DE2441314A1 - METHOD AND DEVICE FOR INCINERATION OF SAMPLES CONTAINING RADIOACTIVE ISOTOPES - Google Patents

Description

24413U

Achilles e B

11, rue Bea-aregard

CH-1200 Geneva

Method and device snr combustion of radioactive j

Samples containing isotopes'

The invention relates to a method and a device for the combustion of radioactive isotopes, in particular samples containing carbon with a mass number of 14 (carbon-14-) and tritium . j

I In many areas, for example in biology, medicine, agriculture, environmental research, today people work with molecules that
marked with carbon-I '+ and tritium. Quantitative
Measurements are used to study distribution, absorption and; the degree of penetration of the chemical products by means of radioactive isotopes is essential. ■>

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INSPECTED

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Today there are several methods to reduce the radioactivity of the Measure samples. One of these methods is liquid scintillation measurement. This method has many advantages. But if the marked chemical product binds with one Ingredient incompatible with the scintillators will not result in any results.

In some cases, it is impossible to dissolve the labeled chemical sample through the usual chemical processes. In these In some cases, the sample must be burned to measure the carbon-14 and tritium quantitatively. From this combustion

14th
if one holds titrated water and CO ^.

Various combustion techniques have been used. One the same is the Schöniger method. This combustion technique was improved by Kalberer and Rutschmann, and further developed by Kelly and Coil, Dobbs, Gupta etc. All these Methods are manual and give good results. However, the separation of the two isotopes is not achieved, which is what the Scintillation measurement of radioactivity made difficult. As another method, Kisielski has a manual method of incineration and separation of carbon-14 and tritium. before Recently, Peterson devised a manual system that would burn and separate isotopes such as carbon-14 and Tritium enables. The invention is based on a system developed by Kaartinen.

When burning biological substances, the carbon-14 and Containing tritium poses many problems. The invention is based on the object of proposing a method and a device, which make it possible to overcome these problems, with the following goals in particular:

- high degree of recovery when incinerating samples labeled with carbon-14,

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- high degree of recovery when burning with tritium marked samples,

- high degree of separation of the two isotopes (if both in the sample are included),. . ·

- slight mutual fusion (contamination),

- high efficiency when burning dried or fresh samples (with more or less large amounts of water),

- High efficiency for samples with a lot of inert material, such as ■ Earth samples, silicon oxide, alumines, etc., which are marked contain organic molecules,

- high efficiency when burning with carbon-14 labeled molecules of complex chemical structure, especially containing sulfur and nitrogen,

- weak memory effect, especially when using coutine of samples with a large radioactivity difference,

- small number of blank combustion samples for checking the memory status,

- little time required for each examination process,

- Creation of the possibility of changing the absorption requirements, in particular by changing the absorption volumes,

- easy operation.

This object is achieved by the invention, which is described in detail below. Among other things, the invention is characterized by an automatic Verbrennungsaniage, which burns dry or fresh, or any other biological substances which radioactive isotopes such as carbon-14 and tritium containing ¹ · The system allows a quantitative

14 -5 accumulation of COp and -Ή obtained during combustion, the introduction of the sample and the performance of the following opera-r functions according to a predetermined and adjustable program. An essential feature is also a tJb er pressure measuring device for Measuring the overpressure in the combustion chamber. The invention has a wide variety of scientific applications, e.g.

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in biology, medicine, agriculture, environmental technology and in other sciences that currently include carbon-14 and used tritium as radioactive molecules

The method according to the invention and the device used are first presented briefly «. The radioactive Samples containing isotopes are placed in a sagger made of quartz inserted. This sagger is inserted into a quartz combustion tube by an automatic, pneumatically controlled system inserted. The combustion takes place in this drill hole. A locking system controlled by a pneumatic piston enables the combustion tube to be closed. The tightness of the combustion tube is made by high temperature resistant Seals reached. The combustion takes place in a stream of oxygen, the flow of which is regulated. on the other hand the device is equipped with a manometer for measuring overpressure inside the combustion tube.

The aging phenomena of the catalytic converters, which are located in the second part of the pipe, change their physical properties. This could make it more difficult for the combustion gases to escape, which could result in explosions inside the combustion tube. The overpressure measuring device allows timely replacement of the catalytic converters.

