- Email: [email protected]
Measurement of toxic heavy metals by neutron activation analysis
TOXICOLOGYANDAPPLIEDPHARMACOLOGY%$178-181(1973)
Measurement
of Toxic
Heavy
Metals Analysis
by
Neutron
Activation
N. D. ECKHOFF,~ R. W. CLACK,~ H. D. ANTHONY~ AND A. P. GRAYS Kansas Agricultural
Experiment Station, Kansas State University, Manhattan, Kansas 66502 Received March 7,1972
Measurementof Toxic Heavy Metals by Neutron Activation Analysis. D., CLACK, R. W., ANTHONY, H.D. ANDGRAY, A.P.(1973). Toxicol. Appl. Pharmacol. 24, 178-181,Neutron activation analysis(NAA) wasusedto identify explicitly the causativeagentin a caseof suspectedheavy element poisoning of livestock that conventional diagnostic techniques left unclear.NAA, usingneutronsfrom a TRIGA Mark11 NuclearReactor and a 25-cc germaniumlithium-drifted semiconductordetector, sequentially revealedthe absenceof toxic concentrationsof mercury in liver and kidney tissuesof an affected carcass,then the absenceof toxic amountsof arsenic,and finally the presenceof antimony in quantitiessufficientto have killed livestock.
ECKHOFF,N.
The absenceof a timely, unambiguous, analytical technique to identify the reason why about 1% (45-50 animals) of the cattle in a medium-sized, central Kansas feedlot died led to our using neutron activation analysis (NAA) (Lyon, 1964). The NAA procedure used in solving the problem follows. METHODS A small (approximately 0.9 g, i.e., about 0.5 ml) sample of kidney tissue and one of liver tissue were taken from the carcassof an afflicted animal. The sampleswere irra-
diated in the Kansas State University TRIGA Mark II Nuclear Reactor for approximately 2 min at a thermal neutron flux of approximately 3 x 10” neutrons/cm2 sec. This procedure produced approximately 0.01-0.1 @i of radioactivity in each sample. Because mercury poisoning was suspected, a 0.0431-g sample of HgO was irradiated simultaneously with the kidney and liver samples. Each sample was counted while positioned near the surface of a 25 cm2, trapezohedral, germanium, lithium-drifted semiconductor detector (Nuclear Diodes), which is constantly cooled by liquid nitrogen (77°K). The resolution of the detector is approxi-
mately 6.0 keV for the 1332.51 keV peak of 6oCo. This detector was connected through a Tennelec linear amplifier (TC-200) to a Technical Measurements Corporation 4096 channel multiparameter analyzer. Table 1contains a listing of pertinent data concerning the four radioisotopes of interest 19’Hg, 76As, rzzSb and 124Sb. 1ContributionNo. 14,Departmentof NuclearEngineering. ’ ContributionNo. 233,Departmentof Pathology. Copyright All rights
0 1973 by Academic Press, Inc. of reproduction in any form reserved.
178
ANALYSIS
FOR
TOXIC
HEAVY
179
METALS
TABLE 1 PERTINENT DATA FOR 19’Hg, 76A~, lz2Sb, AND 124Sb
197H
g
16As 12*Sb
124Sb
Main y-w (kev)
Secondary y-w
77.00 559.09 564.08 602.72
66.00 657.04 692.76 1691.03
Half-life (W
(keW
65.0 26.5 67.3 1442.0
RESULTS
Comparing spectra from the liver and kidney samples with the HgO sample spectrum gave no indication of 19’Hg in either the kidney or liver. A calculation similar to that of Eckhoff et al. (1971) shows the sensitivity (the minimum detectable Hg at 0.1 fractional error, i.e., SD divided by concentration estimate) of this analysis is 5.0 ppm Hg.
NO Sb K CO Amthilafion Background
2754,2243,1732,1368 ,691 , 692, 602,564 1523 1332, 1173 511 1460
:754 732
54
%:a0
lb.00
FIG.
1.
2b.
00
3b.00
Qb.00
sb.oo
CHRNNEL
NUMBER
4 66.00 *IO’
2243
7b.00
sb. 00
r
100.00
Run 326, Liver: 2 min x 225 kW; 88.54 hr decay, 610 min count.
Spectra from liver and kidney samples compared with a y-ray spectrum of 76As taken from a previously collected library of y-ray spectra convincingly matched. For positive identification, the tissue samples were reirradiated in the immediate proximity of a 0.0094-g AsO, sample for 2 min at 1.6 x 1012 n/cm2 sec. Comparing spectra from all three samples revealed a 5 keV difference between the characteristic 559.09 keV 76As peak and peaks resulting from the irradiated tissue samples.
