- Email: [email protected]
Improvements in the non-dispersive atomic fluorescence spectrometric determination of arsenic and antimony by a hydride generation technique
Analytico
Chin&a
Acta,
97 fl978)
51-57
OEisevier Scientific Publishing Company, Amsterdam -
Printed in The Netherlands
IMPROVEMENTS IN THE NON-DISPERSIVE ATOMIC FLUORESCENCE SPECTROMETRIC DETERMINATION OF ARSENIC AND ANTIMONY 33Y A HYDRIDE GENERATXON TK’ECHNIQtiX§
KANJI TSUJII*
and KAZUO
KUGA
Central Resenrch
Laboratory.
Hitachi
Ltd.,
Kokubunji,
Tokyo
(Japan)
(Received 12th July 19’7’7)
A sodium borohydride reduction, with subsequent atomization in a small argonhydrogen-entrained air Game has been developed for the determination of arsenic and antimony by non-dispersive atomic fluorescence spectrometry. The proposed method increases the signal level and decreases the noise level in the system. The detection iiiits for arsenic and antimony are 0.05 ng and 0.1 ng, respectively. The analytical working curves are linear over about four decades of concentration from the detection limits. Tire consumption rates of hydrogen and argon are comparatively low, while the speed of hydride evolution is improved; a peak measurement requires less than 40 s. The technique’ has been applied to the determination of arsenic in steel sampies.
The advantages and disadvantages of a non-dispersive system for atomic fluorescence speetrometry (a_f.s.) have been discussed in a number of publications [I-ItO] . This system offers improved signal levels, because of the large optical aperture and simultaneous detection of multiple lines for the element of interest. However, the noise level is likely to increase depending on the background radiation levels from the atom reservoir. For non-dispersive systems employing flame atomizers, the noise limitations are due to the background radiation from the flame [5-2.01. Hydride generation is now well known as a sensitive pretreatment technique for the determination of arsenic, antimony, selenium, tellurium etc. by atomic spectrometry f II-23]. As reported previously 129, 303, this technique can be applied effectively to non-dispersive systems for a.f.s. for the following reasons: (I.) hydride compounds are easily decomposed in a cool flame, e.g. an argon-hydrogenentrained air flame which emits very low background radiation; (2) the elements of interest are converted to hydrides and isolated from the matrix elements which occasionally cause severe light scattering effects; and (3) most of the elements known to form volatile hydrides have multiple fluoresk’his paper was presented at the 28th Pittsburgh Conference on Analytical Chemistry and Appfied Spectroscopy, Cieveiand, March 1977.
52
cence spectral lines within the spectral response range of a solar-blind photomultiplier, which is often used in non-dispersive af.s. For example, arsenic and antimony have 121311 and 9[32] atomic fluorescence spectral lines in the U.V. region_ In previous work 129,301 the liberated hydrides and hydrogen were stored for a fixed time prior to introduction into the flame atomizer. These studies indicated (I) that the noise level decreases with decreasing hydrogen flowrates; (2) that the hydrogen flow-rate has a lower limit with the hydride generation method described previously, because the pressure increase in the vessel during reduction extin-tihes the flame; and (3) that the system noise limitations are caused by OH band emission spectra (280-320 nm) emitted by the flame, and the noise is decreased by about 90% when a screen is placed between the burner and the detector. To overcome these limitations, a hydride generation method similar to that reported by Thompson and Thomerson [ 241 is coupled with a small argonhydrogenentrained air flame. EXPERIMENTAL Apparatus
Schematic diagrams of the apparatus and the specially manufactured twoslot burner are shown in Figs. 1 and 2. The burner head is situated so that the incident beam from the light source passes parallel to the burner slots. The sources used were Perkin-Elmer electrodeless discharge lamps operated at 10 W (As) and 5 W (Sb), as recommended, by a Perkin-Elmer Model 185-120 power supply. The light beam was focused by a quartz lens (34 mm diam., 60 mm focal length) and refocused by a concave mirror (65 mm diam., 55 mm focal length) just above the burner_ The fluorescent radiation was detected directly by a solar-blind photomultiplier (HTV R166). -4 John Fluke power supply
+-I
/E.D.L.
