Detection of trace Al in model biological tissue with laser-induced breakdown spectroscopy

Laser-induced breakdown spectroscopy (LIBS), which is an excellent tool for trace elemental analysis, was studied as a method of detecting sub-part-per-10(6) (ppm) concentrations of aluminum in surrogates of human tissue. Tissue was modeled using a 2% agarose gelatin doped with an Al(2)O(3) nanoparticle suspension. A calibration curve created with standard reference samples of known Al concentrations was used to determine the limit of detection, which was less than 1 ppm. Rates of false negative and false positive detection results for a much more realistic sampling methodology were also studied, suggesting that LIBS could be a candidate for the real-time in vivo detection of metal contamination in human soft tissue.     

Laser-induced breakdown spectroscopy analysis of solids using a long-pulse (150 ns) Q-switched Nd:YAG laser

Laser-induced breakdown spectroscopy (LIBS) measurements are typically carried out using pulses (<20 ns, >50 mJ) from a flashlamp-pumped electro-optically Q-switched Nd:YAG laser (EO-laser) or excimer laser. Here we report LIBS analyses of solids using an acousto-optically Q-switched Nd:YAG laser (AO-laser) producing 150 ns pulses of lower energy (10 mJ) at repetition rates up to 6 kHz. The high repetition rate allows increased spatial or depth sampling over a given time period compared to the EO-laser. Results of AO-laser based LIBS analysis of (1) steels, (2) soils, and (3) surface stains and dusts are described. Detection limits for Cr, Cu, Mn, Ni, and Si in steel ranged from 0.11 to 0.24% using a commercial polychromator-based detection system with limits 4--30 times lower achieved using a laboratory-based detection system. The minimum detectable masses of Ba, Cr, Mn, and Sr on a metal surface were estimated with 1.2 pg/shot achieved for Sr. Detection limits for Ba and Sr in soil were 296 and 52 ppm, respectively. The temperatures, spectra, and emission decay curves from plasmas generated by the AO- and EO-lasers are compared and some characteristics of particles ablated by the AO-laser are described.     

Hydrogen leak detection using laser-induced breakdown spectroscopy

Laser-induced breakdown spectroscopy (LIBS) is investigated as a technique for real-time monitoring of hydrogen gas. Two methodologies were examined: The use of a 100 mJ laser pulse to create a laser-induced breakdown directly in a sample gas stream, and the use of a 55 mJ laser pulse to create a laser-induced plasma on a solid substrate surface, with the expanding plasma sampling the gas stream. Various metals were analyzed as candidate substrate surfaces, including aluminum, copper, molybdenum, stainless steel, titanium, and tungsten. Stainless steel was selected, and a detailed analysis of hydrogen detection in binary mixtures of nitrogen and hydrogen at atmospheric pressure was performed. Both the gaseous plasma and the plasma initiated on the stainless steel surface generated comparable hydrogen emission signals, using the 656.28 Halpha emission line, and exhibited excellent signal linearity. The limit of detection is about 20 ppm (mass) as determined for both methodologies, with the solid-initiated plasma yielding a slightly better value. Overall, LIBS is concluded to be a viable candidate for hydrogen sensing, offering a combination of high sensitivity with a technique that is well suited to implementation in field environments.     

Elemental analyses and determination of lead content in kohl (stone) by laser-induced breakdown spectroscopy

Elemental analyses of kohl (stone) samples collected from three different parts of the world were performed using laser-induced breakdown spectroscopy (LIBS). The analyses indicated that lead (Pb), copper (Cu), silver (Ag), iron (Fe), calcium (Ca), aluminum (Al), silicon (Si), and sodium (Na) were present in all the kohl samples. In addition to these elements, the sample from Madina, Kingdom of Saudi Arabia (KSA), contained the elements tin (Sn), zirconium (Zr), and antimony (Sb). The sample from Mount Toor, Egypt, also contained Sn. Also, quantitative analysis for lead was carried out by the standard addition method using the LIBS technique. The result showed the presence of 14.12 ± 0.28% by weight of Pb in the sample from Madina, which compares well with the measurement done using atomic absorption spectroscopy (AAS) (13.31 ± 0.46%). The standard addition method used three calibration curves drawn for three emission lines of the LIBS spectra of Pb. The limits of detection (LoD) for these calibration curves varied from 0.27% to 1.16% by weight. The lead contents of the samples from Mount Toor and the local market of Bangladesh were also measured by the AAS technique, and the results were 14.61 ± 0.48% and 8.98 ± 0.35% by weight, respectively. The reason for determining only the lead content in kohl, which may be used as an eye cosmetic, is the adverse effect that lead has on health.     

