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Flameless atomic absorption spectrometry of antimony
Analytica Chimica Acta, 64 (1973) 381-386 © Elsevier Scientific Publishing Company, Amsterdam - Printed in The Netherlands
FLAMELESS ATOMIC ABSORPTION
SPECTROMETRY
381
OF ANTIMONY
MASAAKI YANAGISAWA and TSUGIO TAKEUCHI Department of Synthetic Chepnistry, Faculty of Engineering, Nagoya University, Cilikusa-ku, Nagoya (Japan)
and MASAMI SUZUKI Department of Chemistry, Faculty of Engineering, Mie University, Kamihama.cho, Tsu-shi, .Mie-ken (Japan)
(Received 9th October 1972)
T h e flameless a t o m i c a b s o r p t i o n s p e c t r o m e t r y o f volatile a n d involatile elements has been widely i n v e s t i g a t e d I because o f the high a b s o l u t e sensitivity w h i c h permits the use o f v e r y small samples; the reliability o f t h e t e c h n i q u e is c o m p a r a b l e with that o f the c o n v e n t i o n a l flame m e t h o d . However, n o published i n f o r m a t i o n exists p e r t a i n i n g to the d e t e r m i n a t i o n o f a n t i m o n y by flameless a t o m i c a b s o r p t i o n spectrometry. This p a p e r describes the a t o m i c a b s o r p t i o n b e h a v i o r o f a n t i m o n y w i t h a c a r b o n r o d a t o m i z e r and its a p p l i c a t i o n to m e t a l l u r g i c a l samples. EXPERIMENTAL Apparatus
A V a r i a n T e c h t r o n AA-1000 a t o m i c a b s o r p t i o n s p e c t r o p h o t o r n e t e r was used with a V a r i a n T e c h t r o n M o d e l 61 c a r b o n r o d a t o m i z e r s u b s t i t u t e d for t h e b u r n e r assembly. T h e a t o m i c a b s o r p t i o n signals were r e c o r d e d o n a H i t a c h i Q P D - 5 4 recorder. T h e c a r b o n r o d w a s o f the " M i n i - M a s s m a n n " type w h i c h h a d a 1.5-mm d i a m e t e r transverse hole as the s a m p l e cavity. Light f r o m the h o l l o w - c a t h o d e l a m p was focussed t h r o u g h the c a v i t y a n d t h e a b s o r p t i o n was m e a s u r e d . A r g o n was used as the inert gas. A H i t a c h i h o l l o w - c a t h o d e l a m p was o p e r a t e d at 7 m A to give the o p t i m a l absorption. A 5-/~1 syringe (S.G.E. P t y Ltd., Australia) w a s used to inject samples into the c a r b o n rod. T h e 206.8- a n d 217.6-nrn lines w e r e c o m p a r e d for m e a s u r i n g a n t i m o n y a b s o r p t i o n . T h e line at 206.8 n m s h o w e d a little h i g h e r b a c k g r o u n d noise t h a n that a t 217,6 nm, a n d the latter was t h e r e f o r e used. Reagents
S t a n d a r d a n t i m o n y s o l u t i o n was p r e p a r e d f r o m p o t a s s i u m a n t i m o n y l tartrate. All r e a g e n t s were o f analytical grade. O r g a n i c solvents were purified b y distillation. Procedure
.
,
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A 0.5-td sample was s y r i n g e d into the rod. T h e sample w a s p r e h e a t e d (dried a n d a s h e d ) a n d a t o m i z e d by h e a t i n g with a u n i t r e q u i r i n g a m a x i m u m i n p u t of 3 k W a t 110 V a.c. T h e o p t i m a l c o n d i t i o n s for m e a s u r i n g the a t o m i c a b s o r p t i o n
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M. YANAGISAWA, T. TAKEUCHI. M. SUZUKI
o f a n t i m o n y w e r e a s f o l l o w s : d r y i n g 0.7 V for 20 s ( r o d t e m p e r a t u r e ca. 60°); a s h i n g 1.8 V for 30 s ( r o d t e m p e r a t u r e ca. 180°); a t o m i z a t i o n 5.6 V for 3 s ( r o d t e m p e r a t u r e ca. 2200°). RESULTS AND DISCUSSION
E f f e c t oJ" rod temperature on antimony absorption T h e a n t i m o n y a n a l y t i c a l signal v a r i e d w i t h t h e r o d t e m p e r a t u r e . This r e l a t i o n ship is s h o w n in Fig. I. M e a s u r e m e n t s o f the r o d t e m p e r a t u r e w e r e c a r r i e d o u t w i t h a n o p t i c a l p y r o m e t e r . I n c r e a s i n g t e m p e r a t u r e r e s u l t e d in t h e a b s o r p t i o n p e a k s b e c o m i n g n a r r o w e r a n d higher. H o w e v e r , p e a k - a r e a m e a s u r e m e n t p r o v e d to b e c o n s t a n t a b o v e 1500 °. T h e r e f o r e , p e a k - a r e a m e a s u r e m e n t is r e c o m m e n d e d . N o a n t i m o n y signal w a s o b s e r v e d w h e n t h e r o d t e m p e r a t u r e w a s a p p l i e d for a s e c o n d time. 1 100
2.
100
80
.~. 6 0
20 0
'
"
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'
!
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'
'
J
!
