Low-temperature Plasma Ashing Research Articles

Organic matter removal for continuous flow isotope ratio mass spectrometry analysis of carbon and oxygen isotope compositions of calcite or dolomite in organic‐rich samples

Abstractδ13C and δ18O values of carbonate in organic‐rich samples such as soils, biofilms, and lake sediments have been scarcely used so far in paleo‐environmental, biomineralization, or diagenetic studies because organic matter in high proportions is suspected to alter carbonate isotope analysis. Yet, with the improvement of analytical capabilities and in particular the use of CF‐IRMS, this may not be an issue anymore. To evaluate this, δ13C and δ18O values of calcite or dolomite mixed in various proportions with yeast (used here as a model for immature organic matter) were measured. The results indicate that measurements of calcite or dolomite δ13C and δ18O by CF‐IRMS require organic matter removal only when its weight proportion exceeds that of carbonates. Yeast generated an unidentified molecule during phosphoric acid digestion at 25°C (none at 80°C), which shifted the carbonate δ18O values for yeast proportions higher than 50%. It also generated CO2, but with a noticeable shift in δ13C and δ18O values only at 80°C (none at 25°C) and for yeast proportions higher than 75%. Three methods of organic matter removal were tested: the well‐established NaOCl and H2O2 wet treatments as well as low temperature plasma ashing (LTA) so far seldom examined. LTA removed the isotope shifts, although imperfectly for yeast proportions of 95%, without carbonate dissolution. NaOCl efficiently removed the isotope shifts in all cases but dissolved part of the calcite and dolomite. H2O2 treatment caused severe dissolution of calcite and dolomite while worsening the δ13C and δ18O shifts and should thus be avoided.

Evaluation of plasma cleaning as an approach for the preparation of soil minerals for forensic comparison by photon and electron microscopy.

Although organic material is often used for forensic analysis, a substantial portion of the data gathered for determination of common origin of forensic soil samples is the inorganic, mineralogical composition of the sample, which may be obscured by the presence of soil organic material (SOM). Traditionally, SOM is removed by acidic, alkaline, or peroxide digest, or by combustion, but these techniques risk the damage to or destruction of target minerals of interest. Low-temperature plasma ashing, on the other hand, removes organic materials by exposing them to plasma ions with high-kinetic energy, converting organics to easily removed volatile products (CO, CO2 , H2 O, or methane) while avoiding the thermal alterations caused by heat combustion. This study exposed grains of known mineral types to 20min of a low-pressure O2 plasma generated by a 10MHz frequency generator. Powder x-ray diffraction was chosen as an independent method to evaluate the minerals for chemical or structural changes caused by this ashing process. Side-by-side comparison of before and after diffractograms revealed minimal, if any, variation in the detected 2θ and subsequently calculated d-spacing: differences in d values were found to generally be less than 1%, and most were within Hanawalt Search Index uncertainties by no less than a full order of magnitude. Peak intensity changes were similarly minimal. This study strongly suggests that low-temperature plasma ashing can be used for the isolation of inorganic soil material fraction for forensic soil analysis with little or no concern for potential alteration of the mineral grains.

NO heterogeneous reduction on semi-coke and residual carbon with the presence of O2 and CO

Semi-coke and residual carbon are potential to serve as reducing agents for NO reduction in deep-staged co-combustion, while the impacts of flue gas components, O2 and CO, on NO heterogeneous reduction by semi-coke and residual carbon from practical industrial production have yet to be fully understood. The ash originated from different ashing methods, traditional high-temperature ashing method and low-temperature plasma ashing method, has different component distributions, which is also likely to generate important effects on NO reduction. However, the roles of components within various ash samples in NO-CO homogeneous reduction are still unclear. In this paper, the reactivities of various semi-cokes and residual carbon were experimentally studied for NO reduction using a lab-scale fixed-bed reactor. The experimental results indicate that the reactivities of semi-cokes and residual carbon towards NO reduction increase significantly when the temperature is beyond 700 °C, with more than 80% of NO being reduced at >850 °C. The addition of O2 tends to decrease NO conversion owing to the competition between NO and O2 for reacting with semi-coke. Carbon monoxide contributes to NO reduction significantly because it can not only reduce NO through the homogeneous reaction between CO and NO, but also lower the activation energy of the heterogeneous NO-char reaction. The interaction effects on NO conversion and apparent activation energy vary with the reaction temperature and CO concentration. In addition, ash samples from semi-coke are more efficient catalysts for NO homogeneous reduction than those of residual carbon.

