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Coal fly ash is a waste by-product of the coal fire industry, which generates many environmental problems. Alternative uses of this material would provide efficient solutions for this by-product. In this work, nitric acid-etched coal fly ash labelled with 2-mercaptoethanol or thioglycolic acid was assessed for retention of Al(III), As(III), Cu(II), Cd(II), Fe(III), Mn(II), Hg(II), Ni(II), Pb(II) and Zn(II) ions. The bonding characteristics between the organic compounds with the solid support, as well as with the metal ions, were evaluated using various surface analytical techniques. Visualization of the organically-functionalized coal fly ash particle was possible using scanning electron microscopy (SEM), while the elemental composition of the functionalized material, before and after retention of the metal ions, was obtained by energy dispersive (ED)-X ray spectrometry (XRS) and electrothermal atomic absorption spectrometry (ETAAS). Fourier transform infrared (FT-IR) spectrometry and Raman spectrometry were used to obtain information about the functional groups. It was found that some metal(oid) ions (As, Ni, Pb, Zn) were coordinated through the mercaptan group, while other metal(oid)s (Al, Cd, Cu, Fe, Hg, Mn) were apparently bonded to oxygen atoms. A low-cost and effective solid phase retention system for extraction of heavy metals from aqueous solutions was thus developed.

Laboratory experiments and modeling analysis have been conducted to gain insight on the self-excited unstable flame behaviors of a model gas turbine combustor that utilizes a low-swirl injector (LSI). The combustor consists of a 5.7 cm I.D. LSI firing into 18 cm diameter by 32 cm or 20.3 cm long cylindrical enclosures at atmospheric condition. The experiments involved lean premixed turbulent CH4 (0.6

The simplified bioaccessibility extraction test (SBET) and the stomach phase of the unified bioaccessibility method (UBM) have been modified for use in assessing the bioaccessibility of potentially toxic elements in samples of PM10 collected during routine air quality monitoring. Arsenic, Cd, Cr, Cu, Fe, Mn, Ni, Pb and Zn were measured by inductively coupled plasma mass spectrometry in extracts of synthetic PM samples prepared by loading candidate soil reference material BGS102 onto TX40 (Teflon-coated borosilicate) filters widely used in standard commercial tapered element oscillating microbalance/filter dynamics measurement system (FDMS) ambient particulate monitors. Analysis of blanks revealed two important sources of contamination that had to be controlled in order to achieve reproducible results. The syringe filters used in the SBET released Cu and Zn into sample extracts during filtration and had to be washed with 80 mL of 0.4 M glycine at pH 1.5 immediately prior to use, whilst the FDMS filters used to collect PM10 were found to contain sufficient extractable Zn (ca. 3 μg per filter) to almost double the concentration released by the soil. The latter is a consequence of the use of Zn in filter manufacture and so could not be eliminated, but was successfully overcome by means of blank-subtraction. A ten-fold miniaturisation of the SBET and six-fold miniaturisation of the UBM allowed 0.1 g samples to be processed, with analyte recoveries generally within ±10% of those obtained when the conventional procedures were used. Comparison between results obtained when the modified procedures were applied to soil alone, and when soil was loaded onto FDMS filters, indicated that the presence of the filter had no effect on extraction efficiency, except for Fe, provided blank-correction was performed. Results obtained for As, Cd and Pb when the modified UBM was applied to BGS102 on FDMS filters were 4.40 ± 0.04, 0.224 ± 0.002 and 17.3 ± 0.8 mg kg−1, respectively (n = 3), all within recommended ranges.

Large-scale commercial bioprocesses that manufacture biopharmaceutical products such as monoclonal antibodies generally involve multiple bioreactors operated in parallel. Spectra recorded during in situ monitoring of multiple bioreactors by multiplexed fiber-optic spectroscopies contain not only spectral information of the chemical constituents but also contributions resulting from differences in the optical properties of the probes. Spectra with variations induced by probe differences cannot be efficiently modeled by the commonly used multivariate linear calibration models or effectively removed by popular empirical preprocessing methods. In this study, for the first time, a calibration model is proposed for the analysis of complex spectral data sets arising from multiplexed probes. In the proposed calibration model, the spectral variations introduced by probe differences are explicitly modeled by introducing a multiplicative parameter for each optical probe, and then their detrimental effects are effectively mitigated through a "dual calibration" strategy. The performance of the proposed multiplex calibration model has been tested on two multiplexed spectral data sets (i.e., MIR data of ternary mixtures and NIR data of bioprocesses). Experimental results suggest that the proposed calibration model can effectively mitigate the detrimental effects of probe differences and hence provide much more accurate predictions than commonly used multivariate linear calibration models (such as PLS) with and without empirical data preprocessing methods such as orthogonal signal correction, standard normal variate, or multiplicative signal correction.

Electrothermal atomization of beryllium from graphite and tungsten surfaces was compared with and without the use of various chemical modifiers. Tungsten proved to be the best substrate, giving the more sensitive integrated atomic absorption signals of beryllium. Tungsten platform atomization with zirconium as a chemical modifier was used for the determination of beryllium in several NIST SRM certified reference samples, with good agreement obtained between the results found and the certified values. The precision of the measurements (at 10 microgL(-1)), the limit of detection (3sigma), and the characteristic mass of beryllium were 2.50%, 0.009 microgL(-1) and 0.42 pg, respectively.

International audience; There is an increasing interest in using Raman spectroscopy to identify polymorphic forms and monitor phase changes in pharmaceutical products for quality control. Compared with other analytical techniques for the identification of polymorphs such as X-ray powder diffractometry and infrared spectroscopy, FT-Raman spectroscopy has the advantages of enabling fast, in situ, and nondestructive measurements of complex systems such as suspension samples. However, for suspension samples, Raman intensities depend on the analyte concentrations as well as the particle size, overall solid content, and homogeneity of the solid phase in the mixtures, which makes quantitative Raman analysis rather difficult. In this contribution, an advanced model has been derived to explicitly account for the confounding effects of a sample's physical properties on Raman intensities. On the basis of this model, a unique calibration strategy called multiplicative effects correction (MEC) was proposed to separate the Raman contributions due to changes in analyte concentration from those caused by the multiplicative confounding effects of the sample's physical properties. MEC has been applied to predict the anhydrate concentrations from in situ FT-Raman measurements made during the crystallization and phase transition processes of citric acid in water. The experimental results show that MEC can effectively correct for the confounding effects of the particle size and overall solid content of the solid phase on Raman intensities and, therefore, provide much more accurate in situ quantitative predictions of anhydrate concentration during crystallization and phase transition processes than traditional PLS calibration methods.

