in the formula: c is concentration or count rate; miIs the strength of the sample to be tested; n is an element to be analyzed; α, β, γ, δ are factors for matrix correction; i is the element to be tested: j, k are interference elements.
6. The method for determining multiple elements in atmospheric particulates based on actual samples as standard sample as claimed in claim 1, wherein the repeated determination comprises:
selecting an actual sample with the content of 2-20 times of detection limit for repeated measurement:
or
In the formula wiIs a low content of the standard sample, IBStrength for low content of standard sample, I0The standard deviation of the strength of the blank sample and the low-content actual sample is measured repeatedly for 7 times; if the content-to-intensity ratio obtained from the low content standard sample is not determined, the slope a of the calibration curve is takenAnd (4) generation.
7. The method for measuring multiple elements in atmospheric particulates based on actual samples as standard samples according to claim 1, wherein the detection limit is calculated according to the following formula:
in the formula: m is the counting rate of the unit content of the element; i isbBackground count rate, cps; t isbTime, s, was measured for background.
8. The method for measuring multiple elements in atmospheric particulates based on actual samples as standard sample according to claim 1, wherein the repeated measurement method for measuring the corrected sample components and content detection limit comprises:
6 PM2.5 samples collected on the Teflon filter membrane and a blank filter membrane adopt a large-cycle determination mode, and the measurement is repeated for 7 times; calculating the standard deviation of 3 times of the test results of different samples, and selecting a numerical value with the element content ratio of 2-20; and if the numerical value of 2-20 is not reached, selecting blank filter membrane data to calculate the result. If the multiple sets of data simultaneously satisfy 2-20, taking an average value or a median value; and detecting limit calculation data according to a method obtained by calculating the measurement data.
9. The method for measuring various elements in atmospheric particulates based on actual samples as standard samples as claimed in claim 1, wherein after the calibrated components and content detection limits of the samples are tested by repeated measurement, further precision analysis is performed, the main components and content of the measurement results of the same filter membrane are determined by approximate quantitative software, chemical analysis and rock and mineral identification analysis, and the PM of the environmental air particulates with different loads on the Teflon filter membrane is determined by taking 3 PM with different loads on the Teflon filter membrane2.5Measuring the sample, wherein the allowable content range of the matrix and the interference element is determined;
3 sample wafers are prepared in parallel for analyzing the standard sample, and original measurement data of precision is obtained.
10. An energy dispersion X-ray fluorescence spectrometer for implementing the method for measuring multiple elements in atmospheric particulates based on an actual sample as claimed in any one of claims 1-8.
Technical Field
The invention belongs to the technical field of energy dispersion X-ray fluorescence analysis, and particularly relates to a method for measuring various elements in atmospheric particulates by taking an actual sample as a standard sample.
Background
Particulate pollution is one of the most important pollutants in the air, the first pollutant in the air being particulate in most areas. The particulate matter is derived from man-made sources and natural sources. The man-made source is mainly discharged by man-made activities such as coal burning, fuel oil and industrial production process. The natural source is mainly formed by conveying soil, flying dust and sand dust into the air under the action of wind power. The source identification and quantitative analysis of the atmospheric particulates are important prerequisites for formulating various policies for treating atmospheric particulate pollution. The main chemical components in the atmospheric particulates include inorganic elements, water-soluble ions, organic carbon, elemental carbon and the like. Test data for inorganic elements in ambient air particulates are focused for source resolution.
The annual average primary and secondary concentration limits for lead concentration are both 0.50. mu.g/m3The quaternary mean primary and secondary concentration limits were all 1.00. mu.g/m3And the concentration limit values of the total suspended particulate matters, nitrogen oxides, benzopyrene and other environmental air pollutants are also included. In appendix A of the standard, mercury (0.05. mu.g/m) is added3) Arsenic (6.0 ng/m)3) Cadmium (5.0 ng/m)3) Hexavalent chromium (0.025 ng/m)3) And the reference concentration limits of the metal elements and the fluoride.
The standard for controlling pollution caused by burning domestic garbage (GB 18485-. Pb, Hg, Cd, Cr and metalloid As (5 kinds) are taken As main heavy metal pollutants, and Ni, Cu, Zn, Ag, V, Mn, Co, Tl, Sb and other (9 kinds) heavy metal pollutants are taken into consideration.
TABLE 1 analysis of exhaust gas from incineration facility
TABLE 2 method for determining concentration of atmospheric pollutants in incinerator
As can be seen from tables 1 and 2, the methods cited in the current standards are flame atomic absorption, graphite furnace atomic absorption, ICP-MS, and ICP-OES methods.
