Laser-induced Breakdown Spectroscopy Instrument Research Articles

Quantitative analysis of mineral elements in hair and nails using calibration-free laser-induced breakdown spectroscopy

Human biomarkers, such as hair and nails, often provide a continuous record of element concentration to indicate the nutritional status and metabolic changes. Laser-induced breakdown spectroscopy (LIBS), as a rapid detection method without sample preparation, provides a good alternative for measuring mineral elements in hair and nails. For biomedical applications of LIBS, high-precision and high-sensitivity instruments are commonly used in LIBS systems, such as Mechelle 5000 coupled with iStar ICCD. Their high cost limits the wide application of LIBS instruments. In this work, we used a low-cost autofocus LIBS system to obtain the spectral lines directly from hair and nails. The calibration-free LIBS (CF-LIBS) assisted with the standard reference line method was used to quantify the content ratio of Ca/Na and Mg/Na in hair and nails. The results showed that the relative errors between quantitative results of CF-LIBS and ICP-OES were less than 10% in hair and nails, which verified the accuracy of this method. These results illustrated that CF-LIBS assisted with the standard reference line method is a promising tool for biomedicine.

A study of the effects of gamma radiation on optical components used in specially constructed hot cell laser-induced breakdown spectroscopy (LIBS) instruments

Two innovative hot cell Laser-Induced Breakdown Spectroscopy (LIBS) instruments, designed and built by Applied Photonics Limited, are set to be deployed for the purpose of material characterisation in a high radiation environment. One LIBS instrument uses a ‘through-wall’ optical periscope, where the laser and optical spectrograph are located outside of the hot cell. The second instrument uses a remote probe located within the hot cell, containing a compact Nd:YAG (neodymium-doped yttrium aluminium garnet) passively Q-switched laser and plasma light collection optics.The design of both LIBS instruments means that some optical components (e.g. prisms, lenses, fibre optic cables and, in the case of the in-cell remote probe, a Nd:YAG laser head custom-designed and manufactured by Applied Photonics Ltd) will be exposed to high levels of gamma radiation. This entails that these components must be suitably reliable and gamma radiation resistant to last the duration of the planned work. In this article, we report on the results of a limited study on the effect of gamma irradiation (5 kGy, 25 kGy and 50 kGy absorbed dose using a cobalt-60 gamma source) on the optical properties of BK7 (Crown glass) and Ultra-Violet Fused Silica (UVFS) lenses, both with and without high-energy V-coat anti-reflection coating, and UVFS fibre optic cables. The effect of gamma irradiation on the pulsed laser beam energy output of three passively Q-switched Nd:YAG laser heads was also evaluated. The performance of each of the laser heads was tested before and after gamma irradiation by using an energy meter to measure the laser energy output of each of the three laser heads. The optical transmission properties of the components used for plasma light collection and transmission (i.e. lenses, fibre-optics) were tested using a deuterium-halogen lamp in combination with an optical spectrometer. In this limited study, we found that the BK7 lenses were clearly affected by the gamma radiation in that they became light to dark brown in appearance with increasing gamma irradiation whereas the UVFS optics (coated and uncoated) appeared visually, at least, to be unaffected. The optical transmission tests showed that the BK7 lenses became increasingly opaque to UV-VIS wavelengths with increasing gamma irradiation whereas the UVFS lenses and prisms were not so affected. The high-energy V-coat anti-reflection coatings appeared also to be unaffected by the gamma irradiation levels used in this study, at least within the limits of this investigation. However, the UVFS fibre-optic cables did show a reduction in transmission of UV light with increasing gamma irradiation.

An Improved Sub-Model PLSR Quantitative Analysis Method Based on SVM Classifier for ChemCam Laser-Induced Breakdown Spectroscopy

Laser-induced breakdown spectroscopy (LIBS) is a powerful tool for qualitative and quantitative analysis. Component analysis is a significant issue for the LIBS instrument onboard the Mars Science Laboratory (MSL) rover Curiosity ChemCam and SuperCam on the Mars 2020 rover. The partial least squares (PLS) sub-model strategy is one of the outstanding multivariate analysis methods for calibration modeling, which is firstly developed by the ChemCam science team. We innovatively used a support vector machine (SVM) classifier to select the corresponding sub-model. Then conventional regression approaches partial least squares regression (PLSR) was utilized as a sub-model to prove that our selecting method was feasible, effective, and well-performed. For eight oxides, i.e., SiO2, TiO2, Al2O3, FeOT, MgO, CaO, Na2O, and K2O, the modified SVM-PLSR blended sub-model method was 34.8% to 62.4% lower than the corresponding root mean square error of prediction (RMSEP) of the full model method. In order to avoid that SVM classifiers classifying the spectrum into an incorrect class, an optimized method was proposed which worked well in the modified PLSR blended sub-models.