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1500 2000 ROd t e r n p e r o t u r e (°C)
Fig. 1. Effect of rod temperature on atomization of antimony. I =Peak-height measurement; 2-----peak-area measurement. Antimony taken 2.5 ng (0.1 M HCI).
E f f e c t o f inert ffas flow-rate T h e flow o f inert g a s w a s f r o m t h e t u b i n g b e n e a t h t h e c a r b o n r o d ; a r g o n w a s u s e d as t h e i n e r t gas. V a r i a t i o n s in a r g o n f l o w - r a t e b e t w e e n 0.5 a n d 3.5 l r a i n - 1 h a d n e g l i g i b l e effects. H o w e v e r , t h e f l o w - r a t e o f a r g o n w a s m a i n t a i n e d at 2 1 r a i n - 1 E f f e c t oJ" spectral band width on antimony absorption T h e effect o f s p e c t r a l b a n d w i d t h for t h e m e a s u r e m e n t of the a n t i m o n y a b s o r p t i o n a t 217.6 n m is s h o w n in Fig. 2. T h e o p t i m a l s p e c t r a l b a n d w i d t h a t 217.6 n m w a s 0.2 nm. Detection limit W i t h t h e o p t i m a l c o n d i t i o n s d e f i n e d a b o v e , the d e t e c t i o n limit a n d s e n s i t i v i t y w e r e d e t e r m i n e d at 217.6 n m . T h e limit o f d e t e c t i o n w i t h this d e v i c e for a 0.5-/~1 s a m p l e w a s 10 - 1 ° g. The s e n s i t i v i t y ( f o r 1% a b s o r p t i o n ) w a s 10 - 1 2 g. T o a s c e r t a i n the origin o f t h e a b s o r p t i o n signals, the n o n - a b s o r b i n g a n t i m o n y line a t 217.93 n m w a s c h o s e n as b e i n g c l o s e t o t h e a b s o r b i n g l i n e . I n this c a s e n o
FLAMELESS
A.A.S. O F A N T I M O 1 N Y
383
100 2
o
80
E E o
60 3
o o
40
20
q
I
I
1.0
Sb (ng)
I
I
2.0
Fig. 2. Effect o f s p e c t r a l b a n d w i d t h o n a n t i m o n y a b s o r p t i o n . 1 = 0.2 n m ; 2 = 0 . 5 n m ; 3 ----1.0 n m ; 4-----2.0 n m . A b s o r p t i o n m e a s u r e d a t 217.6 n m . S a m p l e v o l u m e o f a n t i m o n y : 0.5 Id (0.1 M H C I ) .
signal w a s observed, s h o w i n g t h a t the signals at the a n t i m o n y a b s o r b i n g lines o r i g i n a t e d p u r e l y f r o m a t o m i c a b s o r p t i o n by a n t i m o n y .
Reproducibility Aliquots(0,5/zl) of a 2.4 ~g ml - a s o l u t i o n o f a n t i m o n y w e r e r e p e a t e d l y a n a l y z e d u n d e r o p t i m a l c o n d i t i o n s . F i v e d e t e r m i n a t i o n s gave a relative s t a n d a r d d e v i a t i o n o f 3%. T h e r e p r o d u c i b i l i t y o f the a b s o r p t i o n in the p r e s e n c e o f m a t r i x e l e m e n t s w a s a l i t t l e ; p o o r e r t h a n t h a t for p u r e a n t i m o n y s o l u t i o n s . S o l u t i o n s c o n t a i n i n g a n t i m o n y a n d 100-fold ( m o l a r ) a m o u n t s o f l a n t h a n u m w e r e tested. T h e relative s t a n d a r d d e v i a t i o n w a s 4%.
In terferences T h e effects of diverse m e t a l s o n t h e a n t i m o n y a b s o r p t i o n signal w e r e m e a s u r e d . S o l u t i o n s (0.02 r a M ) o f a n t i m o n y c o n t a i n i n g 100-, 1000- o r 2000-fold ( m o l a r ) a m o u n t s o f different foreign i o n s w e r e e m p l o y e d . T h e results o b t a i n e d a r e s h o w n in T a b l e I. T h e c a t i o n s tested w e r e a d d e d as their c h l o r i d e s o r n i t r a t e s ; t h e effects o f t h e i n t e r f e r e n c e s a r e listed as r e c o v e r y o f a n t i m o n y . Silver, c h r o m i u m , v a n a d i u m a n d m o l y b d e n u m s h o w e d significant s u p p r e s s i o n of a n t i m o n y a b s o r p t i o n at t h e 100-fold level, while a l u m i n i u m a n d c a l c i u m p r o d u c e d n o interferences e v e n at t h e 1 0 0 0 - f o l d level. C o p p e r interference w a s s e r i o u s at t h e 1000-fold level a n d a b o v e . H y d r o c h l o r i c a n d nitric acids d i d n o t alter t h e a n t i m o n y a b s o r p t i o n in c o n c e n t r a t i o n s o f less t h a n 0.1 Air. T h e effect o f higher c o n c e n t r a t i o n o f acids w a s n o t t e s t e d b e c a u s e o f c o r r o s i o n o f m i c r o s y r i n g e . J a c k s o n a n d W e s t 2 a t t e m p t e d to c o r r e l a t e the d e g r e e o f i n t e r f e r e n c e w i t h s o m e physical p r o p e r t i e s o f the interfering species for nickel, a n d d e m o n s t r a t e d t h a t s o m e c o r r e l a t i o n s were e v i d e n t ; e l e m e n t s of l o w volatility, i.e. s i m i l a r volatility to