The analysis technologies such as plasma mass spectrometry (ICP-MS), plasma atomic emission spectrometry (ICP-OES), graphite furnace and flame Atomic Absorption Spectrometry (AAS) need to carry out pretreatment-digestion on a sample, and the digestion methods are divided into microwave digestion and electric heating plate digestion. The microwave digestion is to cut the sample into proper size, add proper amount of mixed solution of hydrochloric acid and nitric acid to soak the sample, digest the sample for 15min at 200 ℃, then leach, filter, fix the volume to be measured. The electric heating plate digestion is to cut the sample into proper size, add proper amount of mixed solution of hydrochloric acid and nitric acid to soak the sample, reflux for 2.0h at 100 ℃, leach after cooling, filter and fix the volume to be measured. The two sample pretreatment methods need to add a large amount of mixed acid and heat, so that the environment is polluted, and the sample treatment time is long. ICP-MS can be used for simultaneously analyzing multiple elements, has the advantages of high sensitivity, low detection limit and the like, can be used for simultaneously measuring most elements in an element periodic table, including trace and trace elements, but has the defects of expensive instruments, high requirements on the site environment of a laboratory and high maintenance and use cost, high requirements on the working experience of analysis and test personnel, high technical difficulty and detection capability in only a few laboratories.
AAS is a traditional method for measuring metal elements in atmospheric particulates, the popularization rate of instruments is very wide, most laboratories have relatively mature analysts, but the linear range of a working curve is narrow, single-element measurement is needed, multiple elements cannot be measured simultaneously, and the test time is repeated and tedious. The ICP-OES analysis method has the advantages of wide analysis linear range, high measurement precision, high analysis speed and low interference level, and can simultaneously carry out primary, secondary and trace element analysis on one solution. But requires pre-treatment of the sample. The sensitivity and detection limit of the instrument are not as good as those of ICP-MS. Elements such As Se, Hg, Be, As, Pb, Tl, U and the like cannot meet the requirements of corresponding concentration limit values, and the elements are combined with graphite furnace atomic absorption (GF-AAS) and mercury cold atomic absorption (CV-AAS) technologies to meet the analysis requirements of most elements.
The energy dispersion X-ray fluorescence analysis method belongs to a non-destructive analysis means, has the characteristics of high analysis speed, relatively simple sample processing, no need of sample pretreatment, high analysis precision, safety, environmental protection, simultaneous detection of various elements and the like, and is widely applied to various industries such as steel, mineral products, cement, environment and the like. In the environmental industry, the method is mainly used for measuring inorganic elements in environmental air particles and mainly analyzed by using the method HJ 829-2017. And (4) analyzing the particle element component spectrum, wherein an XRF (X-ray fluorescence) analysis technology is preferred.
However, in routine experimental operation, the energy dispersive X-ray fluorescence analysis method is dependent on a standard sample, and a laboratory is usually based on an inorganic single-element microporous filter membrane standard sample loaded on a Mylar film or a polycarbonate nuclear pore membrane (the content is measured by mu g/cm)2Representing) the method for measuring inorganic elements in the environmental air particles by using the energy dispersion X-ray fluorescence spectrometry is established, the filter membrane of the standard sample which is firstly required by the method and is sold in the market at present is very expensive, each standard sample of the single-element microporous filter membrane needs ten thousand yuan, and a set of curve standard sample needs tens of thousands yuan. Secondly, the standard sample is made of an inorganic single element microporous filter membrane loaded on a Mylar film or a polycarbonate nuclear pore membrane, a Teflon filter membrane is usually selected as a particulate matter collecting filter membrane, the difference of the substrate exists, and the particulate matter loading amount in the ambient air collected on the Teflon filter membrane is not more than 100 mu g/cm in principle2The particulate material is uniformly distributed in a diameter range of at least 30 mm. The background value of the sample can be increased by particles with excessive load, if the load is increased to a certain degree, the sample becomes a thick sample, the data processing mode needs to be changed, and otherwise, the measurement result is low. The resulting sample matrix effects can affect the accuracy of the quantitative analysis results. Because there is a large difference between the actual particulate matter sample and the film standard matrix.
Finally, the standard sample is a single element sample, which is not in accordance with the large environment, and the standard sample of the atmospheric particulates in the current foreign market is extremely limited, and only the standard sample in the table 3 can be referred to. As shown in Table 3
Comparing the only atmospheric particulate standard sample in the current foreign market in table 3 with the inorganic single element microporous filter membrane standard sample loaded on the Mylar film or polycarbonate nuclear pore membrane by the company micromitter in the united states and the actual sample value, it can be found that the content of Al, Ca, Fe, K, Mg, Na, Ti, Zn is higher, and is closer to the actual sample value for detection and can be used As a reference, but the standard sample value is far smaller than the detection limit of an instrument and is far from the actual sample. Therefore, the only atmospheric particulate standard sample in the current foreign market and the inorganic single element microporous filter membrane standard sample loaded on the Mylar film or the polycarbonate nuclear pore membrane by the American Micromatter company do not have much reference value actually, and the requirement of the element content measuring range in the actual sample is difficult to meet.
Through the above analysis, the problems and defects of the prior art are as follows:
(1) methods cited in the current standards are flame atomic absorption, graphite furnace atomic absorption, ICP-MS, and ICP-OES methods. Most instruments are expensive, the requirements on the site environment of a laboratory and the maintenance and use cost are high, the requirements on the working experience of analysis and test personnel are high, the technical difficulty is high, and only a few laboratories have the detection capability. The linear range of the working curve of the detection method of some instruments is narrow, single element measurement is needed, multiple elements cannot be measured simultaneously, and the test time is repeated and fussy. The above methods require pretreatment of the sample, require the use of a large amount of strong acid, and pollute the environment.