It is possible for special applications as a combustion gas to use a mixture of oxygen and ozone, the oxygen being enriched with ozone in a special apparatus must become·

The combustion takes place in the front part of the quartz tube, its Temperature is 900 ° C. In the rear part of the quartz tube are the oxidation catalysts, e.g. copper oxide, such as it is usually used for elemental analysis, as well as specific oxidation catalysts, e.g. a catalyst

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Silver vanadate placed on an inert pad, or a catalyst made of manganese oxide on a platinum grid ,. This last one Catalyst is heated to high temperature.,. while the other heated to et v / a 700 C v / ground.

From the sample that contains carbon-1A and tritium are in the inventive device quantitative amounts of carbon dioxide and won water. The water contains tritium in the form of titrated water and the carbon dioxide contains carbon

14th
in the form of COp «, The separation of the two isotopes and theirs

quantitative absorption occurs through two different devices * The first setup looks like this: The combustion gas that comes out of the furnace at high temperature, is passed through a frozen pipe coil, where the water resulting from the combustion of the sample, especially in the case of a sample from animal organs or substances quantitatively precipitates on the Eohrwandung.

The carbon dioxide containing COp is quantitatively absorbed by an organic base. Ethanolamine _v Phenyläthylamiη or any other base can be used as the base
Salt content r.it the carbonic acid results in a homogeneous solution with toluene or another mixture, which allows the eadioactivity measurement.

Finally, a device is provided that in the
Finally, the sample obtained dissolves oxygen by blowing in a gas such as nitrogen, air or argon.

The further description of the invention makes reference to the attached Drawings. In detail shows:

Fig. 1 shows the functional diagram of the device _:

Fig. 2 shows the arrangement of the various components in the
Housing of the device,

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Pig. 5 a three-dimensional front view of the incinerator, 4 is a spatial rear view of the incinerator, Fig «, 5 a spatial representation of the water catcher, Pig. 6 shows a spatial representation of a separation pipe made of glass and the holder for the scintillation vial and

7 shows a three-dimensional representation of the complete injection system for the organic liquids.

According to FIG. 1, a two-part electric furnace 12 is provided, which consists of a fire-resistant cylinder that is wrapped with two heating coils. These ensure that the Cylinder. The ceramic tube is covered with refractory bricks. The temperature control of the heating coil is done by means of two Thermocouples and an electronic system controlled. The temperature can be determined by the operating personnel for the respective experiment can be set. The combustion takes place in a quartz tube. The loading mechanism for the samples consists of one mechanical assembly that carries a quartz blade 22.

The combustion gas oxygen or oxygen enriched with ozone is contained in a storage container 8. This gas flows through a tube fitting system, which is an absolute Guaranteed tightness in the quartz tube 1. A particularly suitable ßohrverschraubungssystem is one of the type "Serto". The pressure of the "oxygen" is controlled by a suitable System kept constant. The flow rate is determined by a

9 Regulated needle valve. Sin flowmeter allows the Benutzerj to determine the outflow rate. The oxygen supply system is monitored by a safety device. This emits an acoustic signal when there is negative pressure »The" overpressure in the combustion tube is measured by a 4-5 manometer (range from 0 to 600 mm water column). Aging phenomena of the catalytic converters are indicated by overpressure in the combustion tube.

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The combustion gases are released from the combustion tube by means of a heated pipe to a water catcher 11 directed. Therefore the water cannot condense in the connecting pipe. The heating and regulation of the temperature of the Eohres are carried out using suitable equipment. A security system indicates any malfunctions in this heating system.

The water catcher consists of a ^ Ar ^ W ^ / made of glass, plastic or stainless steel coated with a suitable liquid such as ethylene glycol. The liquid is passed through a cooling unit 1A- cooled with a compressor of 1/5 HP. The temperature the liquid can be regulated with the help of a thermostat. The selectable range extends from room temperature up to - 30 ° C. The water catcher can also be made of Peltier elements be cooled.

After the water has been removed from the combustion gases, they are passed through a scintillation vial 4-6, which is attached to the lower part of the Water catcher is fixed, led to the carbon dioxide catcher. When flowing through the water catcher, the gases lose their whole Water. This water was created both by the combustion and was previously contained in the sample.

To increase the radioactivity of the water at the end of the water catcher obtained, a mixture of suitable liquids is poured into the upper part of the water trap according to a predetermined program a valve 4 or 4 'is injected. This liquid solves that Quantitative water, the whole accumulating in the scintillation vial 46. The contents of this bottle can after being deoxygenated, placed in an apparatus for measuring radioactivity by scintillation

The C0 ₂ trap 10 consists of a column made of glass of the "Vigreux" type. This column is equipped with a meat unit and a temperature controller. The temperature can be affected by the

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Operators are hired. The column with that The heating unit and the temperature measuring probe are thermally insulated are mounted in a metal frame. The upper (bearing the Column is connected with a tight connector; In this connection piece are injectors 5> »6 and 7 as well a filter 47 is installed, which consists of a refractory or other material and which flows out of the column Can catch aerosol. In the lower part of the column there is a tight coupling which allows a Attach scintillation vial 48.