180
ECKHOFF
ET AL..
A new energy calibration showed the energy of the peak of interest to be 564.08 keV, a y-ray energy characteristic of l%b. Then irradiation of a 0.0084-g sample of SbO, for 2 min at a neutron flux of approximately 1.6 x 1012 n/cm2 set yielded an antimony
64
Element
Energies
NO
2754,
2243,
(MeV! 1732,1368
Background CO Sb Annihilation
1460 1332, 693, 511
1173 602.
564
1368
1732 1460
-~--lb.oozb.oo
i
30.00 uo.oo- SO.00 6O.Op70.00 80.00 90.00 100.00 CHANNEL
FIG.
2754 2243
NUMBER
Ml0
2. Run 327. Kidney; 2 min x 225 kW; 105.41 hr decay, 150 min count.
lsoiope
Energies
‘=Sb ‘=Sb
1256, 1691,
(MeV) 1141,692, 602
1141 1256 1691 I
FIG.
3. Run 329. Antimony reference.
564
ANALYSISFORTOXICHEAVYMETALS
181
reference spectrum. Comparing spectra collected from the reirradiated liver and kidney samples with the spectrum collected from the SbO, shows an excellent agreement among peak locations (Figs. l-3). Areas of the 564.08 keV peaks from each spectrum yielded concentrations of 45 ppm and 33 ppm Sb in liver and kidney samples, respectively. DISCUSSION Although considerable time elapsed between irradiation and positive identification of antimony, rather than mercury or arsenic, mercury was eliminated from consideration within 30 min after irradiation. The entire analysis was nondestructive. With more experience such analyses can become routine for toxicology laboratories which have accessto NAA facilities. Indeed, this incident illustrates that neutron activation analysis can provide a rapid, nondestructive, and precise diagnostic tool for heavy element toxicity analyses. The origin of antimony compounds that would result in concentrations as high as those we found remains unknown. Study in progress, we hope, may lead to the origin of the antimony compounds. REFERENCES Analysis. Van Nostrand-Reinhold, Princeton. New Jersey. ECKHOFF,N. D., ERVIN,P.F.,CLACK, R. W. AND LAMBERT, J.P.(1971). Sensitivities ofsome heavy metals in typical environmental matrices, Trace Substances in Environmental Health, Vol. 5, Univ. of Missouri, Columbia. LYON, W. S., JR, (1964). Guide to Activation
Measurement
of Toxic
Heavy
Metals Analysis
by
Neutron
Activation
N. D. ECKHOFF,~ R. W. CLACK,~ H. D. ANTHONY~ AND A. P. GRAYS Kansas Agricultural
Experiment Station, Kansas State University, Manhattan, Kansas 66502 Received March 7,1972
Measurementof Toxic Heavy Metals by Neutron Activation Analysis. D., CLACK, R. W., ANTHONY, H.D. ANDGRAY, A.P.(1973). Toxicol. Appl. Pharmacol. 24, 178-181,Neutron activation analysis(NAA) wasusedto identify explicitly the causativeagentin a caseof suspectedheavy element poisoning of livestock that conventional diagnostic techniques left unclear.NAA, usingneutronsfrom a TRIGA Mark11 NuclearReactor and a 25-cc germaniumlithium-drifted semiconductordetector, sequentially revealedthe absenceof toxic concentrationsof mercury in liver and kidney tissuesof an affected carcass,then the absenceof toxic amountsof arsenic,and finally the presenceof antimony in quantitiessufficientto have killed livestock.
ECKHOFF,N.
The absenceof a timely, unambiguous, analytical technique to identify the reason why about 1% (45-50 animals) of the cattle in a medium-sized, central Kansas feedlot died led to our using neutron activation analysis (NAA) (Lyon, 1964). The NAA procedure used in solving the problem follows. METHODS A small (approximately 0.9 g, i.e., about 0.5 ml) sample of kidney tissue and one of liver tissue were taken from the carcassof an afflicted animal. The sampleswere irra-
diated in the Kansas State University TRIGA Mark II Nuclear Reactor for approximately 2 min at a thermal neutron flux of approximately 3 x 10” neutrons/cm2 sec. This procedure produced approximately 0.01-0.1 @i of radioactivity in each sample. Because mercury poisoning was suspected, a 0.0431-g sample of HgO was irradiated simultaneously with the kidney and liver samples. Each sample was counted while positioned near the surface of a 25 cm2, trapezohedral, germanium, lithium-drifted semiconductor detector (Nuclear Diodes), which is constantly cooled by liquid nitrogen (77°K). The resolution of the detector is approxi-
mately 6.0 keV for the 1332.51 keV peak of 6oCo. This detector was connected through a Tennelec linear amplifier (TC-200) to a Technical Measurements Corporation 4096 channel multiparameter analyzer. Table 1contains a listing of pertinent data concerning the four radioisotopes of interest 19’Hg, 76As, rzzSb and 124Sb. 1ContributionNo. 14,Departmentof NuclearEngineering. ’ ContributionNo. 233,Departmentof Pathology. Copyright All rights
0 1973 by Academic Press, Inc. of reproduction in any form reserved.