384
M. YANAGISAWA, T. TAKEUCHI, M. SUZUKI
TABLE I EFFECT OF FOREIGN IONS ON ANTIMONY ABSORPTION (Sample volume, 0.5 /al of 0.02 mM antimony solution, corresponding to 1.2 ng Sb. Drying, 60° for 20 s; ashing, 180° for 30 s; atomization, 2200° for 3 s; measured at 217.6 nm) Foreign ion a
mM
Recovery o f antimony ( % )
Foreign ion~
mM
Recovery o f antimony ( % )
Na Pb Ag Cd Al
2 2 2 2 2 20 2
93 104 84 96 97 101 89
V Mo La Ca Cu
2 2 2 20 2 20 40
76 82 100 103 100 70 54
Cr
a Hydrochloric acid or nitric acid solution (0.1 M) used. r I
nickel, t e n d e d to i n t e r f e r e t h e ' m o s t . H o w e v e r , t h e n a t u r e o f the i n t e r f e r e n c e s was uncertain for antimony. Measurement
combined with extraction
T h e a p p l i c a t i o n o f s o l v e n t e x t r a c t i o n is a t t r a c t i v e in a t o m i c a b s o r p t i o n spect r o m e t r y f o r t h e e l i m i n a t i o n o f interferences. In the flameless m e t h o d , s o l v e n t e x t r a c t i o n has p r o v e d effective for t h e d e t e r m i n a t i o n o f v a r i o u s t r a c e e l e m e n t s w i t h o u t m a t r i x effects. T h e f o l l o w i n g e x t r a c t i o n s y s t e m s for a n t i m o n y w e r e c o m p a r e d : c h l o r i d e a, t r i - n - b u t y l p h o s p h a t e ( T B P ) 4 a n d d i e t h y l d i t h i o c a r b a m a t e ( D D T C ) s. M e t h y l i s o b u t y l k e t o n e was u s e d as o r g a n i c s o l v e n t for t h e c h l o r i d e a n d D D T C c o m p l e x Systems, w h i l e t o l u e n e w a s u s e d for the T B P s y s t e m . All e x t r a c t i o n s w e r e c a r r i e d o u t w i t h 10 m l o f o r g a n i c s o l v e n t f r o m 20 ml o f a q u e o u s a n t i m o n y s o l u tions. C a l i b r a t i o n c u r v e s for t h e e x t r a c t i o n m e t h o d s are s h o w n in Fig. 3. T h e T B P a n d D D ' r C c o m p l e x e x t r a c t i o n s s h o w e d m u c h l o w e r s e n s i t i v i t y t h a n the c h l o r i d e e x t r a c t i o n . I n all c a s e s t h e e x t r a c t a b i l i t y o f a n t i m o n y w a s g o o d ; the l o w e r sensitivities for t h e T B P a n d D D T C c o m p l e x e s m a y be c a u s e d p a r t l y b y the effects p f d i f f e r e n t v i s c o s i t y o f the e x t r a c t s in delivery~into t h e rod, a n d p a r t l y f r o m the f o r m a t i b n o f s o m e i n v o l a t i l e c o m p o u n d s in p r e h e a t i n g . H o w e v e r , the o r i g i n o f t h e l o w e r a b s o r p t i o n f o r the T B P a n d D D T C c o m p l e x e x t r a c t s is n o t k n o w n w i t h c e r t a i n t y a t t h e p r e s e n t t i m e . APPLICATIONS T h e flameless a t o m i c a b s o r p t i o n m e t h o d was a p p l i e d for the d e t e r m i n a t i o n o f a n t i m o n y in m e t a l l u r g i c a l s a m p l e s . S o l v e n t e x t r a c t i o n w a s e s s e n t i a l b e c a u s e o f m a t r i x • effects o n t h e a n t i m o n y a b s o r p t i o n . Procedure
D i s s o l v e 0.5-1 g o f s a m p l e in 5 ml o f a q u a regia. W a r m g e n t l y o n a s t e a m b a t h t o e n s u r e c o m p l e ' t 9 d i s s o l u t i o n . C o o l a n d d i l u t e to 100 ml w i t h 6 M h y d r o c h l o r i c a c i d in a v o l u m e t r i c flask. T r a n s f e r t h e ' a l i q u o t s (less t h a n 50/~g Sb) to a s e p a r a t o r y
F L A M E L E S S A.A.S. O F A N T I M O N Y
385
1OO
1
80
2
I. o
40
3
2O
O c
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I
I
!
t
%0 Sb(ng) 2.0 Fig. 3. Antimony calibration curves. 1 = C h l o r i d e extraction (in M I B K ) ; 2 = D D T C tion (in M I B K ) ; 3 = T B P extraction (in toluene).
