Showing papers in "Fresenius Journal of Analytical Chemistry in 1986"

Chemistry of organic traces in air

Abstract: Wide bore glass capillaries with 0.5–0.7 mm inner diameter and 120 m length can be used in combination with liquid nitrogen cold trap injection for high resolution gas chromatography of air samples up to 100 ml volume. The injected air sample can be extended to a 51 volume and more, if a cryogenic enrichment of the organic traces is done in a specially designed 100 ml cold trap. Five air samples with a broad range of pollution — air of a parking garage as well as air collected by plane at 10 km height between Africa and Brasil — are analyzed for their C1- and C2- organohalogen content. Tetrachloromethane shows for unpolluted as well as for polluted air from the lower troposphere a rather constant mixing ratio, whereas 1,1,1-trichloro-ethane at its baseline concentration can be taken as an indicator for clean air masses up to 10 km in the northern hemisphere. Both compounds are supplementary in their indicator function.

Polycyclic aromatic compounds of environmental and occupational importance

Abstract: This paper describes the preparation and certification of a complementary set of 9 polycyclic aromatic compounds (PAC) for calibration and reference purposes in environmental and occupational analysis, increasing the total number of BCR reference compounds of this class of ubiquitous pollutants to 48. Also presented are newly measured UV-absorption maxima, and a review of the occurrence and biological activities (bacterial mutagenicity tests and animal carcinogenic data) of the compounds in this latest series of PAC reference materials. Although not certified for purity at the time of publication, UV data for picene, a valuable internal standard, are also given.

Chemistry of organic traces in air@@@Chemie organischer Spurenstoffe in Luft.: V. Determination of halogenated C1-C2-hydrocarbons in clean marine air and ambient continental air and rain by high resolution gas chromatography using different stationary phases@@@V. Bestimmung von halogenierten C1-C2-Kohlenwasserstoffen in mariner Reinluft sowie kontinentaler Luft und in Regen mittels hochauflsender Capillar-Gas-Chromatographie auf verschiedenen stationren Phasen

Abstract: ZusammenfassungChlorierte, bromierte und gemischt halogenierte C1- und C2-Kohlenwasserstoffe wurden in marinen Reinluftproben und in Luft und Regen über Süddeutschland bestimmt. Die marine Luftprobenahme fand vor der Küste Portugals an Bord des deutschen Forschungsschiffes „Polarstern” statt. Die Kombination verschiedener analytischer Techniken wie Adsorption auf Tenax TA, thermische Desorption mit Kühlfallen-Zwischenkondensation, Trennung auf DB1 (100% dimethyl-polysiloxane), BP10 (7% cyanopropyl-, 7% phenylmethyl-polysiloxane) und auf gekoppelten Fused-silica-Capillaren und Elektronen-Einfang-Detektion ermöglicht die Identifizierung und Bestimmung von flüchtigen, halogenierten organischen Spurenstoffen in den Luftmassen des Westwindgürtels mit Gehalten von 0.1 pptv bis über 200 pptv.Zur Interpretation der gemessenen Belastung der Luftmassen mit organischen Halogen-Verbindungen wird die relative Konzentration bezogen auf den Tetrachlormethan-Gehalt in der freien Troposphäre eingeführt:RT(A)-Wert = conc.(A)∶conc.(CCl4) in pptv∶pptv. (1)Der Gehalt an Tetrachlormethan ist sowohl in der Nordwie in der Südhemisphäre nahezu konstant, seine zeitliche Änderung liegt im Bereich der derzeitigen Meßgenauigkeit. Tetrachlormethan kann daher als ein interner Standard für unbelastete Luft der unteren Troposphäre betrachtet werden.Regen einer schnell über Westeuropa ziehenden Niederschlagsfront wurde in Ulm gesammelt. Die Untersuchung auf flüchtige Organohalogen-Verbindungen erfolgt durch Ausblasen mit gereinigter Luft und nachfolgender Adsorption auf Tenax TA. Eine Anreicherung der polaren bromierten und gemischt halogenierten Methane im Regen gegenüber den Gehalten in Luft ist klar erkennbar.SummaryChlorine, bromine and bromine-chlorine C1- and C2-hydrocarbons were determined in marine air and in air and rain from southern Germany. Marine sampling was done on board the German research vessel F.S. „Polarstern” near the coast of Portugal. A combination of analytical techniques like adsorption on Tenax TA, thermal desorption with cold trapping, high-resolution gas chromatography on DB1 (100% dimethyl-polysiloxane), BP10 (7% cyanopropyl, 7% phenyl-methyl-polysiloxane) and coupled fused-silica capillary columns and electron-capture detection were used. With these methods it is possible to determine organic trace compounds from 0.1 pptv up to 200 pptv in the air masses of the westwind drift.The concentration of tetrachloromethane in the troposphere of both hemispheres is nearly constant, its annual increase is in the range of the accuracy of determination. Therefore, tetrachloromethane can be taken as a built-in stable internal standard in tropospheric air.RT(A)-value = conc. (A)∶conc. (CCl4) in pptv∶pptv. (1)Calculating theRT-value of a compound A is useful for the interpretation of the organohalogen burden of air masses and for discussing input, output and transport mechanisms.Air and rain of a fast moving rainfront coming from the North Atlantic was sampled in Ulm. The volatiles were purged out of the rainwater with clean air and trapped on Tenax TA. The analysis clearly shows the wash-out effect and the accumulation of the more polar bromine and bromine-chlorine compounds in the rain.

