National Standard Samples Research Articles

Application of the k-Means Algorithm and the Gaussian Mixture Model (GMM) – African Vulture Optimization Algorithm (AVOA) for the Resolution of Overlapping Energy-Dispersive X-Ray Fluorescence (EDXRF) Peaks

Limitations in instrument resolution mean that soil samples analysis using energy-dispersive X-ray fluorescence (EDXRF) often produced overlapping spectral peaks of heavy metals with similar energies. This overlapping of spectral peaks posed a significant problem in the quantitative analysis of heavy metals in soil samples. Therefore, it was necessary to decompose the overlapping peaks. In this paper, a new method for decomposing overlapping peaks was presented in the context of Gaussian Mixture Model (GMM) parameter estimation, combining the k-means algorithm and the African Vulture Optimization Algorithm (AVOA). The data acquired from EDXRF instruments were preprocessed before being input to the k-means algorithm, which produces the output used to initialize the parameters of the GMM. Subsequently, AVOA was employed to optimize the GMM parameters based on a fitness function derived from the data. Ultimately, the optimized GMM parameters obtained through the AVOA process yield the optimal solution for the decomposition of overlapping peaks. This approach effectively addressed the challenge of peak overlap in the determination of heavy metals in soil by EDXRF. Soil samples were obtained from national standard samples, peach gardens, and vegetable-growing regions. The results showed that the maximum absolute errors for the peak channel and peak area were 1.46% and 6.37%, respectively. A comparison of the proposed model with others models indicated that the k-means-GMM-AVOA model exhibits the best performance in terms of speed, accuracy, and stability.

A Current Sensing Biosensor for BOD Rapid Measurement.

In order to improve the practicality of the rapid biochemical oxygen demand (BOD) method, a highly sensitive rapid detection method for BOD that is based on establishing the correlation between current and dissolved oxygen (DO) was developed. In this experiment, Bacillus subtilis was used as the test microorganism, and the embedding method was used to achieve quantitative fixation of microorganisms, which could increase the content of microorganisms and prolong the service life of the biological element. The conductivity (COND) probe is used as a sensing element, so that the testing value can be read every second. In the program, the moving average method is used to process the collected data so that the value can be read every minute. National standard samples were detected to test the accuracy and stability of the method. The results showed that relative error and analytical standard deviations were less than 5%. Different polluted water was tested to evaluate its application range. The results showed that relative error was less than 5%. The results of the method are consistent with the results of the wastewater sample obtained by the BOD5 standard method. The proposed rapid BOD current sensing biosensor method should be promising in practical application of wastewater monitoring.

Simultaneous quantitative analysis of non-metallic elements in coal by laser-induced breakdown spectroscopy assisted with machine learning

Coal is an important part of national energy structure, and the proportion of non-metallic elements will greatly affect its combustion efficiency. In order to achieve rapid and simultaneous quantitative detection of C, H, N in coal, a hybrid model combining laser-induced breakdown spectroscopy (LIBS) with machine learning algorithm is proposed. The detailed operations are as follows: A Nd: YAG laser with wavelength of 1064 nm is selected as excitation source, 14 kinds of national standard coal samples are ablated in air environment. Then selecting spectral data around the wavelength of elements to be measured and normalizing it as input variable of three algorithms. Finally, linear regression, support vector regression and random forest model are used for calibration and prediction. The results indicate that random forest model is more accurate in predicting non-metallic elements in coal than other two models, and the correlation coefficient (R2) value of C, H, N were 0.9844, 0.9625 and 0.9829, the root mean square error (RMSE) were 0.2669, 0.2508 and 0.0335 respectively. Hence, LIBS technique based on different machine learning models can be used to accurately and effectively determine the content of non-metallic elements in coal.

