UV Spectrometer Research Articles

Detection of Martian dust clouds by SPICAM UV nadir measurements during the October 2005 regional dust storm

The SPICAM UV spectrometer onboard Mars Express observed two regional dust storms: on October 24, 2005, near Argyre Planitia and on July 9, 2005, in Hellas Planitia. The measurements were performed in nadir mode. The spectral domain 210–310 nm is considered. A comparison with a prior orbit which passed above almost the same path 6 days before the storm near Argyre Planitia has shown a significant decrease of the radiance factor. The difference grows at shorter wavelengths and shows significant dust absorption in the UV. The data have been used to retrieve the dust optical thickness τ, single scattering albedo w and asymmetry factor g. The fitting of the spectra by a radiative transfer code has revealed a set of solutions which could be constrained by Mie modeling of the parameters τ, w, and g for a gamma particle size distribution. The following estimates of the dust optical parameters are obtained: w = 0.64 ± 0.04 at λ = 300 nm and decreases to 0.6 ± 0.045 at 213 nm, g = 0.86 ± 0.03 at 300 nm and slightly grows to 0.88 ± 0.04 at 213 nm, τ = 2.5 ± 0.5 for the first dust event and τ = 2.0 ± 0.5 for the second one. The obtained values of single scattering albedo are consistent with the Hubble Space Telescope and Mariner 9 results.

EPR of gamma irradiated solid sucrose and UV spectra of its solution. An attempt for calibration of solid state/EPR dosimetry

A simple new approach for independent calibration of solid state/EPR (SS/EPR) dosimetry system is reported. It is based on the fact that: (i) gamma-irradiation of solid sucrose (sugar) induces stable EPR detectable free radicals accompanied by UV detectable brown colour stable in the solid state and in solution; (ii) both the EPR intensity of gamma-irradiated solid sucrose and its solution UV absorbance linearly depend on the absorbed dose high energy radiation and may be independently used for dosimetric purpose; (iii) UV spectrometers are calibrated. The correlation between EPR response and absorbed dose radiation of solid sucrose and UV absorption of its solutions is used in the present communication for calibration purpose. The procedure of sucrose extraction from sucrose-paraffin dosimeters is described. The calibration procedure may be applied to any other (alanine, self-calibrated, etc.) SS/EPR dosimeters, simultaneously irradiated with sucrose.

A LONG PATHLENGTH SPECTROPHOTOMETRIC TEGAFUR DETECTOR USING A LIQUID-CORE WAVEGUIDE

A Liquid-Core Waveguide (LCW) detection system for high sensitive determination of tegaful (FT) was developed. In this system the LCW cell was connected to the end of a hollow cathode lump and the other end to a UV spectrometer. A sample solution containing FT was pumped to the LCW cell through a T-shaped connector. A UV absorption of analyte was detected by the UV spectrometer. The configuration of connectors of LCW cell to the light source and the UV detector was designed. Stable and high responses of FT were obtained in a double tube system in which an edge of LCW cell was covered with another tube with large diameter was set in the T-connector. It was found that the UV absorption response of FT obtained in this LCW system depends on the core length and the concentration of FT. The sensitivity of FT obtained by using 65 cm of the LCW cell length was 10-fold higher than that of using 1 cm cell which was often used with a conventional UV-visible detector.

Colorimetric Diffusion-Reflection Imaging High-Throughput Analysis of Organic or Inorganic Compounds

A colorimetric diffusion-reflection imaging (CDRI) high-throughput analytical technology was developed for library analysis. In the investigation, quartz sands were employed as light diffusion-reflection media. Inorganic and organic compounds with characteristic absorption bands in visible light could be quantified by this method. In the current investigation, compounds such as CrCl3, KMnO4, methylene blue, and acrolein were employed as substrates, and the UV spectrometer and traditional GC (with thermal conductivity detector) were employed to check the reliability of our CDRI technology. The current technology is capable of analyzing more then 100 samples simultaneously. Relative errors below 10% were achieved.

