Chapter 17
Trace Elements in National Institute for Environmental Studies Standard Reference Materials Determination by Instrumental Neutron Activation Analysis
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Shogo Suzuki and Shoji Hirai Atomic Energy Research Laboratory, Musashi Institute of Technology, 971 Ohzenji, Asao-ku, Kawasaki 215, Japan
Concentrations of trace elements in standard reference materials prepared by the National I n s t i t u t e for Environmental Studies of Japan (NIES) were determined by instrumental neutron a c t i v a t i o n analysis (INAA). The reference materials analyzed were: human hair, mussel, tea leaves, vehicle exhaust p a r t i c u l a t e s , Sargasso and unpolished r i c e flour. These specimens were i r r a d i a t e d under optimized conditions at the Musashi I n s t i t u t e of Technology Research Reactor. The activated samples were measured using three methods: conventional γ -ray spectrometry; anticoincidence γ-ray spectrometry; and coincidence γ -ray spectrometry. We could determine more than 50 elements in the majority of samples. The results obtained were in good agreement with the NIES certified and provisional values.
Trace elements p l a y an i m p o r t a n t r o l e i n e n v i r o n m e n t a l , b i o l o g i c a l and m e d i c a l f i e l d s . T h e r e f o r e , e n v i r o n m e n t a l and b i o m e d i c a l samples s h o u l d be a n a l y z e d w i t h good accuracy and p r e c i s i o n . The b e s t approach t o ensure t h e a c c u r a c y and p r e c i s i o n o f a measurement i s t o use a p p r o p r i a t e s t a n d a r d r e f e r e n c e m a t e r i a l s . The N a t i o n a l I n s t i t u t e f o r E n v i r o n m e n t a l S t u d i e s o f Japan (NIES) s u p p l i e s v a r i o u s standard reference materials with c e r t i f i e d values(1). In t h i s paper, We r e p o r t t h e c o n c e n t r a t i o n s o f a number o f t r a c e elements i n the NIES r e f e r e n c e m a t e r i a l s u s i n g i n s t r u m e n t a l neutron a c t i v a t i o n a n a l y s i s (INAA). In c o n v e n t i o n a l INAA, t h e sample i s i r r a d i a t e d w i t h t h e r m a l n e u t r o n s , and s u b s e q u e n t l y counted u s i n g a c o a x i a l Ge d e t e c t o r i n c o n j u n c t i o n with a multichannel pulse height analyzer. We used t h i s system; i n a d d i t i o n , we a l s o used c o n v e n t i o n a l t h e r m a l n e u t r o n i r r a d i a t i o n w i t h o u t a cadmium f i l t e r ; e p i t h e r m a l neutron i r r a d i a t i o n w i t h a cadmium f i l t e r ; c o n v e n t i o n a l 7 -ray s p e c t r o m e t r y w i t h t h e c o a x i a l Ge d e t e c t o r ; and a n t i c o i n c i d e n c e and c o i n c i d e n c e y - r a y 0097-6156/91/0445-0221$06.00/0 © 1991 American Chemical Society
In Biological Trace Element Research; Subramanian, K., et al.; ACS Symposium Series; American Chemical Society: Washington, DC, 1991.
222
BIOLOGICAL TRACE ELEMENT RESEARCH
s p e c t r o m e t r y w i t h the c o a x i a l Ge d e t e c t o r and a w e l l - t y p e Nal (Tl) detector. The v a r i o u s approaches used p e r m i t t e d measurement of a number of elements w i t h h i g h accuracy and p r e c i s i o n ( 2 ) .
