Laser-induced Breakdown Spectroscopy Technique Research Articles

Combination of laser-induced breakdown spectroscopy, and time–of–flight mass spectrometry for the quantification of CoCrFeNiMo high entropy alloys

In this paper, we present the preparation and quantification of the CoCrFeNiMo high entropy alloys that are commonly used in self-propelled stainless steel fabrication, shipbuilding, and other defense industries. Four samples of high entropy alloys, Mo (68.03–77.29%)-Cr (5.24–7.37%)-Fe (5.63–7.92%)-Ni (5.91–8.32%)-Co (5.93–8.36%) were prepared using a standard technique. The as-prepared samples have been quantified by combining Laser-Induced Breakdown Spectroscopy (LIBS) and Laser Ablation Time–of–Flight Mass Spectrometer (LA–TOF–MS) techniques. The LIBS experiments were performed using the second harmonic of a Nd: YAG laser at 532 nm, 100 mJ laser pulse energy, and 5 ns pulse duration, and the emission spectra were registered in the wavelength range from 250 to 870 nm using a set of four miniature spectrometers. It is endorsed that the calibration-free LIBS (CF–LIBS) and the Calibration Curve–Laser-Induced Breakdown Spectroscopy (CC–LIBS) techniques yield the elemental compositions at par with that determined by the LA–TOF–MS, and EDX techniques.

Assessment by laser-induced breakdown spectroscopy of penetration depth in limestones of four nano-biocides based on silver/titanium nanoparticles

• Laser induced breakdown spectroscopy (LIBS) technique for the in-depth analysis of nanoparticles used in cultural heritage field. • Biocidal treatment based on silver/titanium nanoparticles applied to limestone employed in heritage buildings for protective purposes. • High sensitivity LIBS technique for detecting a small amount of nanoparticles treatment. Four biocidal treatments based on nanoparticles were designed and their penetration depths were characterized by laser-induced breakdown spectroscopy (LIBS) technique. This kind of biocidal nanoparticles are being studied to be employed in historic buildings and stone monuments due to their capability to inhibit the growth of biofoulings. The effectiveness of the treatment is related to the penetration depth of the nanoparticles in the limestone pore. For this reason, LIBS depth profiling was used in this work to characterize the diffusion of the nanoparticles in the limestone matrix and to compare the penetration depth of the different treatments. Four different nano-biocides based on silver/titanium dioxide nanoparticles were analysed by LIBS in limestone from Novelda quarry (Alicante, Spain). This limestone has been widely employed in both historical and contemporary buildings in Spain. The positive detection of the emission line of Ag at 338.289 nm was examined in the depth-related emission spectra as evidence of the presence of the silver nanoparticles and derived nanocomposites in the limestone matrix. The LIBS depth-profiles that were generated, showed a decrease of the Ag net signal with depth due to the diffusion of the nanoparticles in the limestone. Furthermore, the comparison of the in-depth sequences of spectra, and of the Ag depth profiles evidenced penetration differences between the nano-biocides which were explained by differences in the hydrodynamic diameter of the nanoparticles that would affect their diffusion in the limestone pore. The results of this assessment demonstrate the capability and potential of LIBS technique for the in-depth characterization of the nanoparticles and for the comparison of the effectiveness of nanoparticles biocidal treatments based on their penetration in the stone matrix.

Model transfer method based on piecewise direct standardization in laser-induced-breakdown spectroscopy.