SPICAM on Mars Express: Observing modes and overview of UV spectrometer data and scientific results

This paper is intended as an introduction to several companion papers describing the results obtained by the SPICAM instrument on board Mars Express orbiter. SPICAM is a lightweight (4.7 kg) UV‐IR dual spectrometer dedicated primarily to the study of the atmosphere of Mars. The SPICAM IR spectrometer and its results are described in another companion paper. SPICAM is the first instrument to perform stellar occultations at Mars, and its UV imaging spectrometer (118–320 nm, resolution ∼1.5 nm, intensified CCD detector) was designed primarily to obtain atmospheric vertical profiles by stellar occultation. The wavelength range was dictated by the strong UV absorption of CO2 (λ < 200 nm) and the strong Hartley ozone absorption (220–280 nm). The UV spectrometer is described in some detail. The capacity to orient the spacecraft allows a great versatility of observation modes: nadir and limb viewing (both day and night) and solar and stellar occultations, which are briefly described. The absolute calibration is derived from the observation of UV‐rich stars. An overview of a number of scientific results is presented, already published or found in more detail as companion papers in this special section. SPICAM UV findings are relevant to CO2, ozone, dust, cloud vertical profiles, the ozone column, dayglow, and nightglow. This paper is particularly intended to provide the incentive for SPICAM data exploitation, available to the whole scientific community in the ESA data archive, and to help the SPICAM data users to better understand the instrument and the various data collection modes, for an optimized scientific return.

Effect of UV scattering on SO2 emission rate measurements

We report the quantitative evaluation of the UV scattering effect on the SO2 emission rate measurement by the compact UV spectrometer system. Plume spectra were obtained simultaneously at three measuring points with different distance to the volcanic plume. The apparent absorbance decreases with increasing distance to the plume and the attenuation becomes stronger at shorter wavelength bands. In addition, the attenuation intensity depends on the SO2 column concentration. The underestimation of the measured absorbance caused by the UV scattering leads to the underestimation of the SO2 emission rate. The attenuation was not significant with any wavelength band (<±10%) at 0.6 km but was 35–50% with shorter wavelength band at 2.6 km distance. The UV scattering effect on the SO2 emission rate estimation can be evaluated by the comparison of the emission rates calculated with different wavelength bands.

Measurement of Air−Water Interfacial Area for Multiple Hysteretic Drainage Curves in an Unsaturated Fine Sand

A new method has been developed to measure fluid-fluid interfacial area during multiple drainages, along with the measurement of hysteretic capillary pressure-saturation (P(c)-S) relationships in unsaturated porous media. The method makes use of an automated device which has been successfully used for rapid measurement of hysteretic P(c)-S relationships, in combination with a novel technique for interfacial area measurement. A pure anionic surfactant, sodium octylbenzene sulfonate (SOBS), is used as a surface-active tracer, and a flow-through UV spectrometer is used to monitor the real-time concentration change of SOBS solution due to adsorption to the fluid-fluid interface during drainage. The Gibbs and Langmuir adsorption equations are applied in combination with a continuous mole balance to calculate interfacial areas. Using this method, air-water interfacial area of a fine sand was measured as a function of capillary pressure and saturation during primary, secondary, and one scanning drainages to explore the influence of drying/wetting history on interfacial area. Results show that 8-20 and 12-22 cm(2)/g more air-water interface was generated in secondary and scanning drainages, respectively, than in primary drainage, with the magnitude of the difference varying as a function of saturation. An advantage of the method is that interfacial tension variations from the method itself are relatively small, typically on the order of 5 mN/m, so measured areas are not skewed by surface-tension-induced changes in interfacial area. In a measurement specifically designed to study the influence of surfactant-induced interfacial tension variations, approximately two times more interfacial area was observed for a 25 mN/m interfacial tension change, in comparison with a system with relatively constant interfacial tension. Implications of results of interfacial area measurements for hysteresis in the three-dimensional relationship between capillary pressure, saturation, and interfacial area are discussed.

Chemically assisted release of transition metals in graphite vaporizers for atomic spectrometry