Field investigation of volcanic deposits on Vulcano, Italy using a handheld laser-induced breakdown spectroscopy instrument

Laser-induced breakdown spectroscopy (LIBS) is an important analytical technique in a variety of fields ranging from in-situ terrestrial geological field investigations to robotic exploration missions of extraterrestrial bodies such as Mars. In this study, the performance of a commercial handheld LIBS instrument was evaluated during an international summer school in 2019 that focused on the exploration of extreme environments on Earth and in space. Several sites on the Eolian island Vulcano (Italy) were investigated with different spectroscopic methods including LIBS. We focus here on the exploration of one particular outcrop with LIBS, where layered and colored ash deposits were observed. Furthermore, a laboratory study was performed to investigate and validate the effect of varying distance of the instrument to the sample. Unsupervised principal component analysis (PCA) for data exploration showed that elemental variations between the layers of the outcrop can be observed with the LIBS data from the handheld instrument. This was further confirmed by a layer-by-layer analysis of elemental correlations and depositional trends. Geologically relevant major elements such as Si, Al, Ca, Fe, K, Mg, and Na could be identified but also minor and trace elements such as F, Li, Mn, and Sr. Our results also show that the effects of varying distances of the instrument to the sample are critical for the quality of the data acquired and hence pose significant challenges to the analysis and interpretation. We propose a dedicated data pre-processing approach, which includes the masking of emission lines of Ar from the locally induced Ar atmosphere, as a possible solution to overcome this challenge. Overall, this study provides a better understanding of the performance and limitations of a handheld LIBS instrument, particularly in the context of future terrestrial and planetary field investigations.

Laser Induced Breakdown Spectroscopy (LIBS): Application to Geological Materials-=SUP=-*-=/SUP=-

Laser-induced breakdown spectroscopy (LIBS) is emerging as an analytical tool for investigating geological materials. The unique abilities of this technique proven its potential in the area of geology. Detection of light elements, portability for in-field analysis, spot detection, and no sample preparation are some features that make this technique appropriate for the study of geological materials. The application of the LIBS technique has been tremendously developed in recent years. In this report, results obtained from previous and most recent studies regarding the investigation of geological materials LIBS technique are reviewed. Firstly, we introduce investigations that report the advancement in LIBS instrumentation, its applications, especially in the area of gemology and the extraterrestrial/planetary exploration have been reviewed. Investigation of gemstones by LIBS technique is not widely reviewed in the past as compared to LIBS application in planetary exploration or other geological applications. It is anticipated that for the classification of gemstones samples, huge data set is appropriate and to analyze this data set, multivariate/chemometric methods will be useful. Recent advancement of LIBS instrumentation for the study of meteorites, depth penetration in Martian rocks and its regolith proved the feasibility of LIBS used as robotic vehicles in the Martian environment. Keywords: LIBS, Gemstone, geological samples, Extra-terrestrial

Combination of high-resolution laser-induced breakdown spectroscopy and least square method for reducing soil carbon overestimation due to iron interference

Laser-induced breakdown spectroscopy (LIBS) has been used for soil carbon (C) estimation by detecting the 247.8561 nm line of atomic carbon (C I). However, the Fe II line at 247.8572 nm interferes with the LIBS C measurement, resulting in C content overestimation. Due to the resolution limitation of common LIBS instruments, Fe II could not be identified and eliminated spectroscopically, and in natural soil the conventional method confirming constant emission intensity ratio of two Fe emission lines (Fe I line at 247.8572 nm and another Fe line which the upper energy level close or equal to the former) could not be used directly. Thus, in order to obtain the C content in soil, a high-resolution spectrometer (0.012 nm resolution) was employed to identify the C and Fe emission lines near 247.8561 nm in the standard reference soils 2709a (San Joaquin Soil) and 2711a (Montana II soil). For interference correction the emission line of Fe at 249.7819 nm was selected due to its constant ratio with delay time, and the least square method was employed to obtain the β coefficient of Fe 247.8572 nm emission line and the α coefficient of C 247.8561 nm emission line. The results demonstrated that suitable emission lines near 247.8561 nm could be identified using the high-resolution spectrometer, and the Fe interference could be reduced, even if the pure Fe 247.8572 nm intensity was unknown for the soil sample. The coefficient of α = 1600 and β = 3.02 were calculated from the case study and then the C content was corrected. With the Fe interference, the percentage of overestimated C was in the range of 15% to 58% in the used soil samples. This method minimizes C overestimation, and is less affected by soil heterogeneity and matrix effects, demonstrating its potential use in soil C quantification.