Effect of cleaning methods on the dissolution of diatom frustules

Experimental studies characterizing the reactivity of siliceous materials, such as biogenic silica from the field or laboratory cultures, typically require organic matter removal prior to experimental analysis. Consequently, it is highly desired to develop and optimize a cleaning protocol that imposes minimal alterations to the reactivity of the siliceous substrate and can be robustly employed among laboratories and investigators. This study offers a quantitative comparison of several methods for removing organic matter associated with biogenic silica to assess their efficacy for use in reactivity studies. Five protocols for organic matter removal were assessed, including combinations of chemical treatments and/or baking, along with low temperature ashing with an oxygen plasma. These methods were tested and evaluated using Thalassiosira pseudonana frustules for mass recovery, organic carbon removal, elemental composition, morphology, structural order, relative abundance of silanol (≡Si-OH) groups, and dissolution rate. An additional experiment was conducted over a longer time scale using Thalassiosira weissflogii and a more realistic seawater matrix. Low temperature plasma ashing was found to be the most suitable for organic matter removal in studies seeking to constrain the short-term dissolution of biogenic silica; this method efficiently removed organic carbon while being the least impactful on frustule dissolution compared to the other cleaning methods evaluated. However, if the line of inquiry for an experiment does not require understanding of short-term dissolution rates, commonly used chemical (e.g. mineral acid, peroxide) and high temperature treatments did not appear to affect the long-term trajectory in biogenic silica dissolution.

Effects of ashing method and blending on ash characteristics of pyrolyzed and gasified semi-cokes

The characterization of ash properties is of benefit for better elucidating the ash-related issues during utilization of semi-coke. Nevertheless, the impact of different ashing methods on ash characteristics of semi-coke still remains unclear, along with the influence of blending various semi-cokes. In the present study, the ashes of pyrolyzed and gasified semi-cokes were prepared from two different methods, low-temperature plasma ashing at <200 °C and traditional muffle ashing at 815 °C to investigate the effects of ashing method on ash characteristics of semi-coke, which has been seldom conducted before. The low-temperature plasma oxidization could consume organic matter without destroying the initial state of mineral species in semi-coke matrix. A variety of analysis techniques including X-ray fluorescence (XRF), X-ray diffraction (XRD) and thermal analysis was performed to study ash composition, mineral phase, thermal volatility, and so on. The results show that the appearance and yield of low-temperature ash (LTA) and high-temperature ash (HTA) are highly related to the ashing approach and the category of semi-cokes. The mass fractions of most oxides contained in LTA are lower than those in HTA. The main difference of mineral phases between LTA and HTA of semi-cokes lies in the existence form of calcium. The ashing method exerts remarkable influences on thermal behaviors of pyrolyzed semi-coke ash but insignificant effect on those of gasified semi-coke. Moreover, the effects of blending pyrolyzed and gasified semi-cokes on the ash compositions and thermal behaviors are significant, while the mineral phases seem to be independent of the blending process.

Analysis of Crystalline Silica Aerosol Using Portable Raman Spectrometry: Feasibility of Near Real-Time Measurement.