Before the start of the combustion, a certain amount of liquid, such as ethanolamine, injected into the vial 48 from a container 49 through a suitable system by means of a valve 3. The mixed kenge can be regulated by the operating staff.

Before entering the sample into the incinerator 12 of the device closes a solenoid valve 2, which is on a connecting line between the two scintillation vials and 48 is connected. This causes the ethanolamine contained in the vial to flow into the CO2 trap due to the gas pressure. In this way, the liquid is heated up on the catalyst. The temperature can be JO to 60 ° C or more.

When the sample is burned, the combustion gases are cooled by the entire absorption liquid which fills the CO ^ trap. After this process, the solenoid valve 2 is opened according to the program. The combustion gases flow through this valve, with the ethanolamine, which now contains the CO ₂ , flowing back into the bottle 48.

A suitable system is then used through the valve 5 an overlying container 50 injected methanol. This methanol dissolves the ethanolamine and the reaction products

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of the ethanol ami η s with carbon dioxide. · Burch the upper part of the COp-Fäiigers is from a further container 51 by means of the Valve 6 and, depending on the type of experiment, a certain volume of a Admitted liquid such as toluene. All of these fluids Methanol, toluene, ethanolamine and the starting materials the connection of the ethanolamine with COp, collect in the vial 48. After it has been flushed with oxygen in a suitable system 52, it can be transferred to a scintillation apparatus for the Radioactivity measurement to be entered ,,. .

The cleaning system 52 consists of a storage container 53 for the cleaning gas, e.g. nitrogen, which is introduced into the two vials via valves through a flow meter 54 is, which for this purpose of two holders 55 up. are taken.

Fig. 2 shows the individual components of the device in their approximately true-to-scale arrangement in a housing. Here, too, the COp catcher is at 10, the water catcher at 11, and the incinerator with 12 and the cooling unit with 14- designated. It is also off this illustration the arrangement of the temperature controller 13, the pneumatic lifting devices 15 for the scintillation vials, the cooled liquid container 16 and the injector 17 can be seen.

Figures 3 I ¹ JId 4 show further details of the incinerator 12. The quartz combustion tube is 430 mm long and has an outer diameter of 30 mm and an inner diameter of 26 mm. It is fixed on two flanges made of stainless steel and aluminum. Two seals 28 made of a material which is commercially available under the trademark “Vitron” ensure that the system is sealed off. The simple installation allows an easy exchange of the quartz tube and the sealing rings. The two oven walls are fixed with screws so that they can be easily exchanged.

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The pneumatic loading system consists of two working cylinders

24 and two guide rods 23 »which are mounted on axial guide bushes 31 with ball bearings and the insertion of the samples allow. The quartz tube is controlled by a pneumatically Flap 20 closed and open. The pneumatic working cylinder is denoted by 19. A solenoid valve with an air throttle

25 regulates and controls the closing speed of the flap 20. An exit opening 29 on the opposite side allows the combustion gases to flow out. The oven envelope is with 18 designated. Furthermore, the two figures show a fastening element 21 for the quartz blade, three solenoid valves 26 and a Limit switch 27 can be seen. / The different parts of the water catcher 11 shows FIG. 5. It is thermally insulated. The connection piece from the furnace to the pipe coil is with 32, the probe to the Heating control with 33 »the access pipe to the cooling pipe coil with 34 and the cooling pipe coil itself is designated by 35. Furthermore, one recognizes from this Fig. 5 a connecting piece 36 of the check valves, the cold chamber 37 »an insulation chamber 38» the insulation material 39 and the temperature controller 13 ·

Fig. 6 shows, among other things, the holder of the scintillation vial, which are designated there by 42, in detail. The holders for the vials are marked 40. These Holders are raised from below with the aid of pneumatic working cylinders 41, whereby the vials are fixed and sealed will. This sealing system also ensures the sealing of the lower part of the water catcher and the COp catcher. "The seal allows in particular the injection of the Absorption liquid, e.g. ethanolamine.

