Application and Development Trends of Spectral Analysis in Draft of Non-Ferrous Metal Standards in China ()
1. Spectral Analysis and Application
Before the 60s of the 20th century, analytical chemistry was mainly based on traditional classical chemical methods [1] . The standard analysis methods issued subsequently were mainly based on titration spectrophotometry gravimetric method and other chemical methods to determine the primary and secondary components of non-ferrous metal products, including ISO793: 1973, ISO795: 1976, ISO796: 1973, ISO797: 1973 and other standard methods, while the analysis technology mainly focused on single element analysis. Analytical chemistry technology had gradually developed into modern analytical chemistry based on instrumental analysis with the development of high-temperature combustion technology and electrochemical technology. Modern spectral analytical chemistry focused on atomic absorption, atomic emission and X-ray characteristic emission, and mainly relied on multi-element simultaneous/in-situ/online analysis technology to analyze the content morphological characteristics surface depth and other information of primary and secondary trace elements. It is precise because of the discovery of atoms electrons protons neutrons cathode rays and X-rays, and the establishment of Ernest Rutherford’s nuclear atom model,
The main spectral analysis techniques of non-ferrous metallurgical analysis mainly included atomic absorption spectroscopy (AAS), inductively coupled plasma emission spectroscopy (ICP-AES), X-ray fluorescence spectroscopy (XRF) and atomic fluorescence spectroscopy (AFS) technology [2] . These analytical methods played an important role in the small-scale pilot expanded and formal production lines of mineral processing & metallurgical processes, and the non-ferrous metal system analysis and testing laboratories had basically introduced a large number of modern analytical equipment. In the traditional non-ferrous metal analysis laboratory supporting analysis system was mainly AAS and AFS spectrometer, such as AAS mainly undertook the determination of copper lead zinc gold silver cadmium magnesium sodium calcium nickel antimony bismuth and other elements in raw ore tailings and metal products, while AFS mainly undertook the determination of arsenic antimony bismuth tin lead selenium tellurium germanium mercury cadmium zinc and other element content. ICP-AES and XRF spectroscopic technologies mainly undertook the analysis of primary secondary and trace elements in non-ferrous metal samples in most non-ferrous metal analysis laboratories. Although AAS and AFS were gradually replaced by modern multi-element simultaneous determination and analysis techniques, they were still important standard technologies in the multi-element analysis system of non-ferrous metal samples, and the instrument combination of AAS and AFS was studied and applied in elemental speciation analysis. Direct reading spectrometer (OES) was mainly used in the analysis of trace impurity elements in high-purity metal materials with a wide wavelength range. Glow discharge emission spectroscopy (GD-OES) was mainly used in surface chemical analysis of metal oxide content analysis Laser-induced breakdown spectroscopy (LIBS) was mainly used in the research stage of rocks, soils, mineral ores and other fields with the advantages of high-energy excitation, simultaneous detection of multiple elements and in situ analysis.
Spectral analysis had become one of the common methods for analyzing the composition of substances as a qualitative and quantitative analysis technique for conventional elements, and it had widely used in the analysis and detection of metal elements in metal materials, geological samples, environmental and water samples, food and crops, petroleum and chemicals, biology and medicine [3] with the development of spectral technology, especially the breakthrough of key modules such as crystal/metal materials, background correction, light source stability, optical path system, detector, data calculation, etc., That was used to further promote the application of spectral technology in the draft of non-ferrous metal standards in China by high-precision quantitative analysis method established by the optical spectrum analyzer.
2. Standard Procedures for Spectral Analysis
The standard procedures for spectroscopy were derived from the verification specifications, operating specifications and general rules of routine spectrometers in daily laboratories. Then, combined with China Nonferrous Metals Standard Quality Information Network (http://www.cnsmq.com/) and CSRES.COM (http://www.csres.com), keyword search was carried out, and AAS ICP-AES XRF AFS OES GD-OES and LIBS had relevant verification standards, general principles and specifications.
The verification regulations of JJD 1001-1991 “Verification Regulation of Atomic-Absorption Spectrophotometer” stipulated the verification conditions, identification methods, national standard sample assessment and evaluation of identification results. GB/T 15337-1994 “General rules for atomic absorption spectrometric analysis” stipulated terms analytical principles reagents and materials instruments and determinations.
