Determination of chromium/VI/ in welding fumes by radionuclide X-ray fluorescent analysis

From all heavy metals being the most significant particulates of air pollutants at working of high-alloy steels from the toxicological viewpoint, chromium is paid main attention at present in many laboratories. Continuing the work in the field of radionuclide X-ray fluorescent analysis of welding aerosols we have suggested and carried out a method for quick Cr/VI/ determination by means of²⁴¹Am radionuclide excitation of characteristic X-ray fluorescent radiation and Si/Li/ spectrometer.     

Determination of heavy metals in welder's working environment using nuclear analytical methods

Technological process of welding is significant source of pollution of working environment with heavy metals. Evaluation of chemical quality of working environment was made by means of radionuclide X-ray fluorescent analysis and activation analysis with fast neutrons. Welding aerosols were sampled by filtration method on Synpor 4 membrane ultra-filters. For selected types of welding filter metals, determination of heavy metals in aerosols was performed.     

Physicochemical characterisation of different welding aerosols

Physicochemical properties important in exposure characterisation of four different welding aerosols were investigated. Particle number size distributions were determined by scanning mobility particle sizer (SMPS), mass size distributions by separation and weighing the individual size fractions of an 11-stage cascade impactor. The size distribution of the primary particles of agglomerates, chemical composition and morphology of the particles were examined by TEM. There were significant differences in the particle number size distributions of the different welding aerosols according to the SMPS determinations. The particle mass size distributions determined gravimetrically were, however, not really different. The dominant range with respect to mass was between 0.1 and 1 μm, regardless of the welding technique. Most of the primary particles in all different welding aerosols had diameters between 5 and 40 nm. All types of primary particles had a tendency to form chainlike agglomerates. A clear size dependence of the particle chemical composition was encountered in the case of manual metal arc welding aerosol. Small particles with diameters below 50 nm were mostly metal oxides in contrast to larger particles which also contained more volatile elements (e.g. potassium, fluorine, sodium, sulphur).     

Development of a procedure for the determination of X-ray fluorescence of metals in aerosols

The precision of the determination of the of heavy metals in aerosols by X-ray fluorescence after their collection on a paper filter is evaluated depending on the chemical composition and weight of unsaturated samples. Recommendations on the choice of the optimal shape of the calibration function and on the conditions for the determination of its coefficients used for the X-ray analysis of unsaturated samples are formulated. A procedure for the X-ray determination of metals in aerosols collected on paper filters is developed; its performance characteristics are presented.     

Determination of Cr(VI) in welding fumes by anion-exchange fast protein liquid chromatography with electrothermal atomic absorption spectrometric detection

The applicability of an anion-exchange fast protein liquid chromatographic-electrothermal atomic absorption spectrometric procedure (FPLC-ETAAS) was investigated for the determination of Cr(VI) in welding fumes after alkaline extraction of aerosols loaded on filters. Gas tungsten arc welding (GTAW) of stainless steel was applied. Samples of welding fumes were collected during regular welding on polycarbonate membrane filters of 8 microm and 0.4 microm pore size (inhalable and respirable aerosols). Alkaline extraction (2% NaOH-3% Na2CO3) of filters in a heated ultrasonic bath was applied to leach Cr from the airborne particulate matter. 0.5 cm3 of sample extract was then injected onto an anion-exchange FPLC column. Tris-HCl buffer (0.005 mol dm(-3), pH 8.0) and the same buffer with NaCl (0.5 mol dm(-3)) were employed in gradient elution (15 min, flow rate 1 cm3 min(-1)). The separated Cr species were determined "off line" by ETAAS in 0.5 cm3 fractions. Cr(VI) was reproducibly and quantitatively eluted from 12.0 to 13.0 min with a maximum peak at 12.5 min. Good repeatability of measurement (+/-3.0%) of alkaline extracts was obtained for Cr(VI). The LOD (3s) was found to be 0.035 microg m(-3) Cr(VI), when 2 m3 of aerosols were collected on the filter. Validation of the procedure was performed by spiking alkaline extracts and by the analysis of standard reference material CRM 545, Cr(VI) in welding dust loaded on a filter. The technique was successfully applied for the determination of Cr(VI) in welding fumes.     

