Mikrobestimmung von Kohlenstoff und Wasserstoff, sowie von 14C, Tritium und Deuterium im Stickstoffstrom

Zusammenfassung Eine mikroanalytische Kohlenstoff-Wasserstoffbestimmung wird beschrieben, bei der die organische Substanz im Stickstoffstrom verbrannt und deren Crackprodukte mit Sauerstoff oxydiert werden. Halogene und Schwefel werden vom Verbrennungskatalysator (nach Körbl) absorbiert, während eventuell entstandene Stickoxide an einer Kupferschicht zur Reduktion gelangen. Die entstandenen Verbrennungsprodukte CO₂ und H₂O können gravimetrisch erfaßt oder bei radioaktiven Proben durch entsprechende Absorptionsmöglichkeiten in einem Flüssigkeits-Szintillationszähler zur Zählung gebracht werden.Stark quenchende einfache, sowie doppelt markierte Proben, die man auch durch Modifikationen des Zählgeräts nicht mehr genau auszählen kann, können mit gleich hoher Zählausbeute wie nichtquenchende erfaßt werden (75% für ¹⁴C und 30% für ³H), da keine störenden Fremdgase die Zählung beeinflussen.Deuterium wird durch Ausmessen der OD-Bande bei 2500 cm^–1 mit einem Infrarot-Spektrometer quantitativ bestimmt.

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Microanalytical determination of carbon and hydrogen, ¹⁴C, tritium and deuterium in a stream of nitrogen

A microanalytical method for the determination of carbon and hydrogen is described. The procedure involves the combustion of the organic substance in a stream of nitrogen and the oxidation of the decomposition products with oxygen. Halogens and sulphur are absorbed by the combustion catalyst (according to Körbl), whereas nitrogen oxides are reduced on a copper surface. The combustion products, CO₂ and H₂O are determined gravimetrically; in the case of radioactive samples they are appropriately absorbed and counted in a liquid scintillation counter. Strongly quenching singly and doubly labelled samples, which cannot be accurately counted even by modification of the counting device, give equally high radioactive yields (75% for ¹⁴C, 30% for ³H), since counting is not influenced by other gaseous impurities. Deuterium is quantitatively determined by measuring the intensity of the OD-signal at 2500 cm^–1 with an infrared spectrometer.

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Herrn Prof. Dr. H. Schmid bin ich für das wohlwollende Verständnis meinen Arbeiten gegenüber zu bestem Dank verpflichtet. Sämtliche Glas- und Quarzgeräte wurden in der Glasbläserei unserer Institute von Herrn B. Thueler angefertigt, wofür ich auch ihm an dieser Stelle danken möchte.     

Radiochemische Untersuchungen zur Verteilung von129J und3H in Bestrahltem Kernbrennstoff aus Leistungsreaktoren

The working techniques used for the investigation of¹²⁹I and³H sectional distribution in highly irradiated UO₂ pellets are described. The analytical samples are taken by a micro drilling technique. For the determination of¹²⁹I concentration in the UO₂ samples neutron activation analysis following iodine separation from uranium and bulk fission products is used.³H is measured by liquid scintillation counting after distillation. Reliability of the analytical results is discussed as well as possible interferences.     

Instrumentelle Kompensation des Quencheffektes bei der Bestimmung von 14C und 35S

Zusammenfassung Ein Quencheffekt tritt auch nach Oxydation der organischen Probe auf. Dieser ist bedingt durch gewisse Verbrennungsprodukte, wie NO₂, Halogene, SO₂ und SO₃. Es wurde gefunden, da\ man den Quencheffekt der Verbrennungsprodukte bei der Bestimmung von ¹⁴C und ³⁵S ausschalten kann, wenn man die Spannung des Data-Photomultipliers bis zu einem gewissen Punkt (Kompensationspunkt) erhöht und die Messung in einem ZÄhlfenster durchführt. Der Kompensationspunkt wird graphisch ermittelt; hierzu mi\t man die ZÄhlrate des reinen Absorbens sowie die ZÄhlrate des Absorbens, das die maximal zu erwartende Menge Verbrennungsprodukt enthÄlt, bei verschiedenen Data-Spannungen. Der Zusammenhang zwischen der instrumenteilen Kompensation und dem Energiespektrum von ¹⁴C wird aufgezeigt. Bei der Bestimmung von Tritium lÄ\t sich der Quencheffekt nicht kompensieren, denn das Energiespektrum von Tritium wird durch eine Quenchverbindung anders beeinflu\t als das Spektrum von ¹⁴C bzw. ³⁵S.

