Direct determination of bromine in plastic materials by means of solid sampling high-resolution continuum source graphite furnace molecular absorption spectrometry

This work investigates the potential of high-resolution continuum source graphite furnace molecular absorption spectrometry for the direct determination of bromine in polymers, which could be interesting in view of the current regulations restricting the use of organobrominated compounds. The method developed is based on the addition of Ca (300 μg) and Pd (30 μg) to favor the formation of CaBr, which is monitored at the main molecular “lines” (rotational spectra) found in the vicinity of 625.315 nm.It was found that accurate results could be obtained for all the samples investigated (polyethylene, polypropylene and acrylonitrile butadiene styrene certified reference materials) using any of the lines studied and constructing the calibration curve with aqueous standards. Furthermore, the combined use of the main four CaBr lines available in the spectral area simultaneously monitored permits to easily expand the linear range up to 2000 ng, provides a limit of detection of 1.8 ng (1.8 μg g^− 1 for a mass of 1 mg) and further improves precision to values between 3–7% RSD. Overall, the method proposed seems suited for the fast and simple control of these types of samples (approximately 10 min for sample are required), circumventing the traditional problems associated with sample digestion (e.g., losses of volatile compounds), and providing sufficient sensitivity to easily comply with regulations.     

Determination of iodine via the spectrum of barium mono-iodide using high-resolution continuum source molecular absorption spectrometry in a graphite furnace

Molecular absorption spectra of the diatomic molecules AlI, GaI, InI, TlI, MgI, CaI, SrI and BaI, generated in a graphite furnace, were studied using a high-resolution echelle spectrometer with the aim of finding a simple, reliable and sensitive analytical method for the determination of iodine. Among them, the barium mono-iodide (BaI) was found to have the strongest absorption bands around 538 nm and 560 nm, each of them consisting of a series of well-resolved rotational lines with half-widths of about 40–50 pm. The strongest BaI line, the band head at 538.308 nm has been evaluated systematically for its analytical use for the determination of iodine. High concentrations of hydrochloric acid (or chloride), hydrofluoric acid (or fluoride), iron, potassium and sodium resulted in significant reduction of the BaI molecular absorption. Apart from this, no other serious spectral or non-spectral interference has been observed. Different chemical forms of iodine, such as iodide, iodate and organically bound iodine produced identical BaI absorption sensitivity. The detection limit for iodine was 600 pg, and the calibration curve was linear up to 250 ng iodine. Two real samples with different chemical forms of iodine were analyzed using the proposed method. One sample was an iodide pill with a specified iodide content of 200 mg, the other one was a thyroid hormone pill with a specified content of 63.5 mg. The results were in good or satisfactory agreement with those of independent methods, the potentiometric titration and the inductively coupled plasma time-of-flight mass spectrometry (ICP-ToF-MS); the deviations were 2% and 8% for the iodide and the thyroid hormone sample, respectively. The relative standard deviation of the analytical results (n = 3) was below 2%.     

Stability of electrons—monomers and dimers—in gamma-irradiated hydroxide glasses

The increase of temperature from 77 K brings about the retrapping of electrons and/or recombination processes manifested by the changes of absorption spectra and ESR signals. The new absorption bands at 700–840 nm, which belong to diamagnetic electron dimers, have been observed at 215–225 K. These species are connected with NaOH·X H₂O hydrates as it has been shown by near-IR spectra. The dispersive kinetic parameters of photobleaching of electrons—monomers and dimers—at 80 K have been measured.     

Study of sub-mJ-excited laser-induced plasma combined with Raman spectroscopy under Mars atmosphere-simulated conditions

Laser-Induced Breakdown Spectroscopy (LIBS) and Raman spectroscopy are complimentary techniques. LIBS yields elemental information while Raman spectroscopy yields molecular information about a sample, and both share similar instrumentation configurations. The combination of LIBS and Raman spectroscopy in a single instrument for planetary surface exploration has been proposed, however challenges exist for developing a combined instrument. We present LIBS and Raman spectroscopy results obtained using a diode pumped, intracavity doubled, Q-switched, Nd:YLF laser operating at 523 nm, which overcomes some of the difficulties associated with a combined instrument. LIBS spectra were obtained with 170 μJ per pulse at 4 Hz repetition rate in a low pressure Mars-simulated atmosphere and Raman spectra produced with 200 mW at 100 kHz. The Nd:YLF laser is switchable between LIBS and Raman spectroscopy modes only by a change in Q-switch repetition rate. Emissions from Ca, Ca II, Fe, Fe II, Mg, Na, and O atom were identified in the μ-LIBS spectrum of oolithic hematite. Evidence was found for a change in plasma dynamics between 7 and 5 Torr that could be explained as a decrease in plasma temperature and electron density below 5 Torr. This is relevant to future Mars exploration using LIBS as the mean surface pressure on Mars varies from 3.75 to 6 Torr. LIBS plasma dynamics should be carefully evaluated at the pressures that will be encountered at the specific Mars landing site.     

