US3682598A - Apparatus for the preparation of liquid form samples for radioactive isotope tracer studies - Google Patents

Apparatus for the preparation of liquid form samples for radioactive isotope tracer studies Download PDF

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US3682598A
US3682598A US820269A US3682598DA US3682598A US 3682598 A US3682598 A US 3682598A US 820269 A US820269 A US 820269A US 3682598D A US3682598D A US 3682598DA US 3682598 A US3682598 A US 3682598A
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sample
liquid
combustion
samples
water
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Niilo H Kaartinen
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Revvity Health Sciences Inc
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Packard Instrument Co Inc
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    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
    • G01N1/00—Sampling; Preparing specimens for investigation
    • G01N1/28—Preparing specimens for investigation including physical details of (bio-)chemical methods covered elsewhere, e.g. G01N33/50, C12Q
    • G01N1/44—Sample treatment involving radiation, e.g. heat
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01T—MEASUREMENT OF NUCLEAR OR X-RADIATION
    • G01T1/00—Measuring X-radiation, gamma radiation, corpuscular radiation, or cosmic radiation
    • G01T1/16—Measuring radiation intensity
    • G01T1/20—Measuring radiation intensity with scintillation detectors
    • G01T1/204—Measuring radiation intensity with scintillation detectors the detector being a liquid
    • G01T1/2042—Composition for liquid scintillation systems
    • G01T1/2047—Sample preparation
    • G—PHYSICS
    • G21—NUCLEAR PHYSICS; NUCLEAR ENGINEERING
    • G21G—CONVERSION OF CHEMICAL ELEMENTS; RADIOACTIVE SOURCES
    • G21G4/00—Radioactive sources
    • G21G4/04—Radioactive sources other than neutron sources

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  • U.S. Cl. 23-262 5 Claims ABSTRACT F THE DISCLOSURE Reiinements are provided in a system for preparing liquid samples for radioactive nuclide assays.
  • a primary sample containing at least one radioactive nuclide oxidizable to a recoverable gas-form oxide is oxidized, and the resulting combustion products are treated for the recovery of the radioactive nuclide oxide as a iinal liquid sample.
  • a gas-form oxide of a non-radioactive isotope of the radioactive nuclide is introduced. This introduction simultaneously increases recovery of the radioactive nuclide and decreases memory of the system.
  • the introduced oxide is water, corresponding to tritium in the primary sample
  • the resulting apparatus is additionally useful for monitoring both memory and background count, for making quenched standard samples uncontaminated by atmospheric oxygen, and for matching water quenching in samples obtained from primary samples of different size.
  • the present invention relates generally to the processing of fluid materials.
  • the invention relates to methods and apparatus for the preparation of samples for radioactive isotope tracer study or, in other words, to the preparation of samples for radioactive nuclide assays. More particularly, the invention concerns an improved system for preparing such samples by oxidation of a primary sample containing one or more radioactive nuclides.
  • combustion solves the fore- 3,682,598: Patented Aug. 8, 1972 going problems in that the combustion products are readily soluble in efficient scintillation solvents and there is little if any difliculty due to color or chemical quench eiiects.
  • An object of the present invention is to provide certain refinements to this system, which refinements are broadly applicable for the improvement of heretofore existing apparatus and methods.
  • a principal object of the present invention is to provide a method and apparatus for increasing the quantitative recovery of radioactive nuclides produced as oxides by the combustion of relatively small samples.
  • An associated object is to improve the separation of individual radioactive nuclides when the primary sample is double-labeled, or in other Words, contains a plurality of radioactive isotopes.
  • a general object of the invention is to provide a rapid, simple, and precise system for monitoring the extent of memory and the memory-free background count of an analytical apparatus.
  • a further object is to provide a method for making quenched standard samples uncontaminated from atmospheric oxygen; previously, quenched standards have been quite cliicult to prepare unless extensive provisions were made for excluding atmospheric oxygen.
  • Another advantage and object of the invention is to provide a system for producing liquid form samples having constant quench characteristics from primary samples of widely different sizes.
  • gure is a schematic diagram of a sample preparation system embodying the present invention, for use in the preparation of liquid form samples for radioactive nuclide assays.
  • a sample preparation system for use in the preparation of samples for radioactive isotope tracer studies, such as studies involving tissue distribution and residue levels of drugs in plants and animals.
  • a sample of the starting material containing the radioactive isotope tracer such as a sample of the plant or animal tissue, is burned to convert the carbon in the starting material to carbon dioxide and the hydrogen to water, and the radioactive isotope tracer is then recovered from the resulting combustion products.
  • radioactive isotope tracer For example, if the particular radioactive isotope tracer employed is 14C, it appears in the combustion products as 14CO2 gas; if the tracer is tritium (3H), it appears in the combustion products as 3H2O in the form of a condensable vapor. Although 14C and 3H are the most commonly employed tracers, it will be understood that a number of other radioactive isotopes may be employed, such as 35S which is converted to sulfate during combustion.