Quantitative energy-dispersive X-ray fluorescence analysis for unknown samples using full-spectrum least-squares regression

The full-spectrum least-squares (FSLS) method is introduced to perform quantitative energy-dispersive X-ray fluorescence analysis for unknown solid samples. Based on the conventional least-squares principle, this spectrum evaluation method is able to obtain the background-corrected and interference-free net peaks, which is significant for quantization analyses. A variety of analytical parameters and functions to describe the features of the fluorescence spectra of pure elements are used and established, such as the mass absorption coefficient, the $$G_{i}$$ factor, and fundamental fluorescence formulas. The FSLS iterative program was compiled in the C language. The content of each component should reach the convergence criterion at the end of the calculations. After a basic theory analysis and experimental preparation, 13 national standard soil samples were detected using a spectrometer to test the feasibility of using the algorithm. The results show that the calculated contents of Ti, Fe, Ni, Cu, and Zn have the same changing tendency as the corresponding standard content in the 13 reference samples. Accuracies of 0.35% and 14.03% are obtained, respectively, for Fe and Ti, whose standard concentrations are 8.82% and 0.578%, respectively. However, the calculated results of trace elements (only tens of μg/g) deviate from the standard values. This may be because of measurement accuracy and mutual effects between the elements.

Analysis of Niobium–Rare-Earth Ores by Inductively Coupled Plasma Mass Spectrometry

To determine the composition of niobium–rare-earth ores by atomic emission spectrometry and inductively coupled plasma mass spectrometry, two procedures are developed for sample preparation based on autoclave decomposition and flux fusion. Autoclave decomposition is carried out in a mixture of HF and HNO3 at a temperature of up to 220°C and a pressure of up to 160 atm using a developed system with resistive heating. Subsequent evaporation to dry salts ensures the removal of F– ions and silicon as SiF4. The residue is dissolved in a mixture of HCl and H2O2 at 160°C under elevated pressure. The resulting solutions (10% with respect to HCl with the addition of H2O2) are diluted before measurements. The dissolution process is monitored for each sample using stable highly enriched isotopes of 91Zr, 100Mo, 149Sm, and 178Hf. The second procedure is based on fusing samples with a mixture of Na2CO3 and Na2B4O7 at 1050°C in a muffle furnace and dissolving the resulting melt in a mixture of HCl and H2O2. The procedures were tested using the national (NFS-23) and foreign standard samples of composition (OREAS-462, 463, 464, 465, Australia) and real samples of niobium–rare-earth ores.

Determination of effective atomic numbers and mass attenuation coefficients of samples using in‐situ energy‐dispersive X‐ray fluorescence analysis

The matrix effect has a major impact on energy‐dispersive X‐ray fluorescence analysis (EDXRFA) and is difficult to be evaluated due to that the contents of some low‐atomic‐number elements cannot be identified by in‐situ EDXRFA. Up to today, the fundamental parameter algorithm proposed by Rousseau has been widely applied to correct the matrix effect. Accordingly, determining the matrix and mass attenuation coefficient (μ/ρ) of sample is a key issue for the fundamental parameter algorithm. In present work, the method to deduce μ/ρ by effective atomic number (Zeff) was studied. First, the relationship between Zeff and coherence to Compton scatting ratio (R) of the incident X‐ray was determined by standard samples. Then, we deduce Zeff and their μ/ρ. The value of μ/ρ deduced by our method is in good agreement with that calculated by WinXCOM, and the relative change (Δ) is less than 7%. We also deduced Zeff and their μ/ρ of Chinese national standard soil samples employing our method and good agreement with the calculated values were also obtained. We found that the agreement between experimental values of μ/ρ with theoretical values by WinXCOM still exists when the energy of the incident X‐ray is greater than 4 keV, and the Δ is less than 10%. The result indicates that our method may be applied directly to in‐situ EDXRFA.

Accelerated ripening of Kedong sufu with autochthonous starter culturesKocuria roseaKDF3 and its protease KP3 as adjuncts