Relationships between growth-bands and paleoenvironmental proxies Sr/Ca and Mg/Ca in hypercalcified sponge: A micro-laser induced breakdown spectroscopy approach

Long classified as coral hydrozoans, Chaetetids are now considered as a group of very shallow marine hyper calcified sponges. As corals do, they grow by adding calcium carbonate under their pellicular living body in such a rhythmic and regular way that we suspect that sclerochronology is possible, based on the hypothetical annual growth bands of their skeleton. Regarding to its accurate lateral resolution of 5 μm by laser shot, micro-LIBS study was chosen to check its potential for such application. The LIBS apparatus is composed of a microscope coupled with a 266 nm Nd-YAG laser, delivering a 4 mJ-power per shot, and an ICCD camera. The acquisition of the spectra is made via the SE 200 spectrograph, on the large 190 nm to 1100 nm wavelength range. The entire longitudinal thin section of the specimen was analysed from the bottom to the top of the Ptychochaetetes section in a multi-elementary cartography for Ca–Mg–Sr elements. Sodium and Barium were also detected but trace amounts. The Mg/Ca concentrations are mainly between 400 and 600 mmol/mol considering an average value for each profile. This study shows that during the Ptychochaetetes growth, an obvious time-dependent heterogeneity in the chemical Mg/Ca and Sr/Ca composition can be observed. These variations demonstrate the possible use of this method for sclerochronological studies.     

Determination of Fluorine, Chlorine, and Bromine by Molecular Absorption Spectrometry

Fluorine was determined by molecular absorption spectrometry (MAS) in a graphite tube furnace, and fluorine, chlorine, and bromine were determined in a flame. For the fluorine work, aluminum nitrate was added as a reagent to produce aluminum fluoride molecules whose absorbance was monitored with emission from a platinum hollow cathode lamp (HCL) at 227.45 nm. A deuterium arc lamp was employed for background correction. For the furnace work, barium nitrate was used as a chemical modifier to increase the absorption signal. After optimization of the chemical and furnace conditions, a detection limit of 160 pg F was obtained, with a linear dynamic range of two orders of magnitude. Graphite furnace MAS was used to accurately determine fluoride in dental rinse and National Institute of Standards and Technology oyster tissue, but the precision was between 21 and 23%. Low recoveries were obtained for the determination of trifluoroacetic acid and l,2,2,3-tetrafluoropropan-1-ol by graphite furnace MAS. The detection limit for F by flame MAS was 13 mg liter⁻¹ which is a factor of 5 lower than the best reported flame MAS detection limit. Chlorine was determined by flame MAS with the aluminum chloride molecule. Excitation was done at 261.4 nm with a lead HCL. and a detection limit of 180mg liter⁻¹ was obtained. Flame MAS of bromine was done by use of AlBr (excitation at 279.0 nm with an arsenic HCL) and InBr (excitation at 284.3 nm with a chromium HCL), but very poor detection limits were obtained: 24.5 g liter⁻¹ and 500mg liter⁻¹, respectively.     

Quantitative Characterization of the Molecular Absorption Spectra in the Ultraviolet Region by Gas Chromatography

The aim of this study was to obtain quantitative characteristics of the ultraviolet absorption spectra as the molecular absorptivity at the wavelength of maximum absorbance. Organic as well as inorganic compounds were explored. A gas chromatography—ultraviolet absorption instrument has been used in the quantitative study of molecular ultraviolet absorption spectra in the vapour phase. The wavelength range studied was between 168 and 330?nm. The absorbance of 170 compounds was determined relative to perchloroethylene and their molecular absorptivities were calculated. For various groups of compounds, these relative absorptivities varied within two to three orders of magnitude. Standard curves were linear within four orders of magnitude from limit of quantification up to an absorption value of 1.5 absorbance units. The noise level was 3?×?10^?5 absorbance units peak to peak at a bandwidth of 1.7?nm and a wavelength range from 180 to 330?nm was preferred. The detection limit for mesitylene was calculated to be 2 pg/s and for naphthalene 1 pg/s with 4?s store cycle time.     