The processes associated with the vaporization of microgram samples and modifiers in a graphite tube ET AAS were investigated by the example of transition metals. The vapor absorption spectra and vaporization behavior of μg-amounts Cd, Zn, Cu, Ag, Au, Ni, Co, Fe, Mn and Cr were studied using the UV spectrometer with CCD detector, coupled with a continuum radiation source. The pyrocoated, Ta or W lined tubes, with Ar or He as internal gases, and filter furnace were employed in the comparative experiments. It was found that the kinetics of atomic vapor release changed depending on the specific metal–substrate–gas combination; fast vaporization at the beginning was followed by slower ‘tailing.’ The absorption continuum, overlapped by black body radiation at longer wavelengths, accompanied the fast vaporization mode for all metals, except Cd and Zn. The highest intensity of the continuum was observed in the pyrocoated tube with Ar. For Cu and Ag the molecular bands overlapped the absorption continuum; the continuum and bands were suppressed in the filter furnace. It is concluded that the exothermal interaction of sample vapor with the material of the tube causes the energy evolution in the gas phase. The emitted heat is dispersed near the tube wall in the protective gas and partially transferred back to the surface of the sample, thus facilitating the vaporization. The increased vapor flow causes over-saturation and gas-phase condensation in the absorption volume at some distance from the wall, where the gas temperature is not affected by the reaction. The condensation is accompanied by the release of phase transition energy via black body radiation and atomic emission. The particles of condensate and molecular clusters cause the scattering of light and molecular absorption; slow decomposition of the products of the sample vapor–substrate reaction produces the ‘tailing’ of atomic absorption signal. The interaction of graphite with metal vapor or oxygen, formed in the decomposition of metal oxide, is the most probable source of chemical energy, which facilitates the vaporization. Intensity of the process depends on chemical properties of the sample and substrate and efficiency of mass and heat transfer by the protective gas. The discussed mechanism of chemically assisted vapor release signifies the energy exchange between all participants of the vaporization process in ET AAS including the matrix, modifier, purge gas and analyte. The finding contributes in the ET AAS theory regarding the mechanisms of vaporization and mass transfer in the presence of matrix and modifiers.

Radical scavenging activity of different floral origin honey and beebread phenolic extracts

Phenolic extracts were isolated from 35 honey and nine beebread samples obtained from different sources in Lithuania by using Amberlite XAD-2 resin. The antioxidant properties of extracts were assessed by the ABTS + radical cation decolourisation and DPPH radical scavenging activity. It was found that all honey and beebread extracts were able to scavenge free radicals, however their scavenging activity varied in a wide range, on average between 43.0% and 95.7%. The preliminary screening of phenolic compounds in honey samples was performed by high-performance liquid chromatography with UV and mass spectrometer detectors. The results obtained showed that all samples contain p-coumaric acid, kaempferol, chrysin and apigenin. This study demonstrates remarkable variations in antioxidant properties and content of phenolic compounds in honey from different sources; these variations should be considered in using honey as a source of natural dietary antioxidants.

Nitrogen dioxide, sulfur dioxide, and ammonia detector for remote sensing of vehicle emissions

A remote sensor for measuring on-road vehicles passing the sensor in real time is described. This sensor expands upon previous technology that measured carbon monoxide, carbon dioxide, and exhaust hydrocarbons in the IR and nitric oxide in the UV. The design adds the capability to measure nitrogen dioxide in the UV with one spectrometer and to measure SO2 and NH3 along with NO in a second UV spectrometer. With these units operating side by side, the major mobile source precursors to secondary aerosol production can be measured simultaneously and in real time. Detection limits for NO2, SO2, and NH3 are 1.2, 0.72, and 0.78 g pollutant per kilogram of fuel, respectively.

Cationic-modified microporous zeolites/anionic polymer system for simultaneous removal of dissolved and colloidal substances from wastewater

The simultaneous removal of both soluble and colloidal contaminants in wastewater has been a challenge. An innovative flocculation/sorption system has been developed in this work, which consisted of a cationic-modified microporous zeolite HY and an anionic polyacylamide-based polymer. The water-soluble anionic polymers act as flocculants for colloidal particles whereas the cationic-modified zeolite functions not only as an absorbent (towards the soluble or dissolved substances) but also a co-factor for the dual-component flocculation system. Such a system has been applied to clarify the wastewater containing the dissolved and colloidal substances (DCS) encountered in the pulp and paper industry. The quaternized zeolite HY was prepared using glycidyltrimethyl-ammonium chloride (GTMA-Cl) as a cationic reagent via a post-grafting approach to create the covalent bonds between GTMA-Cl and silanos (Si-OH) groups on the surface of zeolite HY. The pore structure and surface characteristics of the modified zeolite HY were determined based on XRD, N 2 adsorption and zeta-potential measurements. The sorption of modified zeolite HY towards benzoic acid and dissolved substances in DCS was determined using an UV spectrometer. The dynamic flocculation of DCS induced by the dual-component systems was monitored using a photometric dispersion analyzer (PDA). The results indicated that the simultaneous removal of DCS has been improved substantially due to the synergy between the cationic zeolites and anionic polymers in the dual-component system. The mechanisms involved in flocculation/sorption were also discussed.

