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Two novel methods are described for direct quantitative analysis of NMR free induction decay (FID) signals. The methods use adaptations of the generalized rank annihilation method (GRAM) and the direct exponential curve resolution algorithm (DECRA). With FID-GRAM, the Hankel matrix of the sample signal is compared with that of a reference mixture to obtain quantitative data about the components. With FID-DECRA, a single-sample FID matrix is split into two matrices, allowing quantitative recovery of decay constants and the individual signals in the FID. Inaccurate results were obtained with FID-GRAM when there were differences between the frequency or transverse relaxation time of signals for the reference and test samples. This problem does not arise with FID-DECRA, because comparison with a reference signal is unnecessary. Application of FID-DECRA to 19F NMR data, which contained overlapping signals from three components, gave concentrations comparable to those derived from partial least squares (PLS) analysis of the Fourier transformed spectra. However, the main advantage of FID-DECRA was that accurate (5% error) and precise (2.3% RSD) results were obtained using only one calibration sample, whereas with PLS, a training set of 10 standard mixtures was used to give comparable accuracy and precision.

Previously, we developed a reversed-phase HPLC method compatible to high performance liquid chromatography diffuse reflectance Fourier-transform infrared (HPLC-FTIR) thermospray interface for the analysis of dyes. Dye separation achieved with a mixed-mode (SCX-ODS) column using a small gradient (90 to 80% water with acetic acid) and pH 3.25; 10 to 20% acetonitrile was considered to be suitable for HPLC-FTIR. A constant-voltage setting for the thermospray temperature (227 degrees C) was successfully used for this gradient condition. The HPLC-separated components deposited as a series of concentrated spots on a moving tape were scanned by specially developed HPLC-FTIR software. Excellent repeatability of the thermospray deposition FTIR chromatograms and IR spectra was obtained. The interface-derived spectra of the separated components of formulated and purified reactive dyes were compared and differences in spectral features were observed.

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.

Near-infrared transmission spectroscopy can be complicated by the light scattering from heterogeneous materials. For the examination of an evolving system exhibiting such light scattering, transmission spectra near wavenumber v = 104cm−1were obtained during the hydrolysis of FeCl3solutions. At first, the resulting turbid suspension of cigar-shaped β-FeOOH particles exhibits single-particle scattering, including a Rayleigh regime (attenuation ∞ v4). At later times, the scattering increases strongly as the particles aggregate, and becomes proportional to vα, with α ≈ 2, consistent with scattering models that interpret the structure of aggregates in terms of a fractal dimension dfroughly equal to 2. In all cases investigated, the attenuation due to scattering is spectrally smooth and increases monotonically with wavenumber. It can be written in the simple form vα with 1 ≤ α ≤ 4. While over limited spectral ranges α may be taken independent of v, over wide ranges it decreases with increasing v. This behavior is consistent with the theoretical limits of α = 4 at v = 0, and α = 0 at v = ∞. Overall, the results suggest that a useful form for simulating scattering backgrounds in near-infrared spectroscopy is Avα, with A and α fitted constants.

Made-up ground collected from layers of a trial pit excavated on a former industrial site was treated with artificial rainwater in a series of column leaching and sorption experiments. Metal mobility and the ability of various layers of material obtained from the pit to act as sources or sinks of potentially toxic elements were assessed. Samples from different layers varied in their abilities to raise the pH of rainwater applied at pH 3.5 and 4.3, and this was reflected in the amounts of metals mobilised by the rainwater as it percolated through the soil column. Material from the top two layers of the pit released cadmium, copper, manganese, lead, nickel and zinc to the aqueous phase, but the lower layers, with higher buffering capacity, were able to resist acidification even when the equivalent of 12 months' rainfall (western UK) was applied. Column sorption experiments confirmed the ability of material from layer 4 (48-50 cm) to take up copper, manganese and zinc. Metals were determined in the leachates by flame and electrothermal atomic absorption spectrometry and principle anions by ion chromatography.

