Aleš Hrdlička

Separation of rare earth elements by high performance liquid chromatography using a covalent modified silica gel column

A new modified silica gel material with chemically bound phosphonic acid was tested as lanthanide ions adsorption and their basic characteristics (thermodynamics, stability and physical description) studied. This inorganic chemically active beads (ICABs) are suitable for the solid phase extraction (SPE) and separation of the rare earth elements (REE). The HPLC procedure, using the 10 μm diameter ICAB with chemically immobilized phosphonic acid [alpha]-hydroxyisobutyric acid (HIBA) as the eluent and the post-column derivatization using Arsenazo III as the reagent, was worked out and found efficient to perform a good separation of REE.

Impact of Laser-Induced Breakdown Spectroscopy data normalization on multivariate classification accuracy

Multivariate data analysis (MVDA) is getting popular across the spectroscopic community. To assess accurate results, the obtained data should be preprocessed prior to utilization of any MVDA algorithm. The process of data normalization or “internal standardization” is widely used across a broad range of applications. In this manuscript we investigate the utilization of Laser-Induced Breakdown Spectroscopy (LIBS) coupled with MVDA. However, many articles regarding the use of MVDA on data from LIBS do not provide any information about the data pretreatment. This work describes the impact of LIBS data normalization approaches on MVDA classification accuracy. Also, the impact of classical data preprocessing (mean centering and scaling) exploiting the prior utilization of MVDA was studied. This issue was investigated exploiting simple soft independent modelling of class analogies algorithm. The findings were generalized for three sample matrices (steel, Al alloys, and sedimentary ores). Furthermore, the selection of an appropriate normalization algorithm is not trivial since the spectrum of each sample matrix is composed of a different number of elements and corresponding elemental lines.

Multielemental analysis of prehistoric animal teeth by laser-induced breakdown spectroscopy and laser ablation inductively coupled plasma mass spectrometry

Laser-induced breakdown spectroscopy (LIBS) and laser ablation (LA) inductively coupled plasma (ICP) mass spectrometry (MS) were utilized for microspatial analyses of a prehistoric bear (Ursus arctos) tooth dentine. The distribution of selected trace elements (Sr, Ba, Fe) was measured on a 26 mm×15 mm large and 3 mm thick transverse cross section of a canine tooth. The Na and Mg content together with the distribution of matrix elements (Ca, P) was also monitored within this area. The depth of the LIBS craters was measured with an optical profilometer. As shown, both LIBS and LA-ICP-MS can be successfully used for the fast, spatially resolved analysis of prehistoric teeth samples. In addition to microchemical analysis, the sample hardness was calculated using LIBS plasma ionic-to-atomic line intensity ratios of Mg (or Ca). To validate the sample hardness calculations, the hardness was also measured with a Vickers microhardness tester.

Ag-Cu colloid synthesis: bimetallic nanoparticle characterisation and thermal treatment

The Ag-Cu bimetallic colloidal nanoparticles (NPs) were prepared by solvothermal synthesis from metalloorganic precursors in a mixture of organic solvents. The nanoparticles were characterized by dynamic light scattering (DLS) and small angle X-ray scattering (SAXS). The properties of metallic core and organic shell of the nanoparticles were studied by direct inlet probe mass spectrometry (DIP/MS), Knudsen effusion mass spectrometry (KEMS), double-pulse laser-induced breakdown spectroscopy (DPLIBS), and differential scanning calorimetry (DSC). The transmission electron microscopy (TEM) and scanning electron microscopy (SEM) were used for particle characterization before and after thermal analysis. The experiment yielded results that were for AgCu nanoparticles for the first time. The detected liquidus temperature has been compared with the prediction obtained from calculation of the phase diagram of Ag-Cu nanoalloy. The experimental results show that of near-eutectic composition AgCu nanoparticles possess the fcc crystal lattice. Surprisingly, spinodal decomposition was not observed inside the AgCu nanoparticles at temperatures up to 230°C. The depression of the eutectic AgCu melting point was calculated but not observed. The eutectic AgCu microparticles are formed before melting.

Development of a remote laser-induced breakdown spectroscopy system for investigation of calcified tissue samples

The development of a remote laser-induced breakdown spectroscopy (LIBS) setup with an off-axis Newtonian collection optics, Galilean-based focusing telescope, and a 532 nm flattop laser beam source is presented. The device was tested at a 6 m distance on a slice of bone to simulate its possible use in the field, e.g., during archaeological excavations. It is shown that this setup is sufficiently sensitive to both major (P, Mg) and minor elements (Na, Zn, Sr). The measured quantities of Mg, Zn, and Sr correspond to the values obtained by reference laser ablation-inductively coupled plasma-mass spectrometry (LA-ICP-MS) measurements within an approximately 20% range of uncertainty. A single point calibration was performed by use of a bone meal standard . The radial element distribution is almost invariable by use of LA-ICP-MS, whereas the LIBS measurement showed a strong dependence on the sample porosity. Based on these results, this remote LIBS setup with a relatively large (350 mm) collecting mirror is capable of semiquantitative analysis at the level of units of mg kg−1.

Plasma pencil as an excitation source for atomic emission spectrometry

A 13.56 MHz plasma jet discharge, called a plasma pencil, was investigated. Rotational and excitation temperatures, and electron number densities for the pencil under and without sample load were calculated using OH band spectra, Ar lines and Hβ line, respectively. The rotational temperatures were found to be relatively low at about 800 K, however, excitation temperatures exceeded 4000 K. The plasma was found to be strongly non-isothermal. Some atomic lines of elements were easily observed. Aqueous solution-based aerosols were incorporated into the plasma without desolvation. Standard water solutions of the elements were nebulized into the plasma. The Ar carrier gas and Ar plasma gas flow rates were 0.3 and 4.0 l min−1, respectively. The forwarded power was 140 W. Intensities of the atomic lines, temperatures and electron number densities along the discharge tube were acquired in different positions from the aerosol entrance and an optimal position providing the best signal-to-noise ratio for each line intensity was established. Calibration dependencies for Ca, Cu, Mg, Zn, Li, Na were measured in the rage of 1–100 mg l−1. 3-sigma detection limits in the best observation axial position were (μg l−1): 27 (Ca), 49 (Cu), 58 (Mg), 40 (Li), 13 (Na) and 180 (Zn).

Microbore hplc determination of polyether antibiotics using postcolumn derivatization with Benzaldehyde reagents

Abstract Monensin, narasin, and salinomycin have been separated by HPLC on microbore column packed with octadecyl-bonded silica gel and detected via postcolumn color reaction with derivative of benzaldehyde in packed-bed reactor. Various benzaldehyde reagents have been tested in batch and 4-dimethylaminobenzaldehyde (DMABA) and vanillin selected as most promising ones. Requirements and characteristics of postcolumn reaction with the two reagents have been investigated and optimized and DMABA has been shown as superior over currently used vanillin reagent. The applicability of postcolumn derivatization with DMABA has been demonstrated by monensin assay in premixes and feeds.

Influence of electrode material on hydrogen peroxide generation by DC pinhole discharge

Abstract In this work, several materials were studied as electrodes in a pinhole configuration of a DC plasma discharge to estimate their effect on the efficiency of the discharge, indicated by hydrogen peroxide production. Detection was carried out using a specific titanium reagent. This was combined with ICP-OES analysis of the final solutions to determine the difference between the amount of electrode material released during the discharge operation and electrolysis experiment carried out under the same conditions. It was found that from seven studied electrode materials, graphite gives the best results, while lower cost aluminum and titanium-zinc still work well. The most unsuitable materials were copper and brass; in these cases, no hydrogen peroxide was detected in the cathode part of the reactor. Results obtained by ICP analysis indicate that even in the case of brass, the absence of hydrogen peroxide is due to the presence of copper in the material. It probably affects both directly the phase of discharge creation and propagation and the decomposition reactions. Graphical Abstract

Investigation of multi-layered silicate ceramics using laser ablation optical emission spectrometry, laser ablation inductively coupled plasma mass spectrometry, and electron microprobe analysis

The applicability of laser ablation (LA) inductively coupled plasma (ICP) spectrometry for assessing elemental distributions in layered ceramics was investigated and compared with electron probe microanalysis (EPMA). Ordinary glazed wall tiles were employed as model specimens due to their defined structure and composition. They were used for calibration in the analysis of ancient pottery. A qualitative depth profile was acquired by single-spot laser drilling perpendicular to coatings with a Nd:YAG (1064 nm) laser coupled with an ICP optical emission spectrometer (OES). The lower lateral resolution associated with the laser spot diameter of 1.0 mm led to smoothing of the depth profile due to the averaging of local irregularities. In addition, transverse line scans by ablation across the tile section using an ArF* (193 nm) laser coupled with an ICP mass spectrometer (MS) were performed. LA-ICP-OES depth profiles and LA-ICP-MS transverse scans were validated by EPMA section scans and 2D back-scattered electrons images. The LA-ICP-OES acquisition was less dependent on sample surface and layer irregularities, whereas the transverse line scan over the tile section with the small-spot beam offered insight into the micromorphology of the individual layer. The combined approach revealed the occurrence of individual mineral grains, micro-heterogeneities and the character of interfaces between layers.

Solid-Phase Extraction of Perphenazine from Blood Serum for High Performance Liquid Chromatographic Analysis

Abstract A solid-phase extraction (SPE) process has been developed with the aim of replacing multistage liquid-liquid extraction that is currently used for sample clean-up before the chromatographic determination of perphenazine (PPZ) in serum. The method comprises the trapping of PPZ from 2 mL of serum by 100 mg of silica gel with polymeric C18 phase, followed by rinsing of the endogenous compounds with water and acetonitrile. The drug is eluted with 0.7 mL of methanol and the eluate is evaporated to dryness under stream of air. The residue is dissolved in 100 μL of methanol and 20–μ aliquot is injected onto an HPLC column packed with silica gel modified with cyanopropyl groups. To control the retention and separation of PPZ from the other compounds, ammonium acetate concentration in the mobile phase consisting of 90% v/v methanol has been varied from 10 to 40 mmol/L. The SPE method enabled 86.2+5.0% of PPZ to be recovered which is 12% to 22% more than by liquid-liquid extraction procedure. The repeatabi...