  • the compounds containing the isotope tracers are recovered from the combustion products, and separated from any materials therein which might interfere with the radioactivity determination.
  • the 3H2O is recovered by cooling the combustion products to condense the vapors therein, including the 3H2O, after which the condensed vapors are separated from the remaining gases.
  • the 14CO2 may also be recovered by condensation or freezing at extremely low temperatures, such as by the use of liquid nitrogen for example, but it is more conventional to react the 14CO2 with a liquid trapping agent such as ethanolamine; the resulting reaction product is then recovered and mixed with a liquid scintillator to provide a sample suitable for use in making a radioactivity determination.
  • the sample to be burned is placed in a sample basket which forms a part of the electrical ignition system, and also functions as a catalyst for eiiicient combustion for the sample contained therein.
  • the basket 10 is suitably made of platinum or a platinum-rhodium alloy, so that the basket can be used both as an electircal resistor in the ignition system and as a catalyst for the combustion of the sample.
  • a pair of electrical conductors 11 and 12 extend upwardly from a mounting plate 13, to support the basket 10 at the upper and lower ends thereof, while also making electrical contact with the basket to connect it into the electrical ignition system.
  • the conductors 11 and 12 extend vertically down through the plate 13 and terminate in depending connector pins beneath the plate 13.
  • the mounting plate 13 is supported on the top of a small platform 14 threaded on to the end of a pneumatic piston rod 15.
  • the pneumatic cylinder and piston assembly 16 associated with the rod 1S is actuated to retract the piston rod 15, thereby lowering the basket 10 through an opening 17 in the bottom of a combustion chamber 18.
  • the sample is then loaded in the basket, and the cylinder and piston assembly 16 is actuated to advance the rod 15 and thereby raise the basket 10 through the opening 17 into the combustion chamber 18.
  • a sealing ring 19 mounted in a groove in the outer periphery of the platform 14 engages the tapered Walls of the opening 17 to form a gas-tight seal therewith, as shown in the ligure.
  • the connector pins depending from the plate 13 fit into complementary electrical receptacles 20 in the top of the platform 14.
  • the receptacles 20, in turn, are connected to an electrical igniter circuit including a power source such as battery 21 and an ignition switch 22 for applying an electrical Voltage across the basket 10, which serves as a resistive type heating element in the igniter system.
  • a power source such as battery 21
  • an ignition switch 22 for applying an electrical Voltage across the basket 10, which serves as a resistive type heating element in the igniter system.
  • pure oxygen is supplied to the combustion chamber 18 through a valve 23, a flow meter 24, and a pair of cooperating passageways 25 and 26 formed in the platform 14 and the plate 13.
  • the gas discharge passageway 26 in the plate 13 is positioned directly beneath the center of the basket 10, so that the oxygen is fed directly into the combustion zone.
  • the oxygen flow rate is adjusted, via the valve 23 and flow meter 24, to a level slightly above that required to support combustion of the sample in the basket 10, so that there is a slight excess of oxygen within the combustion chamber. Consequently, there is generally a relatively thin layer of an oxygen-rich atmosphere between the combustion flame and the inside walls of the combustion chamber 18, as indicated by the arrows in the figure. This excess oxygen rises through the combustion chamber and is exhausted from the combustion chamber 18 along with the combustion products through a lateral exit 27 at the top of the chamber.
  • the combustion chamber is open at the upper end thereof with the sidewalls extending upwardly and inwardly above the sample basket so as to approximate the shape of the flame of a burning sample, thereby minimizing the volume of oxygen-rich atmosphere around the ame, and the walls of the combustion chamber are preheated so as to maintain the Wall temperature above the condensation temperature of the vapors contained in the combustion products.
  • the combustion products tend to be swept directly into the exit 27, with the rising layer of oxygen-rich atmosphere along the chamber sidewalls tending to isolate the combustion products from the sidewalls.
  • any combustion products that do contact the chamber walls remain in the gas state, even during initiation of the combustion, because the Walls are pre-heated and maintained at a temperature above the condensation temperature.
  • the walls of the combustion chamber 18 extend vertically upwardly past the sample basket 10, and then slope inwardly above the basket so as to approximate the shape of the flame represented in broken lines.
  • a cylindrical vessel 30 Surrounding the combustion chamber 18 is a cylindrical vessel 30 which defines an annular cavity around the outer surface of the chamber 18 for receiving a preheating iiuid.
  • the upper end thereof meshes with a complementary mounting element 31, while the lower end fits into a complementary hole in the bottom wall of the vessel 30.
  • the fluid contained in the annular cavity between the combustion chamber 18 and the vessel 30 Prior to ignition of the sample contained in the basket 10, the fluid contained in the annular cavity between the combustion chamber 18 and the vessel 30 is heated by means of a heating coil 32 at the lower end of the cavity.