(2) An energy dispersive X-ray fluorescence analysis method is used. Firstly, the standard sample is dependent, the filter membrane price of the standard sample which is firstly needed by the method and is sold on the market at present is very expensive, each standard sample of the single-element microporous filter membrane needs ten thousand yuan, one set of curve standard sample needs more than ten thousand yuan, the standard sample is made of the inorganic single-element microporous filter membrane loaded on the Mylar film or the polycarbonate nuclear pore membrane, the Teflon filter membrane is usually selected as the particulate matter collecting filter membrane by us, the difference of the substrates exists, and the only atmospheric particulate matter standard sample in the current foreign market and the inorganic single-element microporous filter membrane standard sample loaded on the Mylar film or the polycarbonate nuclear pore membrane by American Micromatter company are difficult to meet the requirement of the measuring range of the element content in the actual sample.
The difficulty in solving the above problems and defects is:
(1) there is an expert proposal that it is possible to consider preparing a standard sample from an actual particulate matter sample, and using ICP-OES and ICP-MS measurements or collaborative evaluation of the same sample in multiple laboratories as standard values. The method needs multiple laboratories to participate simultaneously in real time, has high experimental requirements, and is detected by ICP-OES and ICP-MS methods, and the sample is dissolved after pretreatment, so that repeated measurement cannot be carried out.
(2) The feasibility is limited by the amount of the collected sample, and no commercial product is sold in the market. The particulate matter loading in the ambient air collected on a Teflon filter membrane should not exceed 100 mu g/cm in principle2The particulate material is uniformly distributed in a diameter range of at least 30 mm. Too much particulate matter of load can make the sample background value increase, if the load increases to a certain extent, will become thick sample, and the data processing mode needs to change, otherwise, the measuring result can be on the low side, because technical limitation, can't produce the stable controllable of content, and the element that contains is unified to the same filter membrane of big batch content, so still blank at home, can't see the possibility that has filter membrane particulate matter standard sample to market in the short time.
(3) The current standard sample filter membranes on the market are expensive, and the unit lacking the standard filter membrane can establish a standard curve according to the existing conditions under the limitation of laboratory conditions. However, due to the better stability of the XRF instrument, the calibration curve can be used for a long time. The method is a current stage method, and because the whole set of standard film is high in price and easy to damage due to improper use, a certain pressure is applied to custodian by the whole set of standard film of the instrument company or the scientific research unit, and the method is not easy to realize. The whole set of standard film samples of the rental instrument company or the scientific research unit also has the risks of storage and use and is also spent about two ten thousand yuan.
The significance of solving the problems and the defects is as follows: in order to use the energy dispersive X-ray fluorescence analysis method, it becomes possible to replace the methods cited in the current standards, flame atomic absorption, graphite furnace atomic absorption, ICP-MS method, and ICP-OES method. The practical sample is used for replacing a whole set of standard film, so that the problem that the filter membrane of the standard sample sold in the market by the energy dispersion X-ray fluorescence analysis method is expensive is solved. The actual sample is simple and easy to obtain, the content can be known, the problems that the existing standard value is far smaller than the detection limit of an instrument, the difference with the actual sample is larger, too much reference value is not provided, and the requirement of the element content measurement range in the actual sample is difficult to meet are solved, and the concentration range of the actual sample can be selected as required.
Disclosure of Invention
Aiming at the problems in the prior art, the invention provides a method for measuring various elements in atmospheric particulates by taking an actual sample as a standard sample.
In the test operation of the existing method, the energy dispersion X-ray fluorescence analysis method has dependency on a standard sample, a laboratory generally establishes a method for measuring inorganic elements in ambient air particles by using an energy dispersion X-ray fluorescence spectrometry method based on an inorganic single-element microporous filter membrane standard sample loaded on a Mylar film or a polycarbonate nuclear pore film, wherein the content is expressed by mu g/cm 2. Secondly, the standard sample is made of an inorganic single element microporous filter membrane loaded on a Mylar film or a polycarbonate nuclear pore membrane, a Teflon filter membrane is usually selected as a particulate matter collecting filter membrane, the difference of the substrates exists, the loading amount of the particulate matter collected in the ambient air on the Teflon filter membrane is not more than 100 mu g/cm2 in principle, and the loaded particulate matter is required to be uniformly distributed with the diameter within the range of at least 30 mm. The background value of the sample can be increased by particles with excessive load, if the load is increased to a certain degree, the sample becomes a thick sample, the data processing mode needs to be changed, and otherwise, the measurement result is low. The resulting sample matrix effects can affect the accuracy of the quantitative analysis results. Because there is a large difference between the actual particulate matter sample and the film standard matrix.