Analysis of water-soluble fraction of metals in atmospheric aerosols using aerosol counterflow two-jets unit and chemiluminescent detection

A new analytical system for a semi-continuous analysis of water-soluble fraction of particulate metals is described. The system combines the continuous sampling of atmospheric aerosols into deionized water using the Aerosol Counterflow Two-Jets Unit and on-line chemiluminescent detection of water soluble fraction of metals in collected aerosols. The potential of analytical system was studied using Fe³⁺, Cu²⁺ and Co²⁺ as model metals in atmospheric aerosols. The detection limits of particulate Fe³⁺, Cu²⁺ and Co²⁺ (S/N?=?3) are 24, 41 and 0.4?ng?m^?3, respectively. The presented set-up allows the determination of concentration of water-soluble fraction of particulate metals in ‘real time’ with time resolution of 30?min. The system is sufficiently robust for the field application. The method has been applied to the measurement of selected metals in urban TSP (Total Suspended Particles) aerosols in Brno in the Czech Republic. The concentrations of particulate water-soluble Fe³⁺, Cu²⁺ and Co²⁺ were found in the range of 35 to 290, 42 to 462 and 0.5 to 9?ng?m^?3, respectively.     

Cr(III)/Cr(VI) speciation in aerosol particles by extractive separation and thermal ionization isotope dilution mass spectrometry

 An isotope dilution mass spectrometric (IDMS) method, using the formation of positive thermal ions, was developed for Cr(III) and Cr(VI) speciation in aerosol particles. Cr(III) and Cr(VI) spike species, enriched in ⁵³Cr, were applied for the isotope dilution step. After leaching of filter collected aerosol samples by an alkaline solution at pH 13, species separation was carried out by extraction with a liquid anion exchanger in methyl isobutyl ketone. Cr(VI) in the organic phase was re-extracted into an ammoniacal solution and chromium was then isolated from both fractions of species by electrodeposition. Detection limits of 30 pg/m³ for Cr(III) and of 8 pg/m³ for Cr(VI) were achieved in atmospheric aerosols for volumes of air samples of about 120 m³. These low detection limits allowed the determination of chromium species in continental aerosol particles in dependence on different seasons. The Cr(III) /Cr(VI) ratio was always found to be about 0.3 whereas dust from soil erosion, which is probably the primary source of chromium in the atmosphere, showed higher ratios. This indicates that chromium is oxidized in the atmosphere. The accuracy of the method was demonstrated in two interlaboratory comparisons of Cr(VI) determinations in welding dust samples. The IDMS method also contributed to the certification of a corresponding standard reference material organized by the Standard Reference Bureau of the European Union. Chromium speciation, including the determination of elemental chromium Cr(0), was carried out in aerosols of different welding processes for stainless steel. These analyses showed distinct differences in the distribution of chromium species in the welding process and can be used as an exact calibration method for routine methods in this important field of monitoring corresponding working places. Received: 19 August 1996/Revised: 24 September 1996/Accepted: 28 September 1996     

Composition of Radioactive Aerosols in the Shelter Construction of the Chernobyl Nuclear Power Plant in 2000–2015

The results of the physicochemical studies of radioactive aerosols inside and outside the Shelter construction at the Arch construction stage of the Chernobyl Nuclear Power Plant (ChNPP) in 2000–2015 were presented. The dominant isotopes were shown to be cesium, strontium, americium, plutonium, and uranium. They are carried by disperse particles of 2–7 μm. In subreactor rooms, in particular, 012/7, the composition of aerosols is affected by the erosion of the fuel-containing mass formed in 1986. Submicron cesium carrier aerosols appear as a result of evaporation and condensation during fires and welding works. Radiocesium is a well-soluble component of aerosols, while plutonium isotopes are not readily soluble components. In several rooms, the contents of radon, thoron, and their daughter products exceeded the permissible values. In April–June 2011, the intake of radionuclides from the accident at the Japanese Fukushima-1 NPP, which had AMAD of ~0.5 μm, was detected and tracked using Petryanov multilayer filters. The productivity of filtration units under the dusty conditions in the exclusion zone of ChNPP and in fogs and haze was investigated. Hydrophilic prefilters with 7–10 μm fibers were recommended.     