Analytical chemistry with optical sensors

Abstract: Recent advances in opto-electronics, (fiber) optics, and optical spectroscopy have led to the development of a fascinating new chemical sensor technique. The present state of the art in optical sensing technology is briefly described in this review. Major advantages of this type of sensor over others include cheapness, ease of miniaturization and the renunciation of reference cells. Among the disadvantages, mention should be made of interference by ambient light, comparatively small analytical ranges, lack of specificity and lack of low-priced lasers.

Isotope dilution mass spectrometry of inorganic and organic substances

Abstract: Revue comprenant 37 references: les principes, appareillages, techniques, precision, utilisation, developpement futur

Food quality control and studies on human nutrition by mass spectrometric and nuclear magnetic resonance isotope ratio determination

Abstract: The natural abundances of the stable isotopes of the main bioelements in biogenic material are submitted to small variations caused by isotope effects of physical processes and chemical reactions in the natural cycles of these elements. Resulting typical relative abundances (δ-values) of food and food ingredients permit assignments to their origin and treatment and allow the proof of the addition of adulterants.

GC-MS and HPLC analyses of lignin degradation products in biomass hydrolyzates

Abstract: The gas-chromatographic separation of lignin degradation products of hydrolytically degraded biomass (e. g. poplar wood) and their mass spectrometric identification are described. For routine analysis of lignin degradation products of biomass hydrolyzates, a time saving HPLC gradient method using a UV-detection system (280 nm), is described. In addition to reference samples, solutions of hydrothermally degraded biomass were analyzed.

Untersuchungen zur Probenahme und -vorbehandlung von Baumnadeln zur Elementanalyse

Abstract: In dieser Untersuchung der Probenahme und -Vorbehandlung wurden die Elemente Al, B, Ba, Ca, Co, Cr, Cs, Cu, Fe, Hg, K, Mg, Mn, Mo, N, Na, Rb, S, Sb, Sc, Th und Zn berucksichtigt. Deren Bestimmung erfolgte mit der instrumentellen Neutronenaktivierungsanalyse, Flammen- und flammenloser Atomabsorptionsspektrometrie, Spektralphotometrie, Mikrotitrimetrie und der Elementaranalyse. An der Baumart Rotfichte (Picea abies) aus mehreren Standorten wurden die folgenden bei der Nadelprobenahme zu berucksichtigenden Faktoren untersucht: Nadeljahrgang bei gegebener Quirllage, Quirllage bei gegebenem Nadelalter, unterschiedliche Aste bei gegebenem Quirl und Nadelalter, unterschiedliche Positionen bei gegebenem Nadelalter innerhalb eines Astes und der Gesundheitszustand der Baume. Die Probenhomogenitat wurde am Beispiel des Elements Mangan mit Hilfe der Radiotracertechnik nach in situ Markierung ermittelt. Unter Verwendung einer Stripping-Technik wurde der Beitrag der auf der Nadeloberflache abgelagerten Bestandteile zum Nadelgesamtgehalt der Elemente ermittelt. Es wurde die Effizienz der Entfernung der Oberflachenbestandteile beim Waschen der Nadeln mit Wasser und Chloroform untersucht. Auf der Grundlage der erhaltenen Resultate wird ein bestimmtes Vorgehen bei der Probenahme und der Probevorbehandlung vorgeschlagen. Ebenfalls werden die Unsicherheiten einzelner Schritte und die hierdurch bedingte Grenze der Zuverlassigkeit der Elementanalyse von Nadeln aufgezeigt.