The invention provides a method for measuring various elements in atmospheric particulates by taking an actual sample as a standard sample, which selects the actual sample as a standard sample material; selecting a standard sample according to the gradient of the curve when selecting the actual sample as the standard sample; selection of established conditions; correcting interference; the laboratory internal method verifies the experimental result, detection limit, accuracy and precision; and (4) analyzing an actual sample. The invention utilizes the actual sample to replace the expensive single element microporous filter membrane standard sample as the basis, establishes the method for measuring 35 elements in the atmospheric particulate matter PM2.5 by energy dispersion X-ray fluorescence analysis, and solves the problem of establishing the method for measuring the atmospheric particulate matter by energy dispersion X-ray fluorescence analysis.
The invention is realized in such a way that a method for measuring various elements in atmospheric particulates by taking an actual sample as a standard sample comprises the following steps:
establishing a standard curve for an XRF (X-ray fluorescence) method for measuring inorganic elements in atmospheric particulates, and forming a standard series by using actual samples with different contents; preparing a calibration curve of each element content by a calibration sample series with proper gradient;
the method uses energy dispersion X-ray fluorescence, uses a spectrogram fitting method to perform fitting analysis on adjacent overlapping spectral peaks, deducts the influence of interference peaks, and performs spectrum solution by using nonlinear least square fitting under the method of obtaining the peak intensity of the target element characteristic spectral peak.
The invention adopts an empirical coefficient and a scattered ray internal standard method to correct the matrix effect of a prepared sample, and uses a comprehensive mathematical correction formula and multiple regression to calculate the intercept, the slope, the matrix effect and the spectral line overlapping interference factor of the calibration curve;
the corrected sample components and detection limits for the content were tested using repeated assays.
Further, establishing a standard curve for the XRF determination method of inorganic elements in the atmospheric particulates, and forming a standard series by using actual samples with different contents, wherein the uncertainty of a nominal value is 5%; the standard series was constructed with 11-12 different amounts of standards and a blank film.
Further, the preparation method of the sample comprises the following steps:
the filter membranes before and after sampling are respectively weighed for 2 times, the filter membranes are placed in a thermostat with the temperature of 20-23 ℃ and the RH & lt 35-45% for more than 24 hours to constant weight before each weighing, then the filter membranes are weighed, stored in a polystyrene petri dish, sealed by a polyethylene sealing bag and refrigerated at 4 ℃.
Further, the multiple regression method comprises:
in the formula: c is concentration or count rate; miIs the strength of the sample to be tested; n is an element to be analyzed; α, β, γ, δ are factors for matrix correction; i is the element to be tested: j, k are interference elements.
Further, the replicate assay comprises:
selecting an actual sample with the content of 2-20 times of detection limit for repeated measurement:
or
In the formula wiIs a low content of the standard sample, IBStrength for low content of standard sample, I0Blank sample strength, sd 7 times weightRepeatedly measuring the standard deviation of the strength of the blank sample and the low-content actual sample; if the content to intensity ratio obtained for the low content standard is not determined, the slope a of the calibration curve is replaced.
Further, the detection limit is calculated according to the following formula:
in the formula: m is the counting rate of the unit content of the element; i isbBackground count rate, cps; t isbTime, s, was measured for background.
Further, the method for testing the corrected sample components and content detection limits by using the repeated determination method comprises the following steps:
6 PM2.5 samples collected on the Teflon filter membrane and a blank filter membrane adopt a large-cycle determination mode, and the measurement is repeated for 7 times; calculating the standard deviation of 3 times of the test results of different samples, and selecting a numerical value with the element content ratio of 2-20; and if the numerical value of 2-20 is not reached, selecting blank filter membrane data to calculate the result. If the multiple sets of data simultaneously satisfy 2-20, taking an average value or a median value; and detecting limit calculation data according to a method obtained by calculating the measurement data.
Further, after the calibrated sample components and content detection limits are tested by repeated determination methods, precision analysis is further performed, which comprises:
the method provided by the embodiment of the invention has the following precision:
determining the main components and the content of the measurement result of the same filter membrane by using approximate quantitative software, a chemical analysis method and rock and ore identification analysis, and determining that 3 environmental air particulate matters PM with different loads on the Teflon filter membrane are taken2.5Measuring the sample, wherein the allowable content range of the matrix and the interference element is determined;
3 sample wafers are prepared in parallel for analyzing the standard sample, and original measurement data of precision is obtained.
The invention also aims to provide an energy dispersion X-ray fluorescence spectrometer for implementing the method for determining multiple elements in atmospheric particulate matters by taking actual samples as standard samples.
The invention also aims to provide an application of the method in measuring the content of 35 elements in atmospheric particulates by replacing a complete set of standard films with actual samples.
By combining all the technical schemes, the invention has the advantages and positive effects that:
(1) the invention solves the problem that the filter membrane of the standard sample sold in the market by the energy dispersion X-ray fluorescence analysis method is expensive. The actual sample is simple and easy to obtain, the content is known, the requirement of the element content measuring range in the actual sample is met, and the concentration range of the actual sample can be selected according to the requirement. The method integrally solves the problem of standard sample when the energy dispersion X-ray fluorescence is used for analyzing the film sample, so that the method can be better developed and used.