JSY/T 0567-2020 “General rules for inductively coupled plasma optical emission spectrometry” specified the principles of analytical methods, the expression of reagents and materials, instruments, samples, analysis steps, analysis results, and precautions for safe use. CSM 01 01 01 04-2006 “Specification for Uncertainty Evaluation of Measurement Results by Inductively Coupled Plasma Emission Spectrometry” included analysis methods and measurement parameter descriptions, mathematical model establishment, identification and evaluation of uncertainty sources, etc.
XRF had been widely used in China with the advantages of measuring a wide variety of elements, simultaneous determination of primary and secondary trace elements, simple sample preparation, fast analysis speed, etc., and has successively promulgated JB/T 11145-2011 “X-ray fluorescence spectrometer”, JJG 810-1993 “Wavelength Dispersive X-ray Fluorescence Spectrometer”, JY/T 0569-2020 “General rules for wavelength dispersive X-ray fluorescence spectrometry”, JB/T 12962.1~3-2016 “Energy dispersive X-ray fluorescence spectrometer, Part 1: General specification, Part 2: Element analyzer, Part 3: Plating thickness analyzer”. JJF 1133-2005 “Calibration Specification of Gold Gauge Utilizing X-ray Fluorescence Spectrometry” specifies the metrological characteristics, calibration conditions, calibration terms, and calibration methods, calibration result expression, and recalibration interval.
GB/T 21191-2007 “Atomic fluorescence spectrometer” stipulated the classification, requirements, experimental methods, inspection rules and standards, packaging, transportation and storage of atomic fluorescence spectrometer, etc., GB/T 32266-2015 “Method of performance testing for atomic fluorescence spectrometer” specified the method of atomic fluorescence spectrometer performance determination, suitable for single-channel, double-channel and multi-channel atomic fluorescence spectrometers in the laboratory.
JJD1015-1991 “Verification Regulation of Inductively Coupled Plasma spectroanalyzer” specified periodic verification requirements, and can be used with reference to similar instruments of different manufacturers and models.
GB/T 19502-2004 Surface chemical analysis-Glow discharged optical emission spectrometry (GD-OSE)-Introduction to use (ISO14707:2000, IDT). GB/T 32996-2016 Surface chemical analysis-Analysis of metal oxide filmed by glow-discharge optical emission spectrometry (ISO/TS 25138:2010, IDT). GB/T 32997-2016 Surface chemical analysis-General procedured for quantitative compositional depth profiling by glow discharge optical emission spectrometry (ISO 11505:2012, IDT).
GB/T38257-2019 “Laser-induced breakdown spectroscopy” stipulated terms and definitions, basic principles, test conditions, equipment and devices, samples, test procedures, data processing and test reports, JJF (non-ferrous metals) 0008-2021 “Calibration Specification for Laser Induced Breakdown Spectrometers” for the calibration of laser-induced breakdown spectrometers for the composition analysis of non-ferrous metal solid samples. This specification dealt with calibration of wavelength indication errors and repeatability, detection limits, repeatability, and stability. T/CNIA 0109-2021 “Analysis method for non-ferrous metal materials-General rules of application for laser induced breakdown spectroscopy” included general requirements for method principles, instrumentation, test environment, samples, analytical steps, data processing, test reports and safety protection, and it was suitable for qualitative, semi-quantitative and quantitative analysis of metallic and partial non-metallic elements in samples by solid injection using laser-induced breakdown spectrometer.
3. Application
According to the literatures published on https://openstd.samr.gov.cn/bzgk/gb/, http://www.csres.com, http://www.cnsmq.com, the following spectrometric methods including Atomic Absorption Spectrometry (AAS), Inductively Coupled Plasma Atomic Emission Spectrometry (ICP-AES), Direct reading spectroscopy (OES), X-ray fluorescence spectroscopy (XRF), Atomic fluorescence spectroscopy (AFS), Glow discharge emission spectroscopy (GD-OES), and Laser-induced breakdown spectroscopy (LIBS) were frequently applied in the draft of non-ferrous metals standards.
3.1. Atomic Absorption Spectrometry (AAS)
The atomic absorption spectroscopy method was based on the resonance absorption of the characteristic radiation from the light source by the ground state atoms of the measured element in the steam phase, and the characteristic absorption spectrum of the atom was produced, and its absorption value was linearly related to the content of the element to be measured in the sample.