Abuse of the analyte addition technique in atomic absorption spectrometry

Abstract: The analyte addition technique is frequently used in atomic absorption spectrometry, and is often applied routinely to avoid errors in graphite furnace and other techniques for trace element determination. In fact, however, the analyte addition technique can be applied reasonably only if certain prerequirements are fulfilled. The two most important basic rules are that the analyte addition technique can only correct for multiplicative but not for additive systematic errors, and that the added analyte element and the element present in the sample must behave in an analytically identical manner. Careful isoformation is typically required in the graphite furnace technique to fulfil this second requirement. Doing so, however, completely eliminates numerous interferences if at the same time proper atomization conditions and evaluation of integrated absorbance signals are used. This means that the analyte addition technique has become redundant in this case, and that the analytical curve technique can be used for evaluation.

Methodology for the determination of gaseous hydrogen peroxide in ambient air

Abstract: A method for the determination of gaseous hydrogen peroxide in ambient air is described. The cryogenic sampling technique (−45 ° C) employed represents an improvement compared with the impinger technique by diminishing artifacts which are bound to liquid phase production and decomposition, respectively. Results are given of H2O2 measurements from October 1984 to July 1985 in Dortmund (FRG), with mean concentrations of about 30 ppt (v/v). Preliminary results obtained with a coated denuder as a sampling device are also presented.

Formation of polychlorinated dibenzodioxins and dibenzofurans by heating chlorophenols and chlorophenates at various temperatures

Abstract: Polychlorinated dibenzodioxins (PCDD) and polychlorinated dibenzofurans (PCDF) are formed by pyrolysis of chlorophenols and chlorophenates. Under certain conditions the PCDD pattern is completely governed by the chlorine substitution of the starting molecules. Pyrolyses of chlorophenols at elevated temperatures, however, lead to complex PCDD/PCDF mixtures. Nearly all trito heptachlorodibenzodioxin and -dibenzofuran congeners can arise simultaneously from a mixture of only two trichlorophenols. In this case the substitution pattern of the products is no longer influenced by that of the chlorophenols used.

A century of spectral interferences in atomic emission spectroscopy — Can we master them with modern apparatus and approaches?

Abstract: This paper discusses two main aspects of spectral interferences: (1) the handling of the vast amounts of data needed for adequately coping with the lack of selectivity of atomic emission spectroscopy (AES), and (2) the concept of selectivity and the use of selectivity as a major analytical performance characteristic in AES. The main discussion centres about the problem of correctly determining the magnitude of interfering signals in the spectral windows of analysis lines, thus background correction in the widest sense. The approaches are classified into two groups depending on whether the sample concomitants or the gaseous atmosphere in the source contribute unstructured or structured background. The latter situation is emphasized in the subsequent discussion. In this light, the paper reviews data compilations published since in 1884 Hartley laid the foundations of quantitative AES. These compilations are featured as (1) “hardware only” (plates, charts, chart recordings, plots, tables, atlases), (2) “software/hardware conversion” (tape or disk with computer retrieval for data visualization) or (3) “software” only (tape or disk with computer retrieval and processing in combination with data on samples). It is concluded that up to the present most approaches must be categorized as (1) or (2), which means that either the operator looks up and the operator decides or the computer looks up and the operator decides. Only in a few instances are the capabilities of the computer fully exploited and is it the computer which looks up the data and also makes the decisions (“artificial intelligence”). The future should and will see the balance tip into that direction. The second part of the discussion deals with the concept of selectivity and in that context considers the effects of the practical resolving power (“spectral resolution”) on analytical performance in the case of line overlap. A review of early and recent work covers such topics as physical line widths, required spectral resolution, trade-off between spectral resolution and background radiant flux at the detector, and the extent to which modern spectrometers fulfil the conditions for exploiting the benefits of high resolution in ICP-AES. These benefits are discussed in terms of limits of detection, selectivity, and limits of determination. It is shown that, in the case of line overlap, the conventional determination of limits of detection yields irrealistic values, which, in addition, entirely veil the actual benefits of high resolution spectroscopy. The vital profits are related with the selectivity and can be quantitatively expressed in terms of the limit of determination, as defined in this paper. It is concluded that, in the case of line overlap, analytical performance gains much more from an increase in selectivity than from a reduction of conventional detection limits. The full recognition of the implication of this conclusion may still substantially stimulate the further improvement of the analytical performance of AES by the exploitation of high resolution spectroscopy, the optimization of the gaseous atmosphere and the operating conditions of the source, and selective volatilization, where appropriate.