(2) The experimental data of the invention show that the deviation of the measured values of the sample is respectively tested by an inductively coupled plasma mass spectrometry (ICP-MS) plasma atomic emission spectrometry (ICP-AES) and a self-made energy dispersion X-ray fluorescence analysis method, and the result of the method is reliable within the error range required by the national standard.
Drawings
In order to more clearly illustrate the technical solutions of the embodiments of the present application, the drawings needed to be used in the embodiments of the present application will be briefly described below, and it is obvious that the drawings described below are only some embodiments of the present application, and it is obvious for those skilled in the art that other drawings can be obtained from the drawings without creative efforts.
Fig. 1 is a flowchart of a method for determining multiple elements in atmospheric particulates based on an actual sample as a standard sample according to an embodiment of the present invention.
Fig. 2 is a schematic diagram of an actual sample provided by an embodiment of the present invention.
Detailed Description
In order to make the objects, technical solutions and advantages of the present invention more apparent, the present invention is further described in detail with reference to the following embodiments. It should be understood that the specific embodiments described herein are merely illustrative of the invention and are not intended to limit the invention.
Aiming at the problems in the prior art, the invention provides a method for measuring various elements in atmospheric particulates by taking an actual sample as a standard sample, and the invention is described in detail below with reference to the accompanying drawings.
As shown in fig. 1, the method for determining multiple elements in atmospheric particulates based on actual samples as standard samples provided by the embodiment of the present invention includes:
s101, establishing a standard curve for an XRF (X-ray fluorescence) method for measuring inorganic elements in atmospheric particulates, and forming a standard series by using actual samples with different contents; a series of calibration samples with appropriate gradients was prepared as a calibration curve for each element content.
And S102, correcting the matrix effect of the prepared sample by adopting an empirical coefficient and a scattered ray internal standard method, and solving the intercept, the slope, the matrix effect and the spectral line overlapping interference factor of the calibration curve by using a comprehensive mathematical correction formula and multiple regression.
And S103, testing the corrected sample components and content detection limit by adopting a repeated measuring method.
The present invention will be further described with reference to examples and experiments.
1. Configuring an energy dispersion X-ray fluorescence spectrometer;
the Epsilon5 spectrometer uses a three-dimensional geometry optical path to ensure that a high degree of polarization is implemented; the device can work under the conditions of 100kV high voltage and 600W power, and uses Sc/W target materials; for selective excitation of the Na-U elements in the periodic table, 15 secondary targets were configured using a high-purity Ge detector.
2. Establishment of a standard curve:
a standard curve for the XRF determination method of inorganic elements in the atmospheric particulates is established, actual samples with different contents form a standard series, and the uncertainty of a nominal value is 5%. The standard series was constructed with 11-12 different amounts of standards and a blank film.
(1) Selecting an actual sample as a standard sample material; as shown in fig. 2(a) and 2 (b)).
TABLE 4 actual sample values (unit:. mu.g/cm)2)
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
Na
0.084
0.361
0.221
0.215
0.458
0.348
0.374
0.539