Fig. 1. Schematic
diagram
of the apparatus.
53
SO0 ,uL
1+ lt3*‘+
Fig. 2. Two-slot Fig. 3. Hydride
lJNIT:mm
PIFETTE
l”l.NaBH~
SOLUTION
burner. generation
cell.
(Model 412B) was used to provide high voltage (550 V) for the photomultiplier. The signals from the photomultiplier were fed into a lock-in amplifier (Princeton Applied Research Corp., Model HR-8) which was phased with a reference signal from a mechanical light chopper (Princeton Applied Research Corp., Model 125, chopping frequency: 27 Hz). The distance from the burner top to the center of the light beam was 1 cm and from the center of the burner slots to the photomultiplier was about 9 cm. The hydride generation cell (capacity, 90 ml), constructed from borosilicate glass, is shown in Fig. 3. Reagents
Commercially available arsenic(III) and antimony(II1) 1090-ppm standard solutions (Kant0 Chemical Corp.), made from sodium arsenite and antimony trichloride, respectively, were used. An arsenic(V) lOOO-ppm standard solution, prepared by dissolving sodium arsenate, was used when this tecbniquewas applied to the determination of arsenic in steel samples. Sodium borohydride solution (1%) was prepared, just before use, by dissolving sodium borohydride pellets (>98% pure; Alfa Inorgani&). All other reagents were of analyticalreagent grade. Procedure
The four-way stopcock was initially set for argon to pass through the bypass tube. Sodium borohydride solution (l%, 2 ml) was transferred to the hydride generation cell. A sample solution was taken by an Eppendorf 500+ pipette, which was then set as shown in Fig. 3. Next, the four-way stopcock was set to allow argon to pass through the cell. The sample solution was injected into
54
the cell and the reduction products were supplied continuously to the flame by a constant flow of argon gas. The atomic fluorescence signals were recorded, and the peak heights were measured. RESULTS
AND DISCUSSION
The response to arsenic and antimony was independent of the hydrochloric acid concentration from 1 to 8 M; this is similar to the results reported earlier [13, 24j. To minimize the pressure increase in the cell and to prevent reagent contamination, all measurements were made with 1 M hydrochloric acid. Effect of hydrogen flow rate The
effect
of the hydrogen
was measured.
The argon
level dependence
flow-rate
flow-rate
on the hydrogen
on the noise
was kept flow-rate
level and signal
constant
at 1-O 1 min-‘_
is shown
in Fig. 4. The
intensity The noise noise
z z 100-
A
B
E f $j ?55 Yl
C
it -50 *$flj&wl
-w-
$ g
F 2
25\
E E
.
G
I=
OO m+++-wv
-
;i
-
0.5
ow 1.5
1.0 H2
2.0
L min-’
4. Noise level dependence on the hydrogen flow-rate. Argon Cow-rate, 1.0 1 min-*. A, detector box shutter closed. B, detector box shutter open. C, outdoor light cut off. Hydrogen flow-rates: D, 2.0 1 min-‘; E, 1.0 1 min-‘; F, 0.5 1 min-‘; G, 0.25 1 min-‘. Fig.
Fig. 5. Effect of the hydrogen flow-rate on arsenic fluorescence intensity. Argon flow-rate, 1.0 1 min-*.
Fig. 6. Effect of the hydrogen flow-rate on antimdny fluorescence signal. Argon flow-rate, 1.0 1 min-‘. Hydrogen flow-rates: A, 0.7 1 min-‘; B, 0.6 1 min-‘; C, 0.45 1 min-‘;D, 0.35 1 min-’ ; E, 0.25 1 min-I.