Laboratory experiments have been conducted to investigate the fuel effects on the turbulent premixed flames produced by a gas turbine low-swirl injector (LSI). The lean-blow off limits and flame emissions for seven diluted and undiluted hydrocarbon and hydrogen fuels show that the LSI is capable of supporting stable flames that emit x (@ 15% O 2 ). Analysis of the velocity statistics shows that the non-reacting and reacting flowfields of the LSI exhibit similarity features. The turbulent flame speeds, S T , for the hydrocarbon fuels are consistent with those of methane/air flames and correlate linearly with turbulence intensity. The similarity feature and linear S T correlation provide further support of an analytical model that explains why the LSI flame position does not change with flow velocity. The results also show that the LSI does not need to undergo significant alteration to operate with the hydrocarbon fuels but needs further studies for adaptation to burn diluted H 2 fuels.

A new approach for low emission gas turbines was investigated by modifying a typical production high-swirl injector (HSI) for gas turbine combustors to operate in a novel low-swirl mode (LSI). This LSI (S = 0.5) was configured in the laboratory and investigated by particle image velocimetry at firing rates of 9–87 kW (1

Near-infrared spectra of aqueous solutions were collected by using evanescent-field fiber-optic sensors. The spectra of two- and four-electrolyte solutions were analyzed with a partial least-squares (PLS) algorithm to quantify the measurements. Our results indicate that the electrolytes can be identified and simultaneously determined by using the PLS calibration model. Electrolytes in opaque aqueous mixtures were also studied, and the results are compared with results from clear aqueous solutions.

Silica optical fibers have been modified to improve their sensitivity as evanescent wave sensors for liquids. A section of fiber is stripped of its cladding and bent or coiled, which significantly increases the evanescent wave interaction with the surrounding environment. The effect of sensor shape, solute concentration, refractive index, and temperature on the sensor response is discussed.

Infrared (IR) remote sensors calibrated with propane understate volatile organic compound (VOC) concentrations in vehicle exhaust by 30−70% when compared to flame ionization detectors (FID). The difference depends on VOC composition and arises because many organic compounds in vehicle exhaust absorb less IR radiation than propane on a per-carbon basis. This study demonstrates an approach for scaling infrared measurements to reflect more accurately total exhaust VOC emissions from on-road motor vehicle fleets. Infrared versus flame ionization detector response to individual VOC was measured in the laboratory for methyl tert-butyl ether and a range of alkanes, alkenes, and aromatics that are prominent in vehicle exhaust. Overall IR/FID response to real exhaust mixtures was calculated by summing the response contributions of all individual VOC constituents. Average IR/FID response factors were calculated for typical on-road vehicle fleets based on VOC speciation profiles measured in several U.S. roadway tunn...

A procedure to quantify the shape of the absorbance–time profile, obtained during graphite furnace atomic absorption spectrometry, has been used to detect interference effects caused by the presence of a concomitant salt. The quantification of the absorption profile is achieved through the use of the Lipschitz regularity, α 0 , obtained from the wavelet transform of the absorbance–time profile. The temporal position of certain features and their associated values of α 0 provide a unique description of the shape of the absorbance–time profile. Changes to the position or values of α 0 between standard and sample atomizations may be indicative of uncorrected interference effects. A weak, but linear, dependence was found of the value of α 0 upon the analyte concentration for Cr and Cu. The ability of the Lipschitz regularity to detect interference effects was illustrated for Pb, Se and Cu. For Pb, the lowest concentration of NaCl added, 0.005% m/v, changed both the values of α 0 and the peak height absorbance. For Se, no change in the peak height and peak area absorbance signals was detected up to a NaCl concentration of 0.25% m/v. The values of the associated Lipschitz regularities were found to be invariant to NaCl concentration up to this value. For Cu, a concentration of 0.05% m/v NaCl reduced the peak height and peak area absorbance signals by approximately 25% and significantly altered the values of α 0 .

Methods based on AAS, ICP-AES and XRFS have been developed for determination of Cd, Cr, Cu, Mn, Ni, Pb, V and Zn in soil layers from pits excavated on a redundant industrial site. Samples were dried and sieved, and the < 2 mm fraction was ground in a ball mill prior to analysis. For ICP-AES and AAS, Ig sub-samples were digested with aqua regia in a microwave oven. The dry weight detection Limits of the analytes were in the range 2-25 mu g g(-1) for FAAS, 0.003-0.2 mu g g(-1) for ETAAS and 0.04-1.6 mu g g(-1) for ICP-AES. When digests of the industrial soils were analysed, calibration with acid-matched standards gave acceptable accuracy for all the analytes, except for Cd when determined by ETAAS (30-40 % suppression). Despite lack of reference materials of industrial origin, analysis of two soil reference materials by these techniques produced concentrations that were within +/- 10 % of the certified or recommended values for elements extractable with aqua regia. Direct standard-less analysis of a soil reference material with a portable x-ray fluorescence (P-XRF) analyser gave concentrations for a range of elements that were within a factor of 2 of the certified values. When the XRFS and ICP-AES methods were used to analyse the industrial soils, the concentrations obtained were similar (to within 30%) for Cu, Pb and Zn in most of the samples and for Cr, Mn and Ni in some of the samples. The concentrations of V estimated with the P-XRF analyser were 4 to 7-fold higher than those obtained by ICP-AES. The discrepancies were thought to be caused by spectral enhancement interferences in XRFS. Cadmium was not determined accurately by either ICP-AES or P-XRFS owing to spectral interferences. The work has highlighted the importance of analysing samples from across a site and at different depths, when assessing the extent of metal contamination on industrial land.

