Method of manufacture of the chromatographic generator of technetium-99m from irradiated by neutrons molybdenum-98

FIELD: radio-chemistry; methods of production of the chromatographic generator of technetium-99m from the irradiated by neutrons molybdenum-98.

SUBSTANCE: the invention is pertaining to the field of the radio-chemistry, in particular, to the methods of production of technetium-99m for medicine. Determine the specific activity of the molybdenum and the sorptive capacity of the used aluminum oxide in molybdate-ions. The mass of the molybdenum necessary for production of the preset activity of the eluate of technetium-99m determine from the ratio:ATc= 0.867·L·m ln (m)/ln(mox·Wi), where:ATc - activity of the eluate of technetium-99m, Ki; L - the specific activity of molybdenum, Ki/g; m - mass of molybdenum, g;mox - the mass of aluminum oxide in the chromatograph column, g; Wi - the sorptive capacity of the used aluminum oxide in molybdate-ions, g/g. After making of corresponding calculations the solution of molybdenum is applied on the aluminum oxide. The technical result of the invention consists in production of the generator with the required activity of technetium-99m at usage of the minimum quantity of molybdenic raw.

EFFECT: the invention ensures production of the generator with the required activity of technetium-99m at usage of the minimum quantity of molybdenic raw.

1 ex, 2 tbl, 1 dwg

 

The invention relates to the field of radiochemistry, in particular a process for the production of technetium-99m for medicine.

Short-lived radionuclide technetium-99m (99mTC) is a subsidiary of the product β-decay of the isotope molybdenum-99 (99Mo). For rapid separation from the99Mo and subsequent medical use are most commonly used small-sized device - chromatographic technetium generators (RU # 2171512). They represent a small chromatographic column Packed with a sorbent (aluminum oxide), which is applied to the molybdenum-99. All this together with inlet and outlet needles communication is placed in a protective container and transported to medical facilities, where the elution of technetium generator perform 0.9% solution of sodium chloride in the form of the finished product for intravenous injection of sodium pertechnitat,99mTc.

For "charging" of generators required99Mo with high specific activity. In the world, including in Russia, it is separated from fission products of uranium-235. This method produced a large number of related long-lived radioactive waste, which is high environmental hazard and require further processing and recycling. Alternative and virtually waste-free method of getting Mo is the neutron irradiation of the reactor molybdenum targets of natural or enriched molybdenum-98, the reaction98Mo (n, γ)99Mo. With an average thermal neutron flux of 1·1014n/cm2·enriched targets can be obtained specific activity99Mo equal to 6-8 CI/g, which, in principle, sufficient to produce chromatographic generators.

This technology was introduced in the USSR in the reactor INP EN Uz SSR in the early 90-ies, and in 2003 in Russia on the reactor IRT-T Institute of nuclear physics at Tomsk Polytechnic University (Skuridin B.C., Lapwings E.V., Nesterov E.A. Production sorption of technetium-99m generator of enriched molybdenum-98 // Nuclear and radiation physics: proceedings of the 4th international conference, 15-17 September 2004, Almaty: Institute of nuclear physics, 2004, V. 3, s-275).

In the irradiated molybdenum targets for each nuclide formed99Mo has about 104-10-5atoms of stable molybdenum-98 - media. Therefore, for the manufacture of such materials generator with a nominal activity of technetium-99m 0,5 Ki Of 18.5 GBq) and more on the column of the generator it is necessary to adsorb the order of 1 CI99Mo with a total weight of stable molybdenum in excess of 200 mg.

A known method of manufacturing a generator of technetium-99 from irradiated Nate the areas of molybdenum-98 by the reaction (n, γ)99Mo (Mikheev NB, D., Volkov, Rumer IA and other Generator technetium-99m // radiochemistry, 1971, Vol.13, No. 4. - S-633), selected as a prototype, in which the task of drawing on a column of aluminum oxide of a large number of molybdenum through the use of as sorbed form solution limit phosphomolybdate and then create a column of two layers of oxide of Al2About3: sorption, which is applied to the molybdenum, and security - to prevent "breakthrough". The method allows to absorb excess of 0.67 g of molybdenum (metal) on a column with a mass of oxide of Al2O310, however, as shown by our study and as noted in several works (Steigman J. Chemistry of the Alumina Column // Int. J. Appt. Radiat. Isof., 1982, V.33, p.829-834), the presence of stable molybdenum significantly reduces the magnitude of the output of technetium-99m from generator. As a result, by increasing the mass of molybdenum-98 to increase the total activity99Mo on the column of the generator, is not proportional to the increase in the activity allocated99mThe TC. The consequence of this is unproductive consumption of expensive enriched molybdenum-98 (about 2 USD per 1 mg) and reduced consumer characteristics of the generator by increasing the width lacienega profile of technetium-99m. The way the prototype of this factor does not take into account that determines what t his fault.

