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Fast Quantification of Honey Adulteration with Laser-Induced Breakdown Spectroscopy and Chemometric Methods
摘要： Honey adulteration is a major issue in food production, which may reduce the effective components in honey and have a detrimental effect on human health. Herein, laser-induced breakdown spectroscopy (LIBS) combined with chemometric methods was used to fast quantify the adulterant content. Two common types of adulteration, including mixing acacia honey with high fructose corn syrup (HFCS) and rape honey, were quantified with univariate analysis and partial least squares regression (PLSR). In addition, the variable importance was tested with univariable analysis and feature selection methods (genetic algorithm (GA), variable importance in projection (VIP), selectivity ratio (SR)). The results indicated that emissions from Mg II 279.58, 280.30 nm, Mg I 285.25 nm, Ca II 393.37, 396.89 nm, Ca I 422.70 nm, Na I 589.03, 589.64 nm, and K I 766.57, 769.97 nm had compact relationship with adulterant content. Best models for detecting the adulteration ratio of HFCS 55, HFCS 90, and rape honey were achieved by SR-PLSR, VIP-PLSR, and VIP-PLSR, with root-mean-square error (RMSE) of 8.9%, 8.2%, and 4.8%, respectively. This study provided a fast and simple approach for detecting honey adulteration.
关键词： partial least square regression,laser-induced breakdown spectroscopy,adulteration,feature variable,honey
更新于2025-09-23 15:19:57
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An image features assisted line selection method in laser-induced breakdown spectroscopy
摘要： Analytical lines play a crucial role in laser-induced breakdown spectroscopy (LIBS) technology. To improve the classification performance of LIBS, an image features assisted line selection (IFALS) method which based on spectral morphology and the characteristics of Harris corners was proposed. With this method, a classification experiment for 24 metamorphic rock samples was conducted with linear discriminant analysis (LDA) algorithm. The result showed that the classification accuracy was increased from 94.38% of the conventional classification model MLS-LDA (Manual line selection-linear discriminant analysis) to 98.54% of IFALS-LDA. Furthermore, the time required for the whole classification process was decreased from 2768.38 seconds of MLS-LDA to 4.36 seconds of the proposed method, thus the classification efficiency was greatly improved. In addition, compared with the existing automatic line selection method, the convergence rate of IFALS-LDA is significantly faster than that of ASPI (Automatic Spectral Peaks Identification)-LDA. This study demonstrates that LIBS assisted with the image features in machine vision can promote the analytical performance of LIBS technology.
关键词： Laser-induced breakdown spectroscopy,metamorphic rock,image features,linear discrimination analysis,analytical line selection
更新于2025-09-23 15:19:57
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Fast Classification of Geographical Origins of Honey Based on Laser-Induced Breakdown Spectroscopy and Multivariate Analysis
摘要： Traceability of honey is highly required by consumers and food administration with the consideration of food safety and quality. In this study, a technique named laser-induced breakdown spectroscopy (LIBS) was used to fast trace geographical origins of acacia honey and multi-floral honey. LIBS emissions from elements of Mg, Ca, Na, and K had significant differences among different geographical origins. The clusters of honey from different geographical origins were visualized with principal component analysis. In addition, support vector machine (SVM) and linear discrimination analysis (LDA) were used to quantitively classify the origins. The results indicated that SVM performed better than LDA, and the discriminant results of multi-floral honey were better than acacia honey. The accuracy and mean average precision for multi-floral honey were 99.7% and 99.7%, respectively. This study provided a fast approach for geographical origin classification, and might be helpful for food traceability.