Detection of chromium in wastewater from refuse incineration power plant near Poyang Lake by laser induced breakdown spectroscopy

A laser induced breakdown spectroscopy (LIBS) system was developed for determination of toxic metals Cr in wastewater collected from a refuse incineration power plant near Poyang Lake. The plasma was generated by focusing a pulsed Nd:YAG laser at 1064 nm on the surface of liquid. Experimental conditions were optimized for improving the sensitivity and repeatability of the LIBS system through a parametric dependence study in potassium bichromate (K(2)Cr(2)O(7)) aqueous solutions. Calibration curves for Cr I 425.43 and 357.87 nm lines are compared and the limit of detection is found to be 39 and 86 ppm, respectively. This calibration curve of Cr I 425.43 nm has been used for quantification of Cr in wastewater collected from a refuse incineration power plant near Poyang Lake where the concentration of Cr is found to be 97 ppm. The results between LIBS and standard analytical technique such as atomic absorption spectroscopy were compared, and the relative standard deviation was 8.5%.     

Analysis of water ice and water ice/soil mixtures using laser-induced breakdown spectroscopy: application to Mars polar exploration

Recently, laser-induced breakdown spectroscopy (LIBS) has been developed for the elemental analysis of geological samples for application to space exploration. There is also interest in using the technique for the analysis of water ice and ice/dust mixtures located at the Mars polar regions. The application is a compact instrument for a lander or rover to the Martian poles to interrogate stratified layers of ice and dusts that contain a record of past geologic history, believed to date back several million years. Here we present results of a study of the use of LIBS for the analysis of water ice and ice/dust mixtures in situ and at short stand-off distances (< 6.5 m) using experimental parameters appropriate for a compact instrument. Characteristics of LIBS spectra of water ice, ice/soil mixtures, element detection limits, and the ability to ablate through ice samples to monitor subsurface dust deposits are discussed.     

Helium detection in gas mixtures by laser-induced breakdown spectroscopy

Laser-induced breakdown spectroscopy (LIBS) has been evaluated as a tool for monitoring trace levels of helium in gas mixtures consisting mostly of hydrogen. Calibration data for helium in hydrogen was investigated at different helium concentration levels. At high concentrations of helium (>7.25%), the LIBS signal is quenched due to Penning ionization. The hydrogen alpha line (656.28 nm) was observed to broaden as the concentration of helium impurities in the hydrogen gas mixture increased. The helium line at 587.56 nm was selected as the analyte line for helium impurity detection. The effects of laser energy, the delay time between the laser pulse and data acquisition, and the gas pressure on the LIBS signal of helium were investigated to determine the optimum conditions for helium detection. The LIBS signal from the helium line at 587.56 nm shows good linear correlation with helium concentration for He concentrations below 1%. Thus, LIBS can be reliably used to detect the low levels of helium. The limit of detection for helium was found to be 78 ppm.     

Laser-induced breakdown spectroscopy for the environmental determination of total carbon and nitrogen in soils

Soils from various sites have been analysed with the laser-induced breakdown spectroscopy (LIBS) technique for total elemental determination of carbon and nitrogen. Results from LIBS have been correlated to a standard laboratory-based technique (sample combustion), and strong linear correlations were obtained for determination of carbon concentrations. The LIBES technique was used on soils before and after acid washing, and the technique appears to be useful for the determination of both organic and inorganic soil carbon. The LIBS technique has the potential to be packaged into a field-deployable instrument.     