Mechanisms in hydride generation AAS

Abstract: Results of recent studies on the mechanisms playing a role in hydride generation AAS are discussed and compared with results obtained elsewhere. Within 10 ms after mixing the alkaline NaBH4 solution with the acid sample solution, the NaBH4, is decomposed, so hydride formation proceeds even faster. The separation of the hydride from the liquid takes much more time, however. The interference by heavy metal ions is caused by their catalytic action on the NaBH4 decomposition: the reagent is decomposed before it has reacted with the analyte. In the determination of selenium the presence of iodide has a beneficial effect on the interference of heavy metals. This is attributed to a catalytic effect of iodide on the reaction between NaBH4 and Se(IV). The presence of iodide in the NaBH4 solution also has the effect that the concentration of NaBH4 required for complete conversion of Se(IV) to SeH2 is reduced from 0.16 to 0.001%. A discussion is given on some mechanisms that have been proposed for the atom formation in the cuvette. The mechanism may depend on the analyte considered, the temperature and other parameters, and radicals are probably involved. At high analyte concentrations or long residence times of the gas mixture in the cuvette analyte losses may occur by dimerization (As, Se) or condensation (possibly after oxidation). Such effects are promoted by the tube walls. In developing procedures and apparatus, results mentioned should be considered. Several suggestions are discussed.

Determination of 2,3,7,8-tetrachlorodibenzo-p-dioxin in commercial chlorophenols and related products

Abstract: We have recently published a procedure [1] which allows the selective determination of 2,3,7,8-TCDD in the presence of a large excess of other polychlorinated dibenzodioxins (PCDD) and polychlorinated dibenzofurans (PCDF). This method was applied for the determination of 2,3,7,8-TCDD in several samples of chlorophenols and related products.

Laser induced fluorescence and ionization spectroscopy: Theoretical and analytical considerations for pulsed sources

Abstract: Several theoretical considerations are presented for the single resonance (single step) and double resonance (double step) techniques of fluorescence and ionization spectroscopy in flames and plasmas with tunable pulsed dye laser excitation. For short (several nanoseconds) laser pulses, single step excitation with one laser beam followed by collisional ionization can be useful from an analytical point of view even though ionization yields are low because of the short irradiation time. When two lasers, tuned to two connected atomic transitions, are spatially and temporally coincident in the atom cell, the ionization efficiency is greatly enhanced making the technique extremely sensitive, down to pg/ml levels. Atomic fluorescence suffers from losses due to such enhanced ionization process, the losses being more severe the closer the final excited level is to the ionization continuum. It is then shown that double resonance ionic fluorescence in an inductively coupled plasma is more suitable if high sensitivity needs to be achieved. The experimental results were obtained with an excimer laser (XeCl) which simultaneously pumped two dye lasers. The fluorescence and ionization techniques are also compared in terms of the potential interferences expected in the analysis of real samples.