Thus, to date remains unresolved the problem of determining necessary and sufficient mass of molybdenum when given specific activity, providing the desired activity of technetium-99m allocated from the generator.

The technical result from the proposed invention is to obtain a generator with the desired activity of technetium-99m using a minimum quantity of molybdenum raw materials.

The technical problem is solved as follows. As in the known method of making chromatographic generator technetium-99m from neutron-irradiated molybdenum-98, a solution of molybdenum is applied to the aluminum oxide. In contrast to pre-determine the specific activity of molybdenum and sorption capacity of the used alumina by molybdate ions, and the desired weight of molybdenum to provide the specified activity of the eluate technetium-99m is found from the relation:

AndTc=0,867·L·m ln(m)/ln(mOX·WI),

where aTcthe activity of the eluate of technetium-99m, Ki;

L - specific activity of molybdenum, CI/g;

m is the mass of molybdenum, g;

mOX- weight of alumina chromatographic column, g;

WIsorption capacity of the used alumina by molybdate ions, g/g

As is known, the accumulation of technetium-99m-generatore occurs with a periodicity of 22 hours. In a moment of complete accumulation between activities99mTC and99Mo is the equilibrium AndTc=0,867 AndMo.

In General, the activity of technetium-99m allocated from the generator at the moment of its full savings can be found from the relation:

whereT- the total yield of technetium-99m from generator when it elution some volume of saline solution, which further increases do not lead to increased activity of the secreted radionuclide.

Experimental studies conducted more than 150 generators, showed that the relationship between the value ofTand the adsorbed mass of molybdenum is described by the expression:

where k is some adsorption coefficient depending on the weight of alumina in the column of the generator mOXand its sorption capacity WIby molybdate ions MoO42-:

The physical meaning of the sorption coefficient k is as follows. As is known, the adsorption of molybdate - or polymolybdates ions is performed on the active centers of the aluminum oxide, the total number N for which these conditions of preparation of the oxide can be estimated by the equation:

N=mOX·N0,

where N0- the density of active centers in the oxide and uminia.

Accordingly, the amount adsorbed on molybdenum oxide (NMowill be determined by the expression:

where n is the degree of polymerization of molybdenum in the structure of the adsorbed polyanion.

It is well known that the degree of polymerization of atoms of molybdenum depends on the pH of the solution of molybdate. So when changing the pH from 7 to 3 and the lower the degree of polymerization of molybdenum n increases from 1 (molybdate ions) with the subsequent formation of polianionov containing up to 7 (paramolybdate) or more atoms of molybdenum. As a consequence, the magnitude of the sorption containers Wifor molybdate ions and polianionov for the same pH-shaped oxide must differ in the n-times. In the case of adsorption of normal molybdate ions (pH˜7) the number of adsorbed atoms of molybdenum NMoshould most closely match the number of active centers in the oxide of Al2O3. Under these conditions, the formation of the atom99mTC of adsorbed99Mo is an unimpeded exit in an eluting solution. Similarly, when the adsorption of polyanion with n atoms of molybdenum greatest chance for a smooth release of technetium-99m from its structure is presented in the case, when around polyanion will be n or more free (vacant) active centers for p is regsupreme remaining atoms of molybdenum. Thus, the coefficient k characterizes the state of the system, which is the condition of NMo≤N or, equivalently, m≤mOX·WIproviding 100%yield of technetium-99m from generator.

As an example, the drawing shows the experimental dependence of changes in the output of technetium-99m from the mass of adsorbed molybdenum obtained for generators manufactured on the basis of chromatographic alumina (TU 6-09-3916-75). Weight of oxide of Al2O3in the columns was 6,89, Adsorption of molybdenum was carried out from a solution polymolybdates with pH=3. Oxide Al2O3after acidification with hydrochloric acid was washed with water to pH=3. In our case, the coefficient k=0,335. Accordingly, the output of technetium InT=1 (100%) according to relation (2) is achieved when the mass of adsorbed molybdenum m=0,048,

Table 1 shows obtained by experimental values of the coefficient k for oxides of Al2O3with different structure and different values of their masses and sorption capacities for molybdenum adsorbed from a solution with pH=7.

Table 1.
Type oxide Al2About3mOXgWI, g/gln(mOX·WI) k
THE 6-09-3916-756,890,007-3,0320,335
2,810,007-3,930,255
A-611,020,033-3,390,292
A-641,040,010-4,560,213
A-650,900,011-4,610,215

Oxides A-61, A-64 and a-65 manufactured by the method of electrosynthesis (Korobkin CENTURIES, Nesterov E.A., Skuridin B.C. and other Study of the adsorption of Mo on γ-Al2About3with different structure. / / radiochemistry, 2004, vol.46, No. 2. S-147).