Cadmium, chromium, copper, lead, manganese, nickel, vanadium and zinc have been determined in samples of made-up ground from layers of a trial pit excavated on a recently derelict, industrially contaminated site. The pseudototal metal content of the layers was determined following a microwave-assisted digestion with aqua regia. Operational speciation was performed using the BCR three-step sequential extraction procedure. Analyses were carried out by flame or electrothermal atomic absorption spectrometry (FAAS or ETAAS). A suppressive interference (30%) was observed in the determination of cadmium in aqua regia digests by ETAAS, but not in 0.11 mol l ˇ1 acetic acid, 0.1 mol l ˇ1 hydroxylammonium chloride or 1.0 mol l ˇ1 ammonium acetate extracts. Agreement between duplicate samples was acceptable (i.e. within 10%) for most elements in most layers, but some large discrepancies were apparent, especially for lead. The amount of metal extracted in the sequential procedure (i.e. Step 1aStep 2aStep 3aresidual) did not generally agree well with pseudototal digestion. Various layers of the trail pit contained significant levels of contaminant metals, but these were not always in easily mobilized forms. For example, less than 0.2% of the lead (4000 m gg ˇ 1 ) at 65‐85 cm depth was present as exchangeable or acid-soluble species. The study illustrates the importance of considering metal speciation when assessing the mobility of potentially toxic elements in industrially-contaminated land. # 1998 Elsevier Science B.V.

A charge-coupled device (CCD) camera has been used to obtain high-definition video images of the cross-section of the tube in a graphite furnace atomizer. Image processing algorithms have been developed to extract automatically from the images certain features which are of use during the initial set-up and alignment of the atomizer in an atomic absorption spectrometer. These features include the alignment of the tube, the angle of a platform with respect to the vertical axis and the height of an autosampler capillary tip above the tube wall or the platform. In addition, algorithms have been developed to analyse images recorded after sample injection, to detect whether all of the liquid has been deposited correctly into the tube. Detection of the poor injection of a blood serum sample is given to illustrate the usefulness of the algorithm.

Fibrous crystals, up to 2 cm long and 3 μm in diameter, have been observed on an Egyptian limestone relief, stored in a wooden cabinet at the Burrell Collection, Glasgow. X-ray diffraction and infrared spectroscopy have shown that the crystals are identical to an uncharacterised efflorescence first reported in 1971. Ion chromatography was used in conjunction with scanning electron microscopy, x-ray spectrometry, and thermogravimetry to determine the composition of the salt efflorescence. The salt comprises, primarily, calcium, acetate, chloride and nitrate ions. Proton nuclear magnetic resonance spectrometry at 400 MHz was used to establish the degree of hydration. The stoichiometric formula derived from the analyses is Ca3(CH3COO)3Cl(NO3)2· 7H2O. This is a new crystalline salt not previously characterised.

Methods have been developed for the determination of caesium and silver in soil and fungal samples by microwave-assisted aqua regia digestion, followed by electrothermal atomic absorption spectrometry. The procedure was found to be repeatable (for soil, RSD < 5%, n = 3, at caesium and silver concentrations of 1.8 and 0.6 mg g(-1), respectively, and for fungi, RSD < 7%, n = 5, at caesium and silver levels of 20 and 1 mg g(-1), respectively) and reasonably efficient. Silver was recovered quantitatively from reference soils, but only about 80-85% of the caesium present could be extracted. Poorer caesium recoveries (< 70%) were obtained if, as part of the sample preparation procedure, solutions were taken to dryness in glass beakers prior to analysis. The detection limits were 0.02 mg Ag and 0.09 mg Cs per gram of dry soil, which are adequate for the determination of the analytes at typical environmental levels. The methods were applied in the analysis of three types of soil, a peaty podzol, a clay loam and a sandy loam and no significant matrix interferences were observed except in the determination of caesium in the sandy loam. For caesium, non-linear response curves, thought to be due to ionisation interference, were encountered using one atomic absorption spectrometer, but were not observed with the other instrument.

A method is described for the direct determination of selenium in serum or plasma by electrothermal atomic absorption spectrometry with deuterium-arc background correction. Samples are diluted (1 + 2) with a modifier containing palladium nitrate and Triton X-100. Samples are atomised from a L'vov platform in a pyrolytically-coated electrographite tube and peak area signals are measured. Direct determination is possible by using selenium standards matched to the physiological concentrations of sodium chloride, calcium and phosphate. The detection limit is 6 micrograms/L in the original sample. Precision at a selenium concentration of 97 micrograms/L was 2.2% RSD within batch and 3.0% RSD between batch. Accuracy is shown by (i) analysis of a Seronorm reference serum (value obtained 97 +/- 3 micrograms/L; recommended value 96 micrograms/L); (ii) recovery of added selenium (93.3 +/- 6.7% and 98.2 +/- 3.3% at additions of 30 and 60 micrograms/L, respectively) and (iii) comparison of results with mean of all laboratories in an external quality assessment scheme.

A 785 nm diode laser and probe with a 6 mm spot size were used to obtain spectra of stationary powders and powders mixing at 50 rpm in a high shear convective blender. Two methods of assessing the effect of particle characteristics on the Raman sampling depth for microcrystalline cellulose (Avicel), aspirin or sodium nitrate were compared: (i) the information depth, based on the diminishing Raman signal of TiO2 in a reference plate as the depth of powder prior to the plate was increased, and (ii) the depth at which a sample became infinitely thick, based on the depth of powder at which the Raman signal of the compound became constant The particle size, shape, density and/or light absorption capability of the compounds were shown to affect the "information" and "infinitely thick" depths of individual compounds. However, when different sized fractions of aspirin were added to Avicel as the main component, the depth values of aspirin were the same and matched that of the Avicel: 1.7 mm for the "information" depth and 3.5 mm for the "infinitely thick" depth. This latter value was considered to be the minimum Raman sampling depth when monitoring the addition of aspirin to Avicel in the blender. Mixing profiles for aspirin were obtained non-invasively through the glass wall of the vessel and could be used to assess how the aspirin blended into the main component, identify the end point of the mixing process (which varied with the particle size of the aspirin), and determine the concentration of aspirin in real time. The Raman procedure was compared to two other non-invasive monitoring techniques, near infrared (NIR) spectrometry and broadband acoustic emission spectrometry. The features of the mixing profiles generated by the three techniques were similar for addition of aspirin to Avicel. Although Raman was less sensitive than NIR spectrometry, Raman allowed compound specific mixing profiles to be generated by studying the mixing behaviour of an aspirin-aspartame-Avicel mixture.