Selective determination of 2,3,7,8-tetrachlorodibenzo-p-dioxin in the presence of a large excess of other polychlorinated dibenzodioxins and polychlorinated dibenzofurans

Abstract: A procedure is described for the selective separation of 2,3,7,8-TCDD from all other PCDDs and PCDFs. For this purpose the mixture of PCDDs and PCDFs is fractionated on Alumina Woelm B Super I in such a manner that all PCDDs and PCDFs are eluted prior to 2,3,7,8-TCDD. This procedure allows a more sensitive quantitative determination of 2,3,7,8-TCDD in samples which contain 2,3,7,8-TCDD only as a very minor fraction of the other TCDDs or PCDDs and PCDFs. Determination of 2,3,7,8-TCDD in pentachlorophenol and in a waste sample from 2,4-dichlorophenol production by this procedure is described.

N,N-Dialkyl-N′-benzoylnarnstoffe als Fällungs- und Extraktionsreagentien

Abstract: Bei den untersuchten N,N-Dialkyl-N′-benzoylharnstoff-Chelaten fuhrt der Ubergang von S,O- auf Se,O- und S,S-Koordinationsstellen zu einem Stabilitatsgewinn bei Metallionen mit uberwiegendem (b)-Charakter und zu einem Anstieg der Saurestarke der Chelatbildner. N,N-Diethyl-N′-benzoylharnstoff (Koordinationsstellen O,O) bildet unter den Bedingungen der potentiometrischen Titration keine Komplexe.

Multielement analysis of environmental samples by total-reflection X-ray fluorescence spectrometry, neutron activation analysis and inductively coupled plasma optical emission spectroscopy

Abstract: In environmental research and protection trace elements have to be determined over a wide range of atomic number, down to very low concentrations, and in quite different matrices. This challenge requires the availability of complementary analytical methods characterized by a high detection power and few sources of systematic errors. Besides, the capacity of multielement detection is often desired since it facilitates the tackling of many problems in which numerous trace elements are of direct concern. Total reflection X-ray fluorescence, neutron activation analysis and inductively coupled plasma optical emission spectroscopy, in principle, fulfill these requirements quite well. However, each method has its domain, and the application to certain sample species may be less promising. Under this aspect, the paper summarizes some recent developments and investigations, including intercomparisons as far as possible. Various matrices are considered: rainwater and airborne particulates, soil samples, river sediments and suspended particulate matter, river water filtrates, ovean water, and organic matrices. Capabilities and limitations are discussed. Sample preparation techniques are described if they are new or essential for achieving the results given.

Elucidating atomization mechanisms by simultaneous mass spectrometry and atomic absorption spectrometry

Abstract: Mechanisms responsible for atomization of selenium in graphite furnaces and for stabilization that occurs when nickel is added to selenium are investigated by mass analyzing, in real-time, the gaseous species from furnaces heated in vacuum and in atmospheric pressure environments. For the latter case, the analysis is done on a molecular beam formed from free-jet expansion of gases from the furnace. The apparatus for doing this is described. Results from the two experimental techniques, when compared, indicate that the primary loss of selenium at low temperatures is from thermal dissociation of selenium dicarbide. Secondary losses are due to vaporization of the dimer and the oxides. Nickel nitrate inhibits formation of the dicarbide, the dimer and the oxides. Mechanisms that are responsible for these findings are postulated.

A compact electrode assembly for voltammetric measurements with solid electrodes

Abstract: An electrode assembly is presented consisting of a cell compartment of plexiglass and an electronic circuit for automatic performance. It was especially designed for the use with polarographs PAR 264, 264 A, 384 and 384 B when working with solid electrodes. A special attempt was made to reduce the metallic parts of the assembly to a minimum in order to avoid contamination risks when analyzing heavy metals.