AAS had been used since the 50s of the 20th century. Gao Jieping and Li Huachang [4] [5] comprehensively evaluated the progress made by AAS instrument companies at home and abroad in light source, background correction, atomizer, optical path and detector, automation and intelligence, and multi-element simultaneous determination in the 90s. Li Bing [1] pointed out that the development of AAS instrument for multi-element sequential determination of self-continuous light source-high-resolution optical system, AAS spectroscopy instrument had been re-focused.
AAS had been used as the standard analysis method for more than thirty years, mainly used for the determination of trace elements in raw materials, intermediate products, concentrates, metal alloys and their compounds in the non-ferrous metal dressing and metallurgical process, such as copper-lead-zinc raw original and tailing, scopper ores and tailings, laterite nickel ores, copper magnetite, copper concentrates, zinc concentrates, lead and lead alloys, tungsten, molybdenum and other samples. AAS had been used as the arbitration method. AAS in major non-ferrous metal analysis standards was given in Table 1.
In order to solve the problems of interference of coexisting elements to be measured or low strength of the element to be measured, it was usually done by either eliminating the interference element, enriching the element to be measured, or adding a signal enhancer during the sample preparation process. The contents of silver [6] , zinc [7] and aluminum [8] in tin-lead solder samples were determined by AAS, and the tin was separated by hydrochloric acid-hydrobromic acid volatilization after dissolving the sample by hydrobromic acid, hydrochloric acid and hydrogen peroxide to eliminate the influence of matrix tin on the determination. The contents of silver [9] , iron [10] , copper, lead, bismuth [11] , magnesium, nickel, manganese and palladium [12] in gold ingot samples were determined by AAS, and the hydrochloric acid medium test solution was extracted by hydrochloric acid decomposition test material, ethyl acetate extraction, and the hydrochloric acid medium test solution was prepared by aqueous phase concentration to eliminate the influence of matrix gold on the determination.
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Table 1. AAS in major non-ferrous metal analysis standards.
The simultaneous analysis technology of multiple elements had gradually been adopted, along with the development of continuous light source for atomic absorption spectroscopy, high-resolution optical system and other technologies.
3.2. Inductively Coupled Plasma Atomic Emission Spectrometry (ICP-AES)
That was the analysis principle of inductively coupled plasma atomic emission spectrometry which the sample is brought into the plasma torch flame by a carrier gas in a certain form, and is fully evaporated, atomized, excited and ionized in a high temperature and inert atmosphere, emitting characteristic spectral lines of the contained elements. According to the presence of characteristic spectral lines, qualitative analysis was carried out to identify whether the sample contains a certain element, and quantitative analysis which determines the content of the corresponding element in the sample based on the characteristic spectral line intensity.
ICP-AES was suitable for qualitative and quantitative analysis of constant to trace elements in samples, and it had been widely used. ICP-AES in some non-ferrous metal analysis standards was given in Table 2.
The amounts of lead zinc bismuth cadmium chromium arsenic and mercury in gold ore were determined by ICP-AES [13] , and the amounts of lead zinc bismuth cadmium arsenic and mercury were determined by hydrochloric acid and nitric acid dissolution. The amount of chromium was determined by dissolving it with thion mixed acid. In dilute nitric acid medium, under the selected conditions of inductively coupled plasma atomic emission spectrometer, the spectral intensity of each element in the test solution is determined, and the amount of lead zinc bismuth cadmium chromium arsenic and mercury in the sample were calculated according to the standard curve method using yttrium as the internal standard. The lower limit of method element determination can be as low as 0.005% and as high as 5.00%. The amount of silver copper iron lead antimony bismuth palladium magnesium nickel manganese and chromium in 99.95% - 99.99% gold ingots was determined by ICP-AES [14] , and ethyl acetate was extracted and separated from the element to be measured in the aqueous phase after mixing acid to dissolve the sample. The lower limit of this method for elemental determination can be as low as 0.0001%.
3.3. X-Ray Fluorescence Spectroscopy (XRF)
X-ray fluorescence spectroscopy was a qualitative and quantitative analysis method based on the wavelength and intensity of X-ray fluorescence of the elemental characteristics produced after X-ray irradiation of a sample. XRF was an analytical technique for simultaneous determination of primary, secondary and trace multiple elements. Analysis principle: X-ray was a kind of electromagnetic radiation with a short wavelength, and the energy range was between 0.1 - 100 keV. If the sample was irradiated with sub-X-rays emitted by an X-ray tube, the
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Table 2. ICP-AES in some non-ferrous metal analysis standards.
inner electrons of the elements in the sample are excited by it, producing characteristic X-ray fluorescence, or secondary X-rays. By measuring and analyzing the X-ray fluorescence generated by the sample, the elements in the sample could be qualitatively and quantitatively analyzed, and the application in the major non-ferrous metal analysis standards was given in Table 3.
