Single Laser Induced Breakdown Spectroscopy Research Articles

Laser-induced breakdown spectroscopy for rapid and accurate qualitative analysis of elemental composition in fertilizers

Through elemental analysis, laser-induced breakdown spectroscopy (LIBS), a quick and effective analytical method, has enormous potential to advance agriculture. In this context, our study intends to better the fertilizer sector by utilizing LIBS’s capabilities. The main objective is to make it possible to rapidly and accurately analyze the elements in frequently used fertilizers such as nitrophos (NP), diammonium phosphate (DAP), and single super phosphate (SSP). We identify all elements contained in the fertilizers using qualitative and semi-quantitative analysis utilizing a single LIBS shot by noting their matching spectral lines and peak positions. This identification is validated more thoroughly by matching peak positions to the National Institute of Standards and Technology (NIST) database. Phosphorus (P), potassium (K), iron (Fe), calcium (Ca), nickel (Ni), and aluminum (Al) are effectively recognized due to their distinct spectral fingerprints. Our findings highlight the vital need to precisely characterize fertilizer content in order to maximize agricultural yield. Furthermore, our approach presents an efficient means for rapid and precise analysis of fertilizers, offering the advantage of minimal sample requirements.

Strontium isotope analysis using laser-induced breakdown spectroscopy and molecular laser-induced fluorescence at various atmospheric conditions

The strontium isotope was analyzed by the combination system of laser-induced breakdown spectroscopy (LIBS) and molecular laser-induced fluorescence (MLIF). The fluorescence from A1Σ+ → X1Σ+ transition of strontium monoxide was observed by the selective excitation of individual vibrational band heads, and its spectral feature was investigated under atmospheric conditions being adjusted. In the fluorescence spectra of LIBS-MLIF, the signal intensity was improved about 10 times higher than the single LIBS, and each isotopologue could be clearly identified with an isotope shift of about 0.1 nm. By comparing these fluorescence signals, the isotope effect on molecular radicals in laser-induced plasma was investigated. The spatial distribution and the formation kinetics of isotopologues could be influenced by the isotopic effect, which exhibits a unique fluorescence behavior. It is noteworthy that the degree of isotopic effect on radicals could be modulated by controlling the atmosphere. Under the condition of reduced isotope effect, the strontium isotopic abundance could be accurately estimated within the error of 5% by the fluorescence ratio. The present work not only demonstrated the feasibility of LIBS-MLIF for the detection of strontium isotopes, but also provides novel insight into the molecular formation and isotopic effects in laser-induced plasma.

Discrimination of Radix Astragali according to geographical regions by data fusion of laser induced breakdown spectroscopy (LIBS) and infrared spectroscopy (IR) combined with random forest (RF)

Data fusion of Laser-induced breakdown spectroscopy (LIBS) and infrared spectroscopy (IR) combined with random forest (RF) was proposed to identify Radix Astragali from different geographical regions. Firstly, the LIBS and IR spectra of 19 Radix Astragali samples were collected and analyzed. Then, an unsupervised discriminant model based on principal components analysis (PCA) with single LIBS and IR spectra was applied to identify Radix Astragali. The results indicated that three types of Radix Astragali samples can not be accurately distinguished using PCA. To distinguish Radix Astragali accurately, a supervised discriminant model based on RF was applied to identify Radix Astragali. The optimal RF discriminant models based on single LIBS or IR were obtained by selecting appropriate pretreatment methods. In low-level data fusion, the optimal LIBS and IR spectra were concatenated into a matrix to construct RF discriminant model. In mid-level data fusion, feature variables were extracted by variable importance (VI) measurement on basis of low-level fused data and the optimal variables were used as input variables to construct RF discriminant model. The results indicated that the predictive performance of RF model based on data fusion was better than the single LIBS or IR method. The predictive performance of RF model based on mid-level data fusion was best and the corresponding sensitivity, specificity and accuracy for the test set were 0.9667, 0.9833 and 0.9778. Additionally, the modeling time was 6.9 s. Summarily, RF model on basis of data fusion of LIBS and IR can provide a rapid and accurate discriminant method for the Radix Astragali from different regions.