Taking into account the above data, the ratio (2) expression (1) to find the activity of technetium-99m allocated from the generator, depending on the mass of adsorbed molybdenum, takes the form:

The invention is illustrated by examples of specific performance.

Example 1. Sample enriched up to 98.6% of molybdenum-98 mass of 1.1 g irradiated in the channel reactor neutron flux of 1.1·1014n/cm2·C for 160 hours After the "cooling" of the target for 10 h, it was dissolved in 5 ml of 5 M NaOH solution with the addition of 0.5 ml of hydrogen peroxide, and then transferred to polymolybdates with pH=3 by introducing in the received RA is solution of 18.5 ml of 1 M hydrochloric acid. From the resulting solution with a concentration of molybdenumMo=1,1/24=0,046 g/ml select a sample volume of 5 µl, diluted 100 times and determine the volumetric activity99Mo L, which is equal to 8.2 CI/, the same sample without dilution, enter a label in a pre-prepared test tube containing 4-5 ml inactive solution of sodium molybdate with pH=7 and the total content of molybdenum 0,1, After stirring the mixture it also selected a sample of 5 μl and measure the initial activity And0corresponding to 0.1 g of molybdenum.

In chemical beaker with a capacity of 50 ml was placed a portion of oxide of Al2About3the number of M≅1.0 g of the same party oxide, which filled the chromatographic column generators. Bulk density of the oxide of Al2About3in columns averages 6,89, glass injected the contents of the test tube and stirred for 3-5 minutes After carrying out the adsorption and full of the mixture settling select a sample of 5 μl of a layer of mortar over the oxide and measure its activity AndCcorresponding to the amount remaining after the sorption of molybdenum (0,1-M·WI), was the Value of sorption capacity WIcalculated according to equation:

In the above example, the value of WIwas 0,0073, taking into account (2) sorption coefficient k=-1/ln(0,0073·6,89)=0,334. When the treatment tip can is the time obtained higher values of L and k in equation (3) are:

Suppose that the activity of technetium-99m allocated from the generator should be equal to 0.5 CI. Then from (4) determine the amount of works-m ln(m)=0,211. To find the mass of molybdenum m, adsorbed on the column, it is convenient to use the data of table 2 below.

Table 2.
m, g0,040,050,070,090,110,1250,1500,1750,2000,2500,3000,400
-m ln(m)0,1280,1500,1860,2170,243is 0.2600,2850,3050,3220,3470,3610,366

From table 2, we find that the column of the generator must be applied 0.09 g of molybdenum. Since the concentration of molybdenum in the original solution polymolybdates is 0,046 g/ml, the column generator injected 2 ml of solution. Subsequently it is washed with water and saline solution and leave for a few hours for the accumulation of technetium-99m. Measurement of the activity of the eluate99mTC obtained by pumping through the generator 9 ml of 0.9% NaCl solution after 4 hours the donkey rinse, showed that ATc=0,193 Key. Adjusted 0,377 time full accumulation (22 h), the activity of technetium-99m at the time of manufacture was 0,511 Key.

Example 2. The source data are the same as in example 1 with the difference that the activity of technetium-99m allocated from the generator must be equal to 0.3 CI. From the expression (4) find the value of-m ln(m)=to 0.127 and table 2 define the mass of adsorbed molybdenum m=0,040, Meet her volume polymolybdates is 1 ml After washing and exposure of the generator for 4 hours activity selected technetium-99m in the eluate with a volume of 9 ml was equal 0,120 Key, and at the time of manufacture - 0,320 Key.

The proposed method allows to reduce the consumption of molybdenum-98, as well as to optimize sorbents on their mass, sorption characteristics and conditions of preparation.

The method of making chromatographic generator technetium-99m from neutron-irradiated molybdenum-98, including the application of the solution of molybdenum on alumina, wherein the pre-determined specific activity of molybdenum and the sorption capacity of the used alumina by molybdate ions, and the mass of molybdenum required to obtain a given activity of the eluate of technetium-99m, is found from the relation:

AndTc=0,867·L·m ln(m)/ln(mox·WI),

where aTcAK is Yunosti of the eluate of technetium-99m, Ki;

L - specific activity of molybdenum, CI/g;

m is the mass of molybdenum, g;

mOh- weight of alumina chromatographic column, g;

WIsorption capacity of the used alumina by molybdate ions, g/g



 

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1 ex, 1 tbl

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