Compared with energy dispersive X-ray fluorescence spectroscopy (ED-XRF), wavelength dispersive X-ray fluorescence spectroscopy (WD-XRF) was an analytical instrument that entered the analytical laboratory earlier. WD-XRF is an earlier technique that emerged as a standard method.
The amount of copper sulfur lead zinc iron aluminum calcium magnesium and manganese in copper concentrate was determined by glass fusion-wavelength chromatographic X-ray fluorescence spectrometry [15] , and under the combined action of sodium carbonate and lithium nitrate, low-valence elements were oxidized to high-valence elements. According to the dilution ratio of about 1:83, the copper concentrate sample and lithium tetraborate-lithium metaborate mixed flux were melted into the test sheet, and the X-ray fluorescence intensity of the characteristic spectral line of the element to be measured in the test piece was measured under the optimal measurement conditions of the instrument, and the inter-element interference effect was corrected, and the content of the element to be measured in the test piece was obtained from the calibration curve.
The amount of tin antimony arsenic bismuth copper cadmium calcium and silver in lead and lead alloys was determined by WD-XRF [16] , and the surface to be measured of metal samples was directly processed to uniform, flat and smooth, and there were no defects such as cracks, cavities and looseness, and measured in time. No less than 4 pieces of lead and lead alloy standard materials were prepared to determine the X-ray fluorescence intensity of the characteristic spectral lines of each element, and one of the basic parameter method, theoretical α coefficient method, empirical α coefficient method and other methods was selected for matrix effect correction and spectral line interference correction, and the standard curve was drawn. Based on the calibration curve and the measured X-ray fluorescence intensity, the mass fraction of tin, antimony, arsenic, bismuth copper cadmium calcium and silver content in the sample was calculated.
The amount of aluminum chromium iron magnesium manganese nickel and silicon in laterite nickel ore was determined by ED-XRF [17] , the powder sample was pressed or prepared into a glass melt, placed in the beam emitted by the X-ray source, the fluorescence X-ray intensity generated when the sample was excited was determined by the analytical device, and the content of the element to be measured was calculated by the calibration curve.
3.4. Atomic Fluorescence Spectroscopy (AFS)
Atomic fluorescence is an atomic spectroscopic method that uses the fluorescence intensity emitted by atoms during radiation excitation for elemental quantification. AFS can be used to measure the non-dispersive vapor generation-atomic fluorescence spectra of the elements arsenic, antimony, bismuth, selenium, tellurium, lead, tin, germanium, atomic vapor mercury, and volatile compounds zinc, cadmium and other elements that can form hydrides. In 1964, Winefordner and Vickers [18] published the first chemical analysis paper on the
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Table 3. XRF in major non-ferrous metal analysis standards.
determination of mercury, zinc and cadmium by flame atomic fluorescence spectrometry, after which the technology has made great achievements in applied research and standardization in China, Feng Xianjin and Zhang Lianxiang [19] summarized the research of AFS technology in China’s standardization, among which the application in the main non-ferrous metal analysis standards is given in Table 4.
Atomic fluorescence instruments and analysis technology were at the international leading level In China. The amount of arsenic in tungsten ore and molybdenum ore was determined by hydride generation-atomic fluorescence spectrometry [20] , and the sample was decomposed by hydrochloric acid-nitric acid to prepare a sample test solution. Thiourea-ascorbic acid solution reduced pentavalent arsenic in the test solution to trivalent arsenic, and reacted with potassium borohydride to generate hydrogen arsenide, which was loaded into the atomizer by argon, and under the irradiation of arsenic high-intensity hollow cathode lamp, the ground state arsenic atoms were excited to a high-energy state, and when it returned to the ground state, it emits fluorescence of characteristic wavelengths, and its fluorescence intensity was proportional to the content of arsenic in the sample, and the calibration curve was used to quantitatively determine the amount of arsenic in the solution. In the method for determination of mercury in tin concentrate using cold steam generation-atomic fluorescence spectrometry, the sample material was dissolved with hydrochloric acid and nitric acid, and the ionic mercury in the dilute hydrochloric acid medium was reduced to atomic mercury by stannous chloride, and the argon gas was introduced into the quartz furnace atomizer, and the fluorescence intensity of mercury was measured on the atomic fluorescence spectrometer.