A Raman spectroscopy based method has been developed for measurement of trace airborne concentrations of respirable crystalline silica (RCS) using various aerosol sampling and analysis techniques. Three aerosol microconcentration techniques were investigated for effective coupling of collected particulate samples with micro-Raman spectroscopy: (i) direct analysis on a particulate filter after focused aerosol collection using a converging nozzle; (ii) analysis of dried particulate deposit on a filter obtained directly from the aerosol phase using the Spotsampler device; and (iii) analysis of a dried spot (∼1-3 mm diameter) obtained by redepositing the particulate sample, after low-temperature plasma ashing of the filter sample. The deposition characteristics (i.e., spot diameter, shape, and deposit uniformity) of each technique were investigated. Calibration curves were constructed and detection limits were estimated for α-quartz using the A1 Raman Si-O-Si stretching-bending phonon mode at 465 cm-1. The measurement sensitivity could be substantially improved by increasing the signal integration time and by reducing the particle deposition area. Detection limits in the range of 8-55 ng could be achieved by microconcentrating the aerosol sample over a spot measuring 400-1000 μm in diameter. These detection limits were two to three orders of magnitude lower compared to those attainable using current standardized X-ray diffraction and infrared spectroscopy methods. The low detection limits suggest that near real-time measurements of RCS could be achieved with limits of quantification ranging from 2 to 18.5 μg/m3 (at 10 min collection time and 1.2 L/min sampling flow rate), depending on microconcentration technique used. The method was successfully extended to the measurement of α-quartz air concentration in representative workplace aerosol samples. This study demonstrates the potential of portable micro-Raman spectroscopy for near-real time measurement of trace RCS in air.

Electrothermal atomic absorption spectrometric determination of arsenic in essential lavender and rose oils

Analytical procedures for electrothermal atomic absorption spectrometric (ETAAS) determination of arsenic in essential oils from lavender ( Lavendula angustifolia) and rose ( Rosa damascena) are described. For direct ETAAS analysis, oil samples are diluted with ethanol or i-propanol for lavender and rose oil, respectively. Leveling off responses of four different arsenic species (arsenite, arsenate, monomethylarsonate and dimethylarsinate) is achieved by using a composite chemical modifier: l-cysteine (0.05 g l −1) in combination with palladium (2.5 μg) and citric acid (100 μg). Transverse-heated graphite atomizer (THGA) with longitudinal Zeeman-effect background correction and ‘end-capped’ graphite tubes with integrated pyrolytic graphite platforms, pre-treated with Zr–Ir for permanent modification are employed as most appropriate atomizer. Calibration with solvent-matched standard solutions of As(III) is used for four- and five-fold diluted samples of lavender and rose oil, respectively. Lower dilution factors required standard addition calibration by using aqueous (for lavender oil) or i-propanol (for rose oil) solutions of As(III). The limits of detection (LOD) for the whole analytical procedure are 4.4 and 4.7 ng g −1 As in levender and rose oil, respectively. The relative standard deviation (R.S.D.) for As at 6–30 ng g −1 levels is between 8 and 17% for both oils. As an alternative, procedure based on low temperature plasma ashing in oxygen with ETAAS, providing LODs of 2.5 and 2.7 ng g −1 As in levender and rose oil, respectively, and R.S.D. within 8–12% for both oils has been elaborated. Results obtained by both procedures are in good agreement.