A Review of Underwater Laser-induced Breakdown Spectroscopy of Submerged Solids.

Fundamentals to applications of underwater laser-induced breakdown spectroscopy (LIBS) of submerged solid targets are reviewed. Since the deformation of spectral lines caused by plasma confinement has been the most serious problem in underwater LIBS, the methods developed to overcome this effect are overviewed. Deep-sea LIBS, which is the most successful application of underwater LIBS, is described in some detail as well as the hydrostatic pressure effects. Since the downsizing of underwater LIBS instrument is an important task for the applications to on-site measurements, studies on non-gated LIBS are covered. In the subsequent section, the methods for the quantitative analysis of the underwater LIBS signal are reviewed. The basics of the plasma parameters used in quantitative analysis are explained, and various methods of quantitative analysis applicable to underwater LIBS are described.

Quantitative Analysis of Pig Iron from Steel Industry by Handheld Laser-Induced Breakdown Spectroscopy and Partial Least Square (PLS) Algorithm

One of the main objectives in the steel production process is to obtain a blast furnace pig iron of good quality and at the lowest possible cost. In general, the quality of pig iron is evaluated on the basis of its chemical composition determined by X-ray fluorescence laboratory equipment. In the present study, the performance of a handheld (h) laser-induced breakdown spectroscopy (LIBS) instrument in the identification and the quantification of the relevant elements C, Mn, P, Si, and Ti in forty-six blast furnace pig iron samples was tested successfully. The application of two different models, i.e., univariate and multivariate partial least square (PLS) calibration and validation, to the whole LIBS data set showed that the latter approach was much more efficient than the former one in quantifying all elements considered, especially Si and Ti.

Dry Ashing for Signal Enhancement in Laser-Induced Breakdown Spectroscopy (LIBS)

Limited sensitivities of some laser-induced breakdown spectroscopy (LIBS) instruments may impair some applications. Although this drawback can be minimized by instrumental improvements, the complexity of operations and cost increases. In this work the principle of conventional dry ashing for sample preparation was evaluated as a simple and low-cost alternative to improve the sensitivity of LIBS analysis. Botanical, agronomic and industrial samples were analyzed. Samples were dry heated and their LIBS emission signals were evaluated. The results suggest the dry heating caused structural changes in samples providing greater availability of the analyte, which resulted in the enhancement of the signals. As proof of concept, the strategy was applied for Sr determination in plant leaves. Two Sr emission lines, enhanced after sample dry ashing were used. The developed methods showed similar performance featuring a good linear range (10 to 70 μg g−1) with coefficient of correlations higher than 0.99. Additionally, the accurate determination of Sr in apple and peach leaves standard materials was achieved.

Particle Swarm Optimization (PSO) for improving the accuracy of ChemCam LIBS sub-model quantitative method

Laser-induced breakdown spectroscopy (LIBS) is a powerful tool for qualitative analysis of chemical composition on planetary surface. Specifically, the quantitative compositional analysis method is a significant challenge for LIBS instrument onboard the Mars Science Laboratory (MSL) rover Curiosity ChemCam. Partial Least Squares (PLS) sub-model strategy is one of the outstanding multivariate analysis methods for calibration modeling, which is firstly developed by ChemCam science team. However, a troubling key issue is there are many parameters that need to be optimized, which increases the uncertainty of predicting outcomes and is time-consuming. In this study, an automatic parameters selection method based on Particle Swarm Optimization (PSO) tool is introduced. In the process of PSO iteration, RMSE minimization is taken as fitness, and finally the optimal sub-model parameters set is searched. In this way, the authors also get the best PLS latent variables of each sub-model by traversal method. Finally, the PSO PLS sub-model (PSO-PLS-SM) gets significant improvement in accuracy for the expanded Chemcam standards (408). And the RMSE of Si, Al, Ca, Na elements has been reduced by more than 20% relative to the conventional predictions.