  • the iiuid distributes this heat along the walls of the combustion chamber 18 so that the walls are uniformly heated to a temperature above the condensation temperature of the vapors contained in the combustion products to be produced. It has been found that the preheating of the combustion chamber walls to maintain the combustion products in gaseous-form even during ignition, combined with the flame-shaped configuration of the chamber, permits the combustion products to be exhausted from the combustion chamber, on a continuous basis, so efficiently that there is virtually no residue of combustion products deposited on the chamber walls.
  • the illustrative system also prevents condensation within the exit 27 of the combustion chamber 18, since the exit is also surrounded by the preheated fluid in the annular cavity between the combustion chamber 1S and the surrounding vessel 31.
  • provisions are made for introducing into the system one or more gasiform oxides of a non-radioactive nuclide which is an isotope of a radioactive nuclide present in the primary sample.
  • the primary sample contains carbon-14 and tritium, either carbon dioxide or water, or both, are introduced into the system of the invention.
  • water refers to either liquid or gas-form water, although it will be appreciated that at the temperature prevailing within the vessel 30, typically 200 C., the water exists as water vapor, or steam.
  • a manually operated spring-loaded plunger pump 101 draws liquid water Via conduit 102 and a check valve 104 from an enclosed water flask S.
  • the pump 101 discharge is through a similar check valve 106 and conduit 108 through the ambient temperature heater 109 located within the vessel 30.
  • the water is vaporized, and the resulting superheated steam is conveyed via the conduit 110 to the interior of the combustion chamber 18 via a suitable inlet as shown.
  • a stroke volume of about 70 microliters is a convenient capacity for the plunger pump 101.
  • one or more depressions of the pump 101 is associated with each combustion of a primary sample in the combustion chamber 18.
  • non-radioactive carbon dioxide may be introduced into the combustion chamber 18 through a counterpart of the water introduction system described earlier.
  • a four-way valve 11 is connected to a carbon dioxide source via conduit 112, and two ports in the valve 111 are connected to form a sample loop 113.
  • the third port connects via conduit 114 to the cornbustion chamber 18 at a location near that of the end of conduit 110.
  • Carbon dioxide gas under a pressure higher than that within the combustion chamber 18 is collected in the sample loop 113 when the plug of the valve 111 is in position corresponding to nine and twelve oclock. When this plug is rotated 270 clockwise, the entrapped carbon dioxide is discharged into the combustion chamber 18.
  • the amount of water and/or carbon dioxide added to the system via either the plunger pump 101 or the valve 111 depends upon sample size and on the purpose for which the water and/or carbon dioxide is needed.
  • significant increase in the recovery of tritium oxide and in the reduction of memory are achieved with a single 70 milligram injection of liquid water in a system having a gas flow rate of about 0.1 to about 4 CIK liters per minute.
  • the total volume of water vapor used to improve the recovery of radioactive nuclides and to reduce memory is in the range of about 1%, advantageously 10%, to about 50% of the volume of gas flow leaving the combustion chamber 18.
  • a second simultaneous injection, or continuous addition while combustion is occurring will generally suiice.
  • Tritium recovery For tritium recovery carbon dioxide introduction may be omitted and only water injection employed. Tritium, heretofore a difficult material to collect and assay, is almost quantitatively recovered when water is injected into the combustion system.
  • a series of standard quench samples is readily prepared by carrying out a combustion cycle, but in the absence of a primary sample, and introducing a progressive number of 70-milligram amounts of water.
  • liquid samples containing a scintillator, a standard radionuclide, and differing amounts of quench may be prepared in a few minutes.
  • water injection is advantageous for matching quench effects in scintillation samples obtained from hydrogen-containing primary samples of' different sizes. Where, for example, one primary sample is large and another is smaller, counting efficiencies are different by reason of the additional quench attributed to the higher water content produced from the larger sample. If, however, the amount of water is introduced the pump 101 when the smaller of the two samples is being combusted which corresponds approximately to the additional water provided by the larger primary sample, the total amount of water in each respective scintillation sample will be approximately the same, andthe quench and hence the counting efficiencies will likewise be equalized.
  • a particularly useful advantage of the invention is to improve separations of different radionuclides when preparing liquid samples from a multiple labeled primary sample, for example one containing both carbon-14 and tritium.
  • the recovery system is designed to collect water in the vial 51 and carbon dioxide (as carbamate) in the vial 72. Inevitably, however, some carbon dioxide is absorbed in the water-collecting vial 51 and, conversely, some water collects in the CO2-collecting vial 72. Where the amounts of labeled water and CO2 from the primary sample are small, losses of water and CO2 by collection in the incorrect vial can be quite significant.
  • the absolute amount of water and tritium oxide lost to the incorrect vial is constant, but as there is now more water, the relative amount of all water, and particularly tagged water, collected in the water-collecting vial is increased. Otherwise stated, a higher proportion of the tagged water is collected in the proper water-collecting vial 51.
  • the net effect therefore is to improve the resolution of the tagged gases so that, for practical purposes, counting the sample in the water-co1- lecting vial 51 counts essentially all the tritium in the pri- ⁇ mary sample.