complex extrac-
f u n n e l a n d a d d e n o u g h h y d r o c h l o r i c acid to m a k e t h e c o n c e n t r a t i o n 6 M w h e n t h e s o l u t i o n is d i l u t e d to 20 ml. A d d 0.5 ml of 5~,~ (w/v) s o d i u m nitrite s o l u t i o n a n d d i l u t e to 20 ml. S h a k e t h e r e s u l t a n t s o l u t i o n for 1 rain to oxidize a n t i m o n y to t h e p e n t a v a l e n t state. T h e n e x t r a c t a n t i m o n y in 10 ml o f m e t h y l i s o b u t y l k e t o n e b y s h a k i n g for 3 rain. Place the a l i q u o t o f the o r g a n i c p h a s e b y m e a n s o f a syringe into the r o d a n d t h e n a t o m i z e t h e s a m p l e after d r y i n g a n d ashing. R e c o r d t h e a n t i m o n y a b s o r p t i o n at 217.6 n m . P r e p a r e a c a l i b r a t i o n curve by e x t r a c t i n g antimony from standard solutions of antimony. T A B L E II D E T E R M I N A T I O N O F A N T I M O N Y IN S E L E C T E D S A M P L E S Sample
A l u m i n i u m alloy~ (BCS 216/1) C o p p e r alloyb (BCS 183/1) C r u d e copper c
Sb added
(%)
-0.037 -0.20 -0.037
:
Sb f o u n d (%,) Proposed method
F l a m e method a
Certified value
0.049, 0.086, 0.22, 0.41, 0.066, 0.103,
0.043
0.05
0.24
0.24
0.066
0.064 a
0.051 0.084 0.21 0.42 0.064 0.105
" 0.73~o Mn, 0.74~ Mg, 0.40% Fe, 0.10yo Ti, 0 . 1 1 ~ 2n, 0.05~o Pb, 0.05~ Sn, 0.06~o Ni. b 5.17% Zn, 5.01~o Sn, 3.51~o Pb, 0.51% Ni, 0 . 1 4 ~ As, 0 . 5 1 ~ P. c 0.14% Ni, 0.08~o Pb, 0.05~o As, 0.005% Fe, 0.001% Zn, 0.001~o Mg. a Polarographic.
:
386
M. Y A N A G I S A W A , T. T A K E U C H I , M. S U Z U K I
Results o f determinations on selected samples The results o f the d e t e r m i n a t i o n o f a n t i m o n y in selected samples'are presented in T a b l e II. These results indicate that a n t i m o n y can be d e t e r m i n e d with g o o d accuracy, a n d that flameless a t o m i c a b s o r p t i o n s p e c t r o m e t r y c a n be applied successfully to the analysis o f metallurgical samples p r o v i d e d that the a t o m i c a b s o r p t i o n m e a s u r e m e n t is c o m b i n e d with solvent extraction. .Q
•
•
The a u t h o r s express their thanks to N i p p o n Electric V a r i a n Ltd. for the loan of apparatus. SUMMARY
Flameless a t o m i c a b s o r p t i o n s p e c t r o m e t r y of a n t i m o n y has b e e n investigated with a c a r b o n rod device. A n t i m o n y m a y be d e t e r m i n e d in solution at a level o f 10 - ~ ° g with a sample v o l u m e of 0.5 ~el. O p t i m a l c o n d i t i o n s a n d interferences are described. Matrix effects o n a n t i m o n y necessitated a p r e l i m i n a r y solvent extraction of t h e chloride c o m p l e x f r o m h y d r o c h l o r i c acid solution c o n t a i n i n g nitrite with m e t h y l isobutyl ketone. T h e d e t e r m i n a t i o n o f a n t i m o n y in metallurgical samples was s h o w n to be satisfactory. RI~SUMI~
U n e recherche est effectu6e sur la s.pectrom6trie p a r a b s o r p t i o n a t o m i q u e sans flarnme de l'antimoine. O n arrive ~t doser 10- x0 g avec un v o l u m e d'6chantillon de 0.5 pl. O n e x a m i n e les c o n d i t i o n s o p t i m a l e s et les interf6rences. L'influence de la m a t r i c e sur l'antimoine n6cessite une e x t r a c t i o n pr61iminaire clans u n solvant. C e t t e m 6 t h o d e est appliqu6e avec succ6s au d o s a g e de l ' a n t i m o i n e d a n s des 6chantillons m6tallurgiques. ZUSAMMENFASSUNG
Die flammenlose A t o m a b s o r p t i o n s s p e k t r o m e t r i e von A n t i m o n u n t e r Verw e n d u n g einer G r a p h i t s t a b - A n o r d n u n g w u r d e u n t e r s u c h t . 1 0 - ~o g A n t i m o n k a n n in L 6 s u n g bei einem P r o b e n v o l u m e n von 0 . 5 / t l b e s t i m m t w e r d e n . D i e o p t i m a l e n Bed i n g u n g e n u n d die St/frungen w e r d e n angegeben. Matrixeinfl tisse a u f die B e s t i m m u n g von A n t i m o n m a c h t e n es notwendig, v o r h e r den C h i o r i d k o m p l e x aus salzsaurer, nitrithaltiger L/Ssung mit M e t h y l i s o b u t y l k e t o n zu extrahieren. D i e B e s t i m m u n g y o n A n t i m o n in metallurgischen P r o b e n f'tihrte zu zufriedenstellenden Ergebnissen. REFERENCES 1 2 3 4 5
G. F. Kirkbright, Analyst (London), 96 (1971) 609. K. W. Jackson and T. S. West, Anal. Chim. Acta, 59 (1972) 187. M. Yanagisawa, M. Suzuki a n d T. Takeuchi,'Anal. Chim. Acta, 47 (1969) 121. A. A. Yadav and S. M. Khopkar, Bull. Chem. Soc. Jap.,44 (1971) 693. E. B. Sandell, Colorimetric Determination of Traces o f Metals, Interseience, New York, 1959.