Two systems have been compared for the on-line production of infrared spectra of compounds separated by high-performance liquid chromatography (HPLC). System 1 had a thermospray interface to evaporate the mobile-phase solvents and deposit the solutes onto a moving stainless steel belt, for direct analysis by reflection–absorption IR spectrometry. In system 2, the column effluent was split 1:6 and pumped through an ultrasonic nebulizer. The spray was desolvated at reduced pressure in a heated transfer tube and the solutes deposited onto a ZnSe window for direct analysis by transmission IR spectrometry. When system 1 was used for the analysis of reactive dyes, eluent containing ammonium acetate caused a large background spectrum, as a film of unknown composition was formed on the surface of the stainless steel belt. An alternative procedure, without ammonium acetate, was developed with a mixed-mode column containing C18 and cation exchange particles, but variable retention times were obtained. System 2 could be used satisfactorily with eluents containing ammonium acetate, and it produced dye spectra of better resolution than those obtained with system 1. When the dyes were examined under a microscope, the material on the ZnSe window was more uniform and more evenly distributed on a narrower track than were the deposits on the stainless steel belt. Consequently, the peak shape of the IR chromatograms was better with system 2, and a lower detection limit was achieved for reactive blue 74 (9 ng). When mixtures of the pesticides metolcarb and carbofuran were analyzed, a thermospray temperature of 196 °C was required to desolvate the effluent from the HPLC column in system 1. At this temperature, thermal degradation of the pesticides occurred, and no spectrum was recorded from the belt surface. However, with system 2, deposition of the pesticides was achieved at 90 °C, without degradation, and IR spectra/chromatograms were obtained. Overall, the study showed that the infrared chromatograph (IRC) was the more efficient and flexible interface for HPLC Fourier transform infrared (FT-IR) spectrometry.

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.

We describe the application of near-infrared spectroscopy to determine the chemical composition of aqueous samples that simulate hazardous wastes at the DOE Hanford site. Surrogate liquid mixtures are prepared with compositions similar to the actual Hanford liquid wastes. We demonstrate a standard error of precision of approximately 0.06 M for NaNO3 and NaNO2, 0.006 M for Na3HEDTA, and 0.009 M for Na2CO3 by using a 1 mm pathlength and approximately 1 min collection time in the 9000–5400 cm−1 (1.11–1.85 μm) region. Even though most of these electrolytes do not possess characteristic near-infrared bands suitable for quantitative analysis, the use of partial least-squares multivariate calibration makes it possible to correlate spectral differences, based on perturbations in the near-IR water spectrum, and determine each component concentration. The effects of the electrolytes and temperature on the water spectrum are discussed.

We describe the application of near-infrared spectroscopy with partial least-squares (PLS) multivariate calibration to determine the total organic carbon (TOC) content of aqueous organic samples. We demonstrate a standard error of precision of approximately 0.50 mg/mL for the TOC content in aqueous organic mixtures of Na3HEDTA, Na4EDTA, and acetone. The precision of the simultaneous determination of each component in these samples is 1.66 mg/mL (0.0044 M) for Na3HEDTA, 2.62 mg/mL (0.0063 M) for Na4EDTA, and 0.38 mg/mL (0.0065 M) for acetone. Transmission spectra were collected by using a 1 mm pathlength and approximately 1 min collection time in the 6250–5450 cm−1 (1.60–1.83 μm) region, corresponding to the first C–H overtone band. This analysis procedure was developed to ease TOC determination for hazardous aqueous wastes such as those found at the DOE Hanford site.