Discrimination of automotive glass by conjoint Raman and laser-induced breakdown spectroscopy and multivariate data analysis

Conjoint laser-induced breakdown spectroscopy (LIBS) and Raman spectroscopy and high level data fusion were used to discriminate sixteen different glass samples by principal component analysis (PCA). LIBS provides information on the elemental composition of a sample and Raman spectroscopy gives information about the molecular composition. The results were compared to single LIBS and Raman measurements as well as to μ-XRF and SEM-EDS which are also frequently used in glass analysis. The direction dependent Mahalanobis distance between the sample point groups in the space of the most significant principle components was evaluated as a criterion for potential discrimination of the different samples. Very good discrimination (up to 99%) was achieved with conjoint LIBS and Raman and high level data fusion, as well as LIBS alone. The discrimination is based primarily on different contents of trace elements (e.g., Fe, Ti, Ba, Sr), which was confirmed by the μ-XRF and SEM-EDS and differences in fluorescence (detected by Raman). Besides the similar discrimination power of LIBS and conjoint LIBS and Raman, the combination and fusion of LIBS and Raman leads to greater distances between the data in the principal component space due to the additional information added by Raman. This should result in a lower misclassification rate of unknown samples. Results show that conjoint LIBS and Raman spectroscopy can be an alternative in the forensic analysis of glass samples.

Forensic Analysis of Commercial Inks by Laser-Induced Breakdown Spectroscopy (LIBS).

Laser-induced breakdown spectroscopy (LIBS) was tested for all of the relevant issues in forensic examinations of commercial inks, including classification of pen inks on one paper type and on different paper types, determination of the deposition order of layered inks, and analysis of signatures and toners on one questioned document. The scope of this work was to determine the potential of a single LIBS setup that is compatible with portable instruments for different types of ink analysis, rather than building a very large database for inks and papers. We identified up to seven metals characteristic for the examined inks, which allowed to fully discriminate all eight black inks on one type of printing paper. When the inks were tested on ten different papers, the correct classification rates for some of them were reduced for reasons thoroughly studied and explained. The replicated tests on three crossing points, each one involving a pair of blue or black inks, were successful in five cases out of six. In the test simulating documents of forensic interest (questioned documents), LIBS was able to correctly identify the differences in three inks used for signatures on one of the three pages and the use of different printing inks on each page of the document.

Enhancement of long wavelength preheating in dual-beam laser induced breakdown spectroscopy

Dual-beam laser induced breakdown spectroscopy (LIBS) is more sensitive than conventional single-pulse LIBS. A combined configuration of Nd:YAG and CW- CO2 lasers is used to improve the emission intensity of LIBS. The plasma of Al sample was observed under CW-CO2 laser and Nd:YAG laser excitation. The enhancement radiation was obtained from dual-beam LIBS rather than single LIBS, which indicated that IR preheating can cause significant enhancement of plasma. The effects of CO2 laser spot size, laser irradiation time and laser power on plasma emission intensity were investigated. And on this basis, the variation of electron temperature and electron density of plasma with delay time is obtained.

Laser-induced breakdown spectroscopy: Extending its application to soil pH measurements

Acid–base equilibria are involved in almost all the processes that occur in soil. The bioavailability of nutrients for plants, for instance, depends on the solubilization of mineral nutrients in the soil solution, which is a pH-dependent process. The determination of pH in soil solutions is usually carried out by potentiometry using a glass membrane electrode, after extracting some of the soil components with water or CaCl2 solution. The present work describes a simple method for determining the pH of soil, using laser-induced breakdown spectroscopy (LIBS). Sixty samples presenting different textural composition and pH (previously determined by potentiometry) were employed. The samples were divided into a calibration set with fifty samples and a validation set with ten samples. LIBS spectra were recorded for each pelleted sample using laser pulse energy of 115mJ. The intensities of thirty-two emission lines for Al, Ca, H, and O were used to fit a partial least squares (PLS) model. The model was validated by prediction of the pH of the validation set samples, which showed good agreement with the reference values. The prediction mean absolute error was 0.3 pH units and the root mean square error of the prediction was 0.4. These results highlight the potential of LIBS for use in other applications beyond elemental composition determinations. For soil analysis, the proposed method offers the possibility of determining pH, in addition to nutrients and contaminants, using a single LIBS measurement.