The distribution of the individual organic liquids - cocktails called - takes place by the injection device shown in FIG. The five containers 49, 50, 51, 56 and 56 'shown in FIG. 1 are designated by 16 in FIG. 7, for example. the Distribution is accomplished by syringes 43 made of glass. The syringes have a ceramic plunger, which increases their volume

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can easily be regulated between 0 and 10 ml. The syringes are connected by a pneumatic system with working cylinders 41 controllable. The inflow speed of the liquids and the amount of which is adjustable. Stainless steel solenoid valves 26 are precisely placed in the places where the organic liquid must be admitted. The connecting tubes are made of one Plastic inside 2 and outside 4 mm diameter. All connections are mounted with stainless steel connectors. The geese The unit consists of a drawer-like, sliding frame, the slide rails of which are denoted by 44. The rack is therefore easily accessible for refilling the container and for adjusting the amount of liquid.

The electrical control of the device according to the invention consists of individual switches or relays, which control the furnace heating, the cooling unit, the heating of the connector between the Furnace and the water catcher as well as the heating of the COp catcher switch. Several programs are available depending on the needs and the sample. The control program is with a cam system driven by two motors. The cams act on electrical contacts and solenoid valves switch the compressed gas, which the pneumatic pistons emotional.

The system also contains a measuring and safety system, which includes, for example, two counters that show the number of burns count and show the amount of fluid used. An acoustic warning system is switched on automatically, if the combustion gas pressure, the cleaning gas pressure or the Pressure to control the pneumatic system is insufficient.

The device described operates as follows. The combustion program of a sample, the coal

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contains ötoff ~ 14 and tritium. You put the sagger that the ■ Sample contains on the quartz scoop 22. At the same time will also be two scintillation bottles 46 and 48 in the appropriate holders 40 set. You press a start button to start the program to start. The electro-pneumatic system pushes the Vial on the sealing rings. The solenoid valve 2 is open, so that the desired amount of ethanolamine from the container 49 into the Vial 48 injected v / ird. The solenoid valve 2 closes. One minute after closing the solenoid valve 2 opens the shutter 20 of the furnace and the sagger is placed in the incinerator 12 inserted. Two to three minutes later, an acoustic signal indicates the end of the combustion. That Solenoid valve 2 opens. Through the valve 4, a predetermined amount of liquid from the container 56 in the upper part of the Water catcher 11 injected. Fifteen seconds later, through valve 5, a predetermined amount of liquid is drawn from the container 50 injected into the upper (part of the CO ^ catcher 10. Now the flap of the furnace opens again, the sagger is pulled out and the bottles 46 and 48 are lowered. The two small bottles are then removed and placed in the holders 55 of the cleaning system 52. By As the gas flows in from the container 53, the contents of the vials are cleaned of oxygen. The gas flow is over a valve operated by hand. With a clock the stirring time and with a flow meter 54 the exact amount of gas for each vial can be set individually. After the time has elapsed, the gas flowing in is interrupted by means of a solenoid valve and the vials can be removed for scintillation measurement.

A great number of tests were carried out with the installation described above. The following examples show the yield, the reproducibility, the linearity and the memory effect in the most varied of samples labeled with carbon-14 or tritium

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Example 1: Vorbronnu n r j; of p, 10 and 1 00 mg with carbon ^

rne.rkierte r Ben benzoic acid; sta ndar d ■

Decomposition Weight Yield Recovered Sample Decomposition

m g dpjn dpm %

3.370 17,120 16.94-8 99.0

5.025 15,367 15,101 98.3

3.030 15,542 15,225 99.0

10,000 16,510 '16,245 98.7 -

10.155 15,672 15,601 99.5

10.675 15,567 15-085 98.2

100,000 22,557 21,605- 96.6

100,000 14,554-14,404 · -99.1

100.244 18,420 17,705 '96.1

Example 2: Combustion of Benzoic Acid with Carbon-14

Weight of decomposition recovered yield sample decomposition Fi ρ dpm dpm % 0.980 12,681 12,655 100.4 1.020 12,917 15,149 98.2 2.050 25,977. 26,169 99.5 2,000 26,155 25,789 101.4 5.010 58,898 58,802 100.5 5.050 59,277 59,060 100.6 10,000 58.011 58,286 99.5 10,280 55,712 52,266 98.8 50,000 58,605 58,951 99.2 50,000 , 59.094 59,511 98.9

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Example 3: Verbrennu ng of E rdp robes _t depending 47218 Zersetzu ng per minute and 60894 decomposition per minute p ro grams contain. 9.0,% ft ^e s substance remains after use