Electronic state and photosensitivity of metal alkoxides chemically modified with β-diketones

Electronic state and optical absorption spectra of metal alkoxides stabilized with β-diketones (with a variety of substituents) were calculated using first-principle molecular orbital methods. The characteristics of the optical absorption and the mechanism of the photodissociation of alkoxides with irradiation of light are discussed. The position of the first peak observed in the near UV region in the theoretical spectra corresponded to that observed in the experimental spectra with a 25 nm shift toward shorter wavelengths. The first absorption peak observed in the visible range originated from electronic transitions to molecular orbitals, including the antibonding components of the C–O bonding in the chelate ring. The results suggested that the bonding of the chelate rings should be important in controlling the photosensitivity of chemically modified titanium alkoxides.     

Radiation induced DNA strand breaks measured by a modified method of gel scanning

Gel electrophoresis is an effective method for assaying plasmid DNA fractions, and UV lights with long wavelengths such as 315 nm is used to image the gel. In the present work, the sensitivities of detecting the fluorescence emitted from ethidium bromide (EB) stained DNA bands in the gel illuminated with UV lights of various wavelengths were compared. It was found that, in the range 245 to 320 nm, shorter excitation wavelength had higher detection sensitivity, thus 260 nm was selected for further studies. With this excitation light, as little as 0.7 ng DNA was detected. The fluorescence of DNA-EB bands had a good linear response to DNA quantity in a wide range. In addition, measured via this modified method, the yield of DNA strand breaks and the second-order rate coefficient of the reaction between DNA and √OH radical were consistent with many previous studies.     

Near-IR bromine Laser Induced Breakdown Spectroscopy detection and ambient gas effects on emission line asymmetric Stark broadening and shift

Investigation via Laser-Induced Breakdown Spectroscopy of a near-infrared bromine emission line (827.2 nm) with an UltraViolet ablation laser and a gated detector is reported. The effects of ambient pressure and gas species (air, O₂, N₂ and He) on the atomic emission line strength and spectral profile were systematically investigated. Substantially improved signal strength and reduced background radiation are demonstrated near 100 mbar ambient pressure with all gases. Optimal results were achieved when helium was used. Asymmetric broadening and shift of the 827.2 nm bromine line, attributed to pressure-dependent Stark effect has been revealed. This effect is prominent when air, oxygen or nitrogen are present and is much less manifested when helium is used. Possible interpretations of this effect are presented.     

Determination of Chlorine in Plastics via SrCl by Solid-Sampling High-Resolution Continuum Source Graphite Furnace Molecular Absorption Spectrometry

Solid sampling high resolution continuum source molecule absorption spectrometry (SS-HR-CS MAS) was applied for the determination of chlorine in plastic using the strontium monochloride (SrCl) molecule. For this purpose, 10?µL of 20?g L^?1 strontium (prepared from Sr(NO₃)₂) solution were pipetted with aqueous Cl standards or 0.05 to 4?mg of slivered plastic samples on a platform and introduced into the furnace. Chlorine was determined with the molecular absorption of SrCl at 635.862?nm using 1100?°C and 2200?°C for the pyrolysis and vaporization temperatures, respectively. Aqueous standards were used for calibration. The accuracy of the method was evaluated using a certified polyethylene reference material. The limit of detection and characteristic mass values of the method were 2.5?ng and 0.4?ng, respectively. The chlorine concentrations in various polyethylene beverage containers were determined.     

Estimation of calcified tissues hardness via calcium and magnesium ionic to atomic line intensity ratio in laser induced breakdown spectra

Calcified tissues representing three different matrices, namely enamel of human teeth, shells and eggshell, have been studied via Laser Induced Breakdown Spectroscopy (LIBS) technique. The experimental CaII/CaI and MgII/MgI ratios have been measured, in view of the expected correlation between the extent of ionization caused by the laser induced shock wave (SW) and the hardness of the target. The ratio CaII/CaI between the ionic calcium line at 373.69 nm and the neutral line at 428.9 nm is obtained for enamel, shells and eggshell spectra, as well as the ratio MgII/MgI between the ionic magnesium line at 280.26 nm and the neutral line at 285.22 nm. The results show that such spectral lines intensities ratio differs for different matrices and is indeed related to the target materials hardness. It is also found that the MgII/MgI ratio is preferable as an indicator of hardness since these lines are less affected by self absorption. The SW front speed has been measured in the three cases and the obtained values confirm the proportionality to the target hardness. The results here obtained suggest the feasibility of the quantitative estimation of hardness for any other calcified tissues.     