  • the transfer tube 34 which is insulated to maintain the fluids passing therethrough in a gaseous state.
  • the transfer tube 34 is double walled with a metallic inner shell and an insulating outer shell to minimize the heat loss therethrough.
  • the gaseous combustion products are passed through a T connection 40 into a heat exchanger 41 for cooling the exhausted combustion products to condense the vapors therein.
  • the heat exchanger 41 includes an inner member 42 forming a dluid passageway for receiving the combustion products from the tube 34., and an outer shell 43 defining an annular cavity around the inner member 42 for receiving a cooling liquid to maintain the walls of the inner passageway at a temperature of the vapors passing therethrough.
  • the heat exchanger 41 functions to convert the tracer from a vapor to liquid form.
  • the heat exchanger 41 functions to remove the condensable vapors from the tracer gas before it is reacted with the trapping agent.
  • the fluid passageway of the heat exchanger is formed of thermally conductive material designed to provide laminar ilow of gases and vapors passing therethrough in the absence of condensation, and the cross section of the fluid passageway is suiciently small in at least one direction transverse to the fluid flow to provide capillary attraction on the type of liquid condensed within the passageway.
  • the inner member 42 comprises a straight thin walled metal tube having an inside diameter of about 0.05 inch, with a wall thickness of about 0.004 inch, and a length of about 5 inches.
  • the fluid passageway causes droplets of liquid condensate to form along the walls of the passageway, thereby providing extremely ecient heat transfer conditions.
  • This dropwise condensation may be caused or promoted by the capillary nature of the fluid passageway.
  • a pulsating pressure is detected at the inlet of the passageway, and it is believed that drop-wise condensation may account for this pulsating pressure.
  • the .fluid passageway may have forms other than tubular, such as a narrow slot, since capillary attraction is present whenever the surface of a liquid where it is in contact with a solid is elevated by the relative attraction of the molecules of the liquid for each other and for those of the solid.
  • a separating means is connected to the outlet end of the heat exchanger for receiving the combustion products, including the condensed vapors, from the heat exchanger and separating the condensed vapors from the remaining gas products, and control means are associated with the combustion chamber for terminating the oxygen supply and supplying an inert gas to the combustion chamber upon completion of the burning of each sample so as to sweep any residual combustion products out of the chamber and on through the heat exchanger into the separating means.
  • a resilient connector 50 is provided at the lower end of the heat exchanger 41 for connecting the outlet of the uid passageway member 42 to a conventional sample or counting vial 51.
  • the vial S1 is supported on a platform 52 which is biased upwardly against the connector 50 by means of a biasing spring 53 to provide a gas-tight seal around the upper periphery of the vial.
  • a biasing spring 53 to provide a gas-tight seal around the upper periphery of the vial.
  • valve 23 When the combustion of a given sample has been completed, the valve 23 is closed to terminate the oxygen supply to the combustion chamber, and a valve 60 is opened to supply an inert gas such as nitrogen to the combustion chamber via the same flow meter 24 and passageways 25, 26 previously used to supply the oxygen.
  • This inert gas which is supplied under a slight pressure, sweeps upwardly through the combustion chamber 18 so as to purge the chamber of any remaining combustion products, and continues on through the chamber exit 27, the transfer tube 34, and the heat exchanger 41. Consequently, it can be seen that the entire system from the combustion chamber 18 to the sample vial 51 is immediately purged of all gaseous combustion products following each sample combustion, and the purging gas also tends to sweep any remaining liquid condensate out of the heat exchanger.
  • the inert purging gas is discharged from the heat exchanger 41 into the headspace of the sample vial 51 which is used as a part of the liquidgas separating means, it may also be used to purge oxygen from the vial headspace to avoid the quenching effect of such oxygen during analysis of the resultant sample for radioactivity.
  • the throat of the vial may be maintained directly under the nitrogen discharge from the connector 50 by simply tilting the vial laterally, so that the nitrogen purges the headspace of the vial by displacing any oxygen remaining therein to the atmosphere.
  • oxygen is a severe quenching agent, i.e., it distorts the radioactivity measurements made by liquid scintillation counting techniques unless certain steps are taken to compensate for the effect of the quenching agent. Although several means of compensating for such quenching effects are known, they complicate the radioactivity measuring procedure.
  • the inert purging gas is preferably turned off by closing the valve 60, and the inlet of the heat exchanger 41 may be sequentially connected to a pair of liquid supply systems generally indicated at 61 and 62.
  • the first supply system 61 includes a supply vessel 63 containing a liquid solvent of the type conventionally used in the preparation of samples to be subjected to sub-freezing temperatures, so as to maintain the sample in a liquid state. It will be understood that this rst liquid supply system 61 is not normally used in the preparation of samples to be handled at above-freezing temperature.
  • an inert gas such as nitrogen is supplied to the headspace of the supply vessel 63 under a slight pressure, so as to force the liquid solvent through a valve 64 into a metering dispenser 65 including a movable piston 65a.