Constraining Ancient Magmatic Evolution on Mars Using Crystal Chemistry of Detrital Igneous Minerals in the Sedimentary Bradbury Group, Gale Crater, Mars

AbstractUnderstanding magmatic processes is critical to understanding Mars as a system, but Curiosity's investigation of dominantly sedimentary rocks has made it difficult to constrain igneous processes. Igneous classification of float rocks is challenging because of the following: (1) the possibility that they have been affected by sedimentary processes or weathering, and (2) grain size heterogeneity in the observed rock textures makes the small‐scale compositions measured by rover instruments unreliable for bulk classification. We avoid these ambiguities by using detrital igneous mineral chemistry to constrain models of magmatic processes in the source region for the fluvio‐deltaic Bradbury group. Mineral chemistry is obtained from X‐ray diffraction of three collected samples and a new stoichiometric and visual filtering of ~5,000 laser induced breakdown spectroscopy (LIBS) spots to identify compositions of individual igneous minerals. Observed mineral chemistries are compared to those produced by MELTS thermodynamic modeling to constrain possible magmatic conditions. Fractionation of two starting primary melts derived from different extent of adiabatic decompression melting of a primitive mantle composition could result in the crystallization of all minerals observed. Crystal fractionation of a subalkaline and an alkaline magma is required to form the observed minerals. These results are consistent with the collection of alkaline and subalkaline rocks from Gale as well as clasts from the Martian meteorite Northwest Africa 7034 and paired stones. This new method for constraining magmatic processes will be of significant interest for the Mars 2020 mission, which will also investigate an ancient volcaniclastic‐sedimentary environment and will include a LIBS instrument.

Accuracies and detection limits of major, minor, and trace element quantification in rocks by portable laser-induced breakdown spectroscopy

The recent manufacture of portable laser-induced breakdown spectroscopy (pLIBS) instruments has permitted widespread applications of an established analytical technique for in situ geochemical quantifications. This novelty has created a need for investigations comparing the default univariate pLIBS calibration accuracies to custom instrument calibrations based on geological samples and to other modeling methods. Previous research has shown that multivariate models can mitigate some of the matrix effects that cause intensity and concentration non-linearity within LIBS plasmas of rocks. This study thus makes two pLIBS calibration comparisons: one compares partial least squares (PLS) multivariate regression to univariate instrument models, while the other compares the default instrument calibration, intended for general industrial use, to a custom instrument calibration based on rock standards. Both comparisons use root mean squared errors (RMSE) between model-predicted and true standard values of the major oxides Al2O3, CaO, Fe2O3, K2O, MgO, MnO, Na2O, P2O5, SiO2, and TiO2, and minor and trace elements Ba, Cr, Cu, H2O, Li, Ni, Pb, S, and Zn to test calibration accuracies. pLIBS spectra from 2007 diverse rock standards were used for the PLS versus univariate model comparison, while 89 publicly-available geochemical standards were used to compare the default and custom instrument calibrations. PLS models give test accuracies for major elements of ±8.61 wt% for SiO2, ±3.38 for Al2O3, ±0.77 for TiO2, ±3.84 for Fe2O3, ±4.41 wt% for MgO, ±3.08 wt% for CaO, ±1.09 wt% for Na2O, and ±1.52 wt% for K2O. Quantification of trace and minor elements was more accurate with multivariate regression than with univariate instrument models, and the new custom instrument calibration had lower prediction errors for these elements than those of the default models. However, minor and trace element errors from all three calibrations were often greater than the average concentration of the test standards, which suggests that these substances are not well quantified in rocks by pLIBS instruments.

Improvement of the performances of a commercial hand-held laser-induced breakdown spectroscopy instrument for steel analysis using multiple artificial neural networks.

In this article, we present a study on the optimization of the analytical performance of a commercial hand-held laser-induced breakdown spectroscopy instrument for steel analysis. We show how the performances of the instrument can be substantially improved using a non-linear calibration approach based on a set of Artificial Neural Networks (ANNs), one optimized for the determination of the major elements of the alloy, and the others specialized for the analysis of minor components. Tests of the instrument on steel samples used for instrument internal calibration demonstrate a comparable accuracy with the results of the ANNs, while the latter are considerably more accurate when unknown samples, not used for calibration/training, are tested.