Determination of fluorine in tea using high-resolution molecular absorption spectrometry with electrothermal vaporization of the calcium mono-fluoride CaF

High-resolution continuum source molecular absorption of the calcium mono-fluoride molecule CaF in a graphite furnace has been used to determine fluorine in tea after acid digestion, alkaline solubilization and preparation of a conventional aqueous infusion. The strongest absorption ‘line’ of the CaF molecule is at 606.440 nm, which is part of the rotational fine structure of the X²Σ⁺ − A²Π electronic transition; it has a bond dissociation energy of 529 kJ mol⁻¹, which is comparable with other molecules used for fluorine determination. One advantage of using Ca as the molecule-forming reagent is that spectral interferences are extremely unlikely in the spectral range of its strongest absorption. Another advantage is that Ca acts both as molecule forming reagent and chemical modifier, so that no other reagent has to be added, making the method very simple. The only disadvantage is that Ca has a somewhat negative influence on the graphite tube lifetime. The limit of detection was found to be 0.16 mg L⁻¹ F, corresponding to 1.6 ng F absolute, and the calibration curve was linear in the range between 0.5 and 25 mg L⁻¹ with a correlation coefficient of R = 0.9994. The results obtained for a certified tea reference material were in agreement with the certified value on a 95% confidence level. There was also no difference between the results obtained after an acid digestion and an alkaline solubilization for 10 tea samples, based on a paired t-test. The values found in the 10 samples ranged between 42 μg g⁻¹ and 87 μg g⁻¹ F; the tea infusions contained between 21 μg g⁻¹ and 56 μg g⁻¹ F, with an extraction rate between 48% and 74%.     

Feasibility of high-resolution continuum source molecular absorption spectrometry in flame and furnace for sulphur determination in petroleum products

For the first time, high-resolution molecular absorption spectrometry with a high-intensity xenon lamp as radiation source has been applied for the determination of sulphur in crude oil and petroleum products. The samples were analysed as xylene solutions using vaporisation in acetylene-air flame or in an electrothermally heated graphite furnace. The sensitive rotational lines of the CS molecule, belonging to the ?ν = 0 vibrational sequence within the electronic transition X¹∑⁺ → A¹П, were applied. For graphite furnace molecular absorption spectrometry, the Pd + Mg organic modifier was selected. Strong interactions with Pd atoms enable easier decomposition of sulphur-containing compounds, likely through the temporal formation of Pd_xS_y molecules. At the 258.056 nm line, with the wavelength range covering central pixel ± 5 pixels and with application of interactive background correction, the detection limit was 14 ng in graphite furnace molecular absorption spectrometry and 18 mg kg⁻¹ in flame molecular absorption spectrometry. Meanwhile, application of 2-points background correction found a characteristic mass of 12 ng in graphite furnace molecular absorption spectrometry and a characteristic concentration of 104 mg kg⁻¹ in flame molecular absorption spectrometry.The range of application of the proposed methods turned out to be significantly limited by the properties of the sulphur compounds of interest. In the case of volatile sulphur compounds, which can be present in light petroleum products, severe difficulties were encountered. On the contrary, heavy oils and residues from distillation as well as crude oil could be analysed using both flame and graphite furnace vaporisation. The good accuracy of the proposed methods for these samples was confirmed by their mutual consistency and the results from analysis of reference samples (certified reference materials and home reference materials with sulphur content determined by X-ray fluorescence spectrometry).     

Kinetics and mechanism of the photodecomposition of trifluorobromomethane and tetrafluorodibromoethane under the action of light with a wavelength of 253.7 nm

The kinetics of photodecomposition of Halons CF₃Br and C₂F₄Br₂ was studied at different times of the irradiation of a mixture of these substances with oxygen at the wavelength λ = 253.7 nm. Kinetic data were obtained from changes in the absorption spectra in the region of Halon absorption and at a wavelength of 416 nm, which corresponds to the absorption maximum of molecular bromine. Kinetic schemes were proposed for the photodecomposition of CF₃Br and C₂F₄Br₂ at λ = 253.7 nm, and the quantum yields of their photodecomposition at this wavelength were determined.     