  • an inert gas such as nitrogen is supplied to the headspace of the supply vessel 63 under a slight pressure, so as to force the liquid solvent through a valve 64 into a metering dispenser 65 including a movable piston 65a.
  • valve 64 when the valve 64 is turned 90 to its second position, the pressure of the fluid from the supply vessel 63 urges the piston 65a to the left as viewed in the figure until it reaches a preselected stop position, thereby metering a preselected quantity of liquid through the valve 64 and the T connection 40 into the heat exchanger 41.
  • the piston 65a moves to the left, the supply of liquid within the dispenser 65 is continuously replenished through the right hand end thereof.
  • the system when the metered quantity of liquid solvent has been dispensed, the system is ready to dispense the same preselected quantity of liquid the next time the valve 64 is turned 90 It will be understood that the piston 65a moves alternately to the left and to the right during successive dispensing operations.
  • the second liquid supply system 62 is used to feed a preselected quantity of liquid scintillator into the heat exchanger 41 in the same manner described above for the solvent supply system 61.
  • the liquid scintillator is fed from a supply vessel 66 through a four-way valve 67 into a metering dispenser 68, and is dispensed alternately from opposite ends of the dispenser in response to successive 90 turns of the valve 67. From the valve 67, the liquid flows into the T connection 40 and then downwardly through the heat exchanger 41 into the vial 51.
  • a restriction (not shown) may be formed in the transfer line 34 to prevent liquid from backing up into the line 34 from the T connection 40.
  • the liquids from the systems ⁇ 61, 62 flow downwardly through the heat exchanger 41, they are discharged through the connector 50 into the sample vial 51, where they are retained along with the condensed vapors collected previously.
  • connection of the two liquid supply systems to the heat exchanger inlet not only provides a convenient means of supplying these liquids to the sample vial connected to the outlet of the heat exchanger, but also insures that substantially all the condensed vapors are recovered from the Walls of the heat exchanger tube 42.
  • one of the important advantages of the illustrative system is that the radioactive tracer never passes through any valves or other devices having movable parts, thereby facilitating recovery of the tracer and elimination of equipment memory.
  • any uid contained therein changes at a relatively high rate when fluid is owing therethrough.
  • the gases which are separated from the condensed vapors are passed into a reaction column including means for receiving a liquid trapping agent and reacting the gases with the trapping agent as the gases flow through the column.
  • the reaction column is also provided with means for reversing the direction of the Vgas flow through the column for discharging the trapping agent and the reaction product from the column, and a sample vial is connected to the reaction column for receiving the trapping agent and reaction product from the column in response to the reversal of the gas ow.
  • the gases discharged from the first sample vial 51 through the discharge passageway 54 in the resilient connector 50 are passed through a valve 70 which, when in the position shown in the figure, conducts the gases through a connector 71 into a second sample vial 72.
  • the gases From the sample vial 72, the gases enter the lower end of a depending stem 73 of a reaction column 74 comprising a series of smoothly contoured reaction chambers 74a interconnected by smoothly contoured necked down portions 74!) with the interconnecting walls of the chambers 74a and the necked down portions 7411 forming a smooth curvilinear configuration.
  • reaction column 74 When the reaction column 74 is used, i.e., when a radioactive isotope tracer is to be recovered by reaction with a trapping agent, a valve 75 is turned from the position shown in the iigure so as to feed a preselected amount of liquid trapping agent into an inlet stem in the middle of the reaction column 74 just after the oxygen supply to the combustion charnber 18 is turned on.
  • gas is already flowing upwardly through the reaction column 74 when the liquid trapping agent first enters the column.
  • the liquid trapping agent With the particular conguration of reaction column provided by this invention, it has been found that the liquid trapping agent becomes uniformly distributed throughout the various reaction chambers 74a, and such distribution is maintained, as long as gas flows continuously up through the column 74.
  • the upward gas ow through the reaction column causes the liquid trapping agent to become distributed along the walls of the bulbous or enlarged reaction chambers 74a While preventing the trapping agent from owing down through the elongated depending stem 73 at the bottom of the reaction column, so that no liquid trapping agent enters the vial 72.
  • the liquid is supplied by means of a metering device 77 having a movable piston therein with a predetermined stop position.
  • the piston 77a is stopped at the same position during each feeding operation, so that the same amount of liquid trapping agent will be supplied for each sample.
  • the piston 77a in the metering device 77 remains in the position shown in the ligure and no liquid tlows into the inlet stem 76.
  • the output of the device 77 is connected to the inlet stem 76, and subsequent advancement of the plunger 77a dispenses a preselected quantity of trapping agent into the reaction column 74; although a manually actuated plunger 77a is shown in the drawings, it will be understood that the dispensing of the liquid trapping agent could be made automatically responsive to the turning of the valve 75.
  • valve 75 After the metered amount of trapping agent has been fed into the reaction column, the valve 75 is returned to its normal position as illustrated in the figure, and the metering device 77 is automatically refilled with liquid trapping agent from a supply bottle 78, the liquid being fed from the bottle 78 into the metering device 77 by means of pressurized nitrogen in the headspace of the supply bottle 78.