An investigation of Laser Induced Breakdown Spectroscopy for use as a control in the laser removal of rock from fossils found at the Malapa hominin site, South Africa

Laser Induced Breakdown Spectroscopy (LIBS) was used to study the spectra from fossils and surrounding rock recovered from the Cradle of Mankind site at Malapa, South Africa. The objective was to find a suitable spectral line(s), specific to fossils, which could be used as a control signal to limit damage to fossils during high speed laser removal of the encasing rock. The calcified clastic matrix (rock) encasing the fossils was found to emit a variety of complex LIBS spectra. Nevertheless, it was found possible to distinguish fossils in a single LIBS pulse, and without significant damage to the fossil, using spectral lines of neutral phosphorus.

Evaluation of laser induced breakdown spectroscopy for multielemental determination in soils under sewage sludge application

Laser induced breakdown spectroscopy (LIBS) is an atomic emission spectroscopy technique for simple, direct and clean analysis, with great application potential in environmental sustainability studies. In a single LIBS spectrum it is possible to obtain qualitative information on the sample composition. However, quantitative analysis requires a reliable model for analytical calibration. Multilayer perceptron (MLP), an artificial neural network, is a multivariate technique that is capable of learning to recognize features from examples. Therefore MLP can be used as a calibration model for analytical determinations. Accordingly, the present study proposes to evaluate the traditional linear fit and MLP models for LIBS calibration, in order to attain a quantitative multielemental method for contaminant determination in soil under sewage sludge application. Two sets of samples, both composed of two kinds of soils were used for calibration and validation, respectively. The analyte concentrations in these samples, used as reference, were determined by a reference analytical method using inductively coupled plasma optical emission spectrometry (ICP OES). The LIBS–MLP was compared to a LIBS–linear fit method. The values determined by LIBS–MLP showed lower prediction errors, correlation above 98% with values determined by ICP OES, higher accuracy and precision, lower limits of detection and great application potential in the analysis of different kinds of soils.

Simultaneous optimization by neuro-genetic approach for analysis of plant materials by laser induced breakdown spectroscopy

A simultaneous optimization strategy based on a neuro-genetic approach is proposed for selection of laser induced breakdown spectroscopy operational conditions for the simultaneous determination of macro-nutrients (Ca, Mg and P), micro-nutrients (B, Cu, Fe, Mn and Zn), Al and Si in plant samples. A laser induced breakdown spectroscopy system equipped with a 10 Hz Q-switched Nd:YAG laser (12 ns, 532 nm, 140 mJ) and an Echelle spectrometer with intensified coupled-charge device was used. Integration time gate, delay time, amplification gain and number of pulses were optimized. Pellets of spinach leaves (NIST 1570a) were employed as laboratory samples. In order to find a model that could correlate laser induced breakdown spectroscopy operational conditions with compromised high peak areas of all elements simultaneously, a Bayesian Regularized Artificial Neural Network approach was employed. Subsequently, a genetic algorithm was applied to find optimal conditions for the neural network model, in an approach called neuro-genetic. A single laser induced breakdown spectroscopy working condition that maximizes peak areas of all elements simultaneously, was obtained with the following optimized parameters: 9.0 µs integration time gate, 1.1 µs delay time, 225 (a.u.) amplification gain and 30 accumulated laser pulses. The proposed approach is a useful and a suitable tool for the optimization process of such a complex analytical problem.

Spectroscopic analysis of works of art using a single LIBS and pulsed Raman setup

A nanosecond pulsed laser setup has been optimized to perform laser-induced breakdown spectroscopy (LIBS) and pulsed Raman spectroscopy measurements in the field of cultural heritage. Three different samples of artistic/architectural interest with different typologies have been analyzed. The results from the two techniques allowed the identification of the materials used in their manufacture or contaminating them, probably coming from atmospheric pollution and biological activity. No sampling and sample preparation was required before the measurements, and no visual or structural damage was observed. Depth profiling using LIBS was performed in one of the samples, providing elemental information along the different layers composing the object and covering its surface. The quality of the results and the rather short time needed for the measurements and for switching between techniques confirmed the instrument's capabilities and specificity for dealing with objects of artistic or historical interest.