Imaging laser-induced plasma under different laser irradiances

The ablation process of a sample in Laser-Induced Breakdown Spectroscopy (LIBS) is fast and dynamic. Investigating such dynamic process requires a good temporal and spatial resolution in order to understand the physical processes involved. However, the LIBS instrumentation tends to be versatile and price sensitive. For this reason, the goal of this work is to design a basic optomechanic construction satisfying the needs of plasma imaging experiment and providing the necessary performance at the same time. The optomechanic module is simplified and consists of an objective and a gated low-cost CMOS detector. For each experiment, multiple images of the plasma were collected and averaged to achieve a better accuracy. The expansion of plasma is imaged with 0.2 μs temporal resolution where Laser Supported Combustion (LSC) and Laser Supported Detonation (LSD) expansion is observed. The size of plasma is compared with the emitted radiation of analytes of interest. Such data are used for an improvement of the signal stability. We created acalibration model for nickel, where we observed an improvement in coefficient of determination; rising from 0.914 using no standardization to 0.962 with a standardization to the plasma size.

A software system for rapid analysis of plastics using laser-induced breakdown spectroscopy

With the extensive use of plastic products, the recycling and reuse of plastics raises more concerns. Laser-induced breakdown spectroscopy (LIBS) has become a powerful technology for plastic analysis. To meet different analytical requirements, LIBS control system and analysis software was being continuously developed. However, existing software system only can realize the capability of LIBS system control or data analysis (peak detection or material identification). To improve the efficiency of LIBS instrument for plastic analysis, an integrated and full software is needed. In this work, analyis & test software was developed for rapid plastic analysis, which consists of LIBS control platform, plastic database, and analysis module which contains peak detection, qualitative and quantitative analysis. The software performance was validated, which provides an automatic processing for plastic analysis. Design approach of the software can be used for the development of similar instrument software and other samples analysis.

Rapid detection of chromium in different valence states in soil using resin selective enrichment coupled with laser-induced breakdown spectroscopy: From laboratory test to portable instruments

Hexavalent chromium (Cr(VI)) is toxic, but trivalent chromium (Cr(III)) is essential to organisms. Monitoring Cr(VI) and Cr(III) in soil can improve our understanding of Cr biogeochemistry and toxicity. However, it is difficult to rapidly determine Cr in different valences in soil using traditional methods. A new method, resin selective enrichment with laser-induced breakdown spectroscopy, for rapidly determining Cr in different valence states (total Cr, Cr(III), and Cr(VI)) in soil is presented here. The method effectively separated Cr(III) and Cr(VI). The regression coefficients for the total Cr, Cr(III), and Cr(VI) calibration curves were all >0.99. The total Cr and Cr(VI) limits of detection were 19.34 and 35.18 mg/kg, respectively. The total Cr and Cr(VI) relative standard deviations for repeat analyses were 7.69% and 12.98%, respectively. A portable laser induced breakdown spectroscopy instrument for detecting Cr in soil, developed in our laboratory, gave a regression coefficient for the total Cr concentration in soil of 0.993. The results indicated that the method can rapidly and accurately quantify Cr in different valence states in soil. There is potential for miniaturizing the instrument to allow Cr to be determined in soil in the field

Quantification of heavy metals in oils with µL volume by laser induced breakdown spectroscopy and minimazing of the matrix effect

In this work we describe a method for preparation and analysis of oils by Laser Induced Breakdown Spectroscopy (LIBS), aimed to minimize the necessary sample volume and the matrix effect while maximizing the detection sensitivity and measurement's repeatability. The preparation procedure consists in stabilizing the oil sample and silica wafer substrate at a fixed temperature, here of 40 °C, and in delivering an oil droplet on the wafer rotated by a spin coater. In this way, a uniform oil film is obtained, which thickness is controlled through the rotation speed. So prepared target is then scanned by using the LIBS instrument. From comparative measurements on the pure oil and oil containing 2100 ppm of various elements, we studied different potentials sources of the matrix effect. During the sample preparation, above a certain rotation speed the thickness of the liquid film is the same for the two oils although their kinematic viscosities are very different, meaning that the volume sampled by LIBS is the same. The measured oil transmissivity at the laser wavelength of 1064 nm significantly decreases with concentration of impurities, but this effect could be neglected when dealing with very thin films. The plasma formation threshold measured on the bulk oil samples decreases with the impurity content. In case of pure oil, also for the maximum laser energy here used (165 mJ), the plasma is mainly initiated on the wafer while the presence of impurities increases screening of the substrate by the plasma formed directly on the oil. The matrix effect disappears on a very thin film, here of 0.74 μm, where the C I line intensity in plasma does not vary with the total concentration of impurities between zero and 2100 ppm; simultaneously, the plasma emission becomes stable from one laser pulse to another, contrary to the case of a thick liquid layer. At 0.5 μs from the laser pulse the plasma electron density is much higher in presence of oil than on the bare substrate because of the initial plume confinement. In the optimized experimental conditions the plasma emission from oil was very intense although the sample volume probed by each laser pulse was of 0.3 nL only. By choosing properly the signal acquisition delay and the calibration procedure, the latter is dependent on the excitation energy of the analytical lines, we obtained the detection limits of 3.9 ppm, 0.49 ppm, 0.16 ppm and 0.082 ppm for Zn, Cd, Cu and Cr in oil, respectively.