  • the radioactive compound As the gases containing the radioactive isotope tracer, such as 14002 for example, are passed upwardly through the reaction column, the radioactive compound is reacted with the trapping agent, such as ethanolamine for example, to form a reaction product which is held within the reaction chambers 74a along With the liquid trapping agent. 'Ihe amount of reaction product contained in the series of reaction chambers 74a varies along the length of the reaction column, but it has been found that the reaction effected by the particular reaction column configuration provided by this invention traps over 99% of the isotope tracer.
  • the unreacted gases are exhausted from the upper end of the reaction column through a connector member 79 and vented to the atmosphere through a valve 80.
  • reaction column 74 To control the reaction temperature within the column 74, a heat transfer uid is passed through an annular jacket surrounding the column 74.
  • the reaction column provided by this invention provides effective heat transfer with a high degree of eciency when used to carry out gas-liquid reactions. It is believed that the interaction of the upwardly flowing gas ywith the liquid that is held within the enlarged reaction chambers 74a brings all portions of the liquid into intimate contact with the column walls, thereby effecting eicient heat transfer between the liquid and the column walls.
  • the flow of nitrogen gas is continued for a suitable purging period, e.g. 30 seconds, and the valve 70 is then turned 90 so as to conduct the purging nitrogen gas into the upper end of the reaction column 74, thereby effecting a reversal of the direction of gas flow through the column.
  • a suitable purging period e.g. 30 seconds
  • the valve 70 is then turned 90 so as to conduct the purging nitrogen gas into the upper end of the reaction column 74, thereby effecting a reversal of the direction of gas flow through the column.
  • the gas flows downwardly through the reaction column 74, it sweeps the liquids contained therein, including the reaction product formed by reaction of the liquid trapping agent with the gas compound containing the isotope tracer, into the sample vial 72.
  • the gases are discharged from the vial 72 upwardly through the connector 71 and vented to the atmosphere through the valve 70 via passageway 70a therein.
  • the valve 70 is then returned to its original position to resume the gas ow upwardly through the reaction column, and the connector 79 at the upper end of the reaction column 74 may be sequentially connected to a pair of liquid supply systems generally indicated at 81 and 82.
  • the first supply system l81 includes a supply vessel 83 containing a liquid solvent to be used to dissolve the reaction product formed by reaction of the isotope compound with the trapping agent; the solvent may also serve to maintain the resultant sample in a liquid condition where it is to be handled at sub-freezing temperatures, as described previously in connection with the liquid supply system 61.
  • An inert gas such as nitrogen is applied to the headspace of the supply vessel 83 under a slight pressure so as to force the liquid solvent through a valve 84 into a metering dispenser 85 including a movable piston 85a.
  • the piston 85a moves back and forth within the dispenser 85 in response to successive 90 turns of the valve 84, so as to feed a preselected ⁇ quantity of liquid solvent through the valve 84 into the connector 79 each time the valve 84 is turned 90.
  • This liquid liows downwardly into the reaction column 74 and is distributed therethrough in the same manner described previously for the liquid trapping agent supplied through the inlet stem 76.
  • the nitrogen iiow is continued upwardly through the column for a period of about 15 to 4S seconds, depending upon the concentration of CO2 relative to the trapping agent.
  • the valve 70 is then again turned to reverse the gas ow through the reaction column, thereby sweeping the liquid solvent downwardly through the reaction column into the sample vial 72.
  • the valve 70 is then again returned to its original position so that the inert purging gas once again flows upwardly through the reaction column, and the liquid scintillator is metered into the upper end of the reaction column from the second liquid supply system 82. More particularly, liquid scintillator is fed from a supply bottle 86 through a four-way valve 87 into a metering dispenser 88.
  • valve S7 When the valve S7 is turned 90 from the position illustrated in the figure, with the dispenser piston 88a. in the position shown, a preselected quantity of liquid scintillator is forced out of the dispenser by the pressure of the nitrogen in the headspace of the bottle 86, thereby advancing the piston 88a to the left to force liquid through the valve 87 into the connector 79 at the top of the reaction column 74. Due to the upward gas ow through the reaction column, this liquid again provides a scrubbing action on the walls of the reaction column 74.
  • the upward nitrogen flow is continued for about 5 to 10 seconds, at which time the gas iiow is again reversed in the column 74, by turning the valve 70, t0 discharge the liquid scintillator into the vial 72.
  • the liquid supply systems associated with the reaction column 74 provide a rapid and efficient means of achieving recoveries in excess of 99% with attendant low memories of 1/3000 or less.
  • the isotope tracer is passed through only a single valve 70, and then only while it is in the gas form, thereby further facilitating complete recovery of the radioactive tracer.
  • a onegram sample of tritium-labelled organic material is combusted.
  • the combustion is initiated by the electrical igniter, heated to a temperature of about 1500 C., and the oxygen flow rate is set at about two liters per minute.