The Biopersistence of Brazilian Chrysotile Asbestos Following Inhalation

With the initial understanding of the relationship of asbestos to disease, little information was available on whether the two different groups of minerals that are called asbestos were of similar or different potency in causing disease. Asbestos was often described as a durable fiber that if inhaled would remain in the lung and cause disease. It has been only more recently, with the development of a standardized protocol for evaluating the biopersistence of mineral fibers in the lung, that the clearance kinetics of the serpentine chrysotile have been shown to be dramatically different from those of amphibole asbestos, with chrysotile clearing rapidly from the lung. In addition, recent epidemiology studies also differentiate chrysotile from amphibole asbestos. The biopersistence studies mentioned have indicated that chrysotile from Canada and California clear rapidly from the lung once inhaled. However, variations in chrysotile mineralogy have been reported depending upon the region. This is most likely associated with variations in the forces which created the chrysotile fibers centuries ago. In the present study, the dynamics and rate of clearance of chrysotile from the Cana Brava mine in central Brazil was evaluated in a comparable inhalation biopersistence study in the rat. For synthetic vitreous fibers, the biopersistence of the fibers longer than 20 μ m has been found to be directly related to their potential to cause disease. This study was designed to determine lung clearance (biopersistence) and translocation and distribution within the lung. As the long fibers have been shown to have the greatest potential for pathogenicity, the chrysotile samples were specifically chosen to have more than 450 fibers/cm3 longer than 20 μ m in length present in the exposure aerosol. For the fiber clearance study (lung digestions), at 1 day, 2 days, 7 days, 2 wk, 1 mo, 3 mo, 6 mo, and 12 mo following a 5-day (6 h/day) inhalation exposure, the lungs from groups of animals were digested by low-temperature plasma ashing and subsequently analyzed by transmission electron microscopy (at the GSA Corp.) for total chrysotile fiber number in the lungs and chrysotile fiber size (length and diameter) distribution in the lungs. This lung digestion procedure digests the entire lung with no possibility of identifying where in the lung the fibers are located. A fiber distribution study (with confocal microscopy) was included in order to identify where in the lung the fibers were located. At 2 days, 2 wk, 3 mo, 6 mo, and 12 mo postexposure, the lungs from groups of animals were analyzed by confocal microscopy to determine the anatomic fate, orientation, and distribution of the retained chrysotile fibrils deposited on airways and those fibers translocated to the broncho-associated lymphoid tissue (BALT) subjacent to bronchioles in rat lungs. While the translocation of fibers to the BALT and lymphatic tissue is considered important as in cases of human's with asbestos-related disease, there has been no report in the literature of pathological changes in the BALT and lymphatic tissue stemming from asbestos. Thus, if the fibers are removed to these tissues, they are effectively neutralized in the lung. Chrysotile was found to be rapidly removed from the lung. Fibers longer than 20 μ m were cleared with a half-time of 1.3 days, most likely by dissolution and breakage into shorter fibers. Shorter fibers were also rapidly cleared from the lung with fibers 5–20 μ m clearing even more rapidly (T1/2 = 2.4 days) than those < 5μ m in length (T1/2 weighted = 23. days). Breaking of the longer fibers would be expected to increase the short fiber pool and therefore could account for this difference in clearance rates. The short fibers were never found clumped together but appeared as separate, fine fibrils, occasionally unwound at one end. Short free fibers appeared in the corners of alveolar septa, and fibers or their fragments were found within alveolar macrophages. The same was true of fibers in lymphatics, as they appeared free or within phagocytic lymphocytes. These results support the evidence presented by that the chrysotile fibers are rapidly cleared from the lung in marked contrast to amphibole fibers which persist.

The Biopersistence of Canadian Chrysotile Asbestos Following Inhalation

Chrysotile asbestos is often included with other asbestos materials in evaluation and classification. However, chrysotile is a serpentine with markedly different physical and chemical characteristics in comparison to amphiboles (e.g., crocidolite, amosite, tremolite). In contrast to amphiboles, which are solid, rodlike fibers, chrysotile is composed like a rope of many fine fibrils, which tend to unwind. In order to quantify the dynamics and rate by which chrysotile is removed from the lung, the biopersistence of a sample of commercial chrysotile from the Eastern Townships area of Quebec, Canada, labeled QS Grade 3-F, which is the longest commercial grade intended for textile use, was studied. As the long fibers have been shown to have the greatest potential for pathogenicity, the chrysotile samples were specifically chosen to have more than 200 fibers/cm3 longer than 20 µm present in the exposure aerosol. This publication presents the results of this study through 3 mo postexposure. The study design included: (1) Fiber clearance (lung digestions): At 1 day, 2 days, 7 days, 14 days, 1 mo, 3 mo, and 12 mo (to be reported) following a 5-day (6 h/day) inhalation exposure, the lungs from groups of animals were digested by low-temperature plasma ashing and subsequently analyzed by transmission electron microscopy for total chrysotile fibers number in the lungs and chrysotile fiber size (length and diameter) distribution in the lungs. (2) Fiber distribution (confocal microscopy): This procedure was included in order to identify the location of the fibers in the lung. At 1 day, 2 days, 7 days, 14 days, 1 month, and 3 months (to be reported) postexposure, the lungs from groups of animals were analyzed by confocal microscopy to determine the anatomic fate, orientation, and distribution of the retained chrysotile fibrils deposited on airways and in the parenchymal region. Chrysotile was found to be rapidly removed from the lung. Fibers longer than 20 µm were cleared with T1/2 = 16 days, most likely by dissolution and disintegration into shorter fibers. The shorter fibers were also rapidly cleared from the lung, with fibers 5–20 µm clearing even faster (T1/2 = 29.4 days) than those <5 µm in length. The fibers <5 µm in length cleared at a rate (T1/2 = 107 days) that is within the range of clearance for insoluble nuisance dusts. The breaking apart of the longer fibers would be expected to increase the short fiber pool and therefore could account for this difference in clearance rates. The short fibers were not found clumped together but appeared as separate, fine fibrils, occasionally unwound at one end. Short free fibers appeared in the corners of alveolar septa, and fibers or their fragments were found within alveolar macrophages. The same was true of fibers in lymphatics, as they appeared free or within phagocytic lymphocytes. Neutrophil-mediated inflammatory response did not occur in the presence of chrysotile fibers at the time points examined. Taken in context with the scientific literature to date, this report provides new robust data that clearly support the difference seen epidemiologically between chrysotile and amphibole asbestos.