Laser-induced breakdown spectroscopy for rapid accurate analysis of Mg, Ca, and K in edible sea salts.

A compact laser-induced breakdown spectroscopy (LIBS) instrument and a simple sample preparation method were developed for rapid on-site analysis of Mg, Ca, and K in edible sea salt products. The LIBS instrument was assembled using a small diode-pumped solid-state laser and a handheld spectrometer. Aqueous solutions of salts were prepared and sampled by using pieces of filter papers. The dried filter paper was attached on the flat surface of a silicon wafer and then analyzed by LIBS. Calibration curves were obtained using binary mixtures of ${\rm NaCl} {-} {{\rm MgSO}_4}$NaCl-MgSO4, ${\rm NaCl} {-} {{\rm CaCl}_2}$NaCl-CaCl2, and NaCl-KCl and used to estimate the concentrations of Mg, Ca, and K in 13 edible sea salt products. Matrix effects on the results from LIBS were identified in comparison with those from inductively coupled plasma optical emission spectroscopy. This indicates that the matrix of sea salt samples is significantly different from that of the binary mixture standards. The sea salts with known concentrations of Mg, Ca, and K were employed to match the matrices of samples and standards. This improved analysis accuracy remarkably. Furthermore, an alternative indirect method for estimating the concentration of K was suggested on the basis of the strong positive correlations observed between the concentrations of Mg and K in the sea salt samples.

Laser induced breakdown spectroscopy of polymer matrix composites for real-time analysis of trace surface contaminants: A review

Laser induced breakdown spectroscopy (LIBS) is a materials characterization technique that has been advanced and refined to provide in situ, real-time quality control of polymer matrix composite (PMC) surfaces. A LIBS system was designed and assembled at the NASA Langley Research Center in order to detect ultralow concentrations of silicone contamination on carbon fiber reinforced polymer (CFRP) materials. The LIBS instrument provides high sensitivity detection and nearly non-destructive inspection of PMC substrates prior to adhesive bonding. This review focuses on work conducted using LIBS as a characterization tool for surface contaminants for improved adhesive bonding and coating processes of CFRP materials. In addition, this work describes how the LIBS technique was advanced by analyzing the laser parameters, studying the laser-matter interactions, and comparing results to X-ray photoelectron spectroscopy. Discussion is also presented on LIBS instrumentation, recommendations for laser parameters and instrumentation components, LIBS technique maturity, applications, and limitations.

Laser-induced breakdown spectroscopy as a novel readout method for nanoparticle-based immunoassays.

Laser-induced breakdown spectroscopy (LIBS) was examined as a novel method for readout of microtiter plate immunoassays involving nanoparticles (NP). The so-called Tag-LIBS technique is a sensitive method for the detection of specific biomarkers. It was applied to the determination of NP labels using nanosecond ablation sampling. The NP labels were examined from the bottom of a standard 96-well microtiter plate. Thanks to the flexibility of LIBS instrumentation, both the plasma emission collection and the focusing optics arrangements can be collinearly arranged. The experiments showed that silver NPs and gold NPs can be readily quantified on the bottom of the microtiter plate. Utilizing this technique, a sandwich immunoassay for human serum albumin using streptavidin-coated AgNP labels was developed. The assay has a 10ng·mL-1 detection limit which is comparable to the sensitivity of fluorometric readout. The main advantage of this LIBS technique is its wide scope in which it enables a detection of almost any type of NP labels, irrespective to any fluorescence or catalytic properties. Owing to the immediate signal response, the relatively simple instrumentation also enables assay automation. The LIBS capability of multi-elemental analyses makes it a promising and fast alternative to other readout techniques, in particular with respect to multiplexed detection of biomarkers. Graphical abstract Laser-induced breakdown spectroscopy (LIBS) is used as a novel readout method of nanoparticle-based immunoassays in microtiter plates. After formation of sandwich immunocomplex, the analyte concentration is quantified as the signal of Ag nanoparticle labels determined by LIBS.