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The determination of iodine in thyroid gland with epithermal neutrons
A+zlylica
372
SHORT
Chinrica
ncta
Elscvicr Publishing Cor~pany, l’rintcd in The Ncttmrlands
An~,tcrdn~~~
COMMUNICATIONS
The determination
of iodine
in thyroid
gland with epithermal
neutrons
Iodine is an important element in the life sciences and special attention leas heen given to its determination hy neutron activation methods (e.g. refs. 1-4). In humans iodine is closely involved in thyroid metabolism and is accumulated in the thyroid gland. The iodine content of the thyroicl gland has consequently attracted substantial interest. Although thermal neutron activation analysis has usually been applied for the determination of iodine, the technique of cpithermal activation has received little The epithermal method has previously been applied, however, in consideration. connection with i9z viva activation studies”. The aim of the present work was to demonstrate the advantages resulting from the use of epithermal neutron activation analysis of iodine in small thyroid tissue specimens.
Santy’dcs. Nine samples of roughly 50 mg wet weight were prepared from one normal thyroid gland. The gland was first cut into small pieces which were then mixed in order to obtain sample homogeneity. The 5o-mg samples were selected from this mixture. The samples were wrapped in aluminium foil and stored in a refrigerator. Irvndiaticm. The frozen samples together with standards were placecl in a cooled caclmium cylinder of 50 mm height, 20 mm cliameter and o.G mm wall thickness. The cylinder was transfeqed to a stanclard aluminium container, which was inserted in a cryostat in a thermal neutron flux of z -1012 n cm-2 set-1 in the reactor R 1”. The samples were irradiated for ro min. A,fter irradiation the cadmium container was removed, the samples were placed on blocks of dry ice and the aluminium foils were unwrappecl. Menswwmm%. The 1281 activity induced in the samples was evaluated by means of y-spectrometric analysis with a 3” x 3” NaI (Tl)-crystal connected to a zg6-mul,tichannel analyzer (Nuclear Data).
The iodine content measured in each of the 9 samples studied, is given in Table I. The mean value and its standard error amounted to (671 k 15) ,ug g-1 of wet tissue. This result is in agreement with values for normal indiviclualsfl. With the epithermal neutron activation technique, the 1281activity is strongly enhanced comparecl to the ““Na ancl ““Cl activities. In the present instance the “advantage” factor’ was about II. In acldition the 1281activity induced by epithermal activation in small samples, i.e. biopsy samples of 5-ro mg wet weight. is still sufficient for an accurate analysis. (The sample-to-crystal distance was LO cm in this study.) .rlnnl.Clrirrr.A&n, 52 (1970) 372-373
SHORT
CO~IXIUNICATIONS
IODIXE
CONCENTRATION
,su??lplc
ILV.
373
OF9
Corbor.
fiGg-1)
HOMOGENI%ED
SAMI'LES
OPTHE
SAME
TEIYHOID
GLAND
in wrl lissm .-._..--.._ __.__-___
In other biological samples such as those of whole blood, the ZaNa ancl3Xl activities are even more dominant and a chemical separation step is necessary before the rneasurement of the I’-81 activity can bc accomplished. In such cases, however, epithcrmal activation is of interest from the health point of view, since the gross activity of the sample is considerably reduced. In the present study the samples were irradiated in a cryostat in a central reactor channel. In this way the handling procedure was facilitated and the risk of iodine loss by vaporization was avoided. For small aqueous, samples, in particular, e.g. enzyme samples, low-temperature irradiation techniques favour accurate analysis, since on drying before irradiation such solutions leave only a thin film on the container surface. Quantitative removal of this film after irradiation .can present considerable difficulties. Low-temperature irradiation can also be carried out with dry ice- or liquid helium cooling techniques7*“. The authors greatly
appreciate
the technical
assistance of lMiss I. SuNrxJVIsT.
I D. CoalA~ AND C. KRLLERSU~HN, ~~~~~~~~~ Aclivalio~r ‘/‘ech~rir/ucs i?t (Ire Liff: Scieuccs, 13-m. of ari I.A.E.A. Symp., hmst.crdam, 8-12 May rgG7.p. ,103. AND R. Mr\tv~No, _iiVi'ltclcar Aclivcrfiorr 7’echrtiqm.s iu fire Lif;! Scicucfx, 2 17. COTTINI, C;. MAGRO Proc. of an T.A.E.A. Syrnp., hnistcrclan~,%12 May rg67,p. ,419. 3 IC. BODDY AND W. 11. ALEXANDIIR, NmAxzr A cfivctlio?r ‘I’ech?riqrrc!s in Ihr IAifc .%if!mcs, Proc. of a.11 I .A.E.A. Sytnp.. Amstcrclatn, 8-t 2 May rgb7, p, $33. .I J. M. A. LENIHAN, I). COMAR, R. IZIVIERE AND C.TCEI,LEHSHOIIN. Ndtt~e, 214 (1967) 1221. 5 N.BERGLUND, ~>.BRUNE AND B. Sccrifim~c, h'cd. Irbslv. flfclhods, 75 (1gOg) 103. 6 E. J. UNDERWOOD, 'I'uacc! ELwrmrls irr Huntcm ad A Gnu1 Nlr,dyi/imz, Acadctnic Press, New \‘ork-London, fgG2,p.zz.J. 7 I>. Bt~uam, AWLS. China. AC/~, .iG (rgGg) I 7. S D. BRUNB A~ND I-1. WRNZL. Ed. Cltcm., 42 (1970) 51 I.
(Received
May
* Dcpartrncntof
moth, 1970) Meclicinc, Iiarolinslca
Jnstitutct
nt Scrnfinlcrlnsarcttct. Attal.
Stockholm.
Cliim.