FLAMELESS ATOMIC ABSORPTION
SPECTROMETRY
381
OF ANTIMONY
MASAAKI YANAGISAWA and TSUGIO TAKEUCHI Department of Synthetic Chepnistry, Faculty of Engineering, Nagoya University, Cilikusa-ku, Nagoya (Japan)
and MASAMI SUZUKI Department of Chemistry, Faculty of Engineering, Mie University, Kamihama.cho, Tsu-shi, .Mie-ken (Japan)
(Received 9th October 1972)
T h e flameless a t o m i c a b s o r p t i o n s p e c t r o m e t r y o f volatile a n d involatile elements has been widely i n v e s t i g a t e d I because o f the high a b s o l u t e sensitivity w h i c h permits the use o f v e r y small samples; the reliability o f t h e t e c h n i q u e is c o m p a r a b l e with that o f the c o n v e n t i o n a l flame m e t h o d . However, n o published i n f o r m a t i o n exists p e r t a i n i n g to the d e t e r m i n a t i o n o f a n t i m o n y by flameless a t o m i c a b s o r p t i o n spectrometry. This p a p e r describes the a t o m i c a b s o r p t i o n b e h a v i o r o f a n t i m o n y w i t h a c a r b o n r o d a t o m i z e r and its a p p l i c a t i o n to m e t a l l u r g i c a l samples. EXPERIMENTAL Apparatus
A V a r i a n T e c h t r o n AA-1000 a t o m i c a b s o r p t i o n s p e c t r o p h o t o r n e t e r was used with a V a r i a n T e c h t r o n M o d e l 61 c a r b o n r o d a t o m i z e r s u b s t i t u t e d for t h e b u r n e r assembly. T h e a t o m i c a b s o r p t i o n signals were r e c o r d e d o n a H i t a c h i Q P D - 5 4 recorder. T h e c a r b o n r o d w a s o f the " M i n i - M a s s m a n n " type w h i c h h a d a 1.5-mm d i a m e t e r transverse hole as the s a m p l e cavity. Light f r o m the h o l l o w - c a t h o d e l a m p was focussed t h r o u g h the c a v i t y a n d t h e a b s o r p t i o n was m e a s u r e d . A r g o n was used as the inert gas. A H i t a c h i h o l l o w - c a t h o d e l a m p was o p e r a t e d at 7 m A to give the o p t i m a l absorption. A 5-/~1 syringe (S.G.E. P t y Ltd., Australia) w a s used to inject samples into the c a r b o n rod. T h e 206.8- a n d 217.6-nrn lines w e r e c o m p a r e d for m e a s u r i n g a n t i m o n y a b s o r p t i o n . T h e line at 206.8 n m s h o w e d a little h i g h e r b a c k g r o u n d noise t h a n that a t 217,6 nm, a n d the latter was t h e r e f o r e used. Reagents
S t a n d a r d a n t i m o n y s o l u t i o n was p r e p a r e d f r o m p o t a s s i u m a n t i m o n y l tartrate. All r e a g e n t s were o f analytical grade. O r g a n i c solvents were purified b y distillation. Procedure
.
,
.
A 0.5-td sample was s y r i n g e d into the rod. T h e sample w a s p r e h e a t e d (dried a n d a s h e d ) a n d a t o m i z e d by h e a t i n g with a u n i t r e q u i r i n g a m a x i m u m i n p u t of 3 k W a t 110 V a.c. T h e o p t i m a l c o n d i t i o n s for m e a s u r i n g the a t o m i c a b s o r p t i o n
382
M. YANAGISAWA, T. TAKEUCHI. M. SUZUKI
o f a n t i m o n y w e r e a s f o l l o w s : d r y i n g 0.7 V for 20 s ( r o d t e m p e r a t u r e ca. 60°); a s h i n g 1.8 V for 30 s ( r o d t e m p e r a t u r e ca. 180°); a t o m i z a t i o n 5.6 V for 3 s ( r o d t e m p e r a t u r e ca. 2200°). RESULTS AND DISCUSSION
E f f e c t oJ" rod temperature on antimony absorption T h e a n t i m o n y a n a l y t i c a l signal v a r i e d w i t h t h e r o d t e m p e r a t u r e . This r e l a t i o n ship is s h o w n in Fig. I. M e a s u r e m e n t s o f the r o d t e m p e r a t u r e w e r e c a r r i e d o u t w i t h a n o p t i c a l p y r o m e t e r . I n c r e a s i n g t e m p e r a t u r e r e s u l t e d in t h e a b s o r p t i o n p e a k s b e c o m i n g n a r r o w e r a n d higher. H o w e v e r , p e a k - a r e a m e a s u r e m e n t p r o v e d to b e c o n s t a n t a b o v e 1500 °. T h e r e f o r e , p e a k - a r e a m e a s u r e m e n t is r e c o m m e n d e d . N o a n t i m o n y signal w a s o b s e r v e d w h e n t h e r o d t e m p e r a t u r e w a s a p p l i e d for a s e c o n d time. 1 100
2.
100
80
.~. 6 0
20 0
'
"
'
'
!
'
'
'
J
!
.
.
.
.
1500 2000 ROd t e r n p e r o t u r e (°C)
Fig. 1. Effect of rod temperature on atomization of antimony. I =Peak-height measurement; 2-----peak-area measurement. Antimony taken 2.5 ng (0.1 M HCI).