0.457
0.487
0.466
0.517
0.483
0.412
0.386
Mg
0.057
0.086
0.205
0.133
0.169
0.095
0.086
0.147
0.205
0.000
0.250
0.175
0.219
0.073
0.086
Al
0.129
0.459
0.228
0.283
0.320
0.342
0.470
0.589
0.396
0.277
0.413
0.347
0.325
0.358
0.482
Si
0.136
0.858
0.528
0.346
0.523
0.691
0.877
0.548
0.561
0.635
0.589
0.670
0.918
0.459
0.486
P
0.000
0.026
0.039
0.000
0.011
0.055
0.050
0.032
0.047
0.028
0.148
0.094
0.000
0.000
0.104
S
0.000
1.072
1.551
3.037
3.218
1.857
1.344
9.370
9.575
6.834
4.786
3.970
4.725
4.925
8.026
Cl
0.003
0.247
0.067
0.086
1.100
0.168
0.190
1.683
3.343
2.804
1.507
2.796
2.284
2.282
2.424
K
0.006
0.799
0.457
0.622
1.369
0.773
1.085
1.552
2.739
2.195
1.690
1.941
1.328
0.997
1.456
Ca
0.049
0.574
0.283
0.226
0.392
0.549
0.606
0.226
0.478
0.569
0.529
0.524
0.687
0.263
0.380
Ti
0.002
0.023
0.016
0.005
0.017
0.023
0.027
0.029
0.034
0.039
0.024
0.023
0.024
0.025
0.024
V
0.000
0.002
0.000
0.001
0.002
0.000
0.001
0.001
0.002
0.000
0.003
0.002
0.001
0.000
0.001
Cr
0.002
0.004
0.004
0.005
0.008
0.005
0.003
0.009
0.008
0.006
0.008
0.005
0.006
0.008
0.008
Mn
0.012
0.023
0.029
0.017
0.038
0.037
0.038
0.053
0.064
0.064
0.049
0.046
0.058
0.047
0.039
Fe
0.037
0.317
0.261
0.212
0.383
0.388
0.482
0.493
0.578
0.602
0.526
0.404
0.533
0.521
0.441
Co
0.001
0.001
0.000
0.001
0.002
0.002
0.003
0.002
0.002
0.003
0.003
0.001
0.002
0.001
0.000
Ni
0.002
0.002
0.001
0.002
0.003
0.001
0.004
0.002
0.002
0.003
0.002
0.002
0.004
0.003
0.003
Cu
0.006
0.011
0.010
0.012
0.022
0.011
0.012
0.030
0.027
0.023
0.021
0.016
0.016
0.022
0.023
Zn
0.004
0.083
0.063
0.070
0.166
0.137
0.095
0.196
0.258
0.226
0.173
0.139
0.147
0.169
0.197
Ga
0.000
0.000
0.000
0.000
0.000
0.000
0.000
0.000
0.000
0.000
0.000
0.000
0.000
0.002
0.000
As
0.000
0.002
0.003
0.009
0.015
0.005
0.001
0.027
0.014
0.012
0.008
0.008
0.008
0.013
0.012
Se
0.000
0.000
0.000
0.004
0.001
0.000
0.000
0.009
0.000
0.000
0.003
0.000
0.000
0.004
0.009
Br
0.000
0.098
0.000
0.004
0.026
0.005
0.008
0.036
0.038
0.026
0.021
0.016
0.011
0.023
0.015
Rb
0.000
0.000
0.000
0.000
0.002
0.000
0.001
0.002
0.004
0.005
0.002
0.000
0.006
0.003
0.000
Sr
0.016
0.014
0.022
0.014
0.027
0.020
0.010
0.005
0.026
0.023
0.027
0.015
0.018
0.035
0.018
Y
0.027
0.008
0.008
0.005
0.018
0.001
0.011
0.020
0.004
0.000
0.003
0.008
0.036
0.002
0.003
Mo
0.008
0.005
0.008
0.009
0.006
0.005
0.005
0.009
0.004
0.007
0.007
0.010
0.011
0.011
0.009
Pd
0.002
0.012
0.012
0.009
0.014
0.002
0.006
0.006
0.007
0.000
0.004
0.007
0.000
0.002
0.013
Ag
0.008
0.006
0.008
0.006
0.005
0.006
0.008
0.010
0.003
0.004
0.005
0.004
0.004
0.006
0.003
Cd
0.007
0.007
0.006
0.005
0.005
0.009
0.010
0.005
0.012
0.011
0.015
0.010
0.010
0.008
0.009
Sn
0.025
0.029
0.020
0.028
0.027
0.032
0.037
0.043
0.030
0.039
0.040
0.034
0.055
0.034
0.022
Sb
0.013
0.085
0.047
0.014
0.013
0.023
0.023
0.047
0.027
0.031
0.020
0.033
0.032
0.018
0.023
Cs
0.034
0.035
0.046
0.058
0.031
0.054
0.051
0.061
0.043
0.066
0.040
0.041
0.061
0.028
0.050
Ba
0.046
0.035
0.088
0.056
0.105
0.069
0.031
0.087
0.046
0.078
0.080
0.051
0.061
0.065
0.050
La
0.204
0.209
0.212
0.233
0.225
0.254
0.213
0.215
0.249
0.255
0.218
0.216
0.197
0.176
0.211
W
0.749
0.747
0.758
0.736
0.716
0.729
0.780
0.735
0.743
0.758
0.728
0.739
0.763
0.728
0.744
Au
0.086
0.062
0.056
0.074
0.053
0.057
0.054
0.053
0.047
0.044
0.052
0.048
0.045
0.063
0.051
Hg
0.032
0.060
0.029
0.045
0.023
0.045
0.029
0.036
0.027
0.041
0.027
0.044
0.036
0.025
0.041
Pb
0.034
0.039
0.045
0.075
0.169
0.061
0.058
0.225
0.160
0.160
0.088
0.086
0.107
0.141
0.129
As shown in fig. 2 and table 4, with reference to the above data, samples satisfying the range of element content determination in actual samples in as large a range as possible were selected as standards.
(2) When selecting the actual sample as the standard sample, selecting the standard sample according to the gradient of the curve
Table 5 shows that the experimental samples, the actual samples, and the calibration sample series with the appropriate gradient form a curve of the content of each element.