Diesel exhaust quantification by scanning electron microscope with special emphasis on particulate size distribution

The purpose of this study was to investigate the potentials of electron microscopy to quantify diesel exhaust emission from work environments, where the aerosol consists of both diesel fumes and dust particles from pollutant sources. The mass and particles concentrations as well as size distributions were investigated. The size distribution consists of two modes: a group of particles with D min < 0.7 and a group of particles with D min > 1.0 μ m, respectively. The D min in the range 0.7–1.0 μm should be regarded as an interval where there is an overlapping. To distinguish between organic and non-organic components of the particulate, low-temperature plasma ashing was made. This is a very slow oxidizing process that does not affect or disturb non-oxidizable material. The diesel fumes in the samples constitute only a small share of the total mass, while diesel fumes dominate by numbers in those samples. A big difference is observed between the number of concentrations for non-ashed and ashed samples, respectively. However, no significant differences are observed between the volume diagram for non-ashed and ashed samples. One should therefore consider the number of concentrations of particles below 1 μm in diameter rather than the gravimetric concentrations when studying exposure level for diesel exhaust.

Evaluation of Soluble fibers Using the Inhalation Biopersistence Model, a Nine-fiber Comparison

AbstractThe biopersistence of nine fibers was evaluated using an inhalation model. The fibers studied were compositions with different in vitro acellular solubility. The commercial and new glass wool fibers were essentially sodium borosilicates and the commercial and new stone wools were essentially calcium modified silicates. Fischer 344 male rats were exposed to a well-defined rat respirable aerosol (mean diameter of ∼1 μm) at a concentration of 30 mg/m3, 6 h/day for 5 days with postexposure sacrifices at 1 h, 1 day, 5 days, 4 wk, 13 wk, and 26 wk. At sacrifice, the whole lung was removed, weighed, and frozen at -20°C for subsequent digestion by low-temperature plasma ashing. The number and bivariate size distribution of the fibers in the aerosol and lung were determined. At 1 h following the last exposure, the 9 fibers were found to have lung burdens ranging from 7.4 to 33 ° 106 fibers/lung with geometric mean diameters (CMD) of 0.40–0.54 μm. The range of initial lung burdens was found to reflect the d...