Factors that affect quantitative analysis by surface-enhanced resonance Raman scattering (SERRS) have been investigated using azobenzotriazol and reactive dyes. Preaggregation of the silver colloid was the most effective method to obtain repeatable and reproducible scattering. Aggregation by poly(l-lysine) or spermine provided better precision than aggregation by sodium chloride or nitric acid. Repeatable quantitative analysis was achieved with the azobenzotriazol dyes. A linear calibration graph was obtained over different concentration ranges below 10(-)(8) M, depending on the nature of the colloid. Calculations estimate that 10(-)(8) M is the concentration at which monolayer coverage of the dye on the silver colloid is achieved. Above 10(-)(8) M, there was only a minor increase in the scattering intensity from the azobenzotriazol dyes. In contrast, the reactive dyes did not give a response proportional to concentration over the range studied. The different responses obtained for the two types of dye are believed to be caused by differences in the nature of the interaction of the molecules with the silver surface. The conclusion reached is that control of the colloid preparation, aggregation process, and surface chemistry are essential for successful quantitative analysis of dyes on colloidal silver by SERRS.

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 profile obtained during graphite-furnace atomic absorption spectrometry is presented. The procedure is based upon the use of wavelet transforms to produce a number of quantitative measures of the signal variation, called Lipschitz regularities, whose values depend upon the shape of the absorbance profile. The number, position and value of the Lipschitz regularities allow a quantitative description of an individual absorbance profile to be made. A comparison of absorbance profiles is then made by comparing the set of Lipschitz regularities that describe the absorbance peak shape. Changes in the shape of the absorbance profile, between a standard solution and the sample, may be indicative of interference effects that are modifying either the atomization of the analyte, or the removal of the analyte atoms from the observation volume. The Lipschitz regularities can then be used to detect the presence of interference effects. In this paper, the background to wavelet transform theory is given, along with a description of the meaning and calculation of the Lipschitz regularity. An example of the calculation of the Lipschitz regularities for an atomic absorption profile of Cu is presented. In addition, the use of the Lipschitz regularities to determine changes in the absorbance signal profile, due to the presence of a concomitant matrix species, is demonstrated for Pb in the presence of NaCl.

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.

A method using ultrasonication extraction and solid phase extraction (SPE) clean-up for determination of US EPA 16 priority pollutant polycyclic aromatic hydrocarbons (PAHs) in soils by reversed-phase liquid chromatography (RP-LC) with ultraviolet (UV) absorption detection was studied. Separation and detection of the 16 PAHs were completed in 31 min by RP-LC with a C 18 column (Bakerbond PAH 6 PLUS 125×3.0 i.d. mm or Phenomenex ENVIROSEP-PP 125×3.2 i.d. mm), acetonitrile–water gradient elution and UV absorption detection. The detection limits, for a 10 μl of solution injection, determined at 254 nm were less than 1 μg/ml, except for acenaphthene, which was 1.05 μg/ml. Because individual PAHs are present in soils at the ng/g level or below and few sample matrices can be analyzed directly without serious interference, efficient extraction, preconcentration and clean-up of PAHs from the samples are indispensable prior to the determination of the PAHs. Several organic solvents were tested for extraction of the PAHs from soils, and ultrasonication extraction was used for the extraction in acetone of the 16 PAHs in soils. Several SPE procedures were tested and compared, and Supelco 6 ml LC-18 SPE cartridge and acetone:tetrahydrofuran (THF)=1:1 eluant were used for the preconcentration and clean-up of the 16 PAHs in the soil. The method was successfully applied to determine the 16 PAHs in the soil sampled from an industrial land in the UK.

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 system for solvent extraction at elevated temperature and pressure has been constructed from parts of HPLC and GC instruments. The apparatus has been used successfully to remove benzene, toluene, ethyl benzene, p-xylene and cumene from vapour-fortified clay soil. Quantitative recoveries (100 ± 10%) were obtained for all analytes, provided the collection vial was cooled to around –3 °C in an ice–salt mixture. When the performance was compared with that of a commercial, accelerated solvent extraction system, similar levels of ethyl benzene, p-xylene and cumene were extracted. However, the recoveries and, in particular, the reproducibility were significantly better for benzene and toluene with the system developed.