Molecular absorption spectrometry (MAS) by electrothermal evaporation in a graphite furnace-IX Determination of traces of bromide by mas of AlBr after liquid-liquid extraction of bromide with triphenyltin hydroxide

The determination of traces of bromide by molecular absorption spectrometry (MAS) of AlBr (with electrothermal volatilization) is described. It is possible to determine 25 ng of bromide. Many problems are caused by various matrices, so an extraction method for separation (and also preconcentration) was developed. The combination of bromide extraction with triphenyltin hydroxide, stripping with 0.025M barium hydroxide and determination of the extracted bromide by MAS of AlBr (after addition of aluminium ions) gives a very sensitive and selective method for determination of traces of bromide in micro or macro samples, in the presence of large amounts of other species, including chloride and iodide.     

Effect of molecular vibrations on the MD/QC‐simulated absorption spectra

Effect of molecular vibrations on the absorption spectra simulated via a sequential approach combining molecular dynamics (MD) with quantum‐chemical calculations has been investigated. Simulated spectra have been obtained from the time‐dependent density functional theory results averaged over series of molecular geometries retrieved from Born–Oppenheimer MD trajectories. Distributions of bond lengths have been analyzed and related to the features of calculated spectra. For NVE simulations of small systems, absorption spectra exhibit bimodal bandshape as a result of classical treatment of vibrations. For NVE trajectories of larger systems or simulations in the NVT ensemble calculated absorption bands are symmetric, however, they may not agree with the results of Franck–Condon analysis. These results are practical manifestations of effects predicted theoretically from general principles. Consequences for the modeling of absorption spectra have been discussed. © 2013 Wiley Periodicals, Inc.     

乙基紫-脱氧核糖核酸共振发光体系的研究及其分析应用

研究了碱性染料乙基紫与小牛胸腺脱氧核糖核酸(ctDNA)体系的结合反应及其共振发光光谱.在pH5.0～10.0范围内,乙基紫在595nm处有一特征吸收峰,加入DNA后,吸收峰消失,而在507nm处出现新的吸收峰,表明有新的结合物形成.在510nm处出现共振发光峰,其发光强度与DNA浓度呈线性关系,线性范围为0～500ng/mL;检出限(3σ)为1.54ng/mL.方法具有较高的灵敏度和准确度.将该体系用于核酸试样的测定,结果令人满意.     

Investigation of the feasibility to use Zeeman-effect background correction for the graphite furnace determination of phosphorus using high-resolution continuum source atomic absorption spectrometry as a diagnostic tool

The determination of phosphorus by graphite furnace atomic absorption spectrometry at the non-resonance line at 213.6 nm, and the capability of Zeeman-effect background correction (Z-BC) to deal with the fine-structured background absorption due to the PO molecule have been investigated in the presence of selected chemical modifiers. Two line source atomic absorption spectrometers, one with a longitudinally heated and the other with a transversely heated graphite tube atomizer have been used in this study, as well as two prototype high-resolution continuum source atomic absorption spectrometers, one of which had a longitudinally arranged magnet at the furnace. It has been found that Z-BC is capable correcting very well the background caused by the PO molecule, and also that of the NO molecule, which has been encountered when the Pd + Ca mixed modifier was used. Both spectra exhibited some Zeeman splitting, which, however, did not cause any artifacts or correction errors. The practical significance of this study is to confirm that accurate results can be obtained for the determination of phosphorus using Z-BC.     

Pulse radiolysis of 2-[(methacryloyloxy)ethyl]trimethylammonium chloride in aqueous solution

The early stages of the polymerization of 2-[(methacryloyloxy)ethyl]trimethyl ammonium chloride (MADQUAT) in aqueous solution were studied by pulse radiolysis. The rate constant of the reaction of this monomer with OH√ and hydrated electron was measured as 1.5×10¹⁰ and 2.2×10¹⁰ dm³mol⁻¹s⁻¹, respectively. The absorption spectrum of the OH√ adduct to MADQUAT molecule appeared to have a maximum at 290 nm. Its decay depends on the monomer concentration. The shape and maximum of the absorption spectrum of electron adduct to the monomer depend on pH of the solution. In acidic solution, radical anion is formed. It subsequently undergoes reversible protonation giving spectrum with a maximum below 260 nm. In basic solution the spectrum has a maximum at 290 nm. In this case irreversible protonation takes place at the β-carbon atom, giving an -centred carbon radical.