Evaluation of the oncogenic potential of man-made vitreous fibres: The inhalation model

A rodent inhalation model has been developed for the evaluation of the eoncogenic potential of man-made vitreous fibres. It is successful in delivering a quantified dose of wellchacterized fibres to the lungs of rodents, and with it sufficiently high fibre aerosol concentrations were lofted to enable a maximum tolerated dose to be achieved.Fischer 344 male rats were exposed to a well-defined rat-respirable aerosol at concentrations for MMVF of 30,16 or 3 mg m −3, 6 h per day, 5 days per week for 104 weeks with final sacrifice at 20% survival. A control group was exposed to filtered air. The high dose was chosen based upon a 28-day maximum tolerated dose study with refractory ceramic fibres (RCF). The fibre aerosol generation system lofted fibres without breaking, grinding or contaminating the bulk material. Exposure was by flow-past nose-only systems which provided fresh fibre in a laminar stream to each animal individually. The study was performed according to the Good Laboratory Practice regulations.Fibre count, fibre diameter and length distribution, aerosol mass and chemical composition were determined throughout the study. Interim sacrifices were performed at 3 or 6 month intervals for 24 months. At each sacrifice, full necropsy was performed, the accessory lobe removed for subsequent digestion to determine the fibre lung burden and the remaining lobes inflated with fixative for histopathological evaluation. The lungs were evaluated by a pathologist and graded for the degree of macrophage infiltration, bronchiolization, fibrosis and pleural thickening, and were also scored according to the Wagner scale. Lesions were evaluated according to the number of adenomas, carcinomas and mesotheliomas. The accessory lobe was digested by low-temperature plasma ashing and the number, size distribution and chemical composition of the fibres determined.This model provides a sensitive and reproducible method for evaluating existing and new fibres. A variety of different of ceramic, glass, rockwool and slagwool fibres have been evaluated with this model.

Evaluation of the Biopersistence of Commercial and Experimental Fibers Following Inhalation

AbstractThe biopersistence of three fibers was evaluated using an inhalation model. The fibers studied were man-made vitreous fiber (MMVF) 11, a commercially produced glass fiber; Fiber B, a relatively soluble glass fiber; and Fiber J, a synthetic stonewool with a high content of alkaline earth oxides. Fischer 344 male rats were exposed to a well-defined rat respirable aerosol (mean diameter of ≤1 μm) at a target concentration of 30 mg/m3, 6 h/day for 5 days. Following the end of the exposure period, subgroups were sacrificed at 1 h, 1 day, 5 days, 4 wk, 13 wk, 26 wk, and 52 wk. At sacrifice, the whole lung was removed, weighed, and immediately frozen at -20°C for subsequent digestion by low temperature plasma ashing. The number and bivariate size distribution of the fibers in the aerosol and lung were determined. At 1 h following the last exposure, the 3 fibers were found to have similar lung burdens ranging from 7.36-7.72 × 106 fibers/lung with geometric mean diameters of 0.42-0.54 μm. The three fibers ...

An experimental approach to the evaluation of the biopersistence of respirable synthetic fibers and minerals.

The biopersistence of fibers and minerals in the respiratory tract is an important parameter in the toxicity of those materials. The biopersistence of respirable synthetic fibers and minerals in man can be most closely evaluated in an animal model. While acellular and in vitro systems are important for initial evaluation of solubility and durability, they cannot simulate the dynamics of inhalation deposition and clearance and the subsequent systemic reaction to fibers and minerals that occurs in the animal. To evaluate the biopersistence of synthetic fibers, male rats were exposed to a well defined rat respirable aerosol of man-made vitreous fibers (MMVF), 6 hr/day for 5 days. Following exposure, subgroups were sacrificed at intervals ranging from 1 hr to 52 weeks. Following sacrifice, the lungs were removed, weighed, and immediately frozen at 20 degrees C for subsequent digestion by low temperature plasma ashing. The number, size distribution, and chemical composition of the fibers in the aerosol and lung were determined. With this animal model the role of biopersistence in altering the geometry and clearance of fibers can be systematically evaluated. The model also can be applied for the evaluation of the biopersistence of nonfibrous minerals.

Relation between lung asbestos fibre burden and exposure indices based on job history.