  • One 70-milligram shot of water is injected as oxidation begins.
  • the pressure inside the combustion chamber during combustion is less than 0.1 atmosphere above atmospheric pressure.
  • the walls of the combustion chamber are pre-heated and thermostatically maintained at approximately C. which is sucient to prevent any noticeable condensation of the combustion products on the inside walls of the combustion chamber.
  • the combustion products are continuously exhausted through the upper end of the combustion chamber into a heat exchanger, comprising a straight tube of stainless steel having an inside diameter of 0.080 inch, a wall thickness of 0.020 inch, and a length of 10.00 inches.
  • the walls of the tube are maintained at a temperature of about 0 C.
  • condensed vapors including condensed 3H2O drip into the counting vial connected to the lower end of the heat exchanger, While the remaining gases pass on through the vial and are vented to the atmosphere.
  • the combustion of the sample is completed in about 45 seconds, after which the oxygen is turned off and 13 the nitrogen supply to the combustion chamber turned on so that nitrogen is fed into the combustion chamber at a rate of seven liters per minute for about tive to ten seconds.
  • the nitrogen is then shut off and a selected quanity of dioxane (liquid scintillator) is fed from the metering dispenser into the inlet of the heat exchanger.
  • the metering dispenser is preset to feed ten milliliters of the liquid scintillator into the heat exchanger over a period of about tive seconds, after which the liquid supply line to the inlet of the heat exchanger is closed, and the nitrogen feed to the combustion vessel resumed for an additional ltive seconds at a rate of about four liters per minute.
  • the counting vial is removed from the resilient connector at the outlet of the heat exchanger and tilted with the open mount of the vial positioned below the passageway from the heat exchanger outlet so that the nitrogen supplied to the counting vial during this interval purges the vial of oxygen.
  • the vial cap is then quickly threaded onto the vial to seal the sample contained therein in a nitrogen atmosphere, and the sample is analyzed for radioactivity.
  • the illustrative sample preparation system may be used to prepare samples from starting materials labelled with only a single tracer to be recovered either as a condensed vapor or by reaction with a trapping agent, or from double-labelled samples containing tracers to be recovered by both means.
  • the gases discharged from the rst sample vial 51 are, of course, simply passed on through the balance of the system and vented to the atmosphere.
  • any of the manual operations required in the illustrative system may be readily converted to automatic operation.
  • the opening and closing of the oxygen and nitrogen valves 23 and 60, respectively may be controlled by timing mechanisms according to a predetermined time schedule for particular types of samples.
  • the valves 64, 67, 75, 84, and 87 associated with the various liquid supply systems, as well as the valve 70 could be controlled by timing mechanisms according to predetermined time schedules.
  • An apparatus for preparing liquid form samples for radioactive nuclide assays which comprises:
  • means including an enclosed combustion chamber for burning material to produce gaseous combustion products
  • a receptacle within the lower portion of said chamber for holding the material sample to be burned
  • supply means containing an oxide of a non-radioactive isotope of said nuclide having conduit means connected to the combustion chamber,
  • an injection device interposed in said supply means conduit for introducing to said combustion chamber a predetermined iixed amount of gasiform oxide of said non-radioactive isotope of said nuclide from the supply means determined according to the volume of gas flow leaving the combustion chamber, and means for recovering the resulting mixed gasiform oxides of said radioactive nuclide and said nonradioactive nuclide as a liquid form sample.
  • Apparatus of claim 1 wherein said primary sample contains tritium and said gasiform oxide of a non-radioactive isotope is water, and wherein said injection means includes a plunger operated pump and vaporization means disposed in said conduit to convert the Water to a gasiform oxide prior to introduction into the combustion chamber.
  • said recovering means includes heat exchanger means for receiving combustion products and for condensing the condensable vapors therein, and separating means for receiving said combustion products including the condensed vapors from said heat exchanger and separating said condensed vapors from the balance of the combustion products.

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US820269A 1969-04-29 1969-04-29 Apparatus for the preparation of liquid form samples for radioactive isotope tracer studies Expired - Lifetime US3682598A (en)

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DK (1) DK144020C (da)
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Cited By (13)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3844716A (en) * 1971-12-01 1974-10-29 Nuclear Chicago Corp Combustion method apparatus for preparing samples for liquid scintillation counting
US3918911A (en) * 1970-10-09 1975-11-11 Intertechnique Sa Method and apparatus for preparation of liquid samples
US3942938A (en) * 1974-12-06 1976-03-09 Packard Instrument Company, Inc. Combustion system for preparing radioactive samples and the like
JPS5131288A (en) * 1974-09-10 1976-03-17 Sagami Chem Res Kukichu no torichiumu oyobi tanso 14 no hoshano no sokuteihoho oyobi sochi
US3945797A (en) * 1972-02-09 1976-03-23 Chinoin Gyogyszer Es Vegyeszeti Termekek Gyara Rt. Process and apparatus for measuring the isotope content of substances labelled with 3 H or 3 H and 14 C isotopes
US3979503A (en) * 1968-05-14 1976-09-07 Packard Instrument Company, Inc. Method and apparatus for processing fluid materials particularly in the preparation of samples for radioactive isotope tracer studies
US4019864A (en) * 1974-09-10 1977-04-26 Sagami Chemical Research Center Method for measuring radioactivities of tritium and carbon-14 in sample air and apparatus for performing the same method
US4078894A (en) * 1976-11-12 1978-03-14 Raytheon Company Analyzer system with salt extractor
US4194117A (en) * 1977-08-22 1980-03-18 Gross Valery N Arrangement for continuously measuring the radioactivity of solutions of matters in a homogeneous mixture with a liquid scintillator
US4310491A (en) * 1980-03-05 1982-01-12 Hitachi, Ltd. Apparatus for supplying raw liquid and relieving pressure of high-pressure product liquid
FR2592162A1 (fr) * 1985-12-19 1987-06-26 Huels Chemische Werke Ag Appareillage de combustion selon wickbold et jeu d'elements destine a ceux-ci.