IR-spectroscopy of the atmosphere

Abstract: The infrared technique of measuring trace gases in the air has been evolving for many years, with rapid progress during the last ten years. Air pollution research requires such measurements for mixing ratios as low as 10−10. This calls for long optical paths, such as the path from a high altitude observing point to a setting sun. At ground level the best way to achieve a long enough path is to use J.U. White's 3-mirror multiple-pass cell. The infrared method has had its greatest success in the study of the upper atmosphere using balloon-borne spectrometers aimed at the sun. Measurements through the upper atmosphere do not have significant interference from water vapor. At ground level, however, the water vapor absorbs nearly everywhere in the spectrum, and it is necessary to detect the trace gases by the small perturbations they make on the water vapor spectrum. The Fourier transform (FT) spectrometer has been responsible for recent progress. For studies in the lower atmosphere one can obtain superb spectra by combining an FT instrument of about 0.1 cm−1 resolution with a White cell made from mirrors of modest size. Nitrogen-cooled detectors should be used. The path may be in the open air. With an FT instrument, signal fluctuations caused by air turbulence do not appear to introduce noise into the spectrum. This is a result of the multiplexing and the high frequency modulation. Pollutants that have been measured by infrared in ambient air have included HNO3, HNO2, NH3, O3, CO, CO2, SO2, NO, NO2, H2CO, HCOOH, hydrocarbons, peroxy nitrates, HCl and HF. Further study should extend this list.

Ein Verfahren zur Erzeugung und analytischen Charakterisierung von Brandgasen

Abstract: Es wird ein Verfahren beschrieben, mit dessen Hilfe es moglich ist, Substanzen unter definierten Bedingungen bezuglich Temperatur, Sauerstoffangebot und Verweilzeit zu verbrennen und die entstehenden Brandgase analytisch zu erfassen. Die Verbrennungsapparatur wurde unter besonderer Berucksichtigung der Erfordernisse fur die analytische Probenahme konzipiert. Das Verfahren erlaubt es, die unter definierten reproduzierbaren Verbrennungsbedingungen erzeugten Brandgase zu untersuchen und durch Variation der Randbedingungen ein Gesamtbild der bei einem realen Brand moglicherweise entstehenden Stoffe zu erhalten. In drei voneinander unabhangig arbeitenden Laboratorien wurden mit funf Modellstoffen gut ubereinstimmende Analysenergebnisse erhalten.

Hydride generation-graphite furnace atomic absorption spectrometry: new prospects

Abstract: Methods are described for the interference free determination of As and Se in seawater as well as marine tissues and sediments based on the generation of AsH3, and SeH2 using NaBH4 with subsequent trapping in a graphite furnace at 600° C. Calibration is achieved with simple aqueous working curves having sensitivities of 24±4 and 72±17 pg/0.0044 A for As and Se, respectively. Absolute detection limits of 30 pg As and 70 pg Se are estimated. Precision of determination is 2–3% for As and 5–10% for Se.

Determination of nitrate and nitrite by continuous liquid-liquid extraction with a flow-injection atomic-absorption detection system

Abstract: A flow injection system coupled on-line with a continuous liquid-liquid extractor is used for the indirect determination of nitrate and nitrite with an atomic-absorption detection system. These anions form ion-pairs with the copper(I)-neocuproine chelate which are extracted into methyl-isobutyl-ketone, the atomic-absorption signal of copper from the organic phase being proportional to the nitrate or nitrite concentration. The methods proposed herein are suitable for determining nitrate or nitrite at the βg ml−1 level with a sampling frequency of 35 ± 5 h−1. The methods compare favourably with their batch counterparts with regard to sensitivity, selectivity, sample volume and sampling frequency.

Stability spectra for the description of copper-humic complexes A fluorescence quench study*

Abstract: The fluorescence of humic substances (HUS) is quenched by paramagnetic metal ions. This principle was applied to the titration of aquatic HUS with copper(II) under defined reaction conditions (pH 6.8). For the assumption of 1∶1 complex formation conditional stability constants (K′) were determined. Stability spectra are introduced to show the influence of the ligand to metal ratio onK′. For isolated brown-water HUSK′ values range from 2 × 106 to 105 for high and low ligand to metal ratios, respectively. The structure of the stability spectra depends on the origin and kind of the HUS.

Analytical inductively coupled plasma spectroscopies — past, present, and future

Abstract: Plasma analytical spectroscopy now has broad generic implications, because a variety of plasmas have been found useful for spectroscopic analytical applications. Among those of contemporary interest, only the inductively coupled versions have demonstrated their flexibility and analytical merit as atomization cells for atomic flourescence, as excitation cells for atomic emission and as ionization cells for mass spectroscopy. Collectively, these three modes of observation are exerting a major impact on the way elemental analyses are being performed. In spite of their technical and commercial success to date, all three approaches still present many opportunities for creative research. The major driving force behind continuing research efforts is the desire to attain even better accuracy and precision, to achieve even higher powers of detection, to improve the means (hardware and software) for performing analyses with more convenience, confidence and directness, and to better understand the complicated structure and mechanism of the plasma itself on a fundamental level. The experimental approaches being utilized to achieve these goals are reviewed and evaluated. The demands being placed on the analyst by the nature of sample and the analytical information desired is also inspiring the development of major front and back-end innovations. Those innovations that are finding acceptance are critically reviewed.