Combination of sorption tube sampling and thermal desorption with hollow waveguide FT-IR spectroscopy for atmospheric trace gas analysis: determination of atmospheric ethene at the lower ppb level

The determination of organic trace gases in the ambient environment at the lower ppb level is demonstrated based on a novel technique combining sorption tube sampling on Molsieve and Carbosieve S-III, thermal desorption, and detection of the trace analyte by hollow waveguide Fourier transform infrared (HWG-FT-IR) spectroscopy. While ethene concentrations of approximately 5 ppm can be directly observed using HWG-FT-IR, enrichment factors of up to 5000 were achieved by sorption tube sampling and thermal desorption. Detection limits of approximately 1 ppb are reported. Efficient enrichment by the sampling tube is achieved due to the favorable internal volume ( approximately 0.4 cm(3) at a length of 470 mm) of the hollow waveguide serving as a miniaturized gas cell. This new method was validated for ethene by thermodesorption-cryofocusing-GC-FID as the reference method. Analytical performance has been compared for standard gas mixtures and for ethene measurements in urban air. Finally, ethene data from a sampling campaign at two alpine sites in Tyrol/Austria are presented.     

等离子体光栅与光丝非线性耦合诱导击穿光谱

激光诱导击穿光谱技术（laser-induced breakdown spectroscopy,LIBS）是一种分析样品元素信息的有效工具,具有快速、简便、实时的优点,可以对固体、液体和气体中多元素成分进行定性分析和定量检测。但传统的LIBS以及光丝诱导击穿光谱技术（filament-induced breakdown spectroscopy,FIBS）受限于峰值功率钳制,灵敏度难以提高,导致在实际应用中具有一定的局限性,成为LIBS技术发明以来一直面临的重大技术瓶颈。本文从激发源的角度出发,讨论了LIBS和FIBS出现的问题,介绍了近年来优化LIBS技术的研究进展,将多光束耦合形成的等离子体光栅应用于LIBS,在保留其原有优点的基础上,有效克服了等离子体屏蔽效应、基体效应,突破了功率钳制,增强了谱线信号,提高了探测灵敏度和定量分析能力。这些研究将推进LIBS技术在各领域的实际应用,同时为飞秒激光等离子体与其他技术的结合提供了研究思路。     

Effect of laser-induced crater depth in laser-induced breakdown spectroscopy emission features

The influence of crater depth on plasma properties and laser-induced breakdown spectroscopy (LIBS) emission has been evaluated. Laser-induced plasmas were generated at the surface and at the bottom of different craters in a copper sample. Plasmas produced at the sample surface and at the bottom of the craters were spatially and temporally resolved. LIBS emission, temperature, and electronic number density of the plasmas were evaluated. It is shown that the confinement effect produced by the craters enhances the LIBS signal from the laser-induced plasmas.     

Analysis of the absorption layer of CIGS solar cell by laser-induced breakdown spectroscopy

Laser induced breakdown spectroscopy (LIBS) was applied for the elemental analysis of the thin copper indium gallium diselenide (CuIn(1-x)Ga(x)Se(2) [CIGS]) absorption layer deposited on Mo-coated soda-lime glass by the co-evaporation technique. The optimal laser and detection parameters for LIBS measurement of the CIGS absorption layer (1.23 μm) were investigated. The calibration results of Ga/In ratio with respect to the concentration ratios measured by x-ray fluorescence and inductively coupled plasma optical emission spectroscopy showed good linearity.     

Atomic hydrogen emission induced by TEA CO(2) laser bombardment on solid samples at low pressure and its analytical application

Hydrogen emission has been studied in laser plasmas by focusing a TEA CO(2) laser (10.6 microm, 500 mJ, 200 ns) on various types of samples, such as glass, quartz, black plastic sheet, and oil on copper plate sub-target. It was found that H(alpha) emission with a narrow spectral width occurs with high efficiency when the laser plasma is produced in the low-pressure region. On the contrary, the conventional well-known laser-induced breakdown spectroscopy (LIBS), which is usually carried out at atmospheric air pressure, cannot be applied to the analysis of hydrogen as an impurity. By combining low-pressure laser-induced plasma spectroscopy with laser surface cleaning, a preliminary quantitative analysis was made on zircaloy pipe samples intentionally doped with hydrogen. As a result, a good linear relationship was obtained between H(alpha) emission intensity and its concentration.     