The low swirl injector (LSI) is a combustion technology being developed for low-emissions fuel-flexible gas turbines. The basic LSI configuration consists of an annulus of swirl vanes centered on a non-swirled channel, both of which allow for the passage of premixed reactants. LSIs are typically designed by following a general guidance of achieving a swirl number between 0.4 and 0.55. This paper aims to develop a more specific guideline by investigating the effects of varying geometry, i.e. vane angle, vane shape, and center channel size, on the LSI performance. A well-studied LSI provides a baseline for this investigation. Nine LSI variations from this baseline design have been evaluated. All LSI are tested with CH4 fuel at bulk flow velocity of 8 to 20 m/s firing into the open atmosphere. Performance metrics are the lean blowoff limit, the pressure drop, flowfield characteristics and emissions. Results show that the lean blow-off limit and NOx and CO emissions are insensitive to LSI geometric variations. The flowfields of seven LSIs exhibit self-similarity implying their turndown ranges are similar. Reducing the center channel size and/or the use of thin vanes instead of thickened vanes can reduce pressure drop across the LSI. Additionally, all ten LSI share a common feature in that 70% to 80% the premixture flows through the vane annulus. These findings are used to develop a more specific engineering guidelines for designing the LSI for gas turbines.Copyright © 2012 by ASME

Transmission Raman measurements of a 1 mm thick sulfur-containing disk were made at different positions as it was moved through 4 mm of aspirin (150-212 mu m) or microcrystalline cellulose (Avicel) of different size ranges (

The three-stage sequential extraction procedure for speciation of heavy metals, proposed by the Commission of the European Communities Bureau of Reference (BCR), has been applied to a freshwater sediment collected from the River Clyde, Lanarkshire, UK. Initial studies were carried out using flame atomic absorption spectrometry (FAAS). Iron, manganese and zinc could be determined in the sediment extracts by FAAS, but the technique proved insufficiently sensitive for the determination of chromium, copper, nickel and lead. Detection methods based on electrothermal AAS were therefore developed and applied. Furnace conditions were optimised for the determination of the four analytes mentioned, plus molybdenum and vanadium, in acetic acid, hydroxylammonium chloride and ammonium acetate matrices. Interferences by components in the sediment extracts necessitated analysis by the method of standard additions in most cases. The sequential extraction procedure was found to be both repeatable and reproducible. The amounts of analytes released by the sequential extraction procedure plus aqua regia digestion of the residue remaining after extraction were similar to those released by pseudo-total digestion of the sediment (using aqua regia).

A three-stage sequential extraction procedure, following a protocol proposed by a European working group coordinated and supported by the Community Bureau of Reference (BCR), has been applied to two river sediments from an industrial region of East Catalonia, Spain. The extractant solutions were: Step One, acetic acid (0.11 mol l(-1)); Step Two, hydroxylammonium chloride (0.1 mol l(-1), pH 2); Step Three, hydrogen peroxide (8.8 mol l(-1)) oxidation followed by extraction with ammonium acetate (1 mol l(-1), pH 2). The six elements determined in the extracts were Cd, Cr, Cu, Ni, Pb and Zn. Analysis of the extracts was carried out by flame atomic absorption spectrometry (FAAS). There were slight differences in analyte sensitivity between calibrants prepared in the extractant matrices and acidified aqueous calibrants. No significant matrix interferences were found except for Cr in the acetic acid and hydroxylammonium chloride extracts, which required determination by the standard additions method. The other elements (plus all the elements in the ammonium acetate extracts) were determined by direct calibration against calibrant solutions prepared in the same matrices as the samples.

Low Swirl Injector (LSI) technology is a lean premixed combustion method that is being developed for fuel-flexible gas turbines. The objective of this study is to characterize the fuel effects and influences of combustor geometry on the LSI's overall acoustic signatures and flowfields. The experiments consist of 24 flames at atmospheric condition with bulk flows ranging between 10 and 18 m/s. The flames burn CH{sub 4} (at {phi} = 0.6 & 0.7) and a blend of 90% H{sub 2} - 10% CH{sub 4} by volume (at {phi} = 0.35 & 0.4). Two combustor configurations are used, consisting of a cylindrical chamber with and without a divergent quarl at the dump plane. The data consist of pressure spectral distributions at five positions within the system and 2D flowfield information measured by Particle Imaging Velocimetry (PIV). The results show that acoustic oscillations increase with U{sub 0} and {phi}. However, the levels in the 90% H{sub 2} flames are significantly higher than in the CH{sub 4} flames. For both fuels, the use of the quarl reduces the fluctuating pressures in the combustion chamber by up to a factor of 7. The PIV results suggest this to be a consequence of the quarl restrictingmore » the formation of large vortices in the outer shear layer. A Generalized Instability Model (GIM) was applied to analyze the acoustic response of baseline flames for each of the two fuels. The measured frequencies and the stability trends for these two cases are predicted and the triggered acoustic mode shapes identified.« less

An optical interface has been designed to maximise the sensitivity and spatial resolution required when Raman spectrometry is used to monitor a reaction in a micro-reactor, revealing advantages over a conventional commercial probe. A miniature aspheric lens was shown to be better than microscope objectives to focus the probing laser beam onto the sample. The diameters of the exciting and collection optical fibres were also shown to have a significant influence on sensitivity and the signal-to-background ratio, with 62.5 microm diameter 0.28 numerical aperture (NA) fibres found to be best for analysis of liquids in the 150 microm deep channel in the micro-reactor used. With a spectral measurement time of 2 s, it was shown that the probe could monitor the progress of an esterification reaction in real time and quickly optimise the reagent flow rates. The fast response time revealed features related to short-term pump instabilities and micro-reactor rheology effects that would not have been identified without rapid real-time measurements.