Three procedures, matrix matching, plasma optimisation and single-point standard-addition, have been evaluated to ascertain the best procedure for simultaneous multi-element analysis of industrial soils by ICP-AES with CCD detection. A standard reference material, CRM143 from the Bureau Communautaire de Reference (BCR), has been analysed for Cd, Cr, Cu, Mn, Ni and Pb using the three different matrix interference correction procedures. All three procedures give comparable results which are in good agreement with the BCR values, except for Cr. The single-point standard addition procedure was chosen, on the basis of economy and ease of implementation, to correct for matrix interferences in the determination of Cd, Co, Cr, Cu, Mn, Mo, Ni, Pb, Sn and V in soil samples collected from an industrial site in England. Concentrations of some of the elements were found to vary greatly with sampling depth. For example, the concentration of Mn, determined using the atomic line at 279.920 nm, increased from 426 ± 3 μg/g at a depth of 18–28 cm to 5996 ± 144 μg/g at 60–85 cm.

The caesium and silver content of the fruitbodies of fungi growing on some Scottish grassland sites have been measured. The distribution of caesium and silver in the soils has been measured and correlated with ergosterol as a measure of fungal biomass. Soil beneath individual fruitbodies and fairy rings was sampled from a clay loam, grassland site (Hogarth Park) in southwest Scotland, a sandy loam (Troon, southwest Scotland) and a peaty soil (Glensaugh, northeast Scotland). There is little or no information about the translocation of metals in soil by fairy ring fungi. Considerable variation in the ability of the fungi to translocate and accumulate the metals was observed. Cortinarius and Mycena Sp. and Suillus grevillei accumulated caesium and silver, whereas additionally Coprinus comatus, Entoloma Sp., Hygrocybe psittacina and Psathyrella Sp. accumulated silver. Clitocybe and Inocybe Sp., Lycoperdaceae and Marasmius oreades formed the fairy rings. Along diametric transects of each ring in most ...

A passive sampling method has been developed for acetic acid and formic acid vapours in ambient air. The procedure involves collection of the vapours in a Palmes diffusion tube (7.1 cm long and 1.1 cm i.d.) and analysis by ion chromatography. Application of Fick's first law of diffusion allows calculation of the acid vapour concentrations. To validate the procedure, the tubes have been exposed to calculated or known concentrations of acetic acid and formic acid vapours, so that the diffusion coefficients of each acid can be calculated for comparison with theoretical values. Two procedures were used to generate acid vapour concentrations in the range 6–26 mg m −3 . Solutions containing calcium chloride and acetic acid or formic acid were placed in desiccators in which replicate diffusion tubes were exposed. The derived diffusion coefficients of acetic acid and formic acid were 0.110 ± 0.003 and 0.127 ± 0.005 cm 2 s −1 , respectively. An alternative procedure used a 43 dm 3 exposure chamber and acid permeation devices to produce the acid vapour concentrations. The experimentally derived diffusion coefficients obtained with this system were 0.133 ± 0.007 and 0.120 ± 0.008 cm 2 s −1 for acetic acid and formic acid vapours, respectively. The theoretical diffusion coefficients for acetic acid and formic acid vapours are 0.105 and 0.129 cm 2 s −1 , respectively.

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.

Fibrous crystals, consisting principally of calcium, acetate, chloride and nitrate ions on a number of calcareous museum artifacts worldwide, have been examined. Ion chromatography (IC) was used to determine the exact composition of the efflorescence and nuclear magnetic resonance spectrometry (NMR) was used to determine the degree of hydration associated with the salt. Of the twelve samples analysed, eleven salts had the same stoichiometry as Efflorescence X, a novel salt identified from an Egyptian limestone relief sculpture in the Burrell Collection, Glasgow, that has the composition Ca3(CH3,COO)3 Cl(NO3)2 · 7H2O.