Ab Initio Studies on MCH2(OH) and CH3OM(M=H, -, Li, Na)

IntroductionThe greatsynthetic utility of organolithium reagents has been extended by the introduc-tion ofα-lithium-etherreagents[1— 4] .Those reagentsareeasily prepared,and they can be usedas anionic resources to synthesize a large variety of compounds stereo-selectively[5— 8] .Fur-thermore,such reagents can react with nucleophiles like RLi,only a typical reaction of car-benoid[9,1 0 ] .Though the ambidentnature isof greatinterest,only a little work has been doneon model molecule Li CH2 …     

Reductive metalation of unsaturated compounds: the effect of allylic protons

Reductive metalation of alkali metals of hydrocarbons containing labile protons can be accompanied by proton transfer from the hydrocarbon to the derived radical anion and/or dianion. The extent of this reaction as a function of reaction conditions has been studied with trans-1,2-diphenylpropene (I). Three alkali metals, Li, Na and K, and two solvents, diethyl ether (DEE) and tetrahydrofuran (THF) were examined.No significant proton transfer was observed with the Li/DEE, Li/THF or Na/DEE system: the product (III) being the vicinal dianion of (I). In the case of Li/DEE, the limited solubility of the dianion prevented complete conversion of (I) to (III) except in dilute solutions.With Na/THF, substantial amounts of proton transfer occurred to form the substituted allylic anion (V) from (I). The extent of this reaction could be controlled by varying the temperature and was largely suppressed at 0°.Extensive proton transfer resulted with K/THF. However, in this case the allylic anion (V) so formed was further reduced with dimerization to the tetra-anion of 1,2,5,6-tetraphenylhexane, (IX).     

The agglomeration state of nanosecond laser-generated aerosol particles entering the ICP

Fundamental understanding of aerosol formation and particle transport are important aspects of understanding and improving laser-ablation ICP–MS. To obtain more information about particles entering the ICP, laser aerosols generated under different ablation conditions were collected on membrane filters. The particles and agglomerates were then visualised using scanning electron microscope (SEM) imaging. To determine variations between different sample matrices, opaque (USGS BCR-2G) and transparent (NIST SRM 610) glass, CaF₂, and brass (MBH B26) samples were ablated using two different laser wavelengths, 193 and 266 nm. This study showed that the condensed nano-particles (∼10 nm in diameter) formed by laser ablation reach the ICP as micron-sized agglomerates; this is apparent from filters which contain only a few well-separated particles and particle agglomerates. Ablation experiments on different metals and non-metals show that the structure of the agglomerates is matrix-dependent. Laser aerosols generated from silicates and metals form linear agglomerates whereas particle-agglomerates of ablated CaF₂ have cotton-like structures. Amongst other conditions, this study shows that the absorption characteristics of the sample and the laser wavelength determine the production of micron-sized spherical particles formed by liquid droplet ejection.     

An experimental and theoretical evaluation of the nitrous oxide-acetylene flame as an atomization cell for flame spectroscopy

The formation of free atoms from aerosols of metal-containing solutions introduced into nitrous oxide-acetylene flames is examined by: (a) inference from well identified reactions and equilibria prevailing in cooler flames; (b) calculations employing a thermodynamic flame model; and (c) experimental observation of relative free-atom number densities in the flames as a function of stoichiometry. The calculated partial pressures of the major natural flame species and some of the spectroscopically observed minor species are presented as a function of the flow ratio of nitrous oxide to acetylene (p). Predicted relative number densities of Na, Mg, Cu, Fe, Li, Be, Al, W, Ti and Si as a function of p are compared with measured free-atom absorbances in an argon-shielded flame. These comparisons were completed for various heights above the burner tip. The data reported show that: (a) the degree of metal atomization in the nitrous oxide-acetylene flame can be adequately described by the equilibrium state; (b) in general, when solute vaporization is complete, there exists a value of ρ at which atomization is complete for metals that form monoxides with dissociation energies less than ~ 6.5 eV; and (c) certain metals may form carbon-containing compounds in the interconal zone.     