E f f e c t o f inert ffas flow-rate T h e flow o f inert g a s w a s f r o m t h e t u b i n g b e n e a t h t h e c a r b o n r o d ; a r g o n w a s u s e d as t h e i n e r t gas. V a r i a t i o n s in a r g o n f l o w - r a t e b e t w e e n 0.5 a n d 3.5 l r a i n - 1 h a d n e g l i g i b l e effects. H o w e v e r , t h e f l o w - r a t e o f a r g o n w a s m a i n t a i n e d at 2 1 r a i n - 1 E f f e c t oJ" spectral band width on antimony absorption T h e effect o f s p e c t r a l b a n d w i d t h for t h e m e a s u r e m e n t of the a n t i m o n y a b s o r p t i o n a t 217.6 n m is s h o w n in Fig. 2. T h e o p t i m a l s p e c t r a l b a n d w i d t h a t 217.6 n m w a s 0.2 nm. Detection limit W i t h t h e o p t i m a l c o n d i t i o n s d e f i n e d a b o v e , the d e t e c t i o n limit a n d s e n s i t i v i t y w e r e d e t e r m i n e d at 217.6 n m . T h e limit o f d e t e c t i o n w i t h this d e v i c e for a 0.5-/~1 s a m p l e w a s 10 - 1 ° g. The s e n s i t i v i t y ( f o r 1% a b s o r p t i o n ) w a s 10 - 1 2 g. T o a s c e r t a i n the origin o f t h e a b s o r p t i o n signals, the n o n - a b s o r b i n g a n t i m o n y line a t 217.93 n m w a s c h o s e n as b e i n g c l o s e t o t h e a b s o r b i n g l i n e . I n this c a s e n o
FLAMELESS
A.A.S. O F A N T I M O 1 N Y
383
100 2
o
80
E E o
60 3
o o
40
20
q
I
I
1.0
Sb (ng)
I
I
2.0
Fig. 2. Effect o f s p e c t r a l b a n d w i d t h o n a n t i m o n y a b s o r p t i o n . 1 = 0.2 n m ; 2 = 0 . 5 n m ; 3 ----1.0 n m ; 4-----2.0 n m . A b s o r p t i o n m e a s u r e d a t 217.6 n m . S a m p l e v o l u m e o f a n t i m o n y : 0.5 Id (0.1 M H C I ) .
signal w a s observed, s h o w i n g t h a t the signals at the a n t i m o n y a b s o r b i n g lines o r i g i n a t e d p u r e l y f r o m a t o m i c a b s o r p t i o n by a n t i m o n y .
Reproducibility Aliquots(0,5/zl) of a 2.4 ~g ml - a s o l u t i o n o f a n t i m o n y w e r e r e p e a t e d l y a n a l y z e d u n d e r o p t i m a l c o n d i t i o n s . F i v e d e t e r m i n a t i o n s gave a relative s t a n d a r d d e v i a t i o n o f 3%. T h e r e p r o d u c i b i l i t y o f the a b s o r p t i o n in the p r e s e n c e o f m a t r i x e l e m e n t s w a s a l i t t l e ; p o o r e r t h a n t h a t for p u r e a n t i m o n y s o l u t i o n s . S o l u t i o n s c o n t a i n i n g a n t i m o n y a n d 100-fold ( m o l a r ) a m o u n t s o f l a n t h a n u m w e r e tested. T h e relative s t a n d a r d d e v i a t i o n w a s 4%.
In terferences T h e effects of diverse m e t a l s o n t h e a n t i m o n y a b s o r p t i o n signal w e r e m e a s u r e d . S o l u t i o n s (0.02 r a M ) o f a n t i m o n y c o n t a i n i n g 100-, 1000- o r 2000-fold ( m o l a r ) a m o u n t s o f different foreign i o n s w e r e e m p l o y e d . T h e results o b t a i n e d a r e s h o w n in T a b l e I. T h e c a t i o n s tested w e r e a d d e d as their c h l o r i d e s o r n i t r a t e s ; t h e effects o f t h e i n t e r f e r e n c e s a r e listed as r e c o v e r y o f a n t i m o n y . Silver, c h r o m i u m , v a n a d i u m a n d m o l y b d e n u m s h o w e d significant s u p p r e s s i o n of a n t i m o n y a b s o r p t i o n at t h e 100-fold level, while a l u m i n i u m a n d c a l c i u m p r o d u c e d n o interferences e v e n at t h e 1 0 0 0 - f o l d level. C o p p e r interference w a s s e r i o u s at t h e 1000-fold level a n d a b o v e . H y d r o c h l o r i c a n d nitric acids d i d n o t alter t h e a n t i m o n y a b s o r p t i o n in c o n c e n t r a t i o n s o f less t h a n 0.1 Air. T h e effect o f higher c o n c e n t r a t i o n o f acids w a s n o t t e s t e d b e c a u s e o f c o r r o s i o n o f m i c r o s y r i n g e . J a c k s o n a n d W e s t 2 a t t e m p t e d to c o r r e l a t e the d e g r e e o f i n t e r f e r e n c e w i t h s o m e physical p r o p e r t i e s o f the interfering species for nickel, a n d d e m o n s t r a t e d t h a t s o m e c o r r e l a t i o n s were e v i d e n t ; e l e m e n t s of l o w volatility, i.e. s i m i l a r volatility to