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EXPERIMENTAL METHODS P r e p a r a t i o n of Samples and Standards. Human h a i r , mussel, t e a l e a v e s , v e h i c l e exhaust p a r t i c u l a t e s , Sargasso and u n p o l i s h e d r i c e f l o u r ( a l l NIES r e f e r e n c e m a t e r i a l s ) samples of each 8 - 2 0 p o r t i o n s (150 — 1200 mg) were weighed i n t o a c l e a n p o l y e t h y l e n e bag and then double s e a l e d i n a p o l y e t h y l e n e bag. Aqueous, a c i d i c s t a n d a r d s o l u t i o n s g e n e r a l l y recommended f o r atomic a b s o r p t i o n s p e c t r o m e t r y were used as s u r r o g a t e s t a n d a r d s . A l i q u o t e s of 1 0 - 2 0 0 //1 were p i p e t t e d onto c l e a n f i l t e r papers (Toyo R o s h i Co. ) and t h e papers were doubly s e a l e d i n c l e a n p o l y e t h y l e n e bag. I r r a d i a t i o n and y -ray Counting. The samples ( r e f e r e n c e m a t e r i a l s ) and s t a n d a r d s were i n s e r t e d i n t o p o l y e t h y l e n e c a p s u l e s , and were i r r a d i a t e d e i t h e r f o r 30 s, or f o r 5 h a t the Musashi I n s t i t u t e of Technology Research R e a c t o r (MITRR). The two i r r a d i a t i o n s were c a r r i e d out w i t h and w i t h o u t cadmium f i l t e r . The cadmium f i l t e r was made of 1 mm t h i c k cadmium cover. I r r a d i a t i n g and c o u n t i n g c o n d i t i o n s , and the n u c l i d e s used f o r measurement a r e shown i n Table I . The samples were i r r a d i a t e d f o r 30 s; c o o l e d f o r 1-4 min; and counted f o r 5 min u s i n g c o n v e n t i o n a l and a n t i c o i n c i d e n c e y - r a y spectrometry. The same samples were then c o o l e d f o r 12-40 min and s u b s e q u e n t l y counted f o r 9 — 30 min. In the second approach, the samples were i r r a d i a t e d f o r 5 h; c o o l e d f o r 3-10 days; and counted f o r 3 — 1 4 h u s i n g c o n v e n t i o n a l , a n t i c o i n c i d e n c e and c o i n c i d e n c e y - r a y spectrometry. The same samples were a g a i n c o o l e d f o r 12-60 days and s u b s e q u e n t l y counted for 7-40 h. An 85 cm c o a x i a l Ge d e t e c t o r ( r e l a t i v e e f f i c i e n c y 16% and FWHM 1.8 keV a t 1332 keV) was used f o r c o n v e n t i o n a l y -ray s p e c t r o m e t r y . For a n t i c o i n c i d e n c e and c o i n c i d e n c e y -ray s p e c t r o m e t r y , t h e c o a x i a l Ge d e t e c t o r and a l s o a w e l l - t y p e N a K T l ) d e t e c t o r ( 6 i n . Φ X 6 i n . , w e l l 3 i n . Φ X 4 i n . ) were used. The y - r a y working ranges of the N a K T l ) d e t e c t o r were s e t t o about 4 0 - 3 5 0 0 keV and 90-170 keV i n a n t i c o i n c i d e n c e and c o i n c i d e n c e y - r a y s p e c t r o m e t r y , r e s p e c t i v e l y (3). For m o n i t o r i n g the neutron f l u x , about 20 mg of A l w i r e c o n t a i n i n g 0.15% Sb was i r r a d i a t e d t o g e t h e r w i t h the samples and the standards. The neutron f l u x of samples and the s t a n d a r d s was c o r r e c t e d u s i n g the S b and S b a c t i v i t i e s of the i r r a d i a t e d A l wires. 3
1 2 2
1 2 4
y - r a y S p e c t r o m e t r i c A n a l y s i s System. The y -ray s p e c t r o m e t r i c a n a l y s i s system c a l l e d GAMA (Gamma-spectra A n a l y s i s of Musashi I n s t i t u t e of Technology, Atomic Energy Research L a b o r a t o r y ) was developed and c o n s t r u c t e d in-house(4H>). We b u i l t f o u r models of GAMA. The b l o c k diagram of the GAMA-IV system i s shown i n F i g u r e 1. I t c o n s i s t s of an a c q u i s i t i o n p a r t and an a n a l y s i s p a r t . The y - r a y spectrum i s generated w i t h the h e l p of a mini-computer (SORD computer Co.; model M343). The a c q u i s i t i o n area of the
In Biological Trace Element Research; Subramanian, K., et al.; ACS Symposium Series; American Chemical Society: Washington, DC, 1991.