TABLE 5 actual selection of sample values (unit:. mu.g/cm)2)
1
2
3
4
5
6
7
8
9
10
Na
0.084
0.361
0.221
0.215
0.458
0.348
0.374
0.539
0.457
0.487
Mg
0.057
0.086
0.205
0.133
0.169
0.095
0.086
0.147
0.205
0.000
Al
0.129
0.459
0.228
0.283
0.320
0.342
0.470
0.589
0.396
0.277
Si
0.136
0.858
0.528
0.346
0.523
0.691
0.877
0.548
0.561
0.635
P
0.000
0.026
0.039
0.000
0.011
0.055
0.050
0.032
0.047
0.028
S
0.000
1.072
1.551
3.037
3.218
1.857
1.344
9.370
9.575
6.834
C1
0.003
0.247
0.067
0.086
1.100
0.168
0.190
1.683
3.343
2.804
K
0.006
0.799
0.457
0.622
1.369
0.773
1.085
1.552
2.739
2.195
Ca
0.049
0.574
0.283
0.226
0.392
0.549
0.606
0.226
0.478
0.569
Ti
0.002
0.023
0.016
0.005
0.017
0.023
0.027
0.029
0.034
0.039
V
0.000
0.002
0.000
0.001
0.002
0.000
0.001
0.001
0.002
0.000
Cr
0.002
0.004
0.004
0.005
0.008
0.005
0.003
0.009
0.008
0.006
Mn
0.012
0.023
0.029
0.017
0.038
0.037
0.038
0.053
0.064
0.064
Fe
0.037
0.317
0.261
0.212
0.383
0.388
0.482
0.493
0.578
0.602
Co
0.001
0.001
0.000
0.001
0.002
0.002
0.003
0.002
0.002
0.003
Ni
0.002
0.002
0.001
0.002
0.003
0.001
0.004
0.002
0.002
0.003
Cu
0.006
0.011
0.010
0.012
0.022
0.011
0.012
0.030
0.027
0.023
Zn
0.004
0.083
0.063
0.070
0.166
0.137
0.095
0.196
0.258
0.226
Ga
0.000
0.000
0.000
0.000
0.000
0.000
0.000
0.000
0.000
0.000
As
0.000
0.002
0.003
0.009
0.015
0.005
0.001
0.027
0.014
0.012
Se
0.002
0.000
0.000
0.004
0.001
0.000
0.000
0.009
0.000
0.000
Br
0.000
0.098
0.000
0.004
0.026
0.005
0.008
0.036
0.038
0.026
Rb
0.000
0.000
0.000
0.000
0.002
0.000
0.001
0.002
0.004
0.005
Sr
0.016
0.014
0.022
0.014
0.027
0.020
0.010
0.005
0.026
0.023
Y
0.027
0.008
0.008
0.005
0.018
0.001
0.011
0.020
0.004
0.000
Mo
0.008
0.005
0.008
0.009
0.006
0.005
0.005
0.009
0.004
0.007
Pd
0.002
0.012
0.012
0.009
0.014
0.002
0.006
0.006
0.007
0.000
Ag
0.008
0.006
0.008
0.006
0.005
0.006
0.008
0.010
0.003
0.004
Cd
0.007
0.007
0.006
0.005
0.005
0.009
0.010
0.005
0.012
0.011
Sn
0.025
0.029
0.020
0.028
0.027
0.032
0.037
0.043
0.030
0.039
Sb
0.013
0.085
0.047
0.014
0.013
0.023
0.023
0.047
0.027
0.031
Cs
0.034
0.035
0.046
0.058
0.031
0.054
0.051
0.061
0.043
0.066
Ba
0.046
0.035
0.088
0.056
0.105
0.069
0.031
0.087
0.046
0.078
La
0.204
0.209
0.212
0.233
0.225
0.254
0.213
0.215
0.249
0.255
W
0.749
0.747
0.758
0.736
0.716
0.729
0.780
0.735
0.743
0.758
Au
0.086
0.062
0.056
0.074
0.053
0.057
0.054
0.053
0.047
0.044
Hg
0.032
0.060
0.029
0.045
0.023
0.045
0.029
0.036
0.027
0.041
Pb
0.034
0.039
0.045
0.075
0.169
0.061
0.058
0.225
0.160
0.160
(3) Selection of instrumentation conditions
TABLE 6 Epsilon5 ED-XRF measurement parameters
(4) Sample preparation
The filter membranes before and after sampling are respectively weighed for 2 times, the filter membranes are placed in a thermostat with the temperature of 20-23 ℃ and the RH & 35-45% for more than 24 hours to reach constant weight before each weighing, then the filter membranes are weighed by a Sartorius & ME & 5-F, Mettler & M3 microelectronic balance, stored in a polystyrene petri dish, sealed by a polyethylene sealing bag and refrigerated in a refrigerator with the temperature of 4 ℃.
(5) Interference correction
The method adopts an empirical coefficient and a scattered ray internal standard method to correct the matrix effect, uses SuperQ software to synthesize a mathematical correction formula, uses a plurality of standard samples, and simultaneously obtains the intercept, the slope, the matrix effect and the spectral line overlapping interference factor of a calibration curve through the formula and multiple regression. And (3) correcting the overlapping interference, wherein a correction coefficient is obtained by a regression method, and a mathematical model of the method is as follows:
in the formula: c is concentration or count rate; miIs the strength of the sample to be tested; n is an element to be analyzed; α, β, γ, δ are factors for matrix correction; i is the element to be tested: j, k are interference elements
(6) Detection limit
The ED-XRF detection limit analysis employs the following experimental protocol: 3sd method
Selecting an actual sample (polypropylene filter membrane) with the content of 2-20 times of detection limit for repeated measurement;
or
In the formula wiIs a low content of the standard sample, IBStrength for low content of standard sample, I0The sd is the standard deviation of the strength of the blank sample and the low-content (2-20 times detection limit) actual sample repeatedly measured 7 times. If the content to intensity ratio obtained for the low content standard is not determined, the slope a of the calibration curve can be substituted. This method is also called "repeat assay"
The detection limit provided by the embodiment of the invention comprises the following steps:
the calculation is carried out according to the following formula,
in the formula: m is the counting rate of the unit content of the element; i isbBackground count rate, cps; t isbTime, s, was measured for background.