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Summary After combustion of the organic sample a quenching effect is observed, due to several combustion products as NO₂, halogens, SO₂, and SO₃. We found, that it is possible to eliminate quenching of the combustion products in the determination of ¹⁴C and ³⁵S, if the high voltage of the data-photomultiplier is raised to a certain level (compensation point) and if the counting is performed in a window. The compensation point is calculated graphically by determining the counting rate of the pure absorbant and the absorbant plus the highest expected amount of combustion products. The relation between instrumental compensation and the energy spectrum of ¹⁴C is elucidated. It is not possible to compensate quenching in the determination of tritium, because the energy spectrum of ³H is influenced in a different way than the spectrum of ¹⁴C and ³⁵S.

     

Neuere Verfahren zur Analytik von radioaktiven und stabilen Isotopen des Wasserstoffs, Kohlenstoffs, Stickstoffs und Sauerstoffs

Zusammenfassung Mißt man Tritium in der Gasphase mit Propan als Zählgas bei einer definierten Gesamtverstärkung im Arbeitsbereich eines Einkanaldiskriminators mit hoher Dynamik, so ergeben sich wesentlich geringere Nulleffekte, ohne daß die Zählausbeute für Tritium vermindert wird. Bei der zusätzlichen Verwendung einer Antikoinzidenzabschirmung zeigen 150 ml Zählrohre Nulleffekte um 1 ipm. Dadurch erhält man für das Verhältnis Zählausbeute²/Nulleffekt Werte von 2500. Die exakte Zuordnung von Zerfallsenergie und Impulshöhe wird durch einen Peak der 60 keV -Strahlung von Americium-241 erzielt, ohne daß die Geometrie von Zählrohr zur Strahlenquelle von Einfluß ist. Dadurch ist es auch möglich, T und ¹⁴C nebeneinander in Gaszählrohren zu messen. Die Methode wird mit der Flüssigkeitsszintillations-Zählung praktisch verglichen. Es wird ein einfaches Verfahren zur Probenbereitung von ¹⁸O- und D-markierten Proben beschrieben und seine Anwendbarkeit durch zahlreiche massenspektrometrische Analysen bewiesen. Zur ¹⁸O-Bestimmung werden die Substanzen, von wenigen Ausnahmen abgesehen, in geschlossenen Ampullen ohne Chemikalien pyrolysiert. Selbst Stearylalkohol ergibt genügend CO₂. Damit ergibt sich von der manuellen Technik her ein weitgehend einheitliches Verfahren für die Probenbereitung von Verbindungen, die mit D, T, ¹³C, ¹⁴C, ¹⁵N [11] und ¹⁸O markiert sind. Es werden experimentelle Einzelheiten mitgeteilt.

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New methods for the analysis of radioactive and stable isotopes of hydrogen, carbon, nitrogen and oxygen

Measuring tritium in gas counting tubes filled with propane and using a single channel discriminator with great dynamic range yields a considerably lower background, without diminishing the counting yield. If in addition an anticoincidence shield is used, a 150 ml counting tube shows about 1 cpm background. The figure of merit goes up to about 2500. An exact coordination between particle energy and impulse size is reached by the 60 keV -radiation of americium-241, without an influence of the relative geometry of the counting tube and the radiation source. By this procedure it is also possible to measure separately and simultaneously T and ¹⁴C in one counting tube. The method is experimentally compared with liquid-scintillation counting.A simple procedure is described for preparing samples for the determination of ¹⁸O- and D-labelled compounds. The applicability is shown by numerous mass-spectrometric analyses. For determining ¹⁸O, with a few exceptions, the labelled compounds are pyrolized in sealed ampoules without any chemicals. Even stearyl alcohole delivers enough carbon dioxide. By this technique a rather uniform procedure is given for preparing samples in order to measure compounds labelled with D, T, ¹³C, ¹⁴C, ¹⁵N [11] and ¹⁸O. Experimental detailes are presented.

