Laser-based Analytical Techniques Research Articles

Advancing Elemental and Isotopic Analysis of Uranium Mineral Inclusions: Rapid Screening via Laser-Induced Breakdown Spectroscopy and High-Resolution Laser Ablation-ICP-MS Mapping

The work presented herein employs two laser-based analytical techniques (laser-induced breakdown spectroscopy (LIBS) and laser ablation – inductively coupled plasma – mass spectrometry (LA-ICP-MS)) to spatially determine the elemental and isotopic composition of uranium bearing minerals. Uniquely, this work leverages the high-speed applicability of LIBS to “screen” the sample(s) for their elemental constituents. After determining the location of the uranium inclusions (via LIBS), high-resolution LA-ICP-MS was employed to further characterize the inclusions. The high-resolution (sub-µm) capabilities of LA-ICP-MS were able to extract important information from the uranium minerals including discerning its chemical form (e.g., finchite from carnotite, Sr- and K-bearing uranyl vanadates, respectively) as well as their 235U/238U isotopic composition. This approach, LIBS followed by LA-ICP-MS, significantly reduces the analysis time (∼95 %) in comparison to employing a LA-ICP-MS only approach. Furthermore, this work presented a novel approach to analyzing inclusions via a particle/inclusion analysis tool which is commercially available within the iolite 4 software. This tool allowed for a more accurate characterization of the isotopic distribution of the inclusions, as well as allowing for rapid sizing of the inclusions. This analytical approach could readily be applied to other sample types in which the target species (e.g., µm-sized inclusions) are embedded in complex matrices (e.g., cm-sized samples).

Forty Years of Laser-Induced Breakdown Spectroscopy and Laser and Particle Beams

The laser-induced breakdown spectroscopy (LIBS) technique is one of the most promising laser-based analytical techniques. Coincidentally, the LIBS acronym was proposed by Radziemski and Loree in two seminal papers published in 1981, almost at the same time in which the Laser and Particle Beams journal started its publication. In this contribution, the evolution of the LIBS technique is discussed following a chronological collection of key papers in LIBS, some of which were in fact published on LPB.

Laser-based techniques: Novel tools for the identification and characterization of aged microplastics with developed biofilm

Microplastics found in the environment are often covered with a biofilm, which makes their analysis difficult. Therefore, the biofilm is usually removed before analysis, which may affect the microplastic particles or lead to their loss during the procedure. In this work, we used laser-based analytical techniques and evaluated their performance in detecting, characterizing, and classifying pristine and aged microplastics with a developed biofilm. Five types of microplastics from different polymers were selected (polyamide, polyethylene, polyethylene terephthalate, polypropylene, and polyvinyl chloride) and aged under controlled conditions in freshwater and wastewater. The development of biofilm and the changes in the properties of the microplastic were evaluated. The pristine and aged microplastics were characterized by standard methods (e.g., optical and scanning electron microscopy, and Raman spectroscopy), and then laser-induced breakdown spectroscopy (LIBS) and laser ablation inductively coupled plasma mass spectrometry (LA-ICP-MS) were used. The results show that LIBS could identify different types of plastics regardless of the ageing and major biotic elements of the biofilm layer. LA-ICP-MS showed a high sensitivity to metals, which can be used as markers for various plastics. In addition, LA-ICP-MS can be employed in studies to monitor the adsorption and desorption (leaching) of metals during the ageing of microplastics. The use of these laser-based analytical techniques was found to be beneficial in the study of environmentally relevant microplastics.

Strategies for trace metal quantification in polymer samples with an unknown matrix using Laser-Induced Breakdown Spectroscopy