Determination of trace metals in urine with an on-line ultrasound-assisted digestion system combined with a flow-injection preconcentration manifold coupled to flame atomic absorption spectrometry

A flow analysis method with on-line sample digestion/minicolumn preconcentration/flame atomic absorption spectrometry is described for the determination of trace metals in urine. First, urine sample was on-line ultrasound-assisted digested exploiting the stopped-flow mode, and then the metals were preconcentrated passing the pre-treated sample through a minicolumn containing a chelating resin. A home-made minicolumn of commercially available imminodiacetic functional group resin, Chelite Che was used to preconcentrate trace metals (Cu, Fe, Mn and Ni) from urine. The proposed procedure allowed the determination of the metals with detection limits of 0.5, 1.1, 0.8 and 0.8 μg L⁻¹, for Cu, Fe, Mn and Ni, respectively. The precision based on replicate analysis was less than ±10.0%, and the enrichment factor obtained was between 21.3 (Mn) and 44.1 (Ni), for sample volumes between 2.5 and 5.0 mL, and an eluent volume of 110 μL. This procedure was applied for determination of metals in urine of workers exposed to welding fumes and urine of unexposed persons (urine control).     

On the Molecular Structure and Bonding in a Lithium Bismuth Porphyrin Complex: LiBi(TPP)2

A new Bi? Li porphyrin sandwich compound, LiBi(TPP)₂ has been synthesized and characterized (TPP=tetraphenylporphyrin). The unique molecular structure of LiBi(TPP)₂ is such that the Bi sits between the porphyrins and is directed towards the Li. This complex was shown to remain intact in solution by temperature‐dependent 2D NMR spectroscopy. In order to investigate the potential interaction between these two metals, DFT calculations were used and showed a Bi 6s orbital polarized towards Li which could be indicative of a Bi? Li dative bond. This bond is remarkably short, 2.87 Å, and is among the shortest Bi? Li distances seen in a small molecule.     

A neutron activation scheme for the detection and determination of pollutant heavy metals in sewage based fertilizers

A scheme of analysis of heavy metals in sewage based fertilizers, based mainly on direct gamma spectrometry using a Ge(Li) detector, is described. Reversed-phase anion exchange chromatography was used in separating some of the elements with mutually interfering gamma energies. The results are compared with those obtained from atomic absorption and spectrophotometric procedures.     

Neutron activation experiments for bremsstrahlung characterization studies

Activation experiments were conducted to assess the bremsstrahlung continuum produced from the activation of the ⁷Li isotope and the subsequent short-lived 13 MeV beta decay of ⁸Li (T _1/2 = 843 ms). The combination of the high energy beta-decay and the high atomic numbered metals used in piping for ⁷Li liquid metal coolants is a scenario in which bremsstrahlung production is a principal shielding concern. A series of fast pneumatic activation experiments have been performed to obtain the spectral distributions of bremsstrahlung gamma-rays transmitted through stainless steel shield samples. Detectors were used in both pulse-height and multichannel scaling analysis modes for energy spectra determination and half-life verification, respectively. Experimental results were utilized to validate the electron transport and bremsstrahlung production models used in the Monte Carlo MCNP code.     

滤膜冷凝收集-离子色谱法测定固液气溶胶中5种水溶性阴离子北大核心CSCD

水溶性离子是固、液气溶胶的重要组成部分,对于气溶胶的理化性质和空气质量具有重大影响,研究水溶性离子的含量对于大气环境的污染与防治具有深远意义。该研究建立了一种滤膜冷凝收集-离子色谱技术采集固体气溶胶和液体气溶胶并测定其中的5种水溶性阴离子(Cl^(-)、F^(-)、NO^(-)_(3)、NO2^(-)、SO4^(2-))含量的方法。首先,采用固体颗粒过滤器和冷凝收集法分别收集固体气溶胶和液体气溶胶,固体气溶胶以固体颗粒物的形式被收集在固体颗粒过滤器内,液体气溶胶以冷凝液的形式在冷阱中被收集。其次,以离子色谱法对固、液体气溶胶中的水溶性阴离子含量进行检测。在以Dionex IonPac AS11-HC-4μm作为分析柱,流速为1 mL/min,柱温为30℃,淋洗液氢氧化钾(KOH)浓度在0~40 min内由1 mol/L线性增至25 mol/L,进样量100μL的条件下,各离子在40 min内有效分离,5种阴离子在0.1~10 mg/L范围内线性关系良好(相关系数为0.9992~0.9997),检出限低(0.02~0.04 mg/L)。对样品采集条件(采样时间、采样温度和采样流量)进行了优化,结果表明,在采样时间2 h、采样温度-13℃、采样流量1.0 L/min的条件下,可获得较为满意的结果。在优化的条件下分别对实际样品的两类溶胶中的5种阴离子含量进行了检测,测得实际样品的液体气溶胶中5种阴离子含量分别为5.7402μg/m^(3)(F^(-))、1.1599μg/m^(3)(Cl^(-))、3.3233μg/m^(3)(NO^(-)_(2))、2.4861μg/m^(3)(NO^(-)_(3))和0.9745μg/m^(3)(SO^(2-)_(4)),固体气溶胶中5种阴离子含量分别为14.1037μg/m^(3)(F^(-))、5.0398μg/m^(3)(Cl^(-))、9.3052μg/m^(3)(NO^(-)_(2))、8.4528μg/m^(3)(NO^(-)_(3))和5.6314μg/m^(3)(SO^(2-)_(4))。该方法可应用于实际的大气检测中,也为其他离子的采集和分析条件的摸索提供了方法。     