A large number of certified samples are usually required to build models in the quantitative analysis of complicated matrices in laser-induced-breakdown spectroscopy (LIBS). Because of differences among instruments, including excitation and collection efficiencies, a quantitative model made on one instrument is difficult to apply directly to other instruments. Each instrument requires a large number of samples to model, which is very labor intensive and will hinder the rapid application of the LIBS technique. To eliminate the differences in spectral data from different instruments and reduce the cost of building new models, a piecewise direct standardization method combined with partial least squares (PLS_PDS) is studied in this work. Two portable LIBS instruments with the same configuration are used to obtain spectral data, one of which is called a master instrument because its calibration model is directly built on a large number of labeled samples, and the other of which is called a slave instrument because its model is obtained from the master instrument. The PLS_PDS method is used to build a transfer function of spectra between the master instrument and slave instrument to reduce the spectral difference between two instruments, and thus one calibration model can adapt to different instruments. Results show that for multiple elemental analyses of aluminium alloy samples, the number of samples required for slave modeling was reduced from 51 to 14 after model transferring by PLS_PDS, and the quantitative performance of the slave instrument was close to that of the master instrument. Therefore, the model transfer method can obviously reduce the sample number of building models for slave instruments, and it will be beneficial to advance the application of LIBS.

APLICACIÓN DE LA TÉCNICA LIBS EN LA DETECCIÓN DE Ti EN EFLUENTESLÍQUIDOS INDUSTRIALES

In the graphic and textile industries, liquid effluents are generated from the dyes used in the different processes. In these effluents, a heavy metal of great interest, such as Titanium (Ti), is found. This element is not currently contemplated in the environmental legal framework in Argentina, and there are no known diagnostic techniques that are responsible for its measurement. This work studied the feasibility of applying the Laser-Induced Breakdown Spectroscopy (LIBS)technique for detecting Ti in industrial effluents. In the assembly of samples, a possible stabilization method was established for their final disposal, considering the encapsulation in cement for construction. Based on this, four samples were assembled with Portland cement with the addition of ashes, obtained from subjecting the effluents of a graphic industry to a series of physicochemical processes. For a possible quantification process by LIBS, the thin plasma model was proposed, which established the best post-breakdown and integration times for registering the 521.04 nm line ofTi I. As the study’s final results, apost-breakdowntime was 35μs and an integration time of 300 ns. With this, it is intended to optimize the measurement parameters for the analysis and calculation of concentrations, thus promoting the use of the LIBS technique as feasible for this type of measurement.

Identification and differentiation between olive oil from different Al Jouf olive field areas by optical spectroscopic techniques

Identification and determination of the authenticity of the produced oliveoil by potential spectroscopic techniques have become of nutritional importance to human diet. The study of olive oil is significantly important in trade and business due to the commercial fraud that occurs in the associated business. Al Jouf city, which lies in the northern part of the Kingdom of Saudi Arabia, is famous for its production of the finest quality of olive oil in the kingdom. There is a need to develop feasible in situ identification techniques for the recognition of and discrimination between different olive oil products. One main laser spectroscopic technique known for its superiority over other conventional techniques as an elemental analytical tool is laser induced breakdown spectroscopy (LIBS). Inductive couple plasma mass spectrometry is also a well-known conventional technique with very high sensitivity to most of the elements to the range of parts per billion. However, it requires extensive sample preparation and consumes a lot of time. It has been used as a reference technique to validate the results of the LIBS technique. Moreover, phenolic compounds, which are essential in various types of functional food and folk medicine, were investigated using conventional vibrational analytical tools such as Fourier transform infrared spectroscopy.

Rapid Identification of Beached Marine Plastics Pellets Using Laser-Induced Breakdown Spectroscopy: A Promising Tool for the Quantification of Coastal Pollution.

The rapid identification of beached marine micro-plastics is essential for the determination of the source of pollution and for planning the most effective strategies for remediation. In this paper, we present the results obtained by applying the laser-induced breakdown spectroscopy (LIBS) technique on a large sample of different kinds of plastics that can be found in a marine environment. The use of chemometric analytical tools allowed a rapid classification of the pellets with an accuracy greater than 80%. The LIBS spectrum and statistical tests proved their worth to quickly identify polymers, and in particular, to distinguish C-O from C-C backbone pellets, and PE from PP ones. In addition, the PCA analysis revealed a correlation between appearance (surface pellets roughness) and color (yellowing), as reported by other recent studies. The preliminary results on the analysis of metals accumulated on the surface of the pellets are also reported. The implication of these results is discussed in view of the possibility of frequent monitoring of the marine plastic pollution on the seacoast.

