K. Payer

A new automatic combustion method for the liquid scintillation assay of tritium and carbon-14 in singly or doubly labelled organic materials

An automatic, rapid combustion method has been developed for the determination of tritium and14C in singly or doubly labelled organic materials by liquid scintillation counting. The sample is burned in a stream of oxygen. The water formed and its tritium content are retained from the gas stream in an absorber containing a small amount of diethyleneglycol monoethyl ether. Radioactive carbon dioxide, if included in the combustion products, is transferred into 3-methoxypropylamine. The final solutions ready for counting are obtained in less than three minutes. Quantitative collection recoveries for both tritium and14C are achieved and no cross-contamination occurs.

An automatic carbon-14 gas analyzer for organic compounds and biological samples

Abstract The present paper concerns automatic measurement of the radioactivity of substances labeled with carbon-14 isotope. The organic compounds or biological samples are combusted in an oxygen chamber. The oxygen excess is converted by hydrogen into water vapor in a reactor filled with copper and copper oxide. The water is retained by condensation and the carbon dioxide is swept by means of a counting gas, preferably propane or butane or a mixture of such gases, into an anticoincidence counter. The carbon-14 gas analyzer allows the measurement of carbon-14 isotope with high accuracy and sensitivity in a fully automated way, entirely free of manual intervention.

Automatic isotope gas analysis of tritium labelled organic materials

An isotope analytical procedure and an automatic instrument developed for the determination of tritium in organic compounds and biological materials by internal gas counting are described. The sample is burnt in a stream of oxygen and the combustion products including water vapour carrying the tritium are led onto a column of molecular sieve-5A heated to 550 °C. Tritium is retained temporarily on the column, then transferred into a stream of hydrogen by isotope exchange. After addition of butane, the tritiated hydrogen is led into an internal detector and enclosed there for radioactivity measurement. The procedure, providing quantitative recovery, is completed in five minutes. It is free of memory effect and suitable for the determination of tritium in a wide range of organic compounds and samples of biological origin.

A semi-automatic combustion method for the simultaneous determination of3H and35S in doubly labelled organic materials by liquid scintillation counting

A sample preparation method developed for the simultaneous liquid scintillation assay of tritium and35S in doubly labelled organic materials is described. The sample is burnt in a stream of oxygen and the radioactive isotope carriers formed are collected separately for individual counting.35S content of the sample is measured as a dilute sulfuric acid solution, while the tritium is counted as water. The procedure is free of cross-contamination and memory effect, provides quantitative analytical recovery, and the final solutions ready for counting are obtained in twelve minutes.

Isotope gas analysis of tritium-labelled water by means of an automatic apparatus

A procedure and an automatic apparatus designed for the radioactivity measurement of tritium-labelled water in the gaseous phase are described. The method is based on the conversion of water to hydrogen, methane and carbon monoxide in a carbon-packed quartz reactor. The reaction products are swept by hydrogen carrier gas into a piston-type counter tube. Methane is fed to the radioactive gaseous mixture, and the radioactivity of the hydrogen-methane-carbon monoxide mixture is measured in the limited proportional region. The radioactivity values are correlated with the weight of the sample taken and the results are corrected for the ‘memory effect’ obtained in the measurement of inactive water samples. The standard deviation of the procedure, characteristic of its reproducibility, is lower than ±0.5% rel. at preset number of counts.

Anwendung von Mikromethoden in der organischen Isotopengasanalyse

ZusammenfassungVerfahren zur radiochemischen Analyse organischer Substanzen, die mit14C, Tritium bzw.35S markiert sind, wurden angegeben. Diese ähnlich der organischen Mikroanalyse durchführbaren Methoden beruhen auf Messungen der Radioaktivität in der Gasphase ohne Anwendung eines evakuierbaren Systems. Mit weichenβ-Strahlern markierte organische Substanzen lassen sich so mit mikroanalytischer Genauigkeit mit Hilfe einer einfachen Apparatur bei einem Zähleffekt von 96 bis 98% messen.SummaryAtmospheric procedures are presented for the isotopic analysis of organic compounds labelled with14C, tritium or35S. These methods performed similarly to organic microanalyses may be used for radioactive measurements in the gas phase without applying a vacuum system. Radioactive measurements of organic compounds labelled with weak beta-emitters may be carried out by atmospheric methods with microanalytical accuracy in a simple apparatus at a counter efficiency of 96–98%.