The impact of microwave digestion, hot injection of solutions and chemical modification on the analysis of biological samples by electrothermal atomic absorption spectrometry (AAS) has been assessed. The stabilizing effects of palladium and ruthenium modifiers were compared. Although ruthenium has a higher atom appearance temperature, palladium was the more useful modifier when samples other than water were analysed. When 2 μg of palladium (as PdCl2) was preconditioned in hydrogen at 500°C, volatile elements were retained at char temperatures up to 1000–1100°C. This allowed similar atomizer programmes to be used for Cd, Cu, Fe, Mn and Pb and accurate determination of these analytes in solutions of reference materials was achieved aqueous standards. Rapid drying of the solutions by hot injection at 120°C reduced the programme time to just over 1 min. A combination of microwave digestion, hot injection of 40% (w/v) HNO3 solutions and Pd modification produced a rapid and sensitive method for determination of Cd and Pb at sub-μg g−1 levels in vegetable and protein foodstuffs. Palladium modification also proved useful in simultaneous multi-element determination by continuum source AAS. The picogram detection limits obtained for Cr, Mn and Pb were similar to line source AAS values recorded with the same compromise programme. Accurate determination of Cd, Cr, Cu, Mn, Mo and Pb in NIST SRM 1566 Oyster Tissue indicated the potential of continuum source AAS for multi-element determinations. The advantages of palladium modifications were also illustrated for furnace atomic non-thermal excitation spectrometry (FANES) with a hollow-cathode discharge. The maximum char temperatures of Ag, Ga, Hg, Pb, Sb and Se were increased by 300–600°C in the presence of 1 μg of Pd, although the detection limits were a factor of two poorer.

The objective of this study is to conduct laboratory experiments on low-swirl injectors (LSIs) to obtain the basic information for adapting LSI to burn H{sub 2} and diluted H{sub 2} fuels that will be utilized in the gas turbines of the integrated gasification combined cycle coal power plants. The LSI is a novel ultralow emission dry-low NOx combustion method that has been developed for gas turbines operating on natural gas. It is being developed for fuel-flexible turbines burning a variety of hydrocarbon fuels, biomass gases, and refinery gases. The adaptation of the LSI to accept H{sub 2} flames is guided by an analytical expression derived from the flow field characteristics and the turbulent flame speed correlation. The evaluation of the operating regimes of nine LSI configurations for H{sub 2} shows an optimum swirl number of 0.51, which is slightly lower than the swirl number of 0.54 for the hydrocarbon LSI. Using particle image velocimetry (PIV), the flow fields of 32 premixed H{sub 2}-air and H{sub 2}-N{sub 2}-air flames were measured. The turbulent flame speeds deduced from PIV show a linear correlation with turbulence intensity. The correlation constant for H{sub 2} is 3.1 and is higher than the 2.14 value formore » hydrocarbons. The analysis of velocity profiles confirms that the near field flow features of the H{sub 2} flames are self-similar. These results demonstrate that the basic LSI mechanism is not affected by the differences in the properties of H{sub 2} and hydrocarbon flames and support the feasibility of the LSI concept for hydrogen fueled gas turbines.« less

The low-swirl injector (LSI) is a simple and cost-effective lean premixed combustion method for natural-gas turbines to achieve ultra-low emissions (< 5 ppm NOx and CO) without invoking tight control of mixture stoichiometry, elaborate active tip cooling or costly materials and catalysis. To gain an understanding of how this flame stabilization mechanism remains robust throughout a large range of Reynolds numbers, laboratory experiments were performed to characterize the flowfield of natural gas flames at simulated partial load conditions. Also studied was a flame using simulated landfill gas of 50% natural gas and 50% CO2 . Using Particle Image Velocimetry (PIV), the non-reacting and reacting flowfields were measured at five bulk flow velocities. The results show that the LSI flowfield exhibits similarity features. From the velocity data an analytical expression for the flame position as function of the flowfield characteristics and turbulent flame speed have been deduced. It shows that the similarity feature coupled with a linear dependency of the turbulent flame speed with bulk flow velocity enable the flame to remain relatively stationary throughout the load range. This expression can be the basis for an analytical model for designing LSIs that operate on alternate gaseous fuels such as slower burning biomass gases or faster burning coal-based syngases.Copyright © 2006 by ASME

The low-swirl injector (LSI) is a lean premixed combustion technology that has the potential for adaptation to fuel-flexible gas turbines operating on a variety of fuels. The objective of this study is to gain a fundamental understanding of the effect of syngas on the LSI flame behavior, the emissions, and the flowfield characteristics for adaptation to the combustion turbines in integrated gasification combined cycle clean coal power plants. The experiments were conducted in two facilities. Open atmospheric laboratory flames generated by a full size (6.35 cm) LSI were used to investigate the lean blow-off limits, emissions, and the flowfield characteristics. Verification of syngas operation at elevated temperatures and pressures were performed with a reduced scale (2.54 cm) LSI in a small pressurized combustion channel. The results show that the basic LSI design is amenable to burning syngases with up to 60% H2. Syngases with high H2 concentration have lower lean blow-off limits. From particle image velocimetry measurements, the flowfield similarity behavior and the turbulent flame speeds of syngases flames are consistent with those observed in hydrocarbon and pure or diluted hydrogen flames. The NOx emissions from syngas flames show log-linear dependency on the adiabatic flame temperature and are comparable to those reported for the gaseous fuels reported previously. Successful firing of the reduced-scale LSI at 450 K

The combination of palladium/hydrogen matrix-modification and injection of samples into a graphite tube at 120 degrees has allowed the accurate determination of copper, iron, lead and nickel in biological reference materials (urine, milk powder and bovine liver). Palladium modification allowed the use of a standard ashing temperature of 1000 degrees for all four elements. Direct aqueous calibration was applied without the need for standard additions. The total heating cycle, from the start of sample injection, took 45 sec.