Hollow-core optical fiber-based laser-induced breakdown spectroscopy technique for the elemental analysis of pulverized coal

Hollow-core optical fiber-based laser-induced breakdown spectroscopy technique for the elemental analysis of pulverized coal

Vibrational Emission Study of the CN and C2 in Nylon and ZnO/Nylon Polymer Using Laser-Induced Breakdown Spectroscopy (LIBS).

The laser-induced breakdown spectroscopy (LIBS) technique was performed on polymers to study the neutral and ionic emission lines along with the CN violet system (B2Σ+ to X2Σ+) and the C2 Swan system (d3 Пg–a3 Пu). For the laser-based emission analyses, the plasma was produced by focusing the laser beam of a Q-switched Nd: YAG laser (2ω) at an optical wavelength of 532 nm, 5 ns pulse width, and a repetition frequency of 10 Hz. The integration time of the detection system was fixed at 1–10 ms while the target sample was positioned in air ambiance. Two organic polymers were investigated in this work: nylon and nylon doped with ZnO. The molecular optical emission study of nylon and doped nylon polymer sample reveals CN and C2 molecular structures present in the polymer. The vibrational emission analysis of CN and C2 bands gives information about the molecular structure of polymers and dynamics influencing the excitation structures of the molecules. Besides, it was further investigated that the intensity of the molecular optical emission structure strongly depends on the electron number density (cm−3), excitation temperature (eV), and laser irradiance (W/cm2). These results suggest that LIBS is a reliable diagnostic technique for the study of polymers regarding their molecular structure, identification, and compositional analysis.

Laser induced breakdown spectroscopy (LIBS) as a technique to detect copper in plastic and microplastic waste.

Plastic waste is an environmental problematic, not only because of its own contamination, but also because it can act as a vector for other pollutants, particularly metals. In this work, taking advantage of the sensitivity of the LIBS technique, the presence of copper in plastics and microplastics present in a stream that receives effluents from a medium-sized city was determined. The influence of the digestion process on the collected samples was analyzed. On the other hand, copper retention in commonly used plastics submerged in stream water and in a solution prepared in the laboratory was analyzed. This study confirms that both macroplastics and microplastics collected from a stream that receives effluents from a city, can retain copper.

Laser Spectroscopic Characterization for the Rapid Detection of Nutrients along with CN Molecular Emission Band in Plant-Biochar

We report a quantitative analysis of various plant-biochar samples (S1, S2 and S3) by utilizing a laser-induced breakdown spectroscopy (LIBS) technique. For LIBS analysis, laser-induced microplasma was generated on the target surface by using a focused beam through a high-power Nd: YAG laser and optical emission spectra were recorded using a charged coupled device (CCD) array spectrometer, with wavelength ranges from 200 nm to 720 nm. The spectroscopical analysis showed the existence of various ingredients, including H, Li, Ca, Na, Al, Zn, Mg, Sr, Si, and Fe, along with a CN molecular emission band due to B2Σ+ − X2Σ+ electronic transition. By assuming conditions of the plasma is optically thin and in LTE, calibration-free laser-induced breakdown spectroscopy (CF-LIBS) was utilized for the compositional analysis of the ingredients present in the three plant-biochar samples. To lower the uncertainties, we used an average composition (%) of the three plant-biochar samples. The quantitative study of the plant-biochar samples was also achieved using the energy dispersive X-ray (EDX) technique, showing good agreement with the CF-LIBS technique. In addition, statistical analysis, such as principal component analysis (PCA), was performed for the clustering and classification of the three plant-biochar samples. The first three PCs explained an overall ~91% of the variation in LIBS spectral data, including PC1 (58.71%), PC2 (20.9%), and PC3 (11.4%). These findings suggest that LIBS is a robust tool for rapid measurement of heavy as well as light elements, such as H, Li, and nutritional metals in plant-biochar samples.