Providing unique advantages, laser-based analytical techniques such as LIBS have gained more and more popularity for quantitative elemental analysis in the last few years. However, to obtain reliable quantitative results, matrix-matched standards are required. A particular material of interest for quantitative trace metal analysis is synthetic polymers, which is among the most widely used materials in our modern world. As the exact composition of a polymer under investigation (polymer type and applied additives) is often not known, the selection of an appropriate matrix-matched standard is difficult. In this work, we investigate and assess different approaches for quantifying potassium in unknown polymer types or polymers with an unknown composition where matrix-matched standards cannot be employed. This is of great interest in the semiconductor industry where monitoring of mobile ions in applied polymers is crucial, and the composition of the polymer is often not known due to confidentiality. We use the unique capabilities of LIBS, providing adequate sensitivity for potassium, and additionally delivering polymer-specific emission signals. Two different multivariate approaches (Random Decision Forest classification combined with conventional univariate calibration and a Partial Least Squares model) are developed and applied. Therefore, an in-house prepared library of standards of 8 different polymer types (Acrylic, PAN, PI, PMMA, PSU, PVA, PVC and PVP) is prepared. The errors obtained from the multivariate approaches are compared with conventional matrix-matched as well as non-matrix-matched quantification. With our developed approaches, for some samples quantitative determination of potassium in the low μg/g range in unknown polymer types is achieved with a relative error less than 20% which is comparable to conventional matrix-matched quantification. For all other samples, relative errors in the range of 30%–90% are obtained, which offers a precision adequate for many applications. E.g. in the food-packaging- or semiconductor-industry in many cases it is sufficient to determine if the contamination level of a sample with an unknown matrix is below or above a certain threshold. In this case, the developed approach poses a significant improvement compared to non-matrix-matched quantification which often leads to deviations up to a factor 10 or more from the nominal concentration.

Laser-induced breakdown spectroscopy-Raman: An effective complementary approach to analyze renal-calculi.

Presence of renal-calculi (kidney stones) in human urethra is being increasingly diagnosed over the last decade and is considered as one of the most painful urological disorders. Accurate analysis of such stones plays a vital role in the evaluation of urolithiasis patients and in turn helps the clinicians toward exact etiologies. Two highly complementary laser-based analytical techniques; laser-induced breakdown spectroscopy (LIBS) and micro-Raman spectroscopy have been used to identify the chemical composition of different types of renal-calculi. LIBS explores elemental characteristics while Raman spectroscopy provides molecular details of the sample. This complete information on the sample composition might help clinicians to identify the key aspects of the formation of kidney stones, hence assist in therapeutic management and to prevent recurrence. The complementarity of both techniques has been emphasized and discussed. LIBS spectra of different types of stones suggest the probable composition of it by virtue of the major, minor and trace elements detected from the sample. However, it failed to differentiate the crystalline form of different hydrates of calcium oxalate stone. This lacuna was overcome by the use of Raman spectroscopy and these results are compared with conventional chemical analysis.

A multi-technique approach, based on mobile/portable laser instruments, for the in situ pigment characterization of stone sculptures on the island of Crete dating from Venetian and Ottoman period

A versatile analytical methodology is presented, that combines the application of two mobile laser-based analytical techniques, Raman microscopy and laser-induced breakdown spectroscopy (LIBS), for the analysis of materials in historical and archaeological objects and monuments. In the present study, the proposed methodology was employed in the context of analytical campaigns aiming to investigate paint materials used on the island of Crete during the Venetian and Ottoman periods, thirteenth to nineteenth century CE. The first series of campaigns were conducted at the Historical Museum of Crete, Heraklion, Greece, and provided for the first time compositional data concerning the pigment palette used for painting Ottoman sculpture in Crete. In the second series, campaigns were performed outdoors for studying pigments in the sculptured door frames of two small medieval churches situated at rural locations in the greater Heraklion area. Raman and LIBS analyses gather complementary compositional data, molecular and elemental respectively, which, taken jointly, enable, in most cases, identification of pigments and accessory materials in paint layers, providing also stratigraphic information. With both instruments, measurements are performed directly on the surface of the objects or monuments, with no need for any sampling or sample preparation and thus analytical studies can be conducted rapidly and routinely in the context of a museum setting, a conservation laboratory or even outdoors. A standardized procedure that facilitates data collection and interpretation, interdisciplinary cooperation and presentation of results is adopted that optimizes the overall efficiency of the analytical campaigns.