The continued development of a low swirl injector for ultra-low NOx gas turbine applications is described. An injector prototype for natural gas operation has been designed, fabricated and tested. The target application is an annular gas turbine combustion system requiring twelve injectors. High pressure rig test results for a single injector prototype are presented. On natural gas, ultra-low NOx emissions were achieved along with low CO. A turndown of approximately 100°F in flame temperature was possible before CO emissions increased significantly. Subsequently, a set of injectors was evaluated at atmospheric pressure using a production annular combustor. Rig testing again demonstrated the ultra-low NOx capability of the injectors on natural gas. An engine test of the injectors will be required to establish the transient performance of the combustion system and to assess any combustor pressure oscillation issues.Copyright © 2006 by ASME

Ammonia is the primary alkaline gas in the atmosphere and contributes to fine particle mass, visibility problems, and dry and wet deposition. The objective of this research was to measure ammonia and other exhaust emissions from a large sample of on-road vehicles using California phase 2 reformulated gasoline with low sulfur content (~10 ppm by weight). Vehicle emissions of ammonia, NOx, CO, and CO2 were measured in the center bore of a San Francisco Bay area highway tunnel on eight 2-h afternoon sampling periods during summer 1999. Ammonia concentrations were divided by total carbon (mainly CO2) concentrations to compute an emission factor of 475 ± 29 mg L-1 (95% C I.). The molar ratio of nitrogen emitted in the tunnel in the form of ammonia to that emitted in the form of NOx was 0.27 ± 0.01. Emissions of NOx and CO have been measured at this tunnel sampling location since 1994. From 1994 to 1999, emissions decreased by 41 ± 4% for NOx and 54 ± 6% for CO. These reductions include the impacts of turnover in the vehicle fleet and the use of reformulated gasoline. Between 1997 and 1999, when fuel properties did not change significantly, emissions of NOx and CO decreased by 26 ± 2% and 31 ± 3%, respectively. While use of three-way catalytic converters has contributed to decreases in NOx and CO emissions, their use, in combination with fuel-rich engine operation, is the likely cause of the ammonia emissions from motor vehicles observed during this study.

Chromium, manganese, nickel, vanadium and uranium have been determined in inter-tidal sediments collected from locations along the Cumbrian coast. Total concentrations of chromium, nickel and vanadium were determined by electrothermal atomic absorption spectrometry (ETAAS). Manganese was determined by flame AAS and uranium was quantified by alpha particle spectrometry with a surface barrier detector. Two alternative approaches to calibration were investigated in an attempt to obviate the need for routine use of the full standard additions procedure. It was found that the response following a single addition of standard solution, at a concentration 50% of the initial estimate, could be used to correct for the minor interference effects observed. Elevated levels of chromium (39.5 ± 0.9 µg g–1), vanadium (33.0 ± 0.6 µg g–1) and uranium (39.0 ± 1.2 Bq kg–1) were observed at Whitehaven, whilst concentrations of manganese were highest in samples from more northerly locations. The uranium enhancement is due to the extraction of phosphates from ore naturally rich in radionuclides at the nearby Albright and Wilson ‘Marchon’ chemical manufacturing plant. The chromium contamination may also arise from chemical manufacturing, whilst the vanadium is thought to originate from oil spillage. Interferences associated with use of the European Communities Bureau of Reference (BCR) sequential extraction protocol were investigated, and the operationally-defined speciation of chromium, manganese, nickel and vanadium was then determined. Chromium, nickel and vanadium were found mainly in association with the residual sediment phase, except at Whitehaven and Maryport where increases in the oxidizable fractions were apparent. A large proportion of the manganese at all sites was present as exchangeable species, i.e., soluble in 0.11 mol l–1 acetic acid, and this was not affected by sample drying (at 60 °C) nor by storage (for 6 months) prior to extraction.

A microwave digestion procedure was used to prepare samples for determination of total Se by electrothermal atomic absorption spectrometry (ETAAS) with palladium modification. Conversion of organoselenium compounds to inorganic selenium was achieved by heating 100 mg hair with 0.5 ml concentrated nitric acid for 1 min and then, after the addition of 0.5 ml hydrogen peroxide (30 vols.), reheating for a further 8 min. The accuracy of the method was confirmed by analysis of certified hair reference materials containing 2.00 and 0.58 µg g–1 Se. The detection limit is 0.02 µg g–1 Se. A variation of the procedure was used to analyse nail samples. Digestion was achieved by heating 100 mg of nail with 1 ml nitric acid for 2 min and, after the addition of 1 ml hydrogen peroxide, for a further 33 (3 × 11) min. The detection limit for this procedure is 0.03 µg g–1 Se. Analysis of hair reference materials and both hair and nail samples by neutron activation analysis and ETAAS showed reasonable agreement between the techniques. The ETAAS procedure is more rapid and convenient. Analysis of 25 hair samples gave a range of 0.31–0.76 µg g–1 Se (mean value 0.52 ± 0.11 µg g–1) and for 27 nail samples a range of 0.17–0.66 µg g–1 Se (mean value 0.46 ± 0.16 µg g–1) was obtained.

Echelle spectrometers with cross-dispersion are often used in emission spectroscopy owing to their high spectral resolution and good light throughput. The resultant two-dimensional dispersion plane is ideally suited to array detectors such as the charge-injection device (CID) or charge-coupled device (CCD). The successful coupling of an echelle spectrometer with an array detector permits true simultaneous spectroscopy to be performed over a large spectral range. In order to correctly identify spectral features it is necessary to have an accurate wavelength calibration function which maps the CCD/CID pixel co-ordinates to wavelength. A new approach to the wavelength calibration of optical spectrometers with array detection is proposed that does not involve a direct modelling of the spectrometer dispersion. Instead, the difference between an ideal conceptual spectrometer and the physical instrument is modelled. The procedure is able to compensate for the effects of manufacturing tolerances and local temperature and pressure conditions. Preliminary results, obtained by simulation with a computer-modelled echelle spectrometer, has shown that a sub-pixel accuracy in the predicted position of spectral lines can be achieved over a temperature range 5–35 °C.

The chemistry of complexation has been investigated and conditions optimized for on-line preconcentration of CrIII by resins with immobilized quinolin-8-ol or iminodiacetate functional groups. When solutions were buffered to 0.1 mol l–1 acetate at pH 9, the detection limit of CrIII was 6 ng ml–1 for preconcentration on the quinolin-8-ol resin at 6 ml min–1 for 3 min. With the iminodiacetate resin (Muromac A-1), the optimum buffer conditions were 0.1 mol l–1 acetate at pH 4, which gave a CrIII detection limit of 2 ng ml–1(3 min preconcentration at 6 ml min–1). The major ions in sea-water did not interfere with preconcentration of 100 ng ml–1 CrIII by Muromac A-1. However, suppressive interferences were caused by 100 µg ml–1 of Ca2+ or Fe2+ with the quinolin-8-ol resin. Despite having similar log stability constants of complexation with either resin, the interference caused by Ca2+ was much greater than that by Mg2+. Muromac A-1 was used for preconcentration of CrIII in estuarine- and sea-waters, prior to determination by flame atomic absorption spectrometry (FAAS). By reduction of CrVI to CrIII, it was also possible to determine the total concentration of ionic Cr in the waters, which allowed calculation of the CrVI concentration by difference. The CrIII concentration in the samples from the Clyde estuary were 3–8 ng ml–1, with the CrVI concentration about 0.7 ng ml–1. Only CrIII(3 ng ml–1) was found in the sea-water samples from the Cumbrian Coast.