55
level increases s&htly when the shutter of the detector box is opened but decreases to the initial level when outdoor light is cut off. The noise level suddenly increases when the flame is lit, but gradually decreases with decreasing hydrogen flow-rates. The noise level continues to decrease until it reaches the same level as that when the shutter of the detector box is closed. This occurs when the flow-rate decreases to 0.25 1 mm-‘. As reported previously [ 291, the decrease in noise 1eveIis closely related to decreasing OH band (280-320 nm) emission intensities. The visible portion of the flame also decreased with decreasing hydrogen flow-rates. It was about 1 cm when the tip of a metallic wire dipped in a sodium chloride solution was placed in the flame (hydrogen Bow-rate, 0.25 1 min-I). The flame, however, expanded slightly when the sample solution was injected into the ceJ_l. The effects of the hydrogen flow-rate on arsenic and antimony fluorescence intensities are shown in Figs. 5 and 6, respectively. The signal intensity for each element increases with decreasing hydrogen flow rates. This phenomenon was not observed previously f29,303, because the hydrogen flow-rate could not be decreased below 1.7 1 tin-‘, when the earlier hydride generation facility was used. This signal increase is probably caused by an increasing atom residence time in the light path and restriction of atoms in the small flame region. The following measurements were made at flow rates of 0.25 I min-’ of hydrogen and 1.0 1 mm-’ of argon. Detection, limit and analytical working curve The detection limits (S:N= 2) and reagent blanks for arsenic and antimony are shown in Table 1. The detection limits obtained with the former hydride generation cell are also given in Table 1. The improvement factors are 40 for arsenic and 30 for antimony. The detection limits obtained in this study cannot be compared directly with those reported previously becausethe light sources, the burner head, and the optical alignment are different. However, the small argon-hydrogen-+mtrained air flame plays an important role in improving the signal-to-noise ratio. The analytical working curves for arsenic and antimony are shown in Fig. 7. The linear range covers four concentration decades from the detection Emit; TABLE 1 Detection limits and reagent bIa.nks for As and Sb Efement
As
Sb
Detection limit (ng)
Reagent blank (ng)
Present
Previous
Present
hevious
2c291
1 0.5
25[291 -
0.05
0.1
3E301
I
“a’
,
= I
‘3 10
to2
As, Sb,
‘ng
Fig. 7. Analytical working curves for arsenic and antimony.
thisis aboutonedecade superiorto previousdata [29,30].Therelative standarddeviation calculatedfrom7 peak-heightmeasurementsfor0.1 ppm arsenic solution(III) is 1.7%. Determination of arsenic in steel samples This technique was applied to the determination of arsenic in steel samples weighing ca. 0.1 g. The sample was weighed exactly and dissolved in 10 ml of aqua regia; 5 ml of perchloric acid was added and the solution was heated until white perchloric acid fumes were observed. To eliminate any interfering effects of co-existing elements, known to occur in the formation and evolution of arsine 1251, a standard addition method was employed with lOOO-ppm arsenic(V) solution as the standard. The results, shown in Table 2, are in good agreement with the certified values. This technique is also applicable to other elements which form volatile hydrides, e.g. bismuth, germanium, lead, selenium, tin, and tellurium.
Determination of arsenic in carbon steel samples (Japanese Standards of Iron. and Steel) Sample
Arsenic content (%) Certified
No_ 156-l
No.
157-l
No. 158-l
Founda
0.009
0.0093
0.020
0.019 (k 0,001)
(5 0.0003)
0.092
0.093 (2 0.003)
=Aver,ge of 4 determinations (2 standard deviation).