The amount of arsenic mercury cadmium lead and bismuth in gold ore were determined by AFS [21] , and the samples were prepared by water bath and tetraic acid two methods as arsenic-mercury, bismuth and arsenic-bismuth lead-cadmium to be tested, which can realize the simultaneous determination of arsenic and bismuth elements, and the three elements of mercury, cadmium and lead were determined separately. The AFS of arsenic mercury cadmium lead and bismuth in gold concentrates could also be determined simultaneously for multiple elements [22] . The laboratory was equipped with a three-channel fluorescence instrument, which can be sufficient for these analytical methods.
3.5. Direct Reading Spectroscopy (OES)
Direct reading spectrometer was an emission spectrometer, which was mainly an instrument for quantitative analysis of samples by measuring the intensity of characteristic spectral light representing each element when the sample was excited.
The non-ferrous metal standard developed by direct reading spectroscopic analysis method was YS/T 464-2019 “Method for analysis of copper cathode—The optical emission spectrometry”, which used direct reading spectrometry to
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Table 4. AFS in some non-ferrous metal analysis standards.
determine 18 elements such as arsenic antimony bismuth sulfur selenium tellurium iron silver tin nickel lead zinc chromium tin cobalt silicon phosphorus and manganese in cathode copper. The sample preparation was prepared according to the 5.3 copper cathode sampling and sample preparation method in GB/T467-2010, and the copper cathode international standard sample was used as the monitoring sample. A set of standard samples were used for accuracy and precision tests. The smooth plane of the specimen was the upper electrode and the tungsten needle is the lower electrode when measuring, and the specimen was excited with a high-performance spark light source, and the excitation position was changed, and at least four excitation determinations were carried out on the same surface. It needed to take at least four measured values according to the working curve of the instrument and each calibration factor, and the instrument automatically processed the detected data, calculated and outputted the analysis results of arsenic antimony bismuth sulfur selenium tellurium iron silver tin nickel lead zinc chromium cadmium cobalt silicon phosphorus and manganese.
3.6. Glow Discharge Emission Spectroscopy (GD-OES)
Glow discharge emission spectroscopy was a technique mainly used to study the elemental composition of materials. It was mainly used in the field of materials manufacturing to determine whether there was any oxidation, surface treatment or contaminants in or on the sample.
Glow discharge was plasma formed when an electric current passes through a gas. It was generated when a voltage was applied between the cathode and anode in a glass tube containing a low-pressure gas such as helium. This ionized the gas, causing the lamp to glow brightly, which could be kept bright when the applied voltage exceeds the trigger voltage. The color of the light produced depends on the type of gas used in the tube. The excited atoms and ions in the discharge plasma produce different emission spectra for each element, and a single element could produce several different emission spectral lines that made up the light produced by the discharge.
Glow discharge spectrometer consisted of discharge lamp, spectrometer and data detection and analysis system. Spectrometers were used to analyze the emission spectra of gases, while data detection and analysis systems enabled qualitative and quantitative analysis of interactions in gases. Magnetron discharge and radio frequency discharge were the two most common types of glow discharge plasma generators. If a depth distribution of elemental composition up to 150 μm of a sample was required, glow discharge light emission spectroscopy should be used. This was particularly ideal for metals and insulators, which provided fast elemental analysis.
GB/T 32996-2016 “Surface chemical analysis of metal oxide film by glow discharge emission spectrometry” specified the method for determining the thickness, unit area mass and chemical composition of metal oxide film by glow discharge emission spectroscopy. This method was suitable for the determination of oxide film with a thickness of 1 nm - 10,000 nm on metal, and the metal elements of the oxide included one or more of iron chromium nickel copper titanium silicon molybdenum zinc magnesium manganese and aluminum. Other measurable elements included oxygen carbon nitrogen hydrogen, phosphorus and sulfur.