Quantitative determination of absolute organohalogen concentrations in environmental samples by X-ray absorption spectroscopy

An in situ procedure for quantifying total organic and inorganic Cl concentrations in environmental samples based on X-ray absorption near-edge structure (XANES) spectroscopy has been developed. Cl 1s XANES spectra reflect contributions from all Cl species present in a sample, providing a definitive measure of total Cl concentration in chemically heterogeneous samples. Spectral features near the Cl K-absorption edge provide detailed information about the bonding state of Cl, whereas the absolute fluorescence intensity of the spectra is directly proportional to total Cl concentration, allowing for simultaneous determination of Cl speciation and concentration in plant, soil, and natural water samples. Absolute Cl concentrations are obtained from Cl 1s XANES spectra using a series of Cl standards in a matrix of uniform bulk density. With the high sensitivity of synchrotron-based X-ray absorption spectroscopy, Cl concentration can be reliably measured down to the 5-10 ppm range in solid and liquid samples. Referencing the characteristic near-edge features of Cl in various model compounds, we can distinguish between inorganic chloride (Cl(inorg)) and organochlorine (Cl(org)), as well as between aliphatic Cl(org) and aromatic Cl(org), with uncertainties in the range of approximately 6%. In addition, total organic and inorganic Br concentrations in sediment samples are quantified using a combination of Br 1s XANES and X-ray fluorescence (XRF) spectroscopy. Br concentration is detected down to approximately 1 ppm by XRF, and Br 1s XANES spectra allow quantification of the Br(inorg) and Br(org) fractions. These procedures provide nondestructive, element-specific techniques for quantification of Cl and Br concentrations that preclude extensive sample preparation.     

Field portable XRF analysis of environmental samples

One of the critical factors for successfully conducting contamination characterization, removal, and remedial operations at hazardous waste sites is rapid and appropriate response to analyze samples in a timely fashion. Turnaround time associated with off-site analysis is often too slow to support efficient utilization of the data. Field portable X-ray fluorescence (FPXRF) techniques provide viable and effective analytical approaches to meet on-site analysis needs for many types of environmental samples. Applications include the in situ analysis of metals in soils and sediments, thin films/particulates, and lead in paint.     

Laser-induced breakdown spectroscopy of bulk aqueous solutions at oceanic pressures: evaluation of key measurement parameters

The development of in situ chemical sensors is critical for present-day expeditionary oceanography and the new mode of ocean observing systems that we are entering. New sensors take a significant amount of time to develop; therefore, validation of techniques in the laboratory for use in the ocean environment is necessary. Laser-induced breakdown spectroscopy (LIBS) is a promising in situ technique for oceanography. Laboratory investigations on the feasibility of using LIBS to detect analytes in bulk liquids at oceanic pressures were carried out. LIBS was successfully used to detect dissolved Na, Mn, Ca, K, and Li at pressures up to 2.76 x 10(7) Pa. The effects of pressure, laser-pulse energy, interpulse delay, gate delay, temperature, and NaCl concentration on the LIBS signal were examined. An optimal range of laser-pulse energies was found to exist for analyte detection in bulk aqueous solutions at both low and high pressures. No pressure effect was seen on the emission intensity for Ca and Na, and an increase in emission intensity with increased pressure was seen for Mn. Using the dual-pulse technique for several analytes, a very short interpulse delay resulted in the greatest emission intensity. The presence of NaCl enhanced the emission intensity for Ca, but had no effect on peak intensity of Mn or K. Overall, increased pressure, the addition of NaCl to a solution, and temperature did not inhibit detection of analytes in solution and sometimes even enhanced the ability to detect the analytes. The results suggest that LIBS is a viable chemical sensing method for in situ analyte detection in high-pressure environments such as the deep ocean.     