57 REFERENCES 1 P. L. Larkins, R. M. Lowe, J. V. Sullivan and -4. Walsh, Spectrochim. dcta, Part B, 24 (1969) 187. 2 T. J. Vickers and R. M. Vaught, Anal. Chem., 41 (1969) 175. 3 P. D. Warr, Talanta, 17 (1970) 543. 4 D. G. Mitchell and A. Johansson, Spectrochim. Acta, Part B, 26 (1970) 175. 5 P. L. Larkina, Spectrochim. Acta, Part B, 26 (1971) 477. 6 P. L. Larkins and J. B. Willis, Spectrochim. Acta, Part B, 26 (1971) 491. 7 R. C. Elser and J. D. Winefordner, Appl. Spectrosc., 25 (1971) 345. 8 T. J. Vickers, P. J. Slevin, V. I. Muscat and L. T. Farias, Anal. Chem., 44 (1972) 930. 9 V. L Muscat, T. J. Vickers, W. E. Rippetoe and E. R. Johnson, Appl. Speetrose., 29 (1975) 52. 10 E. F. Palermo, A. Montaser and S, R. Crouch, Anal. Chem., 46 (1974) 2154. 11 W. Holak, Anal. Chem., 41 (1969) 1712. 12 E F. Dalton and A. J. Malonoski, At. Absorpt. News]., 10 (1971) 92. 13 F. J. Fernandez and D. C. Manning, At. Absorpt. New&, 10 (1971) 36. 14 R. C. Chu, G. P. Barron and P. A. W. Baumgarner, Anal. Chem., 44 (1972) 1476. 15 F. E. Lichte and R. K. Skogerboe, Anal. Chem., 44 (1972) 1480. 16 R. S. Braman; L. L. Justen and C. C. Foreback, Anal. Chem., 44 (1972) 2195. 17 Y. Yamamoto, T. Kumamaru, Y. Hayashi and R. Tsujino, Ana.i. Lett., 5 (1972) 419. 18 Y_ Yamamoto, T. Kumamaru, Y. Hayashi and T. Kamada, Bunseki Kagaku, 22 (1973) 876. 19 F. J. Schmidt and J. L. Royer, Anal. Lett., 6 (1973) 17. 20 Kwok-Tai Kan, Anal. Lett., 6 (1973) 603. 21 Y. Yamamoto, T. Kumamaru. Y. Hayashi and T. Kamada, Bull. Ckm. Sot. Jpn., 46 (1973) 2604. 22 E. N. Pohock and S. J. West, At. Absorpt. News)., 12 (1973) 6. 23 P. D. Goulden and P. Brooksbank, Anal. Chem., 46 (1974) 1431. 24 K. C. Thompson and D. R. Thomerson, Analyst, 99 (1974) 595. 25 A. E. Smith, Analyst, 100 (1975) 300. 26 K. C. Thompson, Analyst, 100 (1975) 307. 27 T. Maruta and G. Sudoh, Anal. Chim. Acta, 77 (1975) 37. 28 J. A. Fiorino, J. W. Jones and S. G. Capar, Anal. Chem., 48 (1976) 120. 29 K. Tsujii and K. Kuga, Anal. Chim. Acta, 72 (1974) 55. 30 K. Tsujii, K. Kuga and I. Sugaya, Chem. Lett., (1975) 695. 31 R. M. Dagnall, K. C. Thompson and T. S. West, Taknta, 15 (1968) 677. 32 D. Kolihova and V. Sychra, Anal. Chim. Acta, 59 (1972) 477.
Chin&a
Acta,
97 fl978)
51-57
OEisevier Scientific Publishing Company, Amsterdam -
Printed in The Netherlands
IMPROVEMENTS IN THE NON-DISPERSIVE ATOMIC FLUORESCENCE SPECTROMETRIC DETERMINATION OF ARSENIC AND ANTIMONY 33Y A HYDRIDE GENERATXON TK’ECHNIQtiX§
KANJI TSUJII*
and KAZUO
KUGA
Central Resenrch
Laboratory.
Hitachi
Ltd.,
Kokubunji,
Tokyo
(Japan)
(Received 12th July 19’7’7)
A sodium borohydride reduction, with subsequent atomization in a small argonhydrogen-entrained air Game has been developed for the determination of arsenic and antimony by non-dispersive atomic fluorescence spectrometry. The proposed method increases the signal level and decreases the noise level in the system. The detection iiiits for arsenic and antimony are 0.05 ng and 0.1 ng, respectively. The analytical working curves are linear over about four decades of concentration from the detection limits. Tire consumption rates of hydrogen and argon are comparatively low, while the speed of hydride evolution is improved; a peak measurement requires less than 40 s. The technique’ has been applied to the determination of arsenic in steel sampies.