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17.
Trace Elements NIES Standard Reference Materials
SUZUKI & HIRAI
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Partially expand display
NEC PC-9801ES (640kB) ( Monitor V display Figure 1.
Laser printer
Block Diagram of GAMA-W System.
In Biological Trace Element Research; Subramanian, K., et al.; ACS Symposium Series; American Chemical Society: Washington, DC, 1991.
223
In Biological Trace Element Research; Subramanian, K., et al.; ACS Symposium Series; American Chemical Society: Washington, DC, 1991.
ID
Π
I
5 h
5 h
Central thimble
Central thimble
30 s
5 h
Central thimble
Pneumatic transfer
30 s
Irradiation tiie
Pneumatic transfer
Irradiation facility
Cooling tiie 3 8
2 4
3 - 14 h
7 - 40 h
3 -10 d
12 - 6 0 d
8-40 h
1 7 7
1 4 4
l 8 7
1 2 2
8 2
1 2 2
1 0 1
2 3 9
1 4 2
Mo,
In,
9 9 m
1 1 6 m
1 2 5 m
Sn,
5 1
9 5
59
1 4 0
54
8 2
1 1 3
60
1 5 3
1 2 8
5 2
1 1 3
1
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1 7 5
65
1 5 3
65
1 8 7
Dy
86
2 3 3
1 6 0
1 3 1
75
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1 6 5
1 1 5
Ba,
2 0 3
1 2 4
Tc, Yb,
3 9
9 9 m
1,
6 6
1 8 2
1 5 2
58
1 5 3
5
B
Se,
1 3 1
1 3 1
Ba,
1 4 4
1 6 9
1 8 1
1 8 2
Hf
1 4 7
1 1 0 m
1 5 2
2 0 3
2 3 3
1 5 3
1 2 4
1 6 0
1 3 1
1 3 4
S c , Cr, F e , M n , C o , C o , Z n , R b , Sr, Zr, Ag, Sn, Sb, 1, Cs, Ba, Ce, Nd, Eu, Gd, Tb, i70»p γ5 Ta Hg Pa 8 5
2 3 9
4 6
1 9 8
1 1 5 m
7 6
8 0
5 1
t 8 1
1 4 7
60
1 4 0
l 9 8
1 1 0 m
54
7 6
8 0
Na, K, As, Br,"Mo, In, Sb, La, Sm, Au, Np
4 2
2 4
5 6
4 9
9 5
59
7 2
1 6 5
Na, Cl, Mn, Br,
2 8
1 6 9
1 7 0
3 8
14-80 d
6 6
Mg, Al, Ca, Ti, V, Cu,
1 3 1
8 5
1 3 4
5 1
8 6
2 4
12 -40min
5 2
S c , Cr, F e , Mn, C o , C o , Z n , S e , Rb, Sr, Zr, Ag, Sn, Sb, 1, Cs, Ba, Ce, Nd, Eu, Gd, Tb, Tm, Yb, Lu, Hf, Ta, Hg, Pa
4 6
1 7 5
l 6 6
4 2
1 1 5 m
2 7
4 9
Na, K, Ga, As, Br,"Mo, Tc, Cd, In, Sb, La, Pr, Sm, Ho, Yb, W, Au, Np
1 3 9
U 5
2 4
1 2 8
5 6
3 7
Na, Cl, Mn, Br, I, Ba, Dy
2 8
2 7
Mg, Al, S, Ca, Ti, V, Cu,
5 1
Conditions
Nuclide
and Counting
9 - 30min
5mi η
7-40 h
12-60 d
1 — 4 min
3-14 h
9-30min
3-10 d
12-40min
5min
Counting tine
Irradiating
1 — 4 min
Table I
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Trace Elements NIES Standard Reference Materials
SUZUKI & H I R A I
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