3.7. Laser-Induced Breakdown Spectroscopy (LIBS)
Laser-induced breakdown spectroscopy was suitable for the detection and analysis of chemical elements of solid liquid and gaseous substances. The LIBS Basic principle was which the laser emits the laser, and the laser focusing system concentrates the laser to ablate the substance to be analyzed to produce plasma. Atoms molecules or electrons in ions in plasma were excited to an excited state and emit characteristic photons when they transitioned from an upper energy level to a lower energy level. After the plasma radiation collection system collected the characteristic photon signal, it was dispersed by the spectrometer, and the data processing system performs qualitative analysis according to the characteristic spectral lines of the elements, and quantitatively analyzed according to the characteristic spectral line intensity of the elements or the overall spectral information. GB/T 38257-2019 [23] and T/CNIA 0109-2021 provided specifications for draft of standard methods for this technology in the future, and the research work on related analysis methods had been carried out.
4. Summary
The flame absorption part of the atomic absorption spectrometer was mainly used for the determination of constant to trace metals and alkaline earth metal elements, the flame emission part was mainly used for the determination of constant to trace alkali metals and alkaline earth metals, and the atomic absorption part of graphite furnace was mainly used for the determination of trace, ultra-trace metal and non-metallic elements. ICP-AES was widely used with the advantages of low detection limit, high precision, high sensitivity, wide linear range and simultaneous detection of multiple elements, which was not only an experimental instrument for routine laboratory analysis and testing, but also one of the common analysis methods in standard methods. It had the advantage of high-throughput detection to meet the need for more accurate and faster results of secondary and trace element tests, especially in the field of non-ferrous metals. XRF was characterized by a wide variety of analytical elements, a wide range of determination concentrations, high analytical sensitivity, simple sample preparation, and fast detection speed, while its application objects are becoming more and more extensive [24] . AFS was widely used in the analysis of trace and ultra-trace elements with its high analytical sensitivity. OES was simple fast and consumes fewer samples. The outstanding advantage of glow discharge emission spectroscopy was that it can analyze surfaces as well as sample bodies with considerable depth. The method could simultaneously analyze up to 43 elements, including all metals sulfur carbon oxygen chloride and hydrogen. LIBS has the unique advantages of being non-destructive and requiring little or no sample preparation. This technology has the ability to measure any form of sample, real-time online long-distance detection of multiple elements or harsh environments [25] .
Spectral analysis technology plays a crucial role in the analysis and detection of non-ferrous metals. Compared to traditional chemical analysis methods, it has the following advantages:
· The sampling form is flexible, and the representative sampling amount of rare and rare precious metals is less than that of traditional chemical methods;
· The sample pretreatment operation is simple, and there is no need for complex separation operations;
· The reference metal demand is low, and spectral qualitative analysis can be achieved in the known map;
· Fast analysis and high efficiency, set multi-channel instant multi-point acquisition, real-time output through calculator;
· Good selectivity, for the determination of elements and chemicals with similar chemical properties, such as niobium, tantalum, zirconium, hafnium, and rare earth oxides can be separated without interference, as a technical support for the determination of the content of such elements and compounds;
· High sensitivity, trace analysis can be performed using spectroscopy;
· On-site and in-situ non-destructive testing is possible.
5. Development Trend
Spectral analysis technology occupied an important position in the primary secondary trace and trace analysis fields of non-ferrous industry providing an important role in promoting the development of Chinese non-ferrous industry. With the implementation and landing of the “dual carbon” policy, the technical requirements for non-ferrous metals have become more and more stringent, and the revision of standards has developed in the direction of green, environmental protection, energy conservation and high efficiency. Spectral analysis will likely be the direction of future standard development in the following technical areas:
1) Simultaneous determination technology of trace multiple elements;
2) Analysis techniques for elemental morphology and mineral occurrence states;
3) Analysis techniques for light mass elements;
4) On-line sampling and intelligent detection technology for field instruments.
The high-purity non-ferrous metal materials are used in spectroscopic instruments to provide services for the non-ferrous metal industry by improvement of non-ferrous metal material detection technology. The use of characteristic spectrum extraction technologies such as Genetic Algorithms [26] [27] continuum-removal and principal component analysis can achieve a better model for selecting specific variables suitable for wavelength bands, thereby reducing data redundancy and irrelevant information and improving the accuracy of analysis and detection in the field of chemical analysis.
The establishment of the standard system of spectral technology in the standard method of non-ferrous metals will further promote the development of spectroscopic technology in the field of non-ferrous metal analysis.
Acknowledgements
The paper was supported by the project funding of the Key R&D Plan Projects for the 14th Five Year Plan, which was Research and Application of Analysis and Testing Technology and Standard System for Strategic Mineral Beneficiation and Metallurgy (2021YFC2903100 & 2021YFC2903101), thanks to the support for the research group members.