384
M. YANAGISAWA, T. TAKEUCHI, M. SUZUKI
TABLE I EFFECT OF FOREIGN IONS ON ANTIMONY ABSORPTION (Sample volume, 0.5 /al of 0.02 mM antimony solution, corresponding to 1.2 ng Sb. Drying, 60° for 20 s; ashing, 180° for 30 s; atomization, 2200° for 3 s; measured at 217.6 nm) Foreign ion a
mM
Recovery o f antimony ( % )
Foreign ion~
mM
Recovery o f antimony ( % )
Na Pb Ag Cd Al
2 2 2 2 2 20 2
93 104 84 96 97 101 89
V Mo La Ca Cu
2 2 2 20 2 20 40
76 82 100 103 100 70 54
Cr
a Hydrochloric acid or nitric acid solution (0.1 M) used. r I
nickel, t e n d e d to i n t e r f e r e t h e ' m o s t . H o w e v e r , t h e n a t u r e o f the i n t e r f e r e n c e s was uncertain for antimony. Measurement
combined with extraction
T h e a p p l i c a t i o n o f s o l v e n t e x t r a c t i o n is a t t r a c t i v e in a t o m i c a b s o r p t i o n spect r o m e t r y f o r t h e e l i m i n a t i o n o f interferences. In the flameless m e t h o d , s o l v e n t e x t r a c t i o n has p r o v e d effective for t h e d e t e r m i n a t i o n o f v a r i o u s t r a c e e l e m e n t s w i t h o u t m a t r i x effects. T h e f o l l o w i n g e x t r a c t i o n s y s t e m s for a n t i m o n y w e r e c o m p a r e d : c h l o r i d e a, t r i - n - b u t y l p h o s p h a t e ( T B P ) 4 a n d d i e t h y l d i t h i o c a r b a m a t e ( D D T C ) s. M e t h y l i s o b u t y l k e t o n e was u s e d as o r g a n i c s o l v e n t for t h e c h l o r i d e a n d D D T C c o m p l e x Systems, w h i l e t o l u e n e w a s u s e d for the T B P s y s t e m . All e x t r a c t i o n s w e r e c a r r i e d o u t w i t h 10 m l o f o r g a n i c s o l v e n t f r o m 20 ml o f a q u e o u s a n t i m o n y s o l u tions. C a l i b r a t i o n c u r v e s for t h e e x t r a c t i o n m e t h o d s are s h o w n in Fig. 3. T h e T B P a n d D D ' r C c o m p l e x e x t r a c t i o n s s h o w e d m u c h l o w e r s e n s i t i v i t y t h a n the c h l o r i d e e x t r a c t i o n . I n all c a s e s t h e e x t r a c t a b i l i t y o f a n t i m o n y w a s g o o d ; the l o w e r sensitivities for t h e T B P a n d D D T C c o m p l e x e s m a y be c a u s e d p a r t l y b y the effects p f d i f f e r e n t v i s c o s i t y o f the e x t r a c t s in delivery~into t h e rod, a n d p a r t l y f r o m the f o r m a t i b n o f s o m e i n v o l a t i l e c o m p o u n d s in p r e h e a t i n g . H o w e v e r , the o r i g i n o f t h e l o w e r a b s o r p t i o n f o r the T B P a n d D D T C c o m p l e x e x t r a c t s is n o t k n o w n w i t h c e r t a i n t y a t t h e p r e s e n t t i m e . APPLICATIONS T h e flameless a t o m i c a b s o r p t i o n m e t h o d was a p p l i e d for the d e t e r m i n a t i o n o f a n t i m o n y in m e t a l l u r g i c a l s a m p l e s . S o l v e n t e x t r a c t i o n w a s e s s e n t i a l b e c a u s e o f m a t r i x • effects o n t h e a n t i m o n y a b s o r p t i o n . Procedure
D i s s o l v e 0.5-1 g o f s a m p l e in 5 ml o f a q u a regia. W a r m g e n t l y o n a s t e a m b a t h t o e n s u r e c o m p l e ' t 9 d i s s o l u t i o n . C o o l a n d d i l u t e to 100 ml w i t h 6 M h y d r o c h l o r i c a c i d in a v o l u m e t r i c flask. T r a n s f e r t h e ' a l i q u o t s (less t h a n 50/~g Sb) to a s e p a r a t o r y
F L A M E L E S S A.A.S. O F A N T I M O N Y
385
1OO
1
80
2
I. o
40
3
2O
O c
'
I
I
!
t
%0 Sb(ng) 2.0 Fig. 3. Antimony calibration curves. 1 = C h l o r i d e extraction (in M I B K ) ; 2 = D D T C tion (in M I B K ) ; 3 = T B P extraction (in toluene).