Accurately measuring volcanic plume velocity with multiple UV spectrometers

A fundamental problem with all ground-based remotely sensed measurements of volcanic gas flux is the difficulty in accurately measuring the velocity of the gas plume. Since a representative wind speed and direction are used as proxies for the actual plume velocity, there can be considerable uncertainty in reported gas flux values. Here we present a method that uses at least two time-synchronized simultaneously recording UV spectrometers (FLYSPECs) placed a known distance apart. By analyzing the time varying structure of SO2 concentration signals at each instrument, the plume velocity can accurately be determined. Experiments were conducted on Kīlauea (USA) and Masaya (Nicaragua) volcanoes in March and August 2003 at plume velocities between 1 and 10 m s−1. Concurrent ground-based anemometer measurements differed from FLYSPEC-measured plume speeds by up to 320%. This multi-spectrometer method allows for the accurate remote measurement of plume velocity and can therefore greatly improve the precision of volcanic or industrial gas flux measurements.

Monitoring the Rate of Solvolytic Decomposition of Benzenediazonium Tetrafluoroborate in Aqueous Media Using a pH Electrode

Methods have been described by various authors for monitoring the solvolytic decomposition of the benzenediazonium ion (C6H5N2+) using a UV spectrometer. The benzenediazonium ion decomposes to yield nitrogen gas, which produces bubbles in the reaction mixture. If not immediately expelled from the reaction mixture, these bubbles will alter the effective cell path length and interfere with the UV signal. Within the context of an undergraduate laboratory, this can present a formidable problem. Results of this work show that the reaction can be accurately monitored in real time in an unbuffered solution using a pH electrode, whose signal is virtually unaffected by bubbles in the solution. This article discusses the use of pH electrodes to monitor the aqueous solvolysis of the benzenediazonium ion and shows that the results are in reasonable agreement with literature values.

Arranging a channel for monitoring the orientation toward the sun of the Solar Patrol apparatus

This paper discusses the organization of a special supplementary channel in the UV spectrometer of the apparatus of the Solar Patrol space experiment, which is to be installed for experimental operation on the outer surface of the service module of the Russian segment of the International Space Station. It is assumed that the optical axes of the apparatus will be aimed at the center of the sun's disk by means of a solar-oriented platform to within ±1.8°. A channel will be created to estimate the correctness of the orientation of the device toward the sun, and its readings will be used when processing the data of the measurements of the main spectrophotometric channels of the UV spectrometer. It is proposed to use a photocathode mounted in zeroth order of the spectrum of the diffraction grating of the spectrometer as a detector. © 2005 Optical Society of America

Effects of the temperature dependence in PTFE diffusers on observed UV irradiances

The effect of temperature‐dependences on the transmission of PTFE diffusers used in NIWA UV spectrometers is quantified through laboratory and field measurements. It is shown that data taken at temperatures less than 15°C typically require an upward correction of ∼2%.

Ecotoxicity of soils contaminated with industrial and domestic wastewater in western shenyang, China

Soil samples were collected from 7 sites in the up-, mid- and down-reach along and nearby the wastewater irrigation channel, western Shenyang of China. The concentrations of selected pollutants (mineral oil, PAHs--polycycle aromatic hydrocarbons and Cd) were determined by UV spectrometer, HPLC and AAS (atomic adsorption spectrometer) spectrometer, respectively. Toxicity effects of soils were evaluated by seedling emergence test with root length of wheat as the end-point and by earthworms test with the mortality rate and inhibition rates of body weight as endpoints. Results showed accumulation of pollutants for most soils with concentration of 200.2 mg x kg(-1)-1600 mg x kg(-1) for mineral oil, 0.33 mg x kg(-1)-1.81 mg x kg(-1) for Cd and 900.16 mg x kg(-1)-2737.91 mg x kg(-1) for PAHs. The inhibition rates of root elongation were from -20% up to 40%, and mortality rates of earthworms ranged from 0%-40% from the exposure period of two weeks to eight weeks by sampling interval of two weeks, the inhibition rates of earthworm growth were from -19.36% to 34.53%, showing effects of stimulation at 2 weeks to an increasing effects of inhibition at 4, 6 and 8 weeks, respectively. Mortality rates correlated with the loss of body weight of earthworms. This study indicated the potential risk of pollutants of environmental low content in soil by the determination of selected chemicals combined with toxicity indexes.