Application of autochthonous strain Kocuria rosea KDF3 and its protease KP3 as adjuncts for acceleration of Kedong sufu ripening. Kedong sufu was manufactured using autochthonous cultures (batch A), K. rosea KDF3 plus autochthonous cultures (batch B) and protease KP3 plus autochthonous cultures (batch C). The effects of certain key factors on the quality of sufu were analysed during a 150-day ripening period. The physicochemical properties of sufu samples from batches B and C after 120 days of ripening met the national standard requirements and samples from batch A after 150 days of ripening. The sensory evaluations of sufu samples from batches B and C after 120 days of ripening and from batch A after 150 days of ripening showed no significant differences (P > 0·05). Furthermore, the mechanism underlying the shorter ripening time and typical sensory quality of sufu prepared with K. rosea KDF3 or protease KP3 was partly revealed by profiles of peptides and free amino acids. The maturation times of Kedong sufu were shortened by 30 days, and the desired characteristics were obtained by adding K. rosea KDF3 or its protease KP3. Kocuria rosea KDF3 or its protease KP3 can hasten sufu maturation. They could be used as adjuncts or additives for accelerating the ripening of Kedong sufu. This study is the first report of using autochthonous strain K. rosea KDF3 or its protease KP3 as adjuncts for accelerating Kedong sufu ripening. The results are useful for characterizing the ripening of Kedong sufu, and they lay the foundation for pilot plant tests and full-scale plant tests.

A statistical approach to fit Gaussian part of full-energy peaks from Si(PIN) and SDD X-ray spectrometers

A new statistical fitting approach, named Statistical Distribution-Based Analytic (SDA) method, is proposed to fit single Gaussian-shaped K-alpha and K-beta X-ray peaks recorded by Si(PIN) and silicon drift detector (SDD). In this method, we use the discrete distribution theory to calculate standard deviation of energy resolution sigma. The calibration of sigma and energy (E) for two detectors between the energy ranges of 4.5-26 keV are also completed by measuring characteristic X-ray spectra of nineteen types of pure elements. With the spectrum fraction (SF) parameter proposed in this paper, the SDA method can be used to resolve overlapping peaks. In measured spectra, the Gaussian part of X-ray peaks can be fitted by a Gaussian function with two parameters, sigma and SF. This new fitting approach is simpler than traditional methods and it achieves relatively good results when fitting the complex X-ray spectra of national standard alloy samples detected by Si(PIN) and SDD detectors. The chi (r) (2) values are obtained for each spectrum to assess fitting results, and the SDA fitting method gives a preferable fit for the SDD detector.

A Novel Design of BOD Biosensor Based on Immobilized Microbial Biosensor

In this study, an instrument for circulating BOD analysis by microbial sensor has been developed. A Pseudomonas. sp immobilized by PVA, was employed for sensitive material BOD sensor. The measure period was about 8 minutes. Both relative error and analytical standard deviation are less than 5%. The instrument has the advantages of high autoimmunization and short measure period. The accuracy and stability of the instrument measured up the national standard by testing different type waste waters and national standard samples.

Quantitative analysis of chrome in soil samples usinglaser-induced breakdown spectroscopy

We quantitatively analyze the content of element Cr in the national standard soil samples by the method of plasma atomic emission spectroscopy, through using Nd:YAG (Wavelength:1064 nm) laser as an excitation source to induce soil plasma in ambient environment of the laboratory. The calibration curve of element Cr is measured by studying the characteristics of laser-induced breakdown spectroscopy of element Cr in soil under optimal conditions. The experimental results demonstrate that the element content (60—400)×10-6 and the spectral line intensity are in good linear relation, and the relative standard deviation of element analysis of concentration measurement from the standard value is 7.89%. The relative deviation of the quantitative analytic result from the standard value is 5.3%, and the detection limit of Cr in soil is 16.3×10-6. The relative deviation by the internal standard method is 2.7%, which indicates that the internal standard method can improve the accuracy of the measurement. Using the same type of soil to achieve the calibration curves, the relative deviation by the quantitative analysis is 8%.

International committee for radionuclide metrology: Guidelines for international acceptance of radioactivity calibration sources

These Guidelines for the International Acceptance of Radioactivity Calibration Sources were written in response to a request from the International Committee for Radionuclide Metrology (ICRM). They outline the common basis for the quality control of the production of national standard samples of radioactivity. The members of ad hoc committee were: D. Bek-Uzarov Belgrade, Yugoslavia C. Ballaux † Brussels, Belgium P. Christmas † Teddington, England K. Debertin † Braunschweig, Germany D. D. Hoppes † Gaithersburg, MD, U.S.A. J. M. R. Hutchinson, Chairman † Gaithersburg, MD, U.S.A. T. Radoszewski Otwock Swierk, Poland A. Szorenyi Budapest, Hungary H. Volchok, deceased New York, NY, U.S.A. † Writing group members.