The advantages and disadvantages of a non-dispersive system for atomic fluorescence speetrometry (a_f.s.) have been discussed in a number of publications [I-ItO] . This system offers improved signal levels, because of the large optical aperture and simultaneous detection of multiple lines for the element of interest. However, the noise level is likely to increase depending on the background radiation levels from the atom reservoir. For non-dispersive systems employing flame atomizers, the noise limitations are due to the background radiation from the flame [5-2.01. Hydride generation is now well known as a sensitive pretreatment technique for the determination of arsenic, antimony, selenium, tellurium etc. by atomic spectrometry f II-23]. As reported previously 129, 303, this technique can be applied effectively to non-dispersive systems for a.f.s. for the following reasons: (I.) hydride compounds are easily decomposed in a cool flame, e.g. an argon-hydrogenentrained air flame which emits very low background radiation; (2) the elements of interest are converted to hydrides and isolated from the matrix elements which occasionally cause severe light scattering effects; and (3) most of the elements known to form volatile hydrides have multiple fluoresk’his paper was presented at the 28th Pittsburgh Conference on Analytical Chemistry and Appfied Spectroscopy, Cieveiand, March 1977.
52
cence spectral lines within the spectral response range of a solar-blind photomultiplier, which is often used in non-dispersive af.s. For example, arsenic and antimony have 121311 and 9[32] atomic fluorescence spectral lines in the U.V. region_ In previous work 129,301 the liberated hydrides and hydrogen were stored for a fixed time prior to introduction into the flame atomizer. These studies indicated (I) that the noise level decreases with decreasing hydrogen flowrates; (2) that the hydrogen flow-rate has a lower limit with the hydride generation method described previously, because the pressure increase in the vessel during reduction extin-tihes the flame; and (3) that the system noise limitations are caused by OH band emission spectra (280-320 nm) emitted by the flame, and the noise is decreased by about 90% when a screen is placed between the burner and the detector. To overcome these limitations, a hydride generation method similar to that reported by Thompson and Thomerson [ 241 is coupled with a small argonhydrogenentrained air flame. EXPERIMENTAL Apparatus
Schematic diagrams of the apparatus and the specially manufactured twoslot burner are shown in Figs. 1 and 2. The burner head is situated so that the incident beam from the light source passes parallel to the burner slots. The sources used were Perkin-Elmer electrodeless discharge lamps operated at 10 W (As) and 5 W (Sb), as recommended, by a Perkin-Elmer Model 185-120 power supply. The light beam was focused by a quartz lens (34 mm diam., 60 mm focal length) and refocused by a concave mirror (65 mm diam., 55 mm focal length) just above the burner_ The fluorescent radiation was detected directly by a solar-blind photomultiplier (HTV R166). -4 John Fluke power supply
+-I
/E.D.L.
Fig. 1. Schematic
diagram
of the apparatus.
53
SO0 ,uL
1+ lt3*‘+
Fig. 2. Two-slot Fig. 3. Hydride
lJNIT:mm
PIFETTE
l”l.NaBH~
SOLUTION
burner. generation
cell.
(Model 412B) was used to provide high voltage (550 V) for the photomultiplier. The signals from the photomultiplier were fed into a lock-in amplifier (Princeton Applied Research Corp., Model HR-8) which was phased with a reference signal from a mechanical light chopper (Princeton Applied Research Corp., Model 125, chopping frequency: 27 Hz). The distance from the burner top to the center of the light beam was 1 cm and from the center of the burner slots to the photomultiplier was about 9 cm. The hydride generation cell (capacity, 90 ml), constructed from borosilicate glass, is shown in Fig. 3. Reagents
Commercially available arsenic(III) and antimony(II1) 1090-ppm standard solutions (Kant0 Chemical Corp.), made from sodium arsenite and antimony trichloride, respectively, were used. An arsenic(V) lOOO-ppm standard solution, prepared by dissolving sodium arsenate, was used when this tecbniquewas applied to the determination of arsenic in steel samples. Sodium borohydride solution (1%) was prepared, just before use, by dissolving sodium borohydride pellets (>98% pure; Alfa Inorgani&). All other reagents were of analyticalreagent grade. Procedure
The four-way stopcock was initially set for argon to pass through the bypass tube. Sodium borohydride solution (l%, 2 ml) was transferred to the hydride generation cell. A sample solution was taken by an Eppendorf 500+ pipette, which was then set as shown in Fig. 3. Next, the four-way stopcock was set to allow argon to pass through the cell. The sample solution was injected into
54
the cell and the reduction products were supplied continuously to the flame by a constant flow of argon gas. The atomic fluorescence signals were recorded, and the peak heights were measured. RESULTS
AND DISCUSSION
The response to arsenic and antimony was independent of the hydrochloric acid concentration from 1 to 8 M; this is similar to the results reported earlier [13, 24j. To minimize the pressure increase in the cell and to prevent reagent contamination, all measurements were made with 1 M hydrochloric acid. Effect of hydrogen flow rate The
effect
of the hydrogen
was measured.