Coating a total pyrolytic graphite tube with tungsten carbide or lanthanum carbide increased the optimum pyrolysis temperature of B from 850 to > 2200 °C. Addition of a calcium–magnesium modifier to the boron solutions increased the pyrolysis temperature to 1200 °C, whereas a titanium-ascorbic acid modifier had no significant effect. The lowest characteristic mass of B, 0.8 ng, was obtained with the calcium–magnesium modifier. The low temperature loss of boron, without a modifier, was investigated using dynamic secondary-ion mass spectrometry, which confirmed that vaporization of boron species occurs above 900 °C. Boron atomic emission signals were obtained at 850 °C. The poor detection limit of B in ETAAS is due to the inefficient thermal dissociation of the B-containing species (probably oxides and carbides) produced by dissociative desorption of B2O3. Also, once formed, B atoms apparently undergo a series of condensation–vaporization steps, which cause a persistant plateau in the tail of the AAS signal, and result in severe memory effects.

A 256 pixel linear photodiode array (LPDA) detector was fitted to a Spectrametrics echelle spectrometer for measurements by continuum source atomic absorption spectrometry with electrothermal atomization (ET-CSAAS). By selection of appropriate pixel regions, intensity values could be obtained for calculation of absorbance signals integrated over wavelength as well as time. Detection lmits obtained sequentially for Cd, Cr, Cu, Mn, Mo and Pb, with the LPDA, were similar in magnitude (4–24 pg) to those obtained with mechanical wavelength modulation and detection by a photomultiplier tube, using the same atomizer and spectrometer system. The calibration graphs obtained with the LPDA, however, were more useful analytically, as integration of the absorbance signals across the line profile increased the linear range. Four National Bureau of Standards (NBS)[now National Institute of Standards and Technology (NIST)] Standard Reference Materials, (SRMs) 1577a Bovine Liver, 1575 Pine Needles, 1572 Citrus Leaves and 1566 Oyster Tissue were analysed by ET-CSAAS with LPDA detection. The concentrations obtained for Cd, Cr, Cu, Mn, Mo and Pb were generally in good agreement with the certified values.

An automated graphite-probe atomizer was used for the direct analysis of diluted (2- to 12.5-fold) urine samples by electrothermal atomic absorption spectrometry (ETAAS). The method was applied successfully to the determination of Pb in reference materials, quality control urines and patient samples. The concentrations found were mainly in the range 7-93 micrograms dm-3 and agreed well with results obtained by an established ETAAS method, which involved chelation of Pb and solvent extraction into isobutyl methyl ketone. The detection limit, based on three times the standard deviation of the blank, was 4 micrograms dm-3 at 283.3 nm and 2 micrograms dm-3 at 217.0 nm. Although probe atomization removed chemical interferences for peak-area measurements, 10-20% suppression remained for some samples with peak-height measurements.

Determination of Cu, Fe, Mn and Zn in fresh bovine liver and BCR bovine liver and pig kidney reference materials, after digestion at 105 degrees C with nitric acid for various times, showed that the trace elements were completely released after heating for only 20 min. Centrifugation of the samples after digestion improved the separation from undigested fat. This partial-digestion method, based on heating about 0.2 g of sample with 2 ml of nitric acid for 20 min, was tested on a range of biological reference materials and on fresh bovine liver for the four elements. Comparison was made with results obtained after digestion by a recommended hydrogen peroxide--sulfuric acid digestion procedure. Results obtained by inductively coupled plasma atomic emission spectrometry or by flame and graphite-furnace atomic absorption spectrometry showed good agreement between the two digestion procedures, and results for the reference materials agreed well with the certified values. Between-batch precision was better than 4% for Cu, Fe and Zn at levels of 30 to 190, 210 to 320 and 100 to 140 micrograms g-1, respectively. For Mn, the precision varied between 7 and 14% for measured concentrations of 8 to 12 micrograms g-1. The partial-digestion procedure offers simplicity, speed, low cost and the ability to handle a large number of samples at the same time.

A study of the chemistry of aluminium, gallium and indium ions in solution, their behaviour under different pH conditions and their complexation with different buffering reagents was used to develop on-line preconcentration procedures for the determination of the elements by flame atomic absorption spectrometry. The buffers investigated were acetate, ammonium chloride, citrate, maleate, malonate, oxalate, picolinate and tartrate. A column of quinolin-8-ol, immobilized or controlled-pore glass, was used to collect the elements from the buffered solutions. The best buffer for aluminium was 0.1 mol l–1 malonate at pH 10. The optimum buffer for gallium and indium was also 0.1 mol l–1 malonate at pH ranges of 8–10 and 9.2–10, respectively. The use of malonate buffer makes a common procedure possible for all three elements. The collected analyte was eluted from the column with a mixture of hydrochloric and nitric acids, each at a concentration of 1 mol l–1. For a collection time of 3 min, at a flow rate of 6 ml min–1, the detection limit for all three elements was approximately 3 ng ml–1, with enrichment factors of between 70 and 80. Interference effects were studied and the procedures developed were applied to the analysis of natural waters.

The decomposition and vaporization of NaCl, MgCl2 and NiCl2 in an electrothermal atomizer have been studied using ion chromatography, radioactive tracers and flame atomic absorption spectrometry (FAAS). Solutions of the individual chloride salts were injected to deposit 50–200 µg on to a pyrolytic graphite platform in a pyrolytic graphite coated graphite tube. The solutions were dried and then pyrolysed at a temperature in the range 200–1200 °C. The residue on each platform was then analysed to determine the amount in micromoles of metal and chloride remaining at each temperature. This allowed formation of pyrolysis curves for the salts, similar to those produced in conventional electrothermal AAS (ETAAS) for analyte elements. Magnesium chloride and NiCl2 exhibited partial hydrolysis with the heating programme used, but significant vaporization of MgCl2 and NiCl2 also occurred. The decomposition and vaporization of 100 or 200 µg masses of the chloride salts caused pre-atomization step losses of Cd, Ga and Pb, in the range 300–1000 °C, as indicated by radioactive tracer analysis and inductively coupled plasma mass spectrometry. The interference was in the order Ni-Cl2>MgCl2>NaCl. Partial hydrolysis of MgCl2 to MgO minimized the pre-atomization losses of the analytes at higher temperatures due to a chemical modification effect similar to that caused by MgNO3. The study illustrates that, in the presence of high masses (50–200 µg) of chloride salts, pre-atomization loss of analyte elements can be a major cause of chemical interference in ETAAS if too high a char temperature is selected and the use of chemical modification is ignored.