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Wir danken der Deutschen Forschungsgemeinschaft und dem Ministerium für wissenschaftliche Forschung, die einem von uns (H. G.) für 8 bzw. 9 Monate ein Stipendium als wissenschaftlicher Mitarbeiter zur Verfügung stellten. R. T. dankt der Alexander v. Humboldt-Stiftung für ein Stipendium. Frl. E. Wolf und H. Pflaumer sei für ihre zuverlässige und fleißige Mithilfe gedankt. Die Untersuchungen zur ³H-Messung wurden von K. Pelling, Max-Planck-Institut für Biologie, Tübingen, angeregt und z. T. von der Stiftung Volkswagenwerk finanziert.     

Vergleich der Meßgenauigkeit der Szintillations-Zählung 3H- und/oder 14C-markierter Proben durch externe bzw. interne Standardisierung und Anwendung auf die Sauerstoff-Kolben-Verbrennung

After oxygen flask combustion scintillation samples often show an increase in counting rates for several hours. Even after such a time identically prepared samples are statistically significantly more different as one should expect by weighing and pipetting errors. The inconstant cpm values during the first hours and the differences between the samples can mostly be eliminated by quench correction curves (dependence of counting efficiency and external channel ratio upon oxygen concentration). The dpm values achieved according to this method show smaller standard deviations than by internal standardisation. The procedure of the external standardisation was examined for error propagation. A system of toluene/methanol/phenethylamine absorbs carbon dioxide and water quantitatively. With this mixture the following counting efficiencies are achieved: 25% for ³H, 85% for ¹⁴C and for samples containing ³H and ¹⁴C 15% for ³H and 10% for ¹⁴C if the ³H channel is adjusted according to Klein and Eisler.     

The problem of adsorption on silicagel in a liquid scintillation radiometry of14C labelled compounds

By means of liquid scintillation spectrometry we investigated the counting efficiency of the samples containing toluene solution of scintillator (PPO, butyl-PBD, PT) and 1-methyl[2−¹⁴C]imidazolidinone-2 adsorbed on the silicagel, depending on concentration of scintillator, mass of radioactive compound, and mass of another nonactive compound introduced to samples as an impurity. For the sake of comparison the efficiency of counting homogeneous samples and the ones with Ba¹⁴CO₃ deposit was determined. It was found, that the efficiency of detection of a radioactive compound adsorbed on the silicagel is conditioned by composition of adsorptive layer on the support surface.     

Determination of some elements by epithermal neutron activation analysis for the Arctic aerosol

Summary We have determined nineteen trace elements in 685 aerosol filter samples collected during 1964-1978 in northern Finland by the Finnish Meteorological Institute. In this paper we present some procedures and results for very short (~25 s), short (~3-54 min), and medium (12-35 h) lived isotopes as determined by epithermal NAA in conjunction with and without Compton suppression. Elements with a I_γ/σthratio are favorable to be determined by epithermal NAA. Silver was determined by a one minute epithermal irradiation because of a very short ¹¹⁰Ag half-life. Antimony, arsenic, cobalt, bromine, indium, iodine, potassium, silicon, tin, tungsten, and zinc were determined by a ten minute epithermal irradiation. For silver determination, samples were counted without transferring the filter from the irradiated vial, however, for ten minute irradiation all samples were transferred to a non-irradiated vial and counted both in the normal and Compton mode by the HPGe gamma-spectrometry system with a decay time of about 10 minutes and counting time of 15 minutes. Each day a maximum of 16 samples were irradiated and immediately following the short counting, these samples were loaded into an automatic sample changer in sequence of irradiation and counted for an hour in both normal and Compton modes. This has proven to be an extremely cost effective measure thus reducing the need to employ long-lived NAA to analyze other elements such as Ag, Co, Sn and Zn and Ag for air pollution source receptor modeling.     

Activation analysis of tin at nanogram level by liquid scintillation counting of121Sn

Tin is determined at the low nanogram level in biological samples by neutron activation using the pure β⁻emitter¹²¹Sn of half-life 27 hours. The method is based on the concept of extracting tin selectively into an organic phase, which, after addition of a scintillant (PPO), can be directly counted by liquid scintillation counting with near 100% efficiency. Tin is first selectively extracted as its iodide into toluene, stripped and then re-extracted selectively into a toluene solution of N-benzoyl N-phenylhydroxylamine for scintillation counting. Results are given for various biological reference materials.     