The argon
level dependence
flow-rate
flow-rate
on the hydrogen
on the noise
was kept flow-rate
level and signal
constant
at 1-O 1 min-‘_
is shown
in Fig. 4. The
intensity The noise noise
z z 100-
A
B
E f $j ?55 Yl
C
it -50 *$flj&wl
-w-
$ g
F 2
25\
E E
.
G
I=
OO m+++-wv
-
;i
-
0.5
ow 1.5
1.0 H2
2.0
L min-’
4. Noise level dependence on the hydrogen flow-rate. Argon Cow-rate, 1.0 1 min-*. A, detector box shutter closed. B, detector box shutter open. C, outdoor light cut off. Hydrogen flow-rates: D, 2.0 1 min-‘; E, 1.0 1 min-‘; F, 0.5 1 min-‘; G, 0.25 1 min-‘. Fig.
Fig. 5. Effect of the hydrogen flow-rate on arsenic fluorescence intensity. Argon flow-rate, 1.0 1 min-*.
Fig. 6. Effect of the hydrogen flow-rate on antimdny fluorescence signal. Argon flow-rate, 1.0 1 min-‘. Hydrogen flow-rates: A, 0.7 1 min-‘; B, 0.6 1 min-‘; C, 0.45 1 min-‘;D, 0.35 1 min-’ ; E, 0.25 1 min-I.
55
level increases s&htly when the shutter of the detector box is opened but decreases to the initial level when outdoor light is cut off. The noise level suddenly increases when the flame is lit, but gradually decreases with decreasing hydrogen flow-rates. The noise level continues to decrease until it reaches the same level as that when the shutter of the detector box is closed. This occurs when the flow-rate decreases to 0.25 1 mm-‘. As reported previously [ 291, the decrease in noise 1eveIis closely related to decreasing OH band (280-320 nm) emission intensities. The visible portion of the flame also decreased with decreasing hydrogen flow-rates. It was about 1 cm when the tip of a metallic wire dipped in a sodium chloride solution was placed in the flame (hydrogen Bow-rate, 0.25 1 min-I). The flame, however, expanded slightly when the sample solution was injected into the ceJ_l. The effects of the hydrogen flow-rate on arsenic and antimony fluorescence intensities are shown in Figs. 5 and 6, respectively. The signal intensity for each element increases with decreasing hydrogen flow rates. This phenomenon was not observed previously f29,303, because the hydrogen flow-rate could not be decreased below 1.7 1 tin-‘, when the earlier hydride generation facility was used. This signal increase is probably caused by an increasing atom residence time in the light path and restriction of atoms in the small flame region. The following measurements were made at flow rates of 0.25 I min-’ of hydrogen and 1.0 1 mm-’ of argon. Detection, limit and analytical working curve The detection limits (S:N= 2) and reagent blanks for arsenic and antimony are shown in Table 1. The detection limits obtained with the former hydride generation cell are also given in Table 1. The improvement factors are 40 for arsenic and 30 for antimony. The detection limits obtained in this study cannot be compared directly with those reported previously becausethe light sources, the burner head, and the optical alignment are different. However, the small argon-hydrogen-+mtrained air flame plays an important role in improving the signal-to-noise ratio. The analytical working curves for arsenic and antimony are shown in Fig. 7. The linear range covers four concentration decades from the detection Emit; TABLE 1 Detection limits and reagent bIa.nks for As and Sb Efement
As
Sb
Detection limit (ng)
Reagent blank (ng)
Present
Previous
Present
hevious
2c291
1 0.5
25[291 -
0.05
0.1
3E301
I
“a’
,
= I
‘3 10
to2
As, Sb,
‘ng
Fig. 7. Analytical working curves for arsenic and antimony.