ORIENTATION REARRANGEMENT AND AGGREGATION OF OXADIAZOLE TYPE DYE

Monolayer properties of 2-(3,4,5-tris-dodecyloxyl-phenyl)-[1,3,4] oxadiazole based "tripod" dye molecules, P2G, have been studied by Langmuir–Blodgett technique, UV and polarizing microscopic images. Pressure-area isotherm of P2G has transition at 17 mN/m and this transition is believed to be the orientation rearrangement of the molecules from perpendicular to horizontal with respect to the surface normal. The presence of water insoluble hydrophobic single alkyl chains causes restructuring edge-on orientation and aggregation by compression. The H-aggregated structure was observed by UV spectrometer, and the orientation effect was clearly observed by polarizing microscopic images and sum frequency generation.

Spectral in-situ analysis of NO2, NO3, COD, DOC and TSS in the effluent of a WWTP

An in-situ UV spectrometer was applied to the effluent of a WWTP in Switzerland and calibrated using a multivariate calibration algorithm based on PLS regression. Except for nitrite, the calibration was based on comparative measurements of the effluent in the plant laboratory. Samples made of stock solution added to three different matrices prepared in the EAWAG laboratory were used for the nitrite calibration because the effluent concentrations were always in the range of 0.06-0.26 mg/l. The results show very good precision for nitrite and nitrate. The measuring range for COD and DOC was not completely covered by the measurements, so the meaningfulness of the results is limited. Nevertheless the precision obtained for soluble COD is high enough for most applications at WWTPs. The accuracy of the TSS measurement is unsatisfactory as regards effluent limits since the spectrometer used does not cover the wavelength region up to 700 nm, which gives better signals for TSS calibration due to its strong correlation with turbidity.

Preparation of Water-soluble PEGylated Semiconductor Nanocrystals

Abstract We describe the synthesis of water-soluble PEGylated semiconductor nanocrystals and the characterization of their optical properties and colloidal stability by fluorescence and UV spectrometers. The fluorescence intensity of PEGylated CdSe/ZnS in PBS buffer was observed to be 75% of the initial values of conventional CdSe/ZnS in chloroform. The PEGylated CdSe/ZnS exhibited higher fluorescence intensity than PEGylated CdSe and CdSe/CdS in PBS buffer. The colloidal stability of PEGylated QDs in PBS buffer was estimated by transmittance as a function of time at 37 °C. The PEGylated CdSe/ZnS showed a colloidal stable dispersion in PBS buffer during 24 h.

In vitro drug release studies from the polymeric hydrogels based on HEA and HPMA using 4-{(E)-[(3Z)-3-(4-(acryloyloxy)benzylidene)-2-hexylidene]methyl}phenyl acrylate as a crosslinker

Novel crosslinker, 4-{(E)-[(3Z)-3-(4-(acryloyloxy)benzylidene)-2-hexylidene]methyl}phenyl acrylate (AMA) was synthesized using (2Z, 6E)-2,6-bis(4-hydroxybenzylidene)cyclohexanone (HBC) and acryloyl chloride. Two types of crosslinked polymeric hydrogels were prepared from 2-hydroxyethyl acrylate (HEA) and 2-hydroxypropyl methacrylate (HPMA) monomers using AMA as a crosslinking agent. 2′,4-dichloro-5′-fluoro-1-ene-2-(4-hydroxyphenyl)phenone (EHP) (J. Bio Active Compat. Polym. 18 (2003) 219) was used as a drug molecule for monitoring the releasing behaviour of the hydrogels. Morphology of the hydrogels was characterized using optical microscopy (OM) and Scanning Electron Microscopy (SEM) techniques. Several modifications were made in the experimental sections to study the effect of crosslinking percentage (CLP), drug loading percentage (DLP), monomer type (HEA and HPMA) and the pH. Totally 18 experiments were carried out to study the desired parameters in the hydrogels. The drug-releasing rate was monitored by the absorption appeared at 330.5nm using UV spectrometer. It was found that the releasing rate of the drug from the polymeric hydrogels was dependent on the crosslinking density, drug loading percentage, monomer type and pH of the medium.