Automatic isotope gas analysis of tritium labelled organic materials: II. Determination of tritium in organic compounds with a pyrolytic sample decomposition method combined with isotope exchange

An analytical procedure and an automatic apparatus are described for the determination of tritium in organic compounds by gas counting. The sample is pyrolysed in hydrogen atmosphere at 1000°C, then, with hydrogen, the decomposition products are rinsed through a column of molecular sieve-5A heated to 550°C. Tritium in water, hydrogen sulphide, ammonia and hydrogen cyanide is transferred into the hydrogen stream by isotope exchange completed on the column. The inactive water vapor, hydrogen sulphide, ammonia and hydrogen cyanide as well as carbon dioxide are removed from the gas stream by appropriate absorbents, and the radioactive hydrogen together with tritiated methane, carbon monoxide and nitrogen included in the pyrolytic products is led into an internal proportional counter tube for radioactivity measurement. The method provides quantitative recovery, it is free of memory effect and suitable for the rapid assay of a wide variety of organic compounds containing C, H, N, O, S in addition to tritium.

Automation of the gas analysis of14C-labelled compounds utilizing a piston-type counter tube

In this paper an automatic apparatus designed for the radioactivity measurement of14C-labelled organic compounds in the gaseous phase is described. The labelled organic compounds are combusted in a mixture of argon and oxygen. After combustion the oxygen content of the gas is eliminated by passing it through a copper packing. The water and heteroelements present are also removed and the radioactive carbon dioxide gas is swept by argon carrier gas into a piston-type counter tube. In the counter tube the piston forming a dividing wall moves forward in accordance with the rate of combustion and sweeping, and thus sucks the gases leaving the combustion tube into the effective tube volume. The anode wire is carried by a reel located in the piston and a spring device ensures its stretched state. At the end of the sweeping period methane is fed into the counter tube and the activity of the argon—methane—carbon dioxide mixture is measured in the limited proportional region. Manual and automatic operation is possible. The piston-type counter tube provides possibility for strandardization by means of extrapolation and for measurement of absolute activities.

Isotope gas analysis of tritium-labelled organic compounds based on pyrolytical decomposition

SummaryA procedure has been developed for the activity measurement of tritium-labelled organic compounds in the gas phase. The organic compounds are pyrolysed in hydrogen carrier gas at 1150° and the decomposition products are swept through a carbon packing in accordance with the principle of the oxygen determination developed byUnterzaucher andBürger. The radioactive gas mixture obtained from the sample is swept by the hydrogen carrier gas flowing continuously through the reactor into a proportional counter tube, after the addition of propanebutane counter gas. By closure of the counter tube at a suitable moment, the radioactive gas is quantitatively trapped in the counter tube. The activity is measured in the limited proportional region. No memory effect occurs. The preparation of the sample requires 12 minutes; the relative standard deviation of analysis is <0.5%.ZusammenfassungEin Verfahren zur Aktivitätsbestimmung bei tritium-markierten organischen Verbindungen in der Gasphase wurde ausgearbeitet. Die organischen Substanzen werden in Wasserstoff als Trägergas bei 1150° pyrolysiert. Die Zersetzungsprodukte werden wie bei der Sauerstoffbestimmung nachUnterzaucher bzw.Bürger über eine Kohleschicht geleitet. Das radioaktive Gas-gemisch aus der Probe gelangt mit dem kontinuierlich strömenden Trägergas in ein Proportionalzählrohr, nachdem Propan-Butan-Zählgas zugesetzt wurde. Man schließt das Zählrohr im richtigen Augenblick, um das radioaktive Gas quantitativ zu erfassen. Die Aktivität wird im Proportionalbereich gemessen. Ein Memory-Effekt tritt nicht auf. Die Vorbereitung der Probe beansprucht 12 Minuten. Die relative Standardabweichung ist kleiner als 0,5%.