Laser-induced breakdown spectroscopy monitoring of aluminum alloys laser cleaning process

The paper considers an approach to monitoring the condition of the treated surface in real time based on the laser-induced breakdown spectroscopy technique. As a result of the study, the aluminum alloy was cleaned from the plimer coating, spectral analysis was carried out, the relationship between the processing modes and the thickness of the coating being removed was experimentally established, which allows removing the paint coating in one pass without damaging the underlying layers. The optimal spectral range for the control operation, the contrasting spectral lines of the elements that make up the coating, the optimal parameters of laser exposure are determined based on the monitoring data of the spectral signal recorded during laser processing

Characteristics of CaFe Plasma Parameters by Laser-Induced Breakdown Spectroscopy Technique

In this work, the effect of laser energy on the properties of a CaFe plasma generated by a Q-switched Nd: YAG laser at the fundamental wavelength was studied using spectroscopy. The Boltzmann plot and Stark broadening method were used to measure the main plasma parameters (electron temperature and electron density). The electron temperature ranged (1.295 -1.929) eV, the electron density ranged (2.25 - 3) ×1018𝑐𝑚−3, and the laser energy ranged (400 – 700) mJ. Other basic plasma properties were also measured, including the Debye length, and the plasma frequency. Laser energy affects all plasma parameters, according to our results.

Enhanced Laser-Induced Breakdown Spectroscopy for Heavy Metal Detection in Agriculture: A Review.

Heavy metal pollution in agriculture is a significant problem that endangers human health. Laser-induced breakdown spectroscopy (LIBS) is an emerging technique for material and elemental analysis, especially heavy metals, based on atomic emission spectroscopy. The LIBS technique has been widely used for rapid detection of heavy metals with its advantages of convenient operation, simultaneous detection of multi-elements, wide range of elements, and no requirement for the state and quantity of samples. However, the development of LIBS is limited by its detection sensitivity and limit of detection (LOD). Therefore, in order to improve the detection sensitivity and LOD of LIBS, it is necessary to enhance the LIBS signal to achieve the purpose of detecting heavy metal elements in agriculture. This review mainly introduces the basic instruments and principles of LIBS and summarizes the methods of enhanced LIBS signal detection of heavy metal elements in agriculture over the past 10 years. The three main approaches to enhancing LIBS are sample pretreatment, adding laser pulses, and using auxiliary devices. An enhanced LIBS signal may improve the LOD of heavy metal elements in agriculture and the sensitivity and stability of the LIBS technique. The enhanced LIBS technique will have a broader prospect in agricultural heavy metal monitoring and can provide technical support for developing heavy metal detection instruments.

Quantification of dimethoate and chlorpyrifos residues in green leafy vegetables by laser-induced breakdown spectroscopy

The presence of pesticide residues in food represents a significant threat to consumers, mainly due to their toxicity to humans. Evidence has even been found that determines the relationship between many diseases and deaths from ingestion, contact, or mishandling. The need to introduce controls on pesticide residues has become an issue of central concern to society, given the increasing knowledge about the potential dangers associated with the use of pesticides. So the objective of the present study was to evaluate and analyze the feasibility of using the laser-induced breakdown spectroscopy technique as a potential tool for the quantification of dimethoate and chlorpyrifos in green leafy vegetables. For this purpose, reference samples with powdered chard were made using the aforementioned pesticides, with increasing concentrations in a range of 0–80 mg kg−1 and 0–250 mg kg−1, respectively. By applying calibration curves, it was possible to quantify pesticide residues by measuring S (416.26 nm), P (460.21 nm), and Cl (837.59 nm) emission lines, with limits of detection of 1.7 mg kg−1, 0.8 mg kg−1, and 6.9 mg kg−1 respectively. Clear evidence of the applicability of this technique as a potential tool for the study of pesticides in food matrices was established. It was achieved by minimum sample preparation, ensuring a rapid analysis, low application costs, and without toxic waste production. In this way, its use as a preliminary evaluation technique or complementary to the analytical methods traditionally already used is evidenced.