Application of laser-induced breakdown spectroscopy for total carbon quantification in soil samples

The increase of greenhouse gas (i.e., CO(2)) levels in the atmosphere has caused noticeable climate change. Many nations are currently looking into methods of permanent underground storage for CO(2) in an attempt to mitigate this problem. The goal of this work is to develop a process for studying the total carbon content in soils before, during, and after CO(2) injection to ensure that no leakage is occurring or to determine how much is leaking if it is occurring and what effect it will have on the ecosystem between the injection formation and the atmosphere. In this study, we quantitatively determine the total carbon concentration in soil using laser-induced breakdown spectroscopy (LIBS). A soil sample from Starkville, Mississippi, USA was mixed with different amounts of carbon powder, which was used as a calibration for additional carbon in soil. Test samples were prepared by adding different but known amounts of carbon powder to a soil sample and then mixing with polyvinyl alcohol binder before being pressed into pellets. LIBS spectra of the test samples were collected and analyzed to obtain optimized conditions for the measurement of total carbon in soil with LIBS. The total carbon content in the samples was also measured by a carbon analyzer, and the data (average of triplicates) were used as a reference in developing calibration curves for a modified version of the single linear regression model and the multiple linear regression model. The calibration data were then used to determine the total carbon concentration of an unknown sample. This work is intended to be used in the initial development of a miniaturized, field-portable LIBS analyzer for CO(2) leak detection.     

Slag analysis with laser-induced breakdown spectrometry

Laser-induced breakdown spectrometry (LIBS) has been applied for multi-elemental analysis of slag samples from a steel plant. In order to avoid the time-consuming step of sample preparation, the liquid slag material can be filled in special probes. After cooling of the liquid slag and solidification, the samples can be analyzed with LIBS. Chemical analysis of slag is an essential input parameter used for numerical simulations to control liquid steel processing. The relative variation range of element concentrations in slag samples from steel production can amount to up to 30%. A multivariate calibration model is used to take into account matrix effects caused by these varying concentrations. By optimizing the measuring parameters as well as the calibration models, an agreement between the standard X-ray fluorescence (XRF) analysis and LIBS analysis in terms of the coefficient of determination r2 of 0.99 for the main analytes CaO, SiO2, and Fetot of converter slag samples was achieved. The average repeatability of the LIBS measurement for these elements in terms of the relative standard deviation of the determined concentration is improved to less than 1.0%. With these results, the basis is established for future on-line applications of LIBS in the steel-making industry for slag analysis.     

激光诱导击穿光谱及其在元素分析中的应用

激光诱导击穿光谱是一种新的元素分析方法,但仍处于不断完善之中。利用它可以分析不同形态样品的成分,因此在成分分析和微量元素检测方面具有重要的应用前景。本文阐述了激光击穿诱导光谱仪的基本原理和激光诱导击穿光谱在多个领域中的应用,研究内容涉及固体样品、液体样品、气体样品、微量杂质分析和成分深度剖析等,并分析了基体效应、自吸收效应、测量时间、环境气体、激光参数等对激光诱导击穿光谱分析结果的影响。     

Laser-induced breakdown spectroscopy of alkali metals in high-temperature gas

Laser-induced breakdown spectroscopy (LIBS) measurements of alkali in the high-temperature exhaust of a glass furnace show an attenuation of the Na and K LIBS signals that correlates with the stoichiometry of the bath gas surrounding the spark. The results are explained as being due to (1) a strong increase in the concentration of atomic Na and K, resulting in neutral line signal absorption by these atoms, and to (2) a change of phase of the major Na- and K-containing species from an aerosol to a gaseous phase when the gas mixture becomes fuel rich, resulting in a reduced LIBS emission intensity. LIBS sampling at lower temperatures, or in a consistently oxidizing environment, or both are suggested strategies for circumventing these difficulties.