Radioactive tracers 165Dy and 56Mn have been used to investigate the vaporization of Dy and Mn in a graphite furnace. The retention and distribution of the analytes after atomization in pyrolytic graphite coated electrographite (PCG) tubes have been measured and the efficiencies of Dy and Mn vaporization have been compared for wall, platform and probe atomization in total pyrolytic graphite (TPG) tubes. Manganese is vaporized almost completely (95–100%) at 2500 °C by each of the atomization modes, with little retention at the point of initial deposition. Manganese is redeposited at the very ends of the PCG tube and the amount of redeposition increases with the age of the tube. Total pyrolytic graphite (TPG) exhibits lower redeposition of Mn than does PCG and the deposition is mainly on the outside of the tube. Dysprosium is almost totally retained in PCG and TPG tubes. Vaporized Dy is redeposited very rapidly, mainly at the centre of the tube, and causes a memory effect in subsequent heating cycles. About 60% of the Dy is vaporized from the probe at 2750 °C, whereas only 7% is vaporized from the platform. The difference in the vaporization efficiencies is reflected in the atomic absorption spectrometric sensitivities for both procedures. Wall atomization gives the best sensitivity for Dy, but is only 1.5-fold better than for probe atomization. Some comments are given on the possible mechanisms of Dy vaporization and atomization, but mass spectrometry studies are required to give a clearer explanation of the phenomena.

A procedure is described for the determination of Cd, Co, Cr, Mn, Ni and Pb in Seronorm and Lanonorm reference materials and clinical samples. Accurate analyses of diluted specimens were achieved against aqueous standards. The use of high atomization temperatures (2400–2750 °C) minimized chemical interference from matrix components. High temperatues also improved the characteristic mass of Ga for probe electrothermal atomic absorption spectrometry, but caused a reduction in the sensitivity of Pb due to increased diffusional loss effects. The relative standard deviation values reported for Cd in human urine (1.1–7.6 µg dm–3) were mostly

Various masses between 10 and 500 µg of NaCl or MgCl2 were added to 1 ng of Cr, Cu and Mn, 2 ng of Cd and Pb and 4 ng of Co, Mo, Ni and V to study the interferences encountered when wall, platform and probe atomization are applied in continuum source electrothermal atomic absorption spectrometry. No char step was used and a compromise atomization temperature of 2700 °C was selected for simultaneous multi-element measurements. No great difference was observed in the analyte signal recovery values obtained with the three atomization modes when NaCl was the interferent. However, with MgCl2, greater interferences were observed with wall atomization. Overall, probe atomization proved as good as, if not better than platform atomization for the elements considered. With both procedures, freedom from NaCl or MgCl2 interferences was achieved at chloride salt: analyte mole ratios of 1 × 103–1 × 105. Although it was not possible to make a definitive assessment of the procedures responsible for the interferences observed, there was some evidence that vapour-phase chemical effects are more important for MgCl2 than for NaCl, occlusion of Cd, Mn and Pb occurs in NaCl and expulsion of Co, Cr, Cu, Mn and Ni occurs due to co-vaporization with NaCl.

Knowledge of the chemistry of Al in solution, its behaviour under different pH conditions and its complexation with different buffering reagents has been used to devise and optimize an on-line preconcentration procedure for the determination of Al by flame atomic absorption spectrometry. A column of 8-hydroxyquinoline immobilized on controlled-pore glass is used to collect Al in a buffer of 0.1 mol dm–3 malonate at pH 10. The Al is eluted into the nebulizer of a dinitrogen oxide–acetylene flame with a mixture of 1 mol dm–3 HCl and 1 mol dm–3 HNO3. For a collection period of 3 min at a flow rate of 6 cm3 min–1, the detection limit is 3 ng cm–3 with an enrichment factor of 76. The method has been applied successfully to river and sea-waters.

A method is described in which liquid samples are deposited by a conventional autosampler on to a tubular graphite probe positioned inside a 7.5 mm i.d. Pye Unicam SP-9 atomiser cuvette. The tube-probe has certain advantages in comparison with the flat probe systems described previously. In particular, the precision of determinations in acid media is improved since the sample solution is better confined within the atomiser and hence the effects of droplet spreading are curtailed. Also, the tube-probe is shown to reduce diffusional loss effects at high atomiser temperatures, in comparison with flat probe operation. The characteristic mass values obtained for volatile and medium volatile elements are similar for tube and flat probes. Since a greater sample volume (up to 40 μl) can be deposited and dried in the tube-probe, improved detection limits are anticipated for these elements. For more involatile elements, the greater mass of the tube-probe results in poorer sensitivity by a factor of × 3 for V and × 4 for Cr.

In electrothermal atomisation, the rapid volatilisation of a sample into a hot constant temperature environment is recognised as a desirable condition for improved atom formation and the control of vapour phase interferences.

A simple and rapid method is described for the determination of trace metals in foodstuffs. The procedure combines slurry sample introduction with an oxygen ash step that helps to remove much of the organic matrix before the atomisation stage. A thickening agent, Viscalex HV 30, is used to give stable suspensions containing 0.1–10% m/V powdered sample material and calibration is achieved by “within tube” standard additions. The method has been applied successfully to the determination of Cd, Cu and Pb in a variety of vegetable and protein foodstuffs, and Cd, Cu, Mn, Pb and Zn in single cell protein. Detection limits vary depending on the slurry concentration used and the matrix analysed, but values of 1 ng g−1 for Cd in brussel sprouts and 13 ng g−1 for Pb in liver were achieved. The effects of particle size distribution on signal precision and matrix interferences have been evaluated.