Wet flue gas desulfurization scrubbers can be retrofitted for combined removal of SO 2 and NO x from flue gas by adding a newly developed iron(II) thiochelate to limestone slurries. This additive enhances the solubility of NO in limestone slurries by binding NO to form iron nitrosyl thiochelates. The bound NO is then converted to an ammonium ion by iron metal, regenerating the active iron(II) catalyst for continued NO capture. The conditions of the chemical regeneration of iron(II) thiochelate have been studied. This chemical reduction method is efficient, simple, and cost-effective. Integrated tests of this new iron additive on a bench-scale system have been conducted. A turbulent contact absorber was employed to test simultaneous removal of NO and SO 2 with iron(II) thiochelate in a limestone slurry. The steady-state NO removal efficiency depends on the operating conditions of an absorber, the iron chelate concentration, the fraction of the flow diverted for regeneration, and the conditions used in the regeneration reactor. The bench-scale test results were used to develop a prediction of the performance of a full-scale spray absorber.

Improvements have been made to the traditional partial least squares (PLS) regression and cross-validation procedures. The new PLS procedure copes more effectively with non-analyte interference in multicomponent determinations and provides an estimate of the interference spectrum. The interference spectrum can be used to partially or quantitatively correct the measured spectrum before determination of analyte concentrations. Hence the accuracy of analysis is improved. The modified cross-validation procedure reduces computer time by a factor of three, for the assessment of the number of principal components, compared with the conventional method.

Nitrous acid (HONO) is an important tropospheric air pollutant. Photolysis of HONO produces hydroxyl radicals that promote ozone formation. HONO may also adversely affect human health. Sources of HONO include both direct emission from combustion processes and secondary atmospheric formation from nitrogen oxides (NOx). The relative contribution of these sources to ambient HONO concentrations is not well known. In this study, HONO and NOx emissions from on-road vehicles were measured at the Caldecott Tunnel during summer 1995. The Caldecott Tunnel is located on a heavily used highway in the San Francisco Bay area. The mean and median model years of vehicles observed during this study were 1989.3 and 1990, respectively. Nitrous acid was collected on sodium carbonate-coated glass annular denuders; NOx concentrations were measured using chemiluminescent analyzers. Average HONO concentrations in the tunnel exhaust and background air were 6.9 ± 1.4 and 0.7 ± 0.3 ppb, respectively. The average HONO/NOx ratio in m...

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.

Two procedures were compared for the determination of citrate in plasma protein solution (PPS). Ion chromatography with gradient elution was preferred to an enzymatic—spectrophotometric method for citrate concentrations in the range 0.4–11 mg l−1. Better comparisons of results by both methods were obtained for citrate concentrations at the g l−1 level, as dilution of the PPS reduced interferences in the enzymatic procedure.

An iron(II) thiochelate has been developed for use an an additive in a wet flue gas scrubber for simultaneous removal of SO{sub 2} and NO{sub x} from flue gas. The additive enhances the solubility of NO in scrubbing liquor by binding NO to form an iron nitrosyl thiochelate. The effect of oxygen on NO absorption in iron(II) thiochelate aqueous solutions, as well as in iron(II)(EDTA) solutions, has been studied. The results showed that the iron(II) thiochelate is more resistant to oxidation by oxygen than the conventional iron(II)(EDTA) additive. Parametric studies of the absorption efficiency of NO were performed in a bench-scale Turbulent Contact Absorber (TCA). Based on the bench-scale test results, a prediction of the performance of a full-scale spray absorber has been made. 15 refs., 7 figs.

The iron(II) bis(2,3-dimercapto-1-propanesulfonate) (Fe2+(DMPS)2) complex is a newly developed metal thiochelate for the removal of NOx from flue gas. The mass transfer and kinetics of the absorption of NO in aqueous Fe2+(DMPS)2 solutions have been studied in a stirred reactor. Factors influencing the NO absorption rate, such as pH, Fe2+(DMPS)2 concentration, and the ratio of Fe2+ to DMPS have been investigated. The forward rate constant of the Fe2+(DMPS)2−NO complexation reaction has been determined to be 1.1 × 108 L/mols at pH 7.2 and 50 °C.