关键词： geographical origin,classification,honey,laser-induced breakdown spectroscopy,multivariate analysis
更新于2025-09-23 15:19:57
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Laser-induced breakdown spectroscopy of uranium in the VUV range
摘要： Quantitative analysis of impurities in nuclear materials is necessary in a number of areas, including process control during manufacturing, quality control of products, or for nuclear forensics purposes. Due to the important handling constraints induced by the samples radioactivity and their containment inside airtight enclosures, optical analytical techniques have great advantages over standard ones that require sample preparation, like ICP-based techniques. Therefore, laser-induced breakdown spectroscopy (LIBS) is developed for fast quantitative analysis of impurities in uranium. Actinides are well-known to have a very large number of emission lines in the UV-visible spectral range, hence making the detection of trace or minor elements a real challenge. Therefore, in this study we explored the vacuum ultraviolet range (VUV), i.e. below 200 nm, in order to investigate if this spectral region is more favorable for elemental analysis of uranium by LIBS. As practically no data on VUV spectroscopy of uranium are available, we first analyzed the spectra obtained to assess the spectral density of uranium lines, both in the UV and VUV. Then, the detection limits of two elements, carbon and vanadium, were estimated. It was found that, in spite of a less dense and less intense uranium background in the VUV, this spectral region is not relevant for metal impurities whose spectra are marginally analytically useful in the VUV. Conversely, for non-metals having intense lines in the VUV, the detection limit can be significantly better than in the UV. This was already known for non-nuclear samples. This study extends that conclusion to nuclear materials and has important practical consequences on the implementation of a LIBS analyzer in a nuclear facility.
关键词： vanadium,uranium,Laser-induced breakdown spectroscopy,impurities detection,carbon,VUV range
更新于2025-09-23 15:19:57
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Quantification of calcium in infant formula using laser-induced breakdown spectroscopy (LIBS), Fourier transform mid-infrared (FT-IR) and Raman spectroscopy combined with chemometrics including data fusion
摘要： Laser-induced breakdown spectroscopy (LIBS), Fourier transform mid-infrared (FT-IR) and Raman spectroscopy combined with chemometrics were investigated to quantify calcium (Ca) content in infant formula powder (INF). INF samples (n=51) with calcium content levels (ca. 6.5-30 mg Ca/100kJ) were prepared in accordance with the guidelines of Commission Directive 2006/125/EC. Atomic absorption spectroscopy (AAS) was used as the reference method for Ca content determination. To predict Ca content in INF samples, partial least squares regression (PLSR) models that developed based on LIBS, Raman and FT-IR spectral data, respectively. The model developed using LIBS data achieved the best performance for the quantification of Ca content in INF (R2 (cross-validation (CV))-0.99, RMSECV-0.29 mg/g; R2 (prediction (P))-1, RMSEP-0.63 mg/g). PLSR models that developed based on data fusion of Raman and FT-IR spectral features obtained the second best performance (R2CV-0.97, RMSECV-0.38 mg/g; R2P-0.97, RMSEP-0.36 mg/g). This study demonstrated the potential of LIBS, FT-IR and Raman spectroscopy to accurately quantify Ca content in INF.