The potential of combining laser-induced breakdown spectroscopy and Raman spectroscopy data for the analysis of wood samples

We report on combining the surface analysis technique of Laser-induced Breakdown Spectroscopy (LIBS) with Raman spectroscopy. The combination of both techniques enables to study the chemical composition of the sample in a broader context when combining elemental and molecular information. Obtained elemental and molecular spectra are characteristic for individual biological samples (e.g., organs and cells) and are considered as a fingerprint. In this study, Raman spectroscopy is used for the detection of important molecular complexes in selected wood samples, e.g., accurate lignin and cellulose content on distinct spots of the sample surface. We chose Raman as a standard reference technique that is used for the lignin/cellulose ratio estimation. To complement the molecular information, LIBS technique was employed for the imaging of essential nutrients, e.g., Ca, Na, and K. Consequently, the contribution from both analytical techniques was combined and changes in the molecular content were visually correlated to the abundance of nutrition elements and show a direct dependence between the two signal responses. Thus, we can get specific answers to relation of lignin and cellulose formation with nutrients within the plant tissue. This evidence may then be helpful for the study of the effect of various environmental and stress factors.

Geochemistry study of soil affected catastrophically by tsunami disaster triggered by 2004 Indian Ocean earthquake using a fourth harmonics (λ = 266 nm) Nd:YAG laser induced breakdown spectroscopy

In this work, laser induced breakdown spectroscopy (LIBS) analysis of the soil samples collected from Aceh, a place in Indonesia worst affected by 2004 Indian Ocean tsunami, was conducted. In the LIBS experimental system, a high energy pulsed laser beam was focused on the tsunami affected soil samples and the atomic emission lines, originating from the laser induced plasma were recorded using locally developed laser induced breakdown spectrometer. Our results show that the concentrations of many elements especially terrestrial markers, namely titanium, iron, and carbonate marker such as magnesium, are higher in the tsunami-affected samples than that in the unaffected samples collected from the same neighborhood. The quantification of Ti, Fe and Mg were carried out using Ti II 334.94, Fe I 438.35, and Mg I 277.98 nm atomic transition lines respectively by drawing the calibration curve by preparing the samples of known concentrations in unaffected soil matrix. In order to ensure accurate quantification, the local thermal equilibrium of the laser-induced plasma was verified using Mc Writher criterion, for which the plasma temperature was estimated using linearized Boltzmann plot for six iron atomic transition lines and the electron number density in the plasma was estimated using Stark broadened Fe I 540.4 nm atomic lines. The estimated temperature and electron number density of the laser induced plasma are 9642 K and 3.5 × 10 16 cm −3 respectively. The concentrations of Ti, Fe and Mg in tsunami unaffected soil are 0.09, 3.2 and 0.02 w/w% and in tsunami affected soil are 0.14, 7.9 and 0.048 w/w% respectively. These values are in good agreement with XRF data. The elemental ratios extracted from LIBS signal intensity revealed that LIBS emission intensity ratios of several elements, such as Si/Ti, Al/Ti and Sr/Ba are potential candidates as the distinctive geochemical signature for identification the soil impacted and unimpacted by the 2004 Indian Ocean giant tsunami. The advantage of using LIBS for the elemental analysis is that the sample can be analyzed in its pristine form without any need cumbersome sample preparation method, which has the risk of bringing in external additives through chemicals used for the sample preparation. Other advantages of LIBS technique are that the analysis can be in situ and can be carried out remotely.