US5328662A (en) * 1991-09-10 1994-07-12 Cogema-Compagne Generale Des Matieres Nucleaires Installation for carrying out several successive chemical reactions in the same container
US20170022059A1 (en) * 2015-07-22 2017-01-26 Perkinelmer Health Sciences, Inc. Processes and apparatuses for reclamation and purification of tritium

Families Citing this family (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US4008393A (en) * 1970-09-11 1977-02-15 Intertechnique S.A. System and method of liquid scintillation counting

Cited By (15)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3979503A (en) * 1968-05-14 1976-09-07 Packard Instrument Company, Inc. Method and apparatus for processing fluid materials particularly in the preparation of samples for radioactive isotope tracer studies
US3918911A (en) * 1970-10-09 1975-11-11 Intertechnique Sa Method and apparatus for preparation of liquid samples
US3844716A (en) * 1971-12-01 1974-10-29 Nuclear Chicago Corp Combustion method apparatus for preparing samples for liquid scintillation counting
US3945797A (en) * 1972-02-09 1976-03-23 Chinoin Gyogyszer Es Vegyeszeti Termekek Gyara Rt. Process and apparatus for measuring the isotope content of substances labelled with 3 H or 3 H and 14 C isotopes
US4019864A (en) * 1974-09-10 1977-04-26 Sagami Chemical Research Center Method for measuring radioactivities of tritium and carbon-14 in sample air and apparatus for performing the same method
JPS5131288A (en) * 1974-09-10 1976-03-17 Sagami Chem Res Kukichu no torichiumu oyobi tanso 14 no hoshano no sokuteihoho oyobi sochi
JPS5817435B2 (ja) * 1974-09-10 1983-04-07 ザイダンホウジン サガミチユウオウカガクケンキユウシヨ クウキチユウ ノ トリチウム オヨビ タンソ １４ ノ ホウシヤノウ ノ ソクテイホウホウ オヨビ ソウチ
US3942938A (en) * 1974-12-06 1976-03-09 Packard Instrument Company, Inc. Combustion system for preparing radioactive samples and the like
US4078894A (en) * 1976-11-12 1978-03-14 Raytheon Company Analyzer system with salt extractor
US4194117A (en) * 1977-08-22 1980-03-18 Gross Valery N Arrangement for continuously measuring the radioactivity of solutions of matters in a homogeneous mixture with a liquid scintillator
US4310491A (en) * 1980-03-05 1982-01-12 Hitachi, Ltd. Apparatus for supplying raw liquid and relieving pressure of high-pressure product liquid
FR2592162A1 (fr) * 1985-12-19 1987-06-26 Huels Chemische Werke Ag Appareillage de combustion selon wickbold et jeu d'elements destine a ceux-ci.
US5328662A (en) * 1991-09-10 1994-07-12 Cogema-Compagne Generale Des Matieres Nucleaires Installation for carrying out several successive chemical reactions in the same container
US20170022059A1 (en) * 2015-07-22 2017-01-26 Perkinelmer Health Sciences, Inc. Processes and apparatuses for reclamation and purification of tritium
US9682860B2 (en) * 2015-07-22 2017-06-20 Perkinelmer Health Sciences, Inc. Processes and apparatuses for reclamation and purification of tritium

Also Published As

Publication number Publication date
IL33095A0 (en) 1969-11-30
CH527417A (fr) 1972-08-31
DE1949048B2 (de) 1972-10-19
FI53503C (fi) 1978-05-10
CA936349A (en) 1973-11-06
DK144020B (da) 1981-11-16
DK144020C (da) 1982-04-26
FR2041960A5 (da) 1971-02-05
NL6914732A (da) 1970-11-02
JPS4944199B1 (da) 1974-11-27
DE1949048A1 (de) 1970-11-12
FI53503B (da) 1978-01-31
GB1279648A (en) 1972-06-28
BE739558A (da) 1970-03-02
SE371697B (da) 1974-11-25

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