关键词： Fourier transform mid-infrared,laser-induced breakdown spectroscopy,chemometrics,Raman spectroscopy,calcium,infant formula
更新于2025-09-23 15:19:57
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High-accuracy prediction of carbon content in semi-coke by laser-induced breakdown spectroscopy
摘要： Semi-coke, as one kind of special coal resource with relatively high concentration carbon and low volatility, plays an important role in the coal chemical industry and city clean. Laser-Induced Breakdown Spectroscopy (LIBS) has been proved as an effective way to make an online analysis for the coal products. However, the lower volatility of semi-coke makes it hard to be pressed into a slice to get a smooth surface for a uniform laser-irradiation. Therefore, it is necessary to find an effective way to realize a high-accuracy LIBS detection for semi-coke application. Herein, two feasible ways of sample preparation are tried, one easy way is directly painting semi-coke powders on a tape that suitable for online fast monitoring, and the other complicated way is to mix binder into the semi-coke powder then that the uniformly and tightly coal slices are obtained, thus to improve the repeatability of measurement. Moreover, a totally new algorithm, support vector machine (SVM) combined with partial least square (PLS) regression(SVM-PLS), is utilized to establish an effective prediction model to make a high prediction accuracy. The coefficient of determination (R2), root mean square error of prediction (RMSEP), and average relative error (ARE) are 0.944, 0.90%, and 0.80%, respectively. In comparison with the result of the traditional PLS model, the SVM residual correction greatly improves the quality of the calibration curve and makes RMSEP and ARE reduced 0.17%, thus improves the prediction accuracy, which is much better than basic PLS regression. Meanwhile, the prediction error from binder mixed semi-coke slice is significantly reduced compared to that with directly painting samples on a tape. The maximum relative errors (MRE) are 2.71% and 5.19%, and the average RSD of the characteristic peaks are 12.1% and 16.2%, respectively, indicating that the easy way with painting sample on tape has little prediction uncertainties. Finally, in a three-day random test, the average RMSEP is 1.89% and average ARE is 1.74%, which also proves the binder additive can effectively reduce the matrix effect and enhance the stability of the spectrum for semi-coke measurement. The result proposes the proper LIBS analysis on semi-coke is a feasible and promising approach for on-line prediction of such kind of coal sample.
关键词： LIBS,prediction accuracy,Laser-Induced Breakdown Spectroscopy,semi-coke,carbon content,SVM-PLS
更新于2025-09-23 15:19:57
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Concentric multipass cell enhanced double-pulse laser-induced breakdown spectroscopy for sensitive elemental analysis
摘要： Although double-pulse laser-induced breakdown spectroscopy (DP-LIBS) is regarded as a promising technique in trace element analysis, its limit of detection (LOD) is not sufficient for some applications. The enhancement of spectral signal is the key to further improve the sensitivity of DP-LIBS. To further increase the sensitivity of DP-LIBS, a concentric multipass cell (CMC) enhanced DP-LIBS (CMC-DP-LIBS) technique is proposed for the first time, which makes full use of the energy of reheating laser by multi-reflection in CMC to enhance the spectral signal and lower LOD. 2.3 times signal enhancement of Mn I 403.08 nm line and 2.3 times decrease of LOD of Mn on the surface of zinc bulk compared with traditional orthogonal reheating DP-LIBS were attained. The signal enhancement factor can reach to 3.6 theoretically with the increase of reflectivity and the sizes of mirrors of CMC. This CMC-DP-LIBS provides a new approach to further improve the sensitivity of DP-LIBS and promotes its application in trace element detection.
关键词： Double-pulse,Concentric multipass cell enhancement,Laser-induced breakdown spectroscopy,Detection limit
更新于2025-09-23 15:19:57
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Plasma chemistry produced during laser ablation of graphite in air, argon, helium and nitrogen
摘要： Laser-induced plasma chemistry produced during the ablation of graphite targets at atmospheric pressure in air, argon, helium and nitrogen was studied through time-resolved atomic and molecular emission spectroscopy. The plasma plume and plasma chemistry were generated by focusing a 6-mm diameter, 212 mJ, 1064-nm nanosecond Nd:YAG laser to a spot size of about 1 mm diameter over graphite samples of 99.9% pureness. The atomic emissions C I 247.86 nm, N I 821.50 nm and O I 777.19 nm, and the molecular bands C2 (473.71 nm) and CN (359.04 nm and 388.30 nm) were monitored as a function of time (0.2 to 220 μs). While the C I and C2 emissions followed a near-exponential decay, the CN emission in air and nitrogen showed an emission behavior characterized by two local maxima at 0.2 μs and 20-30 μs after the plasma ignition. The first maximum was explained by the early plasma chemistry produced by the ablated carbon species and the confining background gas, whereas the second maximum was attributed to atomic recombination and shock wave-induced excitation of the plasma plume. Two main effects were observed when the ablation was produced in different background gases. First, the presence of oxygen (≈21%) in air had a negligible effect on atomic lines; however, the CN emission intensity and lifetime were significantly reduced in comparison with an atmosphere of 100% nitrogen. This was attributed to the reduction of nitrogen species as reaction partners during the plasma chemistry in air. Secondly, due to the assumed higher plasma temperature in Ar, this gas favored the emission intensity and lifetime of atomic species but hindered the formation of C2 species. Because the collection optics of the emission spectroscopy system was configured in backscatter mode, which integrates over the entire plasma volume and gate time without spatial resolution, the time-resolved behavior of the plasma emissions were only related to the number density of emitters but not to specific locations in the plasma volume.