Optimising precision in standard additions determinations

Abstract: The effect of the size of the added increment in standard additions determination on precision is evaluated by computer simulation. The precision obtained for different modes of calculating results is compared for double and single additions. The use of double additions up to the top of the linear range, combined with calculation of results by a weighted linear regression, is recommended.

Distinction of coals and their extracts by field ionization mass spectrometry and pattern recognition

Abstract: For the first time, uni- and multivariate statistical methods have been performed, using data sets of pyrolysis (Py)-field ionization (FI)-mass spectrometry (MS) in the range from m/z 70 to m/z 1,000. Py-FIMS is a suitable tool to characterize the volatile fractions of different coals and their pyridine extracts in vacuum. The features of this method are reduced mass spectrometric fragmentation and thermal production of high-mass primary fragments. Heating in the range from 50 to 500° C with a rate of 0.4° C/s gives very similar spectra and high relative abundance of every possible ion between m/z 200 and m/z 800, therefore it is not easy to distinguish the coals and their extracts. However, by non-linear mapping, all coals investigated and their corresponding extracts are clearly separated. Feature scaling using Fisher ratios showed, that the most characteristic ions for obtaining this clear differentiation are only of minor relative abundance. The examples of three different coals and their pyridine extracts shown here, indicate the potential of the combination of mass spectrometric and chemometric methods for detecting slight differences in very complex mixtures of substances or pyrolysates of fossil fuels.

Schwermetall-Spurenbestimmung mit einem kompakten Thermionen-Quadrupol-Massenspektrometer

Abstract: Es wird ein Verfahren beschrieben, welches eine Spurenbestimmung der Schwermetalle Pb, Cd, Tl, Cu und Zn durch massenspektrometrische Isotopenverdunnungsanalyse bei Verwendung eines kompakten Thermionen-Quadrupolgerates erlaubt. Mit dieser Methode werden sehr verschiedenartige Probenmaterialien, wie Klarschlamme, Boden, Sediment, Phosphaterz und Mullasche analysiert. Die angewandten Aufschlusverfahren ermoglichen grundsatzlich eine Unterscheidung zwischen dem Totalgehalt der Schwermetalle sowie dem in Konigswasser loslichen Anteil. Als Isolierungsmethoden werden alternativ eine elektrolytische Abscheidung und eine ionenaustausch-chromatographische Abtrennung diskutiert. Dabei ermoglicht eine gemeinsame Elektrodeposition der Elemente Pb, Cd, Tl und Cu auch die entsprechende massenspektrometrische Oligoelementbestimmung. Diese ist auf Proben mit nicht zu extremen Schwermetallgehalten anwendbar. Dagegen kann die Methode bei chromatographischer Abtrennung der Elemente ohne Einschrankung eingesetzt werden. Soweit Standard-Referenzmaterialien analysiert werden, stimmen die Ergebnisse mit den zertifizierten Werten uberein. Vergleiche mit den massenspektrometrischen Ergebnissen bei Verwendung eines Magnetgerates zeigen innerhalb der Fehlergrenzen identische Werte, so das mit dem kompakten und einfach handhabbaren Quadrupolgerat fur die definitive Methode der massenspektrometrischen Isotopenverdunnungsanalyse eine breitere Anwendung als bisher offen steht. Die Nachweisgrenzen des beschriebenen Verfahrens liegen fur Pb bei 3 ng/g (Elektrolyse) bzw. 13 ng/g (Ionenaustauscher), fur Cu bei 2 ng/g, fur Cd und Tl bei 6 ng/g und fur Zn bei 27 ng/g. Damit konnen alle umweltrelevanten Materialien der beschriebenen Art auf die genannten Schwermetalle hin analysiert werden.