Determination of alkali metals in control and AD brain samples by different techniques

Several metals are suspected or known to be involved in neurological disorders such as Alzheimer's disease (AD), therefore, elemental distribution studies have received intense attention for years. The present work focuses on a group of lesser studied elements in this context, alkali metals.Previously, an adequate neutron activation analysis (NAA) method has been developed and applied successfully for the determination of Na, K, Rb and Cs in brain samples of control subjects. This work has been extended to include AD patients, so that average values, distribution patterns and interpersonal variability could be compared and possible correlation between control and AD data could be studied.Despite the merits of the technique, its drawbacks are evident. Therefore, applicability of rapid spectrochemical methods as alternatives has been investigated. ICP-AES has been used for analysis of Li, Na and K. No interferences were observed, but ultrasonic nebulisation was needed for Li quantification. Rb and Cs were measured by ICP-MS with In as internal standard. Agreement between different techniques is found to be good for Na, K and Rb, while Cs values show somewhat higher differences.     

Comparison of different sampling heads applied for investigation of welding fume

Welding fume samples were collected in two Hungarian welding plants, where different types of steels were welded with metal active gas (MAG) welding. Welding fumes were sampled with “fixed point” and personal sampling techniques applying different sampling heads: Institute of Occupational Medicine (IOM) sampler and conical inhalable sampler (CIS) for the inhalable aerosol fraction and the Higgins-Dewell (HD) cyclone for the respirable fraction. When sampled, the welding fume samples were digested with the mixture of nitric acid and hydrogen peroxide in a closed vessel microwave digestion system. The Cr, Mn, Ni and Co contents of the solutions were determined by inductively coupled plasma atomic emission spectrometry (ICP-AES) and inductively coupled plasma mass spectrometry (ICP-MS). Iron was analysed only by the ICP-AES method. Metal concentrations of the workplace air were calculated for the three samplers, and the results were compared to each other. The differences of the metal concentrations determined by the different inhalable sampling heads, which were paired during the sampling, proved not to be significant. Therefore, the IOM and CIS heads can be equally used for the sampling of welding fume. Finally, the distributions of metals were determined between the inhalable and respirable fractions. Metal concentrations in the respirable aerosol fraction were 57-98% of the concentrations in the inhalable fraction. These high rates of metals in the respirable aerosol call the attention to the increased health risk of the welding fume.     

Determination of the speciation of chromium from a bicycle factory discharge

The discharge from a bicycle factory in Dar-es-Salaam was analysed for dissolved trace metals so as to monitor what was being introduced onto the environment. An X-ray Fluorescence Spectrophotometer with a Si (Li) detector connected to a multichannel analyser Canberra 40 series was used for the analysis. Computation of the peaks and results was done by a Professional Deck 350 computer. The elements contained in the discharge were Ca (596 ppm), Ti (369 ppm), Cr (11 ppm), Zn (0.98%) and Sr (73.5 ppm). Further analysis of the speciation of chromium revealed that there was Cr(III) (9 ppm) and Cr(VI) 2 ppm. The level of Cr(VI) was considered too high considering its toxicity.