关键词： Atomic-molecular emissions,Laser-induced breakdown spectroscopy,Plasma chemistry,Graphite
更新于2025-09-23 15:19:57
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Influence of aluminum nanoparticles and binders on the laser initiation of cyclotrimethylenetrinitramine
摘要： Aluminum nanoparticles were added into cyclotrimethylenetrinitramine (RDX) to enhance the laser absorption and lower the initiation energy of pulse laser. Polyvinyl acetate (PVA), polyvinyl butyral (PVB), and fluororubber (F2314) were added into RDX as binders to prepare the RDX-based composite explosives with desirable mechanical behavior. The influence of aluminum nanoparticles and binders on the light absorption, thermal behavior, laser initiation energy and the electron temperature in aluminum plasma were investigated using reflectance spectroscopy, differential scanning calorimetry, laser initiation and laser-induced breakdown spectroscopy. Results showed that the addition of aluminum nanoparticles could prominently lower the laser initiation energy of the RDX-based explosives. The RDX doped with 2.0% aluminum nanoparticles could be reliably initiated with 1.5 J/cm2 laser energy (1064 nm, 8 ns). The laser initiation energy increased to 1.7, 2.4 and 2.9 J/cm2 with the additions of 0.5%, 1.0% and 2.0% F2314 binders, respectively. When the addition of PVA and PVB increased to 2.0%, the RDX-based explosives couldn’t be initiated by pulse laser. When the pulse laser radiated on the surface of the RDX-based composite explosives, the aluminum nanoparticles absorbed the laser energy and were heated to high temperature to initiate the explosives. The addition of binders can provide desirable mechanical behavior, but the laser initiation energy increased because the heat transmission from aluminum nanoparticles to RDX was hindered.
关键词： Laser initiation,Laser-induced breakdown spectroscopy,Binder,Aluminum nanoparticle
更新于2025-09-19 17:13:59
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Forensic soil analysis using laser-induced breakdown spectroscopy (LIBS) and Fourier transform infrared total attenuated reflectance spectroscopy (FTIR-ATR): Principles and case studies
摘要： Soils are crucial trace evidence that can establish or exclude the relationship between a suspect, victim, or an object at a particular scene, which could contribute to building a case. Laser-induced breakdown spectroscopy (LIBS) and Fourier transform infrared-attenuated total reflectance (FTIR-ATR) spectroscopy have been demonstrated to be effective techniques for soil characterization owing to its being rapid, non-destructive, and convenient analysis with little sample preparation requirements. Therefore, the principles of LIBS and FTIR-ATR techniques for soil forensic analysis in typical soil samples were investigated and their practical feasibility was tested by applying the techniques to forensic soil samples in two criminal cases. Principal component analysis (PCA) of a typical soil sample indicated that five typical soil types were clearly distinguished by LIBS and FTIR-ATR spectra. Variations in the soil elements (i.e., Si, Mg, Al, Ca, K, O, and N) and functional groups (i.e., O?H/N?H, C=C/C=O, Si?O, CO3 2?, Al?OH, and NH2) are crucial indicators for soil identification. The casework results demonstrated that both LIBS and FTIR-ATR show great potential for forensic soil analysis in future cases.
关键词： forensics,laser-induced breakdown spectroscopy,criminalistics,Soil identification,mid-infrared attenuated reflectance spectroscopy
更新于2025-09-19 17:13:59