Lung asbestos burden was compared with exposure indices derived from job history interviews in 42 male subjects originating from the Montréal Case-Control Study project, 12 of whom had documented asbestos exposed job histories. Job interview data consisting of a chronological timetable of job histories were translated into detailed exposure indices by an expert group of hygienists and chemists. Total and individual asbestos fibre type concentrations were quantified by transmission electron microscopy with fibre identification by energy dispersive chi ray spectrometry after deparaffinisation of tissue blocks and low temperature plasma ashing. Geometric mean or median asbestos content was higher in subjects with an asbestos exposed job history than those without for retained dose of amosite, total commercial amphiboles, and total asbestos fibre. Except for crocidolite fibre diameter, which was significantly less in the lungs of exposed workers, no consistent differences were found in measurements of fibre dimension for any fibre type. Subgroups of subjects exposed to silica, metals, or smokers and non-smokers without significant occupational exposure showed varying patterns of lung asbestos fibre type deficit compared with the asbestos exposed subgroup. There was an overall trend for higher lung asbestos content proportional to higher exposure indices for asbestos representing concentration, frequency, and reliability. These exposure indices as well as duration of exposure (in years) were independent predictors of total asbestos content in regression analyses when combined in a model with age. Stepwise regression indicated that exposure concentration was the most important variable, explaining 32% of the total variation in total asbestos content. Smoking, whether expressed in ever or never smoked dichotomy or in smoked-years, had no relation to lung asbestos content in this model.

Elemental analysis of solid samples by low temperature plasma ashing and microwave acid digestion

Sixteen elements (Mn, Zn, Cu, Fe, B, Sr, Ba, Cr, Pb, As, Cd, Ni, Co, Se, Sb, Hg) were determined in oils, sediments, plants and marine organisms by Inductively Coupled Plasma Atomic Emission Spectrometry (ICP-AES) or by Graphite Furnace Atomic Absorption Spectroscopy (GF-AAS) after plasma ashing followed by microwave acid digestion with HNO3/HCl/H2O2. Soil and sediment samples were treated directly in the microwave oven without ashing, but the complete procedure must be applied in case of high organic content. The method was tested on a variety of standard reference materials. Good recoveries were obtained for most of the considered trace elements with less time and reagents consumption than conventional open vessels acid digestion procedures. Hg was determined with good recovery in soil samples by the same method and in organic materials by a modified procedure involving digestion of fresh material with nitric acid in a reflux quartz system.

Sources of error in low temperature plasma ashing procedures for quantitative mineral analysis of coal ash

Using low temperature ashing in an oxygen plasma, the mineral matter in coals can be isolated and studied. A quantitative X-ray diffraction (XRD) technique has been developed, using accepted procedures, for the analysis of minerals (illite, gypsum, kaolinite, quartz, ankerite and pyrite) in low temperature coal ash (LTA). This XRD method should theoretically produce mineral totals approaching 100%, unless non-crystalline material is present. However, working with material ashed to constant weight gave mineral totals of between 50% and 80%; totals generally being lowest when the ash content of the coal was low. Further work showed that this shortfall was due to residual organic matter that can be removed by repeated fine-grinding and ashing.

パイロハイドロリシス−ガスクロマトグラフィーによる生体試料中総フッ素定量の検討

For determining the total fluorine (F) level in biological samples containing organofluorine (organic F) compounds, we used pyrohydrolytic F separation and gas chromatography for the determination of F in the resulting aqueous HF solution (PyH-GC method).We investigated the operating conditions of the apparatus for PyH which was developed by Itai et al. and the recovery of F using calf serum. In order to examine the suitability of the PyH-GC method for determining various organic F compounds, we applied four analytical methods including the PyH-GC method to test the recovery rates of six organic F compounds and then compared the F values obtained from each method.Furthermore, for confirming the applicability of the PyH-GC method to determine low level F in biological samples, we applied both the PyH-GC method and the low temperature plasma ashing method followed by GC (LTA-GC method) to determine the total F in the blood plasma of rats which had been given 6-fluoro-tryptophan (6-FT).The results were as follows:(1) Concerning pyrohydrolysis, the best results were obtained when the temperature of the steam generator was 95°C, sample quantities were 300μl or 0.3-0.4g, and highly purified oxygen was used. When NaF, NH4F, 6-FT or CaF2 was added to calf serum, good reproducibility and recovery rates were obtained without addition of any acid flux for total F determination. The detection limits in this method were 4ng/ml for serum and 3ng/g for soft tissue.(2) In comparing the four determining methods, the diffusion method using a strong acid proved to be deficient and the AlF molecular absorption method showed low recovery rates for half of the organic F compounds examined. Although the PyH-GC method showed a low recovery rate for 4-fluorobenzophenone which has a low melting point, it showed fairly good recovery rates for the other organic F compounds; the LTA-GC method showed the best recovery rate.(3) The total F values in the plasma of the rats resulted in an excellent agreement between the samples pretreated with LTA and those with PyH. This result indicates that both methods are suitable for determining F in 6-FT and its metabolite in the plasma.However, it is better to use the PyH-GC method for determination of total F in biological samples because it is more rapid and simpler than the LTA-GC method.