A da,
52 (1970) 372-373
372
SHORT
Chinrica
ncta
Elscvicr Publishing Cor~pany, l’rintcd in The Ncttmrlands
An~,tcrdn~~~
COMMUNICATIONS
The determination
of iodine
in thyroid
gland with epithermal
neutrons
Iodine is an important element in the life sciences and special attention leas heen given to its determination hy neutron activation methods (e.g. refs. 1-4). In humans iodine is closely involved in thyroid metabolism and is accumulated in the thyroid gland. The iodine content of the thyroicl gland has consequently attracted substantial interest. Although thermal neutron activation analysis has usually been applied for the determination of iodine, the technique of cpithermal activation has received little The epithermal method has previously been applied, however, in consideration. connection with i9z viva activation studies”. The aim of the present work was to demonstrate the advantages resulting from the use of epithermal neutron activation analysis of iodine in small thyroid tissue specimens.
Santy’dcs. Nine samples of roughly 50 mg wet weight were prepared from one normal thyroid gland. The gland was first cut into small pieces which were then mixed in order to obtain sample homogeneity. The 5o-mg samples were selected from this mixture. The samples were wrapped in aluminium foil and stored in a refrigerator. Irvndiaticm. The frozen samples together with standards were placecl in a cooled caclmium cylinder of 50 mm height, 20 mm cliameter and o.G mm wall thickness. The cylinder was transfeqed to a stanclard aluminium container, which was inserted in a cryostat in a thermal neutron flux of z -1012 n cm-2 set-1 in the reactor R 1”. The samples were irradiated for ro min. A,fter irradiation the cadmium container was removed, the samples were placed on blocks of dry ice and the aluminium foils were unwrappecl. Menswwmm%. The 1281 activity induced in the samples was evaluated by means of y-spectrometric analysis with a 3” x 3” NaI (Tl)-crystal connected to a zg6-mul,tichannel analyzer (Nuclear Data).
The iodine content measured in each of the 9 samples studied, is given in Table I. The mean value and its standard error amounted to (671 k 15) ,ug g-1 of wet tissue. This result is in agreement with values for normal indiviclualsfl. With the epithermal neutron activation technique, the 1281activity is strongly enhanced comparecl to the ““Na ancl ““Cl activities. In the present instance the “advantage” factor’ was about II. In acldition the 1281activity induced by epithermal activation in small samples, i.e. biopsy samples of 5-ro mg wet weight. is still sufficient for an accurate analysis. (The sample-to-crystal distance was LO cm in this study.) .rlnnl.Clrirrr.A&n, 52 (1970) 372-373
SHORT
CO~IXIUNICATIONS
IODIXE
CONCENTRATION
,su??lplc
ILV.
373
OF9
Corbor.
fiGg-1)
HOMOGENI%ED
SAMI'LES
OPTHE
SAME
TEIYHOID
GLAND
in wrl lissm .-._..--.._ __.__-___
In other biological samples such as those of whole blood, the ZaNa ancl3Xl activities are even more dominant and a chemical separation step is necessary before the rneasurement of the I’-81 activity can bc accomplished. In such cases, however, epithcrmal activation is of interest from the health point of view, since the gross activity of the sample is considerably reduced. In the present study the samples were irradiated in a cryostat in a central reactor channel. In this way the handling procedure was facilitated and the risk of iodine loss by vaporization was avoided. For small aqueous, samples, in particular, e.g. enzyme samples, low-temperature irradiation techniques favour accurate analysis, since on drying before irradiation such solutions leave only a thin film on the container surface. Quantitative removal of this film after irradiation .can present considerable difficulties. Low-temperature irradiation can also be carried out with dry ice- or liquid helium cooling techniques7*“. The authors greatly
appreciate
the technical
assistance of lMiss I. SuNrxJVIsT.
I D. CoalA~ AND C. KRLLERSU~HN, ~~~~~~~~~ Aclivalio~r ‘/‘ech~rir/ucs i?t (Ire Liff: Scieuccs, 13-m. of ari I.A.E.A. Symp., hmst.crdam, 8-12 May rgG7.p. ,103. AND R. Mr\tv~No, _iiVi'ltclcar Aclivcrfiorr 7’echrtiqm.s iu fire Lif;! Scicucfx, 2 17. COTTINI, C;. MAGRO Proc. of an T.A.E.A. Syrnp., hnistcrclan~,%12 May rg67,p. ,419. 3 IC. BODDY AND W. 11. ALEXANDIIR, NmAxzr A cfivctlio?r ‘I’ech?riqrrc!s in Ihr IAifc .%if!mcs, Proc. of a.11 I .A.E.A. Sytnp.. Amstcrclatn, 8-t 2 May rgb7, p, $33. .I J. M. A. LENIHAN, I). COMAR, R. IZIVIERE AND C.TCEI,LEHSHOIIN. Ndtt~e, 214 (1967) 1221. 5 N.BERGLUND, ~>.BRUNE AND B. Sccrifim~c, h'cd. Irbslv. flfclhods, 75 (1gOg) 103. 6 E. J. UNDERWOOD, 'I'uacc! ELwrmrls irr Huntcm ad A Gnu1 Nlr,dyi/imz, Acadctnic Press, New \‘ork-London, fgG2,p.zz.J. 7 I>. Bt~uam, AWLS. China. AC/~, .iG (rgGg) I 7. S D. BRUNB A~ND I-1. WRNZL. Ed. Cltcm., 42 (1970) 51 I.
(Received
May
* Dcpartrncntof
moth, 1970) Meclicinc, Iiarolinslca
Jnstitutct
nt Scrnfinlcrlnsarcttct. Attal.
Stockholm.
Cliim.
A da,
52 (1970) 372-373