Compared to the sample

decomposition

dpm

recovered decomposition dpm

yield

1.00050 1.00035 1.00005 1.00165. 1.00270 1.00395

47,242

47.235 47.220 60.994 61,158 61.136

47,278 48,682 47,294 60,241 60,625 61,137

100.1

103.1

100.2 98.8 99.3

100.1

Example 4: Incineration of blood samples containing various amounts of radioactive benzoic acid labeled with carbon-14

Blood volume decomposition recovered yield the benzoin decomposition acid ml dmp dmp % 0.03 13,213 13.4-86 102.1 0.03 13,278 13,303 100.2 0.10 13,149 13,184 100.3 0.20 12,955 12,930 99.8 0.30 13,213 12,785 96.8

Example 5: Combustion of molecules labeled with carbon-14 , which in their structure contain 12.5% nitrogen and 9 Mo sulfur

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Weight of decomposition recovered yield Sample of the stick decomposition fabric GATE dpm dpm % 2.055 27,142 28.002 103.2 2.025 26,746 26,847 100.4 4.975 65,710 ¹ 65,642 99.9 4,990 65,908 65,821 99.9 9,950 65,776 65,485 99.6 10.495 65,974 65,142 98.7 49,800 66,040 65,580 99.0 50,440 65,908 64,945 98.5 100.290 65,908 64,913 98.5 100.505 66.106 66.053 99.9

Example 6: Combustion of tritiated benzoic acid

Weight of decomposition recovered yield sample decomposition HE dpm dpm % 3.005 28,692 28,565 98.9 5.050 19,692 18,800 96.5 20.060 167,514 167,694 100.1 50.105 265.9 ^ 5 269.128 101.2

Example 7 · Comparison of the burns of fresh and dried out biological substances (skeletons of rats) after treatment with a drug labeled with carbon-14

yesC ± per 100 mg (fresh) MCi per 100 mg (dried out )

0.6525 0.6158 0.6522 0.6375

0.6343 i 0.0150

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0.6995 0.6435 0.5939 0.6025

0.6320 ± 0.0422

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Example of Qi burning; of doubly labeled 5 0rcg-benzoic acid _: samples which contain carbon-14 and tritium in different proportions

Ratio: ¹⁴ C : -Ή like 1: 1 yield ¹⁴ C Decomposition recovered % decomposition 99.5 dpm dpm 99.1 11,297 11,235 11,297 11.199

decomposition

dpm

11,772 11,325

decomposition recovered dpm

12,358 11,816

yield

10,466 10,237 97.8 9,977 9,769 98.0 Ratio: ¹⁴ C: % like 1:10 decomposition recovered yield decomposition dpm dpm %

105.0 104.0

decomposition

dpm

decomposition recovered dpm

yield

98,055 99,326

98.168 96.216

100.0 97.0

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Example 9: Memory ef fect "Nac h waxed it onei_ radio activity at a second combustion of non-radioactive St of f_

1. Burn 2. Vei-burn Hemory effect

cpm cpm %

10,305 15,560 37,313

96 0.9 72 0.5, 470 1.3

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Claims (1)

A η _s ρ γ 'ü, before. (λ.j method and device for the Verb.ren.mmg of biological, inert or other substances containing radioactive isotopes, especially carbon-14 and tritium, characterized in that the samples are completely burned in a combustion gas stream and that from the combustion gases the isotopes are quantitatively absorbed in two different facilities and thereby separated. 2. Apparatus for performing the method according to claim 1, characterized in that one according to a predetermined, adjustable Program working manipulator is provided, which da ^ introducing the samples into the combustion chamber, the supply the necessary reagents and the seal and Release of the sampling vessels takes place automatically. 5. Apparatus for performing the method according to claim 1, characterized by a cooled water catcher with adjustable temperature, which provides a quantitative amount of the water during the Catches the combustion of titrated water, 4-, device according to claim 3 »characterized by a Carbon dioxide scavenger, which is a quantitative amount of the during the Ah Combustion intercepts COp formed, whereby the combustion gas during the entire combustion time through the entire absorbent liquid flows. 5. Device according to one of the preceding claims, characterized by a pneumatic control system for closing of the incinerator and for the automatic introduction of the samples into the combustion chamber. 6. Device according to one of the preceding claims, characterized through a syringe and valve unit, which the reagents and scintillation fluids to the predetermined Places. 509812/0776 2U13U 7. 'Device according to one of the preceding claims, characterized through a cleaning system to eliminate the after the burning of oxygen dissolved in the scintillation liquid according to a preselectable program. 8. Device according to one of the preceding claims, characterized by means of an electromechanical system that allows programming of the various process steps using kits such as solenoid valves and relays. 5 09812/0776 Blank page