Flame stability and equivalence ratio assessment of turbulent partially premixed flames

This study is geared toward generating highly stabilized partially premixed flames at various levels of turbulence and partially premixing. Therefore, with the help of the laser-induced breakdown spectroscopy (LIBS) technique, a new burner was constructed and employed to quantitatively estimate the mixture equivalence ratio (Φ) within the flame. Two turbulence generator disks, five degrees of partial premixing, and two fuels were used to assess the flame stability. Natural gas (NG) and liquefied petroleum gas (LPG) were used as fuels. The LIBS spectrum's most common atomic emission lines which include hydrogen, nitrogen, oxygen, and carbon, were chosen to establish the correlation between emission lines' intensity and the flame's mixture equivalence ratio. The results showed that the stability of NG flame was less sensitive to the variation of the partially premixing levels. In contrast, the LPG flames were more susceptible to the variation of the mixing degree. At a lower level of partially premixing, NG flames were more stable, and as the mixing degree increased, the stability of NG flames was reduced compared to LPG flames. In addition, the results showed that the equivalence ratio radial profiles are more homogeneous and have lower RMS fluctuation for the wider slot of the turbulence generator disc. Furthermore, the larger turbulence generator disk's higher turbulent intensity contributed in posting the mixing process and enhancing mixture homogeneity over even shorter recess distances than the smaller disk generator.

Fast identification of mural pigments at Mogao Grottoes using a LIBS-based spectral matching algorithm

To quickly identify the mineral pigments in the Dunhuang murals, a spectral matching algorithm (SMA) based on four methods was combined with laser-induced breakdown spectroscopy (LIBS) for the first time. The optimal range of LIBS spectrum for mineral pigments was determined using the similarity value between two different types of samples of the same pigment. A mineral pigment LIBS database was established by comparing the spectral similarities of tablets and simulated samples, and this database was successfully used to identify unknown pigments on tablet, simulated, and real mural debris samples. The results show that the SMA method coupled with the LIBS technique has great potential for identifying mineral pigments.

Rapid identification of volatile organic compounds and their isomers in the atmosphere

Isomers are widely present in volatile organic compounds (VOCs), and it is a tremendous challenge to rapidly distinguish the isomers of VOCs in the atmosphere. In this work, laser-induced breakdown spectroscopy (LIBS) technology was developed to online distinguish VOCs and their isomers in the air. First, LIBS was used to directly detect halogenated hydrocarbons (a typical class of VOCs) and the characteristic peaks of the related halogens were observed in the LIBS spectra. Then, comparing the LIBS spectra of various samples, it was found that for VOCs with different molecular formulas, although the spectra are completely the same in elemental composition, there are still significant differences in the relative intensity of the spectral lines and other information. Finally, in light of the shortcomings of traditional LIBS technology in identifying isomers, machine learning algorithms were introduced to develop the LIBS technique to identify the isomers of atmospheric VOCs, and the recognition results were very good. It is proved that LIBS combined with machine learning algorithms is promising for online traceability of VOCs in the atmospheric environment.

Towards robust calibration models for laser-induced breakdown spectroscopy using unsupervised clustered regression techniques

One of the caveats of laser-induced breakdown spectroscopy technique is the performance for quantification purposes, in particular when the matrix of the sample is complex or the problem spans over a wide range of concentrations. These two questions are key issues for geology applications including ore grading in mining operations and typically lead to sub-optimal results. In this work, we present the implementation of a class of clustered regression calibration algorithms, that previously search the sample space looking for similar samples before employing a linear calibration model that is trained for that cluster. For a case study involving lithium quantification in three distinct exploration drills, the obtained results demonstrate that building local models can improve the performance of standard linear models in particular in the lower concentration region. Furthermore, we show that the models generalize well for unseen data of exploration drills on distinct rock veins, which can motivate not only further research on this class of methods but also technological applications for similar mining environments.