complex extrac-
f u n n e l a n d a d d e n o u g h h y d r o c h l o r i c acid to m a k e t h e c o n c e n t r a t i o n 6 M w h e n t h e s o l u t i o n is d i l u t e d to 20 ml. A d d 0.5 ml of 5~,~ (w/v) s o d i u m nitrite s o l u t i o n a n d d i l u t e to 20 ml. S h a k e t h e r e s u l t a n t s o l u t i o n for 1 rain to oxidize a n t i m o n y to t h e p e n t a v a l e n t state. T h e n e x t r a c t a n t i m o n y in 10 ml o f m e t h y l i s o b u t y l k e t o n e b y s h a k i n g for 3 rain. Place the a l i q u o t o f the o r g a n i c p h a s e b y m e a n s o f a syringe into the r o d a n d t h e n a t o m i z e t h e s a m p l e after d r y i n g a n d ashing. R e c o r d t h e a n t i m o n y a b s o r p t i o n at 217.6 n m . P r e p a r e a c a l i b r a t i o n curve by e x t r a c t i n g antimony from standard solutions of antimony. T A B L E II D E T E R M I N A T I O N O F A N T I M O N Y IN S E L E C T E D S A M P L E S Sample
A l u m i n i u m alloy~ (BCS 216/1) C o p p e r alloyb (BCS 183/1) C r u d e copper c
Sb added
(%)
-0.037 -0.20 -0.037
:
Sb f o u n d (%,) Proposed method
F l a m e method a
Certified value
0.049, 0.086, 0.22, 0.41, 0.066, 0.103,
0.043
0.05
0.24
0.24
0.066
0.064 a
0.051 0.084 0.21 0.42 0.064 0.105
" 0.73~o Mn, 0.74~ Mg, 0.40% Fe, 0.10yo Ti, 0 . 1 1 ~ 2n, 0.05~o Pb, 0.05~ Sn, 0.06~o Ni. b 5.17% Zn, 5.01~o Sn, 3.51~o Pb, 0.51% Ni, 0 . 1 4 ~ As, 0 . 5 1 ~ P. c 0.14% Ni, 0.08~o Pb, 0.05~o As, 0.005% Fe, 0.001% Zn, 0.001~o Mg. a Polarographic.
:
386
M. Y A N A G I S A W A , T. T A K E U C H I , M. S U Z U K I
Results o f determinations on selected samples The results o f the d e t e r m i n a t i o n o f a n t i m o n y in selected samples'are presented in T a b l e II. These results indicate that a n t i m o n y can be d e t e r m i n e d with g o o d accuracy, a n d that flameless a t o m i c a b s o r p t i o n s p e c t r o m e t r y c a n be applied successfully to the analysis o f metallurgical samples p r o v i d e d that the a t o m i c a b s o r p t i o n m e a s u r e m e n t is c o m b i n e d with solvent extraction. .Q
•
•
The a u t h o r s express their thanks to N i p p o n Electric V a r i a n Ltd. for the loan of apparatus. SUMMARY
Flameless a t o m i c a b s o r p t i o n s p e c t r o m e t r y of a n t i m o n y has b e e n investigated with a c a r b o n rod device. A n t i m o n y m a y be d e t e r m i n e d in solution at a level o f 10 - ~ ° g with a sample v o l u m e of 0.5 ~el. O p t i m a l c o n d i t i o n s a n d interferences are described. Matrix effects o n a n t i m o n y necessitated a p r e l i m i n a r y solvent extraction of t h e chloride c o m p l e x f r o m h y d r o c h l o r i c acid solution c o n t a i n i n g nitrite with m e t h y l isobutyl ketone. T h e d e t e r m i n a t i o n o f a n t i m o n y in metallurgical samples was s h o w n to be satisfactory. RI~SUMI~
U n e recherche est effectu6e sur la s.pectrom6trie p a r a b s o r p t i o n a t o m i q u e sans flarnme de l'antimoine. O n arrive ~t doser 10- x0 g avec un v o l u m e d'6chantillon de 0.5 pl. O n e x a m i n e les c o n d i t i o n s o p t i m a l e s et les interf6rences. L'influence de la m a t r i c e sur l'antimoine n6cessite une e x t r a c t i o n pr61iminaire clans u n solvant. C e t t e m 6 t h o d e est appliqu6e avec succ6s au d o s a g e de l ' a n t i m o i n e d a n s des 6chantillons m6tallurgiques. ZUSAMMENFASSUNG
Die flammenlose A t o m a b s o r p t i o n s s p e k t r o m e t r i e von A n t i m o n u n t e r Verw e n d u n g einer G r a p h i t s t a b - A n o r d n u n g w u r d e u n t e r s u c h t . 1 0 - ~o g A n t i m o n k a n n in L 6 s u n g bei einem P r o b e n v o l u m e n von 0 . 5 / t l b e s t i m m t w e r d e n . D i e o p t i m a l e n Bed i n g u n g e n u n d die St/frungen w e r d e n angegeben. Matrixeinfl tisse a u f die B e s t i m m u n g von A n t i m o n m a c h t e n es notwendig, v o r h e r den C h i o r i d k o m p l e x aus salzsaurer, nitrithaltiger L/Ssung mit M e t h y l i s o b u t y l k e t o n zu extrahieren. D i e B e s t i m m u n g y o n A n t i m o n in metallurgischen P r o b e n f'tihrte zu zufriedenstellenden Ergebnissen. REFERENCES 1 2 3 4 5
G. F. Kirkbright, Analyst (London), 96 (1971) 609. K. W. Jackson and T. S. West, Anal. Chim. Acta, 59 (1972) 187. M. Yanagisawa, M. Suzuki a n d T. Takeuchi,'Anal. Chim. Acta, 47 (1969) 121. A. A. Yadav and S. M. Khopkar, Bull. Chem. Soc. Jap.,44 (1971) 693. E. B. Sandell, Colorimetric Determination of Traces o f Metals, Interseience, New York, 1959.