Discriminating crude oil grades using laser-induced breakdown spectroscopy

The analysis of crude oil using laser-based analytical techniques such as laser-induced breakdown spectroscopy (LIBS) has become of great interest to various specialists in different fields such as geology, petro-chemistry and environmental science. In this work, a detailed study is presented wherein the implementation of an efficient and simple LIBS technique to identify the elemental constituents of crude oil and to distinguish between different grades of petroleum crude oil is discussed.Laser-induced plasma (LIP) technique has been used in this work for direct measurements of atomic, ionic and molecular species in dry crude oil samples with API gravities ranging between 18 and 36. The technique was implemented using the first harmonic of a pulsed Nd-YAG laser source. Atomic and molecular emission bands were observed, consisting of characteristic spectral lines of atoms and diatomic molecular bands, namely from C, H, Si, Na, Ca, Mg, AL, Fe, Ti, Mo, C2 and CN. The intensities of high-resolution spectral lines for some atoms and molecules of elements such as Ca, Na, Fe, Mo, C2 and CN were evaluated at different wavelengths along the obtained spectra. The molecular bands and the elemental spectral lines were used to assess the possibility of adopting the LIBS technique in differentiating between crude oil samples with different American Petroleum Institute (API) gravity values. The results indicate the presence of a distinct correlation between the API gravity values of the various oil samples and the spectral line intensities of the elements and some molecular radical constituents. In addition, the possibility of identifying the API gravity values of unknown oil samples is also indicated.

Algal biomass analysis by laser-based analytical techniques--a review.

Algal biomass that is represented mainly by commercially grown algal strains has recently found many potential applications in various fields of interest. Its utilization has been found advantageous in the fields of bioremediation, biofuel production and the food industry. This paper reviews recent developments in the analysis of algal biomass with the main focus on the Laser-Induced Breakdown Spectroscopy, Raman spectroscopy, and partly Laser-Ablation Inductively Coupled Plasma techniques. The advantages of the selected laser-based analytical techniques are revealed and their fields of use are discussed in detail.

Uranium determination in groundwater using laser spectroscopy

AbstractThe aim of this work is to review the laser-based analytical techniques for the quantitative determination of uranium in aqueous solutions. Among the various types of laser-based analytical techniques, two different spectroscopic techniques based on the measurement of laser-induced luminescence of hexavalent uranium ions [U(VI)] in groundwater are reviewed in detail. In the first technique, called time-resolved laser fluorescence spectroscopy, the time-resolved laser-induced luminescence intensities of U(VI) as a function of uranium concentration are measured to obtain the calibration curve. In the second technique, which is based on the simultaneous measurement of the U(VI) luminescence and Raman scattering of water, the calibration curve is obtained by measuring the ratio of the luminescence intensity of U(VI) to the Raman scattering intensity of water for the quantitative determination of uranium. A limit of detection of 0.03 μg/l was achieved at an excitation wavelength of 266 nm using these laser spectroscopic techniques. The results determined using these techniques are in good agreement with the results determined by inductively coupled plasma mass spectrometry (ICPMS). Thus, these laser-based analytical techniques will be useful to personnel requiring a rapid determination of uranium before the shipment of samples to an accredited laboratory, where relatively intricate and expensive apparatuses, such as ICPMS and radiochemical spectrometry, are used.

Analytical techniques in art, archaeology and conservation science

This special issue of Analytical and Bioanalytical Chemistry is dedicated to the use of analytical techniques in the field of cultural heritage. It contains a selection from the contributions presented in Berlin during the TECHNART 2011 conference on non-destructive and microanalytical techniques in art and cultural heritage. The contributions to the conference covered a wide range of advanced X-ray, ion and neutron beam techniques with special emphasis on microanalysis [X-ray fluorescence (XRF), particle-induced X-ray emission (PIXE), X-ray diffraction, scanning electron microscopy–energy-dispersive X-ray analysis] and confocal microscopy (3D micro-XRF, 3D micro-PIXE). Other contributions focussed on Fourier transform IR and Raman microscopy, UV–Vis and near-IR absorption, reflectance and fluorescence methods and other laser-based analytical techniques. Finally, contributions on the use of magnetic resonance spectroscopy, highperformance liquid chromatography and gas chromatography coupled with mass spectrometry, and optical imaging in addition to coherence techniques were also presented. As usual, mobile spectrometry played a major role in the TECHNART conference. Studies of cultural objects often comprise questions on their origin and dating and attribution to artists or workshops. Sometimes stylistic and art-historical examination coupled with information from contemporary technological treatises and secondary literature may be sufficient to answer such questions. However, in many cases the missing information can be deduced from the physical and chemical properties of the artefacts. In its individual materiality, each cultural asset is the result of a wide variety of influences (e.g. production, storage, restoration, preservation). So investigations of physical properties and chemical composition generate important input for answering cultural-historical questions that cannot be solved by historical and philological methods alone. Because of recent technological developments, instrumental diagnostics in art and culture are winning recognition in such fields of transdisciplinary research. Intimately connected with archaeometric investigations are conservation and restoration studies: the development of reversible restoration or conservation concepts requires knowledge of the material compositions and ageing phenomena of the artefacts. The growing importance of physical and chemical diagnostics in the field of cultural heritage is reflected in a variety of conferences, workshops and journals. Hence, the dissemination of new developments in analytical technologies is an important prerequisite for further progresses in such a field of transdisciplinary research. All in all, this special issue represents the state of the art, illustrating how different techniques and different methods can be successfully applied to analytical investigations in the field of cultural heritage. I would like to thank all authors for submitting convincing and newsworthy contributions, all referees for constructive and conducive comments, and finally the central editorial office and the editors for their friendly cooperation.