178
ANALYSIS
FOR
TOXIC
HEAVY
179
METALS
TABLE 1 PERTINENT DATA FOR 19’Hg, 76A~, lz2Sb, AND 124Sb
197H
g
16As 12*Sb
124Sb
Main y-w (kev)
Secondary y-w
77.00 559.09 564.08 602.72
66.00 657.04 692.76 1691.03
Half-life (W
(keW
65.0 26.5 67.3 1442.0
RESULTS
Comparing spectra from the liver and kidney samples with the HgO sample spectrum gave no indication of 19’Hg in either the kidney or liver. A calculation similar to that of Eckhoff et al. (1971) shows the sensitivity (the minimum detectable Hg at 0.1 fractional error, i.e., SD divided by concentration estimate) of this analysis is 5.0 ppm Hg.
NO Sb K CO Amthilafion Background
2754,2243,1732,1368 ,691 , 692, 602,564 1523 1332, 1173 511 1460
:754 732
54
%:a0
lb.00
FIG.
1.
2b.
00
3b.00
Qb.00
sb.oo
CHRNNEL
NUMBER
4 66.00 *IO’
2243
7b.00
sb. 00
r
100.00
Run 326, Liver: 2 min x 225 kW; 88.54 hr decay, 610 min count.
Spectra from liver and kidney samples compared with a y-ray spectrum of 76As taken from a previously collected library of y-ray spectra convincingly matched. For positive identification, the tissue samples were reirradiated in the immediate proximity of a 0.0094-g AsO, sample for 2 min at 1.6 x 1012 n/cm2 sec. Comparing spectra from all three samples revealed a 5 keV difference between the characteristic 559.09 keV 76As peak and peaks resulting from the irradiated tissue samples.
180
ECKHOFF
ET AL..
A new energy calibration showed the energy of the peak of interest to be 564.08 keV, a y-ray energy characteristic of l%b. Then irradiation of a 0.0084-g sample of SbO, for 2 min at a neutron flux of approximately 1.6 x 1012 n/cm2 set yielded an antimony
64
Element
Energies
NO
2754,
2243,
(MeV! 1732,1368
Background CO Sb Annihilation
1460 1332, 693, 511
1173 602.
564
1368
1732 1460
-~--lb.oozb.oo
i
30.00 uo.oo- SO.00 6O.Op70.00 80.00 90.00 100.00 CHANNEL
FIG.
2754 2243
NUMBER
Ml0
2. Run 327. Kidney; 2 min x 225 kW; 105.41 hr decay, 150 min count.
lsoiope
Energies
‘=Sb ‘=Sb
1256, 1691,
(MeV) 1141,692, 602
1141 1256 1691 I
FIG.
3. Run 329. Antimony reference.
564
ANALYSISFORTOXICHEAVYMETALS
181
reference spectrum. Comparing spectra collected from the reirradiated liver and kidney samples with the spectrum collected from the SbO, shows an excellent agreement among peak locations (Figs. l-3). Areas of the 564.08 keV peaks from each spectrum yielded concentrations of 45 ppm and 33 ppm Sb in liver and kidney samples, respectively. DISCUSSION Although considerable time elapsed between irradiation and positive identification of antimony, rather than mercury or arsenic, mercury was eliminated from consideration within 30 min after irradiation. The entire analysis was nondestructive. With more experience such analyses can become routine for toxicology laboratories which have accessto NAA facilities. Indeed, this incident illustrates that neutron activation analysis can provide a rapid, nondestructive, and precise diagnostic tool for heavy element toxicity analyses. The origin of antimony compounds that would result in concentrations as high as those we found remains unknown. Study in progress, we hope, may lead to the origin of the antimony compounds. REFERENCES Analysis. Van Nostrand-Reinhold, Princeton. New Jersey. ECKHOFF,N. D., ERVIN,P.F.,CLACK, R. W. AND LAMBERT, J.P.(1971). Sensitivities ofsome heavy metals in typical environmental matrices, Trace Substances in Environmental Health, Vol. 5, Univ. of Missouri, Columbia. LYON, W. S., JR, (1964). Guide to Activation