thisis aboutonedecade superiorto previousdata [29,30].Therelative standarddeviation calculatedfrom7 peak-heightmeasurementsfor0.1 ppm arsenic solution(III) is 1.7%. Determination of arsenic in steel samples This technique was applied to the determination of arsenic in steel samples weighing ca. 0.1 g. The sample was weighed exactly and dissolved in 10 ml of aqua regia; 5 ml of perchloric acid was added and the solution was heated until white perchloric acid fumes were observed. To eliminate any interfering effects of co-existing elements, known to occur in the formation and evolution of arsine 1251, a standard addition method was employed with lOOO-ppm arsenic(V) solution as the standard. The results, shown in Table 2, are in good agreement with the certified values. This technique is also applicable to other elements which form volatile hydrides, e.g. bismuth, germanium, lead, selenium, tin, and tellurium.
Determination of arsenic in carbon steel samples (Japanese Standards of Iron. and Steel) Sample
Arsenic content (%) Certified
No_ 156-l
No.
157-l
No. 158-l
Founda
0.009
0.0093
0.020
0.019 (k 0,001)
(5 0.0003)
0.092
0.093 (2 0.003)
=Aver,ge of 4 determinations (2 standard deviation).
57 REFERENCES 1 P. L. Larkins, R. M. Lowe, J. V. Sullivan and -4. Walsh, Spectrochim. dcta, Part B, 24 (1969) 187. 2 T. J. Vickers and R. M. Vaught, Anal. Chem., 41 (1969) 175. 3 P. D. Warr, Talanta, 17 (1970) 543. 4 D. G. Mitchell and A. Johansson, Spectrochim. Acta, Part B, 26 (1970) 175. 5 P. L. Larkina, Spectrochim. Acta, Part B, 26 (1971) 477. 6 P. L. Larkins and J. B. Willis, Spectrochim. Acta, Part B, 26 (1971) 491. 7 R. C. Elser and J. D. Winefordner, Appl. Spectrosc., 25 (1971) 345. 8 T. J. Vickers, P. J. Slevin, V. I. Muscat and L. T. Farias, Anal. Chem., 44 (1972) 930. 9 V. L Muscat, T. J. Vickers, W. E. Rippetoe and E. R. Johnson, Appl. Speetrose., 29 (1975) 52. 10 E. F. Palermo, A. Montaser and S, R. Crouch, Anal. Chem., 46 (1974) 2154. 11 W. Holak, Anal. Chem., 41 (1969) 1712. 12 E F. Dalton and A. J. Malonoski, At. Absorpt. News]., 10 (1971) 92. 13 F. J. Fernandez and D. C. Manning, At. Absorpt. New&, 10 (1971) 36. 14 R. C. Chu, G. P. Barron and P. A. W. Baumgarner, Anal. Chem., 44 (1972) 1476. 15 F. E. Lichte and R. K. Skogerboe, Anal. Chem., 44 (1972) 1480. 16 R. S. Braman; L. L. Justen and C. C. Foreback, Anal. Chem., 44 (1972) 2195. 17 Y. Yamamoto, T. Kumamaru, Y. Hayashi and R. Tsujino, Ana.i. Lett., 5 (1972) 419. 18 Y_ Yamamoto, T. Kumamaru, Y. Hayashi and T. Kamada, Bunseki Kagaku, 22 (1973) 876. 19 F. J. Schmidt and J. L. Royer, Anal. Lett., 6 (1973) 17. 20 Kwok-Tai Kan, Anal. Lett., 6 (1973) 603. 21 Y. Yamamoto, T. Kumamaru. Y. Hayashi and T. Kamada, Bull. Ckm. Sot. Jpn., 46 (1973) 2604. 22 E. N. Pohock and S. J. West, At. Absorpt. News)., 12 (1973) 6. 23 P. D. Goulden and P. Brooksbank, Anal. Chem., 46 (1974) 1431. 24 K. C. Thompson and D. R. Thomerson, Analyst, 99 (1974) 595. 25 A. E. Smith, Analyst, 100 (1975) 300. 26 K. C. Thompson, Analyst, 100 (1975) 307. 27 T. Maruta and G. Sudoh, Anal. Chim. Acta, 77 (1975) 37. 28 J. A. Fiorino, J. W. Jones and S. G. Capar, Anal. Chem., 48 (1976) 120. 29 K. Tