Optical detection setup utilizing light emitting diodes (LEDs), 50 nL L-shaped silica capillary detection cell (L-cell), and low-cost CCD spectrometer is described in this work. Experimental configuration can be equipped with two different LEDs for absorbance measurement and other two LEDs for fluorescence excitation. This setup is capable of simultaneous multi-wavelength monitoring of absorbance and fluorescence when light produced by the individual LEDs and light emitted by the fluorescent analytes is resolved in the spectrum outputted by the CCD spectrometer. Effective optical path of the 0.25 μm I. D. L-cell is 1 mm. Absorbance baseline noise is 1 mAU due to use of low-cost and relatively noisy CCD spectrometer and LED drivers. Nevertheless, the setup can detect adenosine 5'-monophosphate down to micromolar concentration. Performance of fluorescence monitoring allows detection of 5·10-10 M fluorescein when 23 mW 470 nm LED is used for excitation. The dynamic range of absorbance and fluorescence measurement is 867:1 and 1622:1, respectively. Separation of test mixture (alkylbenzenes and polyaromatic hydrocarbons) demonstrate the effective use of the detector for simultaneous absorbance and fluorescence detection with 0.2 × 150 mm packed capillary column. The benefits of the setup are relative simplicity, compact design and the fact that it can be operated without any optical filters, slits, and extremely precise positioning of the optical elements.

• Klíčová slova
• CCD spectrometer, Light emitting diodes, Microcolumn liquid chromatography, Miniaturised detection cell, Simultaneous absorbance-fluorescence detection,
• Publikační typ
• časopisecké články MeSH

A proof-of-concept study of a new detector based on a thin plastic scintillator monitored by a Charge-Coupled Device (CCD) camera designed for monitoring and characterisation of Linac photon beams is presented. The response of the detector is compared with radiochromic film using 6 and 18 MV radiotherapeutic beams. We have observed: (i) all instruments survived the secondary radiation fields during Linac operation, (ii) it was possible to process the measured data using statistical techniques and (iii) the processed data from the CCD camera qualitatively correspond to film dosimetry results. A statistical technique based on the selection of minimal values provides the clearest results. Quantitatively, CCD and film results can only be compared as 6 to 18 MV response rates. We have observed that the rates from the CCD data are systematically higher than the rates from film dosimetry. Differences are not too high, namely 1.9-2.4 times the combined standard deviation.

• MeSH
• částice - urychlovače * MeSH
• filmová dozimetrie metody   MeSH
• plastické hmoty * MeSH
• radiometrie MeSH
• Publikační typ
• časopisecké články MeSH
• Názvy látek
• plastické hmoty * MeSH

In this article, we introduce a new ring artifacts reduction procedure that combines several ideas from existing methods into one complex and robust approach with a goal to overcome their individual weaknesses and limitations. The procedure differentiates two types of ring artifacts according to their cause and character in computed tomography (CT) data. Each type is then addressed separately in the sinogram domain. The novel iterative schemes based on relative total variations (RTV) were integrated to detect the artifacts. The correction process uses the image inpainting, and the intensity deviations smoothing method. The procedure was implemented in scope of lab-based X-ray nano CT with detection systems based on charge-coupled device (CCD) and scientific complementary metal-oxide-semiconductor (sCMOS) technologies. The procedure was then further tested and optimized on the simulated data and the real CT data of selected samples with different compositions. The performance of the procedure was quantitatively evaluated in terms of the artifacts' detection accuracy, the comparison with existing methods, and the ability to preserve spatial resolution. The results show a high efficiency of ring removal and the preservation of the original sample's structure.

• Klíčová slova
• CCD detector, high-resolution X-ray computed tomography, relative total variation, ring artifacts reduction, sCMOS detector,
• MeSH
• algoritmy MeSH
• artefakty * MeSH
• fantomy radiodiagnostické MeSH
• počítačová rentgenová tomografie MeSH
• počítačové zpracování obrazu * MeSH
• rentgenové záření MeSH
• Publikační typ
• časopisecké články MeSH

This contribution introduces a new type of setup for fast sample analysis using laser-induced breakdown spectroscopy (LIBS). The novel design combines a high repetition rate laser (up to 50 kHz) as excitation source and an acousto-optical modulator (AOM) as a fast switch for temporally gating the detection of the emitted light. The plasma radiation is led through the active medium of the AOM where it is diffracted on the transient ultrasonic Bragg grid. The diffracted radiation is detected by a compact Czerny-Turner spectrometer equipped with a CCD line detector. Utilizing the new combination of high repetition rate lasers and AOM gated detection, rapid measurements with total integration times of only 10 ms resulted in a limit of detection (LOD) of 0.13 wt.% for magnesium in aluminum alloys. This short integration time corresponds to 100 analyses/s. Temporal gating of LIP radiation results in improved LODs and consecutively higher sensitivity of the LIBS setup. Therefore, an AOM could be beneficially utilized to temporally detect plasmas induced by high repetition rate lasers. The AOM in combination with miniaturized Czerny-Turner spectrometers equipped with CCD line detectors and small footprint diode pumped solid state lasers results in temporally gateable compact LIBS setups.

• Publikační typ
• časopisecké články MeSH

The crystal structure and charge density of hydrogen (2,4-diaminopyrimidin-1-io)methyl]phosphonate monohydrate, C(5)H(9)N(4)O(3)P x H(2)O, have been determined by means of single-crystal X-ray diffraction. Diffraction data were collected at 105 K with Mo K alpha radiation to a resolution of sin theta/lambda = 1.08 A(-1). A four-circle diffractometer equipped with a CCD area detector was used to collect 50 161 reflections over 3 d. 6082 unique reflections with I > 3 sigma(I) were used in the multipole model to map the deformation electron density and gave the final statistical factors R(F) = 0.0329, wR(F) = 0.0235 and g.o.f. = 1.37. Structure determination revealed that two O atoms in the crystal structure of the title compound act as hydrogen-bond acceptors for more than one hydrogen bond. Examination of deformation electron density maps showed preferential polarization of the lone-pair electron density of the two O atoms into the shortest hydrogen bonds.

• Publikační typ
• časopisecké články MeSH

An La(2)Co(1.7) crystal was investigated by single-crystal neutron and X-ray diffraction. The neutron measurement was performed with a Laue white-beam technique at 15 K and room temperature, using a large position-sensitive detector. The X-ray measurements were obtained at room temperature from a CCD detector. The average structure of La(2)Co(1.7) is hexagonal with cell parameters a = 4. 885 (1), c = 4.273 (2) A and space group P6(3)/mmc. The satellites are located at the vertices of small hexagons perpendicular to the c axis. The modulated crystal was indexed assuming a sixfold twinned 3 + 1 dimensional structure with q = (alpha, 0, gamma). The structure was solved in the pseudoorthorhombic cell, with a = 8.461 (1), b = 4. 885 (1), c = 4.273 (2) A, in the superspace group C2/m(alpha, 0, gamma). Owing to space requirements, the Co atoms cannot fit precisely into the octahedral sites of the La h.c.p. (hexagonal close packing). Instead, the Co atoms adopt a different periodicity, which is not commensurate with the periodicity of the La atoms. Two structure models have been refined in order to describe this behaviour, one using the sawtooth function for the positional modulation of cobalt and the other describing the structure as a composite system. The chemical composition calculated from the composite model is La(2)Co(1.8 (1)) with the estimated standard deviation arising from the variation of q for different samples. In both models lanthanum is incommensurately modulated, while the position of cobalt seems not to be affected by any relative periodic displacement.

• Publikační typ
• časopisecké články MeSH

A miniaturized post-column fluorimetric detection cell for capillary separation methods based on optical fibers and liquid core waveguides (LCWs) is described. The main part of the detection cell is a fused-silica capillary coated with Teflon AF serving as an LCW. The optical fibers are used both for coupling the excitation source with the detection domain in the LCW and for the axial fluorescence collection from the LCW end. The latter fiber is connected with a compact CCD spectrometer that serves for the rejection of the scattered excitation light and for the fluorescence signal detection. The proposed design offers a compact fluorescence detector for various microcolumn separation techniques without optical elements such as filters or objectives. Moreover, its construction and optical adjustment are very simple and the whole system is highly miniaturized. The function of the detection cell is demonstrated by CE of amino acids labelled by fluorescein-based tags. Separations of different standard amino acid mixtures and plasma samples are presented. The comparison of plasma amino acid levels of individuals being in good health with those of patients with inherited metabolic disorders is also shown.

• MeSH
• aminokyseliny krev   izolace a purifikace   MeSH
• elektroforéza kapilární metody   MeSH
• fluorescenční spektrometrie přístrojové vybavení   MeSH
• lidé MeSH
• miniaturizace MeSH
• optická vlákna MeSH
• technologie optických vláken MeSH
• Check Tag
• lidé MeSH
• Publikační typ
• časopisecké články MeSH
• hodnotící studie MeSH
• práce podpořená grantem MeSH
• Názvy látek
• aminokyseliny MeSH

The paper deals with the concept of simple automated creation of gradient profile of the mobile phase for gradient-elution sequential injection chromatography (GE-SIC). The feasibility and merits of this concept are demonstrated on the separation and simultaneous assay of indomethacin as active principle and of its two degradation products (5-methoxy-2-methylindoleacetic acid and 4-chloro-benzoic acid) in a topical pharmaceutical formulation. The GE-SIC separation was performed with a FIAlab(®) 3000 SIC set-up (USA) equipped with an Onyx™ Monolithic C18 (25 mm × 4.6mm, Phenomenex(®)) column, a six-port selection valve, a 5-mL syringe pump and a fiber-optics UV CCD detector. Ketoprofen was used as an internal standard (IS). The gradient elution was achieved by automated reproducible mixing of acetonitrile and aqueous 0.2% phosphoric acid in the holding coil of the SIC system. Different profiles of the gradient elution were tested. The optimal gradient using two mobile phases 30:70 and 50:50 of acetonitrile/0.2% phosphoric acid (v/v) was achieved under the optimum flow rate 1.2 mL min(-1). The chromatographic resolution R between the peaks of all solutes (including the IS) was >2.00. The repeatability of retention times was characterized by the RSD values 0.18-0.30% (n=6). Net separation time was 3.5 min and the mobile phase consumption was 4.5 mL for a single GE-SIC assay. The figures of merit of the novel GE-SIC method compared well with those of conventional HPLC.

• Publikační typ
• časopisecké články MeSH
• práce podpořená grantem MeSH

A proof of concept of a novel pervaporation sequential injection (PSI) analysis method for automatic non-chromatographic speciation analysis of inorganic arsenic in complex aqueous samples is presented. The method is based on hydride generation of arsine followed by its on-line pervaporation-based membrane separation and CCD spectrophotometric detection. The concentrations of arsenite (As(III)) and arsenate (As(V)) are determined sequentially in a single sample zone. The leading section of the sample zone merges with a citric acid/citrate buffer solution (pH 4.5) for the selective reduction of As(III) to arsine while the trailing section of the sample zone merges with hydrochloric acid solution to allow the reduction of both As(III) and As(V) to arsine at pH lower than 1. Virtually identical analytical sensitivity is obtained for both As(III) and As(V) at this high acidity. The flow analyzer also accommodates in-line pH detector for monitoring of the acidity throughout the sample zone prior to hydride generation. Under optimal conditions the proposed PSI method is characterized by a limit of detection, linear calibration range and repeatability for As(III) of 22 μg L(-1) (3sblank level criterion), 50-1000 μg L(-1) and 3.0% at the 500 μg L(-1) level and for As(V) of 51 μg L(-1), 100-2000 μg L(-1) and 2.6% at the 500 μg L(-1) level, respectively. The method was validated with mixed As(III)/As(V) standard aqueous solutions and successfully applied to the determination of As(III) and As(V) in river water samples with elevated content of dissolved organic carbon and suspended particulate matter with no prior sample pretreatment. Excellent relative recoveries ranging from 98% to 104% were obtained for both As(III) and As(V).

• Klíčová slova
• Hydride generation, Inorganic arsenic, Pervaporation, Sequential injection analysis, Speciation,
• MeSH
• arseničnany izolace a purifikace   MeSH
• arsenikové přípravky chemie   MeSH
• arsenitany izolace a purifikace   MeSH
• chemické látky znečišťující vodu izolace a purifikace   MeSH
• kalibrace MeSH
• koncentrace vodíkových iontů MeSH
• kyselina citronová chemie   MeSH
• limita detekce MeSH
• průtoková injekční analýza metody   MeSH
• řeky chemie   MeSH
• spektrofotometrie přístrojové vybavení   metody   MeSH
• Publikační typ
• časopisecké články MeSH
• práce podpořená grantem MeSH
• Názvy látek
• arsenic acid MeSH Prohlížeč
• arseničnany MeSH
• arsenikové přípravky MeSH
• arsenitany MeSH
• arsenite MeSH Prohlížeč
• arsine MeSH Prohlížeč
• chemické látky znečišťující vodu MeSH
• kyselina citronová MeSH

Intensified charge-coupled devices (ICCDs) comprise the advantages of both fast gating detectors and spectrally broad CCDs into one device that enables temporally and spectrally resolved measurements with a few nanosecond resolution. Gating of the measured signal occurs in the image intensifier tube, where a high voltage is applied between the detector photocathode and a microchannel plate electron multiplier. An issue arises in time-resolved luminescence spectroscopy when signal onset characterization is required. In this case, the transient gate closing process that causes the detected signal always arises in the middle of the ICCD chip regardless of the spectral detection window--the so-called irising effect. We demonstrate that in case when the detection gate width is comparable to the opening/closing time and the gate is pretriggered with respect to the signal onset, the irising effect causes the obtained data to be strongly distorted. At the same time, we propose a software procedure that leads to the spectral correction of the irising effect and demonstrate its validity on the distorted data.

• Publikační typ
• časopisecké články MeSH