Fast neutron activation analysis of bulk coal samples for alumina,silica and ash

The fast neutron activation technique was applied to bulk samples (≈11 kg) of Australian black coal. The determination of alumina is based on the reaction ²⁷Al(n,p)-²⁷Mg by counting the 0.844-MeV peak (t_{$\text{1}\text{2}$} = 9.4 min). Silica is determined by means of the reaction ²⁸Si(n,p)²⁸Al; the 1.78-MeV peak (t_{$\text{1}\text{2}$} = 2.3 min) is counted and a correction for the interference from alumina is applied. The ash content is based on the correlation between ash and the sum of alumina and silica. The accuracies (1 SD) for the determination of alumina, silica and ash were 0.52% Al₂O₃, 0.79% SiO₂ and 1.02% ash, respectively. The ash, alumina and silica contents of the samples were in the ranges 8.8–37.5%, 1.3–10.3% and 6.4–22%, respectively.     

Bestimmung von Sulfid-, Sulfit- und Thiosulfat-Ionen nebeneinander in Bariumcarbonat und Strontiumcarbonat

In one sample the total “iodine titer” is determined by iodometric titration in acid medium. In a new sample the SO₂ from the sulphite ion is determined after distillation in presence of mercury(II)chloride from hydrochloric acid medium and in a third sample the thiosulphate ion is determined by iodometric titration in presence of cadmium acetate and formaldehyde. The concentration of sulphide ion is calculated from the results of the three titrations as difference. This method can be applied to the determination in magnesium carbonate and calcium carbonate. Standard deviation is ±0.0007% and ±0.0089% for SO₃ ^2? and S₂O₃ ^2?, respectively.     

Darstellung,Schwingungsspektren und Kristallstrukturanalyse von Di- und Trifluor-tetramethylammonium-Salzen

Synthesis, Vibrational Spectra, and Crystal Structure Analysis of Di- and Trifluoro-tetramethylammonium Salts The tetramethylammonium salts (CH₃)₃NCH₂F⁺ ( II ), (CH₃)₃NCHF₂⁺ ( III ), and (CH₃)₃NCF₃⁺ ( IV ) were prepared by quaternation of the corresponding fluoromethylamines. III was also generated from (CH₃)₃N and Zn/CF₂Br₂/KF in acetonitrile. II , III , and IV were characterized by NMR and vibrational spectroscopy, a normal coordinate analysis being undertaken for IV . The crystal structures of the iodides of III and IV have been determined. In both cations the N? CH₃ distances are on the average ( III 1.508(2) Å; IV 1.514(5) Å) longer than the N? CF valencies ( III 1.497(4) Å; IV 1.491(6) Å).     

Development of a sequential method for the determination of238U,234U,232Th,230Th,228Th,228Ra,226Ra,and210Pb. in environmental samples

A sequential analytical method for the determination of²³⁸U,²³⁴U,²³²Th,²³⁰Th,²²⁸Th,²²⁸Ra,²²⁶Ra and²¹⁰Pb in environmental samples was developed. Uranium and thorium isotopes are first chromatographically sepaaated using tri-n-octyl phosphine oxide (TOPO) supported on silica gel. The uranium isotopes are determined by alpha-spectrometry following extraction with TOPO onto a polymeric membrane. Thorium isotopes are co-precipitated with lanthanum fluoride before counting in an alpha spectrometer. Radium isotopes and²¹⁰Pb are separated by co-precipitation/precipitation with mixed barium/lead sulphate. Radium-226 is determined by gross alpha counting of the final BaSO₄ precipitate and²²⁸Ra by gross beta counting of the same source. Lead-210 is determined through beta counting of its daughter product²¹⁰Bi.     

Synthese und Charakterisierung von Natriumcyanamid

Synthesis and Characterization of Sodium Cyanamide The synthesis of Na₂CN₂ was carried out by reaction of sodium amide with sodium hydrogen cyanamide at 200 °C, in vacuum. Single crystals were obtained while heating the product (500 °C, 8 days) in silver crucibles. The title compound was characterised by single crystal X‐ray diffraction and IR‐spectroscopy (C2/m; Z = 2, a = 5.0456(3), b = 5.0010(3), c = 5.5359(3) Å; β = 110.078(5)°; R1 = 3.18%, wR2 = 6.35%, GOF = 1.078). The CN₂^2– units are linear exhibiting a C–N bond length of 1.236(1) Å, while sodium is coordinated by five nitrogen atoms forming a square pyramid. The structural relationships to aristotypic Na₂HgO₂ are pointed out.     