Since the detection limit is related to the matrix of the sample, different samples differ in their composition and content, and thus the detection limit of each component also differs.
The laboratory was repeated with 6 PM2.5 samples (5#, 6#, 7#, 8#, 9#, 10#) collected on teflon filter membranes. The measurement sequence adopts a large-cycle measurement mode, namely blank filter membranes, 5#, 6#, 7#, 8#, 9#, 10#, and blank filter membranes, 5#, 6#, 7#, 8#, 9#, 10#, …, and the measurement is repeated for 7 times. Calculating the standard deviation of 3 times of the test results of different samples, and selecting a numerical value with the element content ratio of 2-20. If the requirement is not met, the blank filter data is selected for calculation. If multiple sets of data simultaneously satisfy this condition, an average or median value is taken. The calculated method detection limit data calculated from the measured data are shown in table 7.
TABLE 7 detection limit test data (g/cm)2)
(7) Precision degree
The method provided by the embodiment of the invention has the following precision:
in order to accurately analyze a sample, main components and contents of a measurement result of the same filter membrane are determined by Omnian approximate quantitative software, a chemical analysis method and rock and ore identification analysis. On the basis, the measurement conditions are respectively determined according to the measurement conditions in the table 8, and the method determines that 3 pieces of PM with different load amounts on the Teflon filter membrane are taken2.5The sample (1#, 2#, 3#) is measured, and the allowable contents of matrix and interference element are measuredAnd (3) a range. 3 sample pieces were prepared in parallel for the standard sample, and analyzed according to the measurement conditions in Table 8, and the original measurement data of the laboratory precision experiment are shown in Table 8
Table 8 verification of experimental method precision data
3. Application of the actual sample:
(1) accuracy of
The actual sample determined according to the present invention was used as a standard sample material to establish a curve method, and the national institute for standards and standards sample may provide the national NIST SRM 2783 reference for testing for accuracy analysis, with the results shown in table 9.
Table 9 verification of experimental method accuracy test data
And (3) testing date:2020 08 17
the data in Table 9 show that the actual sample of the standard sample determined according to the invention is used as the standard sample material to establish the curve method, and the measured value of the sample is compared with the accurate value within the error range required by the national standard, which indicates that the method has accurate measuring result.
(2) Stability of
The actual samples determined according to the present invention were used as standard sample materials, and the stability analysis was performed by establishing a curve method, and the analysis results are shown in table 10.
Table 10 verification of experimental method stability test data
The data in table 10 show that the standard sample is used as a standard sample material according to the actual sample determined by the invention, a curve method is established, and the measured value of the sample is compared with the stability within the error range required by the national standard, which indicates that the measurement result of the method is stable.
(3) Comparison of results with different methods
An energy dispersive X-ray fluorescence analysis method is used to replace the methods of flame atomic absorption, graphite furnace atomic absorption, ICP-MS and ICP-OES cited in the current standard. The samples were directly tested and tested by inductively coupled plasma mass spectrometry (ICP-MS) plasma atomic emission spectrometry (ICP-AES) and homemade energy dispersive X-ray fluorescence analysis, respectively, to compare the results of the different methods, with the analysis results shown in table 11.
Table 11 shows the results of the different methods of the experimental method compared to the test data
The data in Table 11 show that the deviation of the measured values of the samples respectively measured by inductively coupled plasma mass spectrometry (ICP-MS) plasma atomic emission spectrometry (ICP-AES) and self-made energy dispersive X-ray fluorescence analysis method is within the error range required by the national standard, which indicates that the method has reliable results.
In the description of the present invention, "a plurality" means two or more unless otherwise specified; the terms "upper", "lower", "left", "right", "inner", "outer", "front", "rear", "head", "tail", and the like, indicate orientations or positional relationships based on the orientations or positional relationships shown in the drawings, are only for convenience in describing and simplifying the description, and do not indicate or imply that the device or element referred to must have a particular orientation, be constructed in a particular orientation, and be operated, and thus, should not be construed as limiting the invention. Furthermore, the terms "first," "second," "third," and the like are used for descriptive purposes only and are not to be construed as indicating or implying relative importance.
The above description is only for the purpose of illustrating the present invention and the appended claims are not to be construed as limiting the scope of the invention, which is intended to cover all modifications, equivalents and improvements that are within the spirit and scope of the invention as defined by the appended claims.