Importance of quantitative trace analysis in industry today

Trace analysis in the industrial analytical laboratory represents a substantial portion of the overall lab workload. This paper will explore some of the kinds of analyses that are done, why they are done, and what the limitations are to our current capabilities. Industry represents the full diversity of analytical problems, and even within one company, such as BP America, important trace quantitation problems can arise from petroleum products, ceramics, minerals, biological materials, chemicals, catalysts, and, of course, environmental samples relating to all of these. It would be impossible to review all of the trace analytical methods used for such a diverse set of samples, to compare relative merits, or to in any way survey the field of trace analysis in industry. Rather, this paper looks at certain major themes that are driving the entire area, overlapping many techniques in each case. For all of the diversity of quantitative industrial trace analysis, three motivational themes seem to dominate: samples where the trace quantity provides the value to a product; samples where trace species degrade the value of a product; and, samples where trace species represent a potential hazard to human, animal or plant life. In suggesting these categories, and in the subsequent discussion, I am removing from the realm of trace analysis problems in which the analyte is in high concentration but small quantity. For some techniques these may present the same problem as low concentration trace analysis, but increasingly, we find that instrumentation has evolved considerably in the ability to handle small samples. The first category, trace quantities as key to product value, is probably most noticeable in importance today for the electronics industry. While classical chemistry recognized the importance of certain trace elements or compounds, it was the electronics industry, beginning in the earliest days of the transistor and continuing to the present, that turned this into a picoscience. Examples in other aspects of chemistry and materials science abound. Modern heterogeneous catalysts have derived selectivity and activity from trace elements. Metallurgists, ceramists, and polymer scientists can bring about significant improvements in material properties by adding trace quantities of appropriate substances. The analytical challenge here has been considerable. In many cases we are asked to analyze very low levels, with a high degree of quantitation, and on solid phases. It is the latter point that probably has provided the greatest challenges and the most innovative solutions. The triumphs of SIMS, an industrial innovation, despite its being a destructive technique, are to be particularly noted in this field. Many advances have also come from Fourier transform techniques, in NMR, IR, and mass spectrometry. Even in such well developed areas as atomic spectroscopy, the introduction of low temperature plasma ashing and acid digestion using sealed Teflon vessels has permitted dissolution of solids with almost no loss or contamination. There still remains much to be done. While SIMS provides some depth profiling, we continue to be challenged by deep interfaces. These are of great importance, but analytical methodology for reaching and analyzing them is decades behind our ability to deal with surfaces. The second area is also a well established problem in the electronics industry, but pervades much of the rest of chemistry. While some trace elements provide catalyst selectivity, others are potent catalyst poisons. Relatively low levels of metals in coke (iron, nickel, vanadium) result in substantial drops

Low-temperature ashing of organic materials for determination of chloride

The low-temperature plasma ashing technique was applied to organic materials containing sodium chloride and residual ash was analyzed for chloride using ion chromatography. Recovery of the chloride was approximately 50%, while 20–30% of the chloride had been converted to chlorate. The remaining fraction of the chloride could have been volatilized due to electron and ion bombardments onto the sample surface within the glow discharge region. Pretreatment of the sample by impregnating with potassium carbonate improved the recovery of the chloride to 90% with practically no production of chlorate.