Optimization of liquid scintillation counting techniques for the determination of carbon-14 in environmental samples

The goal of this work was to optimize the liquid scintillation counting techniques for the determination of¹⁴C in stack effluent gases and in environmental samples such as biological and air samples. Carbon-14 activities in most environmental samples were measured with the direct CO₂ absorption method. The highest figures of merit were found through the variation of Carbosorb E and Permafluor V ratio, and measurement windows. The best condition was an 1:1 volume ratio. Average 2.35 g of CO₂ was reproducibly absorbed in the 20 ml mixture within 40 minutes. The counting efficiency determined by repeated analysis of NIST oxalic acid standard and the background count rate were measured to be 58.8±1.4% and 1.88±0.06 cpm, respectively, in case of saturated solution. The correction curves of counting efficiency for partially saturated solutions and for saturated solutions with quenching were prepared, respectively. The overall uncertainty of the sample specific activity for near background levels was estimated to be about 7% for 4 hours counting at 95% confidence level. Stack effluent gas samples were measured by a gel suspension counting method. After precipitation of CO₂ in the form of BaCO₃, 140 mg of which was mixed with 6 ml H₂O and 12 ml of Instagel XF. The counting efficiency was measured to be 71.5±1.7% and the typical sensitivity of this technique was about 510 mBq/m³ for a 100 min count at a background count rate of 4.7 cpm. For the benzene counting method measurements were performed with a mixture of 3 ml benzene and 1 ml of scintillation cocktail (5 g of butyl-PBD in 100 ml of scintillation-grade toluene) in a low potassium 7 ml borosilicate glass vial. The counting efficiency and the background count rate were measured to be 64.3±1.0% and 0.51±0.05 cpm, respectively. The long-term stability of samples has been checked for all the counting techniques over a two week period, during which no apparent change in counting efficiency and background level was found.     

Simultane Dezimilligrammbestimmung von Kohlenstoff, Wasserstoff und Stickstoff in organischen Substanzen

Zusammenfassung Die früher beschriebene Methode für die simultane Dezimilligrammbestimmung von Kohlenstoff, Wasserstoff und Stickstoff ist weiter entwickelt worden. Stickstoff wird unter vermindertem Druck gemessen und Kohlendioxid und Wasser werden ausgefroren und nicht mehr mit Lauge absorbiert. Die Standardabweichungen von 17 direkt nacheinander ausgeführten Analysen von Substanzen mit weit verschiedener Zusammensetzung (enthaltend unter anderem Fluor, Chlor, Brom, Jod, Schwefel, Phosphor und Kalium) betrugen für Kohlenstoff 0,21%, Wasserstoff 0,23% und Stickstoff 0,10% (nur sechs der analysierten Substanzen enthielten Stickstoff). Die Zuverlässigkeit der Methode ist sehr gut. In der Regel brauchen nur Einzelanalysen ausgeführt zu werden.

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Summary The earlier described method for the simultaneous decimilligram determination of carbon, hydrogen and nitrogen has been further developed. Nitrogen is measured at reduced pressure and carbon dioxide and water are frozen out and no longer absorbed in potassium hydroxide. The standard deviations of a series of 17 analyses of samples with widely different compositions (containing among other elements fluorine, chlorine, bromine, iodine, sulfur, phosphorus and potassium) were: 0.21% for carbon, 0.23% for hydrogen and 0.10% for nitrogen (only six of the analyzed substances contained nitrogen). The reliability of the method is very good. As a rule it is not necessary to carry out duplicate analyses.

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Frühere Mitteilung W. Kirsten⁴.

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Die Arbeit wured durch Unterstützung durch die schwedischen staatlichen medizinischen und naturwissenschaftlichen Forschungsräte ermöglicht.     

Analyse von Paraformaldehyd

Zusammenfassung Es wird ein Radiogaschromatograph zur Bestimmung von ¹⁴C oder ¹¹C in organischen Substanzen beschrieben, in dem alle Verbindungen nach Durchlaufen der Trennsäule kontinuierlich verbrannt werden. Wasser, NO₂ und SO₂ werden beim Durchlauf durch Absorptionsröhrchen entfernt und das CO₂ bei Raumtemperatur durch eine WLF-Zelle und ein inneres Proportionalzählrohr geleitet. Dies Verfahren ist besonders geeignet für hochsiedende Verbindungen und umgeht die Probleme, die bei der Heizung von Zählrohren auftreten.Die Verwendung von Co₃O₄ als Verbrennungskatalysator macht eine genaue Temperaturkontrolle des Verbrennungsofens überflüssig. Die Vollständigkeit von Verbrennung und Absorption und die Konstanz des Zählrohr-Wirkungsgrades unter verschiedenen Bedingungen werden demonstriert.