14C analysis via intracavity optogalvanic spectroscopy

A new ultra sensitive laser-based analytical technique, intracavity optogalvanic spectroscopy (ICOGS), allowing extremely high sensitivity for detection of 14C-labeled carbon dioxide has recently been demonstrated. Capable of replacing accelerator mass spectrometers (AMS) for many applications, the technique quantifies zeptomoles of 14C in sub micromole CO 2 samples. Based on the specificity of narrow laser resonances coupled with the sensitivity provided by standing waves in an optical cavity, and detection via impedance variations, limits of detection near 10 −15 14C/ 12C ratios have been obtained with theoretical limits much lower. Using a 15 W 14CO 2 laser, a linear calibration with samples from 5 × 10 −15 to >1.5 × 10 −12 in 14C/ 12C ratios, as determined by AMS, was demonstrated. Calibration becomes non-linear over larger concentration ranges due to interactions between CO 2 and buffer gas, laser saturation effects and changes in equilibration time constants. The instrument is small (table top), low maintenance and can be coupled to GC or LC input. The method can also be applied to detection of other trace entities. Possible applications include microdosing studies in drug development, individualized sub-therapeutic tests of drug metabolism, carbon dating and real time monitoring of atmospheric radiocarbon.

Lasers in the Analysis of Cultural Heritage Materials

This article reviews laser-based analytical techniques, which find applications in the field of cultural heritage diagnostics, providing information about the chemical composition of materials, at the atomic or molecular level. Lasers are intense sources of light featuring unique characteristics that have been exploited in order to enhance the performance of certain spectroscopic techniques such as Raman or fluorescence spectroscopy, or even produce new schemes of analysis, including, for instance, non-linear or remote sensing spectroscopy as well as laser ablative sampling and excitation. In parallel, with advances in laser and detector technology, compact, mobile instrumentation is becoming available that permits broader use of such laser-based techniques for analysis of materials in works of art and archaeological findings.

Intracavity optogalvanic spectroscopy. An analytical technique for 14C analysis with subattomole sensitivity.

We show a new ultrasensitive laser-based analytical technique, intracavity optogalvanic spectroscopy, allowing extremely high sensitivity for detection of (14)C-labeled carbon dioxide. Capable of replacing large accelerator mass spectrometers, the technique quantifies attomoles of (14)C in submicrogram samples. Based on the specificity of narrow laser resonances coupled with the sensitivity provided by standing waves in an optical cavity and detection via impedance variations, limits of detection near 10(-15) (14)C/(12)C ratios are obtained. Using a 15-W (14)CO2 laser, a linear calibration with samples from 10(-15) to >1.5 x 10(-12) in (14)C/(12)C ratios, as determined by accelerator mass spectrometry, is demonstrated. Possible applications include microdosing studies in drug development, individualized subtherapeutic tests of drug metabolism, carbon dating and real time monitoring of atmospheric radiocarbon. The method can also be applied to detection of other trace entities.

Laser Tweezers Raman Spectroscopy Detects Differences between Normal Human Lymphocytes, Activated Lymphocytes and Leukemia.

Raman spectroscopy is a laser-based analytical technique that enables chemical characterization of molecules in a sample. It is based on the inelastic scattering of photons by molecular bond vibrations. A Raman spectrum obtained from single cells is an intrinsic molecular fingerprint of the sample, revealing detailed information about DNA, RNA, protein, lipid, and carbohydrate content as well as macromolecular conformations. This technique is rapid, non-invasive and non-destructive. We have demonstrated that single-cell laser tweezers Raman spectroscopy (LTRS) reliably discriminates between normal human T- and B-lymphocytes and their transformed, Jurkat-T and Raji-B, counterparts. Herein the same technique is used to discern normal human T- and B-cells from T- and preB-leukemia cells. Also, demonstrated are Raman spectra changes that result from the activation of normal T-cells with a combination of TPA and ionomycin, and normal B-cells by cross linkage of surface immunoglobulin. T- and B-cells were isolated from healthy volunteers. T- and preB-leukemia cells were isolated from patient samples. Spectra are both compared directly and analyzed by principal component analysis. Significant Raman spectra differences in characteristic DNA and protein signals discriminate between normal cells and their leukemia counterparts. Human leukemia cells were indistinguishable from Jurkat-T and Raji-B cells. Changes in spectra that result from cell activation and proliferation only partially account for the spectra changes of leukemia cells. These data demonstrate the utility of LTRS to discern normal lymphocytes from both transformed cells and leukemia cells.

Analysis of pigments in polychromes by use of laser induced breakdown spectroscopy and Raman microscopy

Two laser-based analytical techniques, Laser Induced Breakdown Spectroscopy (LIBS) and Raman microscopy, have been used for the identification of pigments on a polychrome from the Rococo period. Detailed spectral data are presented from analyses performed on a fragment of a gilded altarpiece from the church of Escatrón, Zaragoza, Spain. LIBS measurements yielded elemental analytical data which suggest the presence of certain pigments and, in addition, provide information on the stratigraphy of the paint layers. Identification of most pigments and of the materials used in the preparation layer was performed by Raman microscopy.

Laser-induced breakdown spectroscopy and Raman microscopy for analysis of pigments in polychromes

A polychrome from the Rococo period was analysed by use of two laser-based analytical techniques, laser-induced breakdown spectroscopy (LIBS) and Raman microscopy. The analysis, performed on a fragment of a gilded altarpiece from the church of Escatrón, Zaragoza, Spain, provided detailed spectral data that have been used for the identification of pigments. LIBS measurements yielded elemental analytical data that suggest the presence of certain pigments and, in addition, provide information on the stratigraphy of the paint layers. Identification of most pigments and of the materials used in the preparation layer was performed by Raman microscopy.

Pigment Identification in Painted Artworks: A Dual Analytical Approach Employing Laser-Induced Breakdown Spectroscopy and Raman Microscopy

The combined application of two laser-based analytical techniques—laser-induced breakdown spectroscopy (LIBS) and Raman microscopy—for pigment identification on painted artworks is demonstrated. Detailed spectral data are presented from analyses performed on a 19th century Byzantine icon, which was examined in order to identify the pigments used in the original painted structure, as well as in interventions carried out subsequently for restorative purposes. LIBS measurements yielded elemental analytical data which suggest the presence of certain pigments and, in addition, provide information on the stratigraphy of the paint layers. Identification of most pigments and of the materials used in the preparation layer was performed by Raman microscopy.

Apparatus for the detection and removal of vapor phase alkali species from coal-derived gases at high temperature and pressure

A high-pressure, high-temperature apparatus has been developed for the analysis of sorbents capable of removing alkali compounds to the concentration levels required by advanced, coal-fired power generating systems. The reactor is capable of operating at temperatures up to 1200 °C and pressures up to 2.0 MPa. A laser-based technique—photofragment fluorescence—enables in situ analysis of the sodium content in a gas stream before and after a sorbent bed thereby determining the efficiency of the alkali removal by the various sorbents studied (typically alumino-silicate clays). The design and development of both the reactor and the laser-based analytical technique is described.

Laser Resonance Ionization Mass Spectrometry for Krypton-81 Analysis

A new laser-based analytical technique is described for isotope selective noble gas atom counting. The method has been used to detect 81Kr atoms in a groundwater sample.