This paper describes an improvement of the procedure, proposed previously (Spectrochim. Acta, Part B, 48 (1993) 1517), to provide information about multiplicative and spectral interferences at lines selected for the analysis of samples. The new version of the procedure only requires intensity scans across an analyte line when three solutions are aspirated: a standard solution, the sample solution and the sample spiked with the analyte standard solution. The third solution can be omitted if multiplicative interference is not of interest. Like the initial method, the present procedure does not require or assume information about the sample composition nor is the preparation of solutions of suspected interferents required. Figures of merit, namely the structured background factor, and the overall spectral interference have been devised and are used with the true detection limit at a line for line evaluation and selection. As the nonanalyte concomitant contribution to the measured spectrum is estimated, automatic background correction is possible. The proposed method not only allows selection of the spectral line, but can give a good estimate of the analyte concentration prior to a full quantitative analysis.

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.

Soil fungi accumulate radiocaesium from contaminated soil and it has been hypothesised that this may alter the plant availability and movement of the radionuclide in soil. The effect of twice-monthly addition of an aqueous suspension of the fungicide ‘Captan’ on the changes in a peaty podzol soil at 2 sites, contaminated 2 or 3 years earlier by the injection of 134Cs, has been quantified. The sites had different soil acidity and vegetation cover. The less acid soil (pHwater 5.0) had been improved by the addition of lime and fertilizer and was reseeded with grass and clover. The more acid soil (pHwater 3.8) was under hill grasses, herbs and heather. On both sites the addition of fungicide did not alter the amount or concentration of radiocaesium in plant material sampled monthly or the depth distribution of radiocaesium in the soil profile. The concentration of the fungal constituent, ergosterol, in the soil, measured monthly, was unaffected by the fungicide treatment but evidence was obtained from a pot experiment to show that ergosterol decomposes slowly in cold, wet soils. On the more acid soil, two weeks after the last application of fungicide, there was a decline in active fungi as measured by fluorescein diacetate staining. Chloroform fumigation of the more acid soil resulted in a small increase in the amount of 134Cs exchangeable with 1 M ammonium acetate. Radiocaesium in seven different fungi grown in pure culture was found to be almost entirely extractable (> 95%) with 1 M ammonium acetate. Another, Amanita rubescens, showed some retention and 88% was extractable. These findings do not preclude the fungal biomass as an important soil component controlling plant availability of radiocaesium from acid, organic soils by maintaining radiocaesium in a biological cycle, but make it unlikely that any fixation by fungi in a chemical sense is involved.

An X-ray photoelectron spectroscopy study has been conducted on a series of nitrogen-sulfur compounds to characterize the charge shifts on the nitrogen and sulfur atoms in the molecules. In all of the compounds, the sulfur was found to have a 1s binding energy equivalent to a formal charge of +6. The nitrogen 1s binding energies varied in a systematic manner that reflected the change in oxidation state. The XPS results have been used to provide insight into the formation of these compounds in two reaction systems.

Despite the existence of various methods to remove cosmic spikes from Raman data, only a few of them are suitable for process Raman spectroscopy. The disadvantages of these algorithms include increased analysis time, low accuracy of spike detection, or reliance on variable parameters that must be chosen by trial and error in each case. We demonstrate a novel approach to detecting cosmic spikes in process Raman data and validate it using a wide range of experimental data. This new method features a multistage spike recognition algorithm that is based on tracking sharp changes of intensity in the time domain. The algorithm effectively distinguishes cosmic spikes from random spectral noise and abrupt variations of Raman peaks, allowing accurate detection of both high and low intensity cosmic spikes. The procedure is free from variable user-defined parameters and operates reliably in a fully automated manner with a wide range of time-series process Raman data sets containing more than 40 to 50 spectra.

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 (

Raman spectra have been obtained for a number of intermediates and products of the reaction of nitrite iron with bisulphite ion. This is the first direct observation of all stable species in this reaction system. The dynamics of the species have been investigated at several nitrite and bisulphite concentrations that resemble those found in realistic power plant flue gas wet scrubbers.

Addition of metal chelates in a wet stack gas scrubber to improve removal efficiency of both NO and SO/sub 2/ could provide a major new dimension to environmental control technology without requiring major capital modification to existing power plants. Criteria for an effective metal chelate additive include large absorption capacity and rapid binding rate of NO, and rapid regeneration rate of metal chelates from nitrosyl metal chelates by reaction with absorbed SO/sub 2/ in aqueous solutions. The thermodynamics and kinetics of chemical reactions involved are discussed. Laser Raman spectroscopy, gas chromatography, and mass spectrometry have been employed to directly and unambiguously identify some reaction intermediates and products.

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).

The effects of various buffering reagents and pH conditions were investigated by flame atomic absorption spectrometry to optimise complexation of T13+ with quinolin-8-ol (8-Q), immobilised on controlled-pore glass beads in a 5-cm column. As Tl3+ is a softer acid than the other trivalent cations of the Group III elements, the effects of the buffers are different from those observed previously for Al3+, Ga3+ and In3+. A mixed buffer of 0.1 mol l−1 acetate and 0.1 mol l−1 ammonium chloride at pH 10 proved most successful, although 0.1 mol l−1 maleate was also satisfactory over a pH range of 4–10. As thallium normally exists as Tl+ in solution, an oxidation method was developed to convert the ions to Tl3+, which is more efficiently complexed by 8-Q. Addition of 1–10 μl of bromine per 100 ml of sample was sufficient to oxidise Tl+ without heating. Excess bromine was removed by addition of phenol. With a flow-rate of 6 ml min−1, the detection limit of Tl3+ is 3 ng ml−1, for a 3-miri preconcentration time. The enrichment factor under these conditions is 55 and the characteristic concentration is 2 ng ml−1. The major ions in sea water did not interfere with Tl3+ preconcentration and the tolerable limits of Fe3+, Cu2+ and Al3+ are high enough to permit analysis of river and sea waters. The method was applied successfully to the determination of thallium in potassium-enriched table salt. It was also shown that the concentrations of Tl+ and Tl3+ in a solution can be derived using the described procedure, allowing speciation of inorganic thallium.

The ergosterol content of soil can be used as an indicator of fungal activity. A method has been developed for the extraction and determination of ergosterol in organic soils, as part of a study to assess the correlation between fungal activity and the sequestration of metal pollutants. The moisture content of the soil affected the extraction process. Four consecutive extractions with methanol removed >95% of the ergosterol that can be obtained from the fresh sample (63% moisture) by exhaustive extraction. By freeze drying the soils prior to extraction (a) up to 35% more ergosterol was extracted after a single extraction, (b) >90% of the recoverable ergosterol was collected in two extractions and (c) the repeatability of the extraction was improved. Storage of soil extracts in the absence of light prevents degradation of ergosterol. A previously reported method for determination of ergosterol by HPLC has been improved by modification of the eluant composition. With 46% methanol/46% acetonitrile/8% dichloromethane, ergosterol was eluted with good resolution approximately 8 min after injection of 20 mul of the extract. The detection limit of the HPLC method was 0.5 mug/ml ergosterol, equivalent to 0.06 mug/g in 25 g fresh soil. Changes in ergosterol contents of peaty soil treated with fungicide, and in samples of the peaty podzol and a humus iron podzol in the vicinity of fungal fruiting bodies, have been determined.

The oxidative decomposition of nitrogen-sulfur oxides, formed by the reaction of nitrite ion and hydrogen sulfite ion in aqueous solution, has been investigated. The oxidants used in this study included hydrogen peroxide, nitrogen dioxide, and ozone. There was a wide range of susceptibility to oxidation among the compounds studied. Ozone was a better oxidant than nitrogen dioxide and hydrogen peroxide under the conditions used. The rate expression for the reaction of hydrogen peroxide with hydroxylamine was found to be -d[H[sub 2]O[sub 2]]/dt = k [H[sub 2]O[sub 2]] [NH[sub 2]OH], where k = (7.3 [+-] 0.5) [times] 10[sup [minus]4] M[sup [minus]1] s[sup [minus]1] at 25 C.

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.