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Summary A radiogaschromatograph for the determination of ¹⁴C or ¹¹C in organic substances by continuous combustion of the column effluents and internal proportional flow counting of the resulting CO₂ at room temperature is described. Water, SO₂, and NO₂ are continuously removed by absorption. This method is particularly suitable for the analysis of high boiling compounds and avoids the problems associated with heated counters.The use of Co₃O₄ as combustion catalyst makes accurate temperature control of the combustion furnace unnecessary. Completeness of combustion and absorption and constancy of counter efficiency under varying conditions are demonstrated.

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Nach Arbeiten, die mit Mitteln der US-Atomenergiekommission durchgeführt wurden.

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Die vorliegende Arbeit ist ein Teil der Dissertation von Bodo Diehn, KU 1963.     

Determination of Bromide,Chloride, and Fluoride in Cigarette Tobacco by Ion Chromatography after Microwave-Induced Combustion

A microwave-induced combustion (MIC) method was applied for cigarette tobacco digestion and further determination of bromide (Br), chloride (Cl), and fluoride (F) by ion chromatography (IC). Samples (up to 500 mg) were combusted at 20 bar of oxygen. Combustion was complete in less than 30 s, and analytes were absorbed in (NH₄)₂CO₃ solutions. A reflux step, not available in other systems, was applied to improve analyte absorption. Absorbing solution with 50 mmol L^?1(NH₄)₂CO₃ was selected because it showed recovery close to 100% for samples containing spikes of halogens. Accuracy of the proposed procedure was evaluated by analysis of certified reference materials and the agreement was better than 97% for all analytes using 50 mmol L^?1 (NH₄)₂CO₃ as absorbing solution and 5 min of reflux. Temperature during combustion was higher than 1400°C and the residual carbon content was always lower than 1%. With the use of the MIC system, up to eight samples could be processed simultaneously, and a single absorbing solution was suitable for all analytes. Limits of quantification by MIC and further IC determination were 0.50, 0.20, and 0.10 µg g^?1 for Br, Cl, and F, respectively.     

Über Polyphosphide von Chrom,Mangan, Ruthenium und Osmium. Synthese und Kristallstruktur von RuP4 und OsP4

On Polyphosphides of Chromium, Manganese, Ruthenium, and Osmium. Synthesis and Crystal Structure of RuP₄ and OsP₄ The new compounds RuP₄ and OsP₄ were prepared by annealing thr elemental components in the presence of iodine. Well developed crystals were obtained by reaction of the components in liquid tin. RuP₄ is triclinic, space group P1 , a = 7.519(8), b = 7.145(7), c = 4,713(5) Å, α = 100.48(10), β = 90.35(10), γ = 111.08(11)°, Z = 3. The structure was determined and refined from diffractometer data: R = 0.049 for 3532 F values, Ru is octahedrally surrounded by P. The P atoms are in tetrahedral coordination of Ru and P. All near neighbour interactions can be interpreted as two-electron bonds. This results in formal oxidation number +2 for Ru (d⁶ system). Thus, while the metal atoms in the related compounds CrP₄(Cr in d₄ configuration) and MnP₄ (d₅ configuration for Mn) form Cr chains and Mn pairs respectively, no short metal-metal interactions are present in RuP₄ · OsP₄ is isotypic with RuP₄ · CrP₄ and MnP₄ were prepared in the presence of iodine or from the tin melt without the application of pressure.     

The determination of traces of mercury in solid fuels by high-temperature combustion and cold-vapour atomic absorption spectrometry

A high-temperature combustion technique is described for the determination of mercury in coal, coal products including ash, and other samples of environmental interest. The liberated mercury is absorbed in an acidified potassium permanganate solution and determined by cold-vapour atomic absorption spectrometry. The vapour generation assemblage is constructed of standard ground-joint glassware, and is designed to produce non-transient signals suitable for either analog or digital recording devices. Accuracy and precision for 1-g coal samples is 0.02 μg g^-1.