Ota Samek

Application of laser-induced breakdown spectroscopy to in situ analysis of liquid samples

A realization of laser-induced breakdown spectroscopy for real-time, in situ and remote analysis of trace amounts in liquid samples is described, which is potentially applicable to the analysis of pollutants in water in harsh or difficult-to-reach environments. Most of the measurements were conducted using a fiber assembly that is capable of both delivering the laser light and collecting the light emitted from the micro plasma, up to about 30 m from the target area. Alternatively, a telescopic arrangement for line-of-sight measurements was employed, with a range of 3 to 5 m. For internal standardization and the generation of concentration calibration curves, reference lines of selected elements were used. In the majority of cases calibration against the matrix element hydrogen was employed using the H?, H?, and H? lines, but also spiking with selected reference species was utilized. In order to provide high reliability and repeatability in the analyses, we also measured plasma parameters such as electron density, plasma temperature, and line- shape functions, and determined their influence on the measurement results. Numerous elements, including a range of toxic heavy metals, have been measured over a wide range of concentrations (Al, Cr, Cu, Pb, Tc, U, and others). Limits of detection usually were in the range of a few parts per million; for several elements even lower concentrations could be measured.

Quantitative laser-induced breakdown spectroscopy analysis of calcified tissue samples

Ž. We report on the application of laser-induced breakdown spectroscopy LIBS to the analysis of important minerals and the accumulation of potentially toxic elements in calcified tissue, to trace e.g. the influence of environmental exposure, and other medical or biological factors. This theme was exemplified for quantitative Ž detection and mapping of Al, Pb and Sr in representative samples, including teeth first teeth of infants, second teeth .Ž

Raman Microspectroscopy of Individual Algal Cells: Sensing Unsaturation of Storage Lipids in vivo

Algae are becoming a strategic source of fuels, food, feedstocks, and biologically active compounds. This potential has stimulated the development of innovative analytical methods focused on these microorganisms. Algal lipids are among the most promising potential products for fuels as well as for nutrition. The crucial parameter characterizing the algal lipids is the degree of unsaturation of the constituent fatty acids quantified by the iodine value. Here we demonstrate the capacity of the spatially resolved Raman microspectroscopy to determine the effective iodine value in lipid storage bodies of individual living algal cells. The Raman spectra were collected from three selected algal species immobilized in an agarose gel. Prior to immobilization, the algae were cultivated in the stationary phase inducing an overproduction of lipids. We employed the characteristic peaks in the Raman scattering spectra at 1,656 cm−1 (cis C═C stretching mode) and 1,445 cm−1 (CH2 scissoring mode) as the markers defining the ratio of unsaturated-to-saturated carbon-carbon bonds of the fatty acids in the algal lipids. These spectral features were first quantified for pure fatty acids of known iodine value. The resultant calibration curve was then used to calculate the effective iodine value of storage lipids in the living algal cells from their Raman spectra. We demonstrated that the iodine value differs significantly for the three studied algal species. Our spectroscopic estimations of the iodine value were validated using GC-MS measurements and an excellent agreement was found for the Trachydiscus minutus species. A good agreement was also found with the earlier published data on Botryococcus braunii. Thus, we propose that Raman microspectroscopy can become technique of choice in the rapidly expanding field of algal biotechnology.

Sensitive and selective spectrochemical analysis of metallic samples: the combination of laser-induced breakdown spectroscopy and laser-induced fluorescence spectroscopy ☆

Abstract In order to improve on analytical selectivity and sensitivity, the technique of laser-induced fluorescence spectroscopy (LIFS) was combined with laser-induced breakdown spectroscopy (LIBS). The main thrust of this investigation was to address analytical scenarios in which the measurement site may be difficult to access. Hence, a remote LIBS+LIFS arrangement was set up, and the experiments were carried out on samples surrounded by air at atmospheric pressure, rather than in a controlled buffer gas environment at reduced pressure. Representative for proof of principle, the detection of aluminium, chromium, iron and silicon at trace level concentrations was pursued. These elements are of importance in numerous chemical, medical and industrial applications, and they exhibit suitable resonance transitions, accessible by radiation from a pulsed Ti:sapphire laser system (its 2nd and 3rd harmonic outputs). All investigated elements have an energy level structure in which the laser-excited level is a member of a group of closely-spaced energy levels; thus, this allowed for easy off-resonant fluorescence detection (collisional energy transfer processes). Since numerous of the relevant transition wavelengths are within a narrow spectral interval, this opens the possibility for multi-element analysis; this was demonstrated here for Cr and Fe which were accessed by rapidly changing the tuneable laser wavelength.

Single-pulse laser-induced breakdown spectroscopy of samples submerged in water using a single-fibre light delivery system

Abstract Using a novel laser-induced breakdown spectroscopy set-up, accurate quantitative analysis of samples submerged in liquids has been demonstrated. The measurements were conducted using a single-fibre plus plastic tube assembly of 20 m length. This delivered the ablation laser light pulse and a buffer gas flow to the sample surface, and collected the light emitted by the micro-plasma for analysis. No distil optics were used at the sample end of the fibre. Argon, nitrogen and compressed air were used as buffer gases; while the rare gas resulted in slightly better signal-to-noise ratios, most analytical measurements were carried out with nitrogen for convenience and to provide comparability with in-air measurements. Detection limits and reproducibility were comparable to those achieved for the same samples placed in standard ambient air, with all other experimental conditions unchanged. In standard steel samples, detection limits of 310±45, 325±48 and 455±55 ppm for Cr, Mn and Si, respectively, could be achieved. Pattern recognition algorithms were used to identify, for classification, spectra of specimen submerged in turbid and non-transparent liquids.

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.

Raman microspectroscopy of algal lipid bodies: β-carotene quantification

Advanced optical instruments can serve for analysis and manipulation of individual living cells and their internal structures. We have used Raman microspectroscopic analysis for assessment of β-carotene concentration in algal lipid bodies (LBs) in vivo. Some algae contain β-carotene in high amounts in their LBs, including strains which are considered useful in biotechnology for lipid and pigment production. We have devised a simple method to measure the concentration of β-carotene in a mixture of algal storage lipids from the ratio of their Raman vibrations. This finding may allow fast acquisition of β-carotene concentration valuable, e.g., for Raman microspectroscopy assisted cell sorting for selection of the overproducing strains. Furthermore, we demonstrate that β-carotene concentration can be proportional to LB volume and light intensity during the cultivation. We combine optical manipulation and analysis on a microfluidic platform in order to achieve fast, effective, and non-invasive sorting based on the spectroscopic features of the individual living cells. The resultant apparatus could find its use in demanding biotechnological applications such as selection of rare natural mutants or artificially modified cells resulting from genetic manipulations.

Following the mechanisms of bacteriostatic versus bactericidal action using Raman spectroscopy.

Antibiotics cure infections by influencing bacterial growth or viability. Antibiotics can be divided to two groups on the basis of their effect on microbial cells through two main mechanisms, which are either bactericidal or bacteriostatic. Bactericidal antibiotics kill the bacteria and bacteriostatic antibiotics suppress the growth of bacteria (keep them in the stationary phase of growth). One of many factors to predict a favorable clinical outcome of the potential action of antimicrobial chemicals may be provided using in vitro bactericidal/bacteriostatic data (e.g., minimum inhibitory concentrations—MICs). Consequently, MICs are used in clinical situations mainly to confirm resistance, and to determine the in vitro activities of new antimicrobials. We report on the combination of data obtained from MICs with information on microorganisms’ “fingerprint” (e.g., DNA/RNA, and proteins) provided by Raman spectroscopy. Thus, we could follow mechanisms of the bacteriostatic versus bactericidal action simply by detecting the Raman bands corresponding to DNA. The Raman spectra of Staphylococcus epidermidis treated with clindamycin (a bacteriostatic agent) indeed show little effect on DNA which is in contrast with the action of ciprofloxacin (a bactericidal agent), where the Raman spectra show a decrease in strength of the signal assigned to DNA, suggesting DNA fragmentation.

Evaluation of 3-hydroxybutyrate as an enzyme-protective agent against heating and oxidative damage and its potential role in stress response of poly(3-hydroxybutyrate) accumulating cells

Poly(3-hydroxybutyrate) (PHB) is a common carbon- and energy-storage compound simultaneously produced and degraded into its monomer 3-hydroxybutyrate (3HB) by numerous bacteria and Archae in a metabolic pathway called the PHB cycle. We investigated 3HB as a chemical chaperone capable of protecting model enzymes, namely lipase and lysozyme, from adverse effects of high temperature and oxidation. Heat-mediated denaturation of lipase in the presence or absence of 3HB was monitored by dynamic light scattering (DLS) revealing a significant protective effect of 3HB which increased as its concentration rose. Furthermore, when compared at the same molar concentration, 3HB showed a greater protective effect than the well-known chemical chaperones trehalose and hydroxyectoine. The higher protective effect of 3HB was also confirmed when employing differential scanning calorimetry (DSC) and lysozyme as a model enzyme. Furthermore, 3HB was capable of protecting lipase not only against thermal-mediated denaturation but also against oxidative damage by Cu2+ and H2O2; its protection was higher than that of trehalose and comparable to that of hydroxyectoine. Taking into account that the PHB-producing strain Cupriavidus necator H16 reveals a 16.5-fold higher intracellular concentration than the PHB non-producing mutant C. necator PHB−4, it might be expected that the functional PHB cycle might be responsible for maintaining a higher intracellular level of 3HB which, aside from other positive aspects of functional PHB metabolism, enhances stress resistance of bacterial strains capable of simultaneous PHB synthesis and mobilization. In addition, 3HB can be used in various applications and formulations as an efficient enzyme-stabilizing and enzyme-protecting additive.

Laser ablation for mineral analysis in the human body: integration of LIFS with LIBS

Trace mineral analysis of the body is invaluable in biology, medicine and dentistry when considering the role of mineral nutrition and metabolism in the context of maintaining human health. The presence of key elements in the body, such as boron, calcium, chromium, copper, iron, silicon and zinc are known to be of vital importance, but are often found to be present in inadequate quantity. In sharp contrast, the accumulation of other elements, such as aluminum, cadmium, lead and mercury is less favorable, since frequently these metals are already toxic at extremely low concentration levels, interfering with essential chemical processing of vitamins and minerals. Here we report on the application of laser-induced breakdown spectroscopy and laser-induced fluorescence spectroscopy to the analysis of important minerals and toxic elements within the body. Samples from different parts of the body have been studied, including specimens of skin tissue, finger nails and teeth. It is particularly noteworthy that specific sample preparation was not needed for any of these laser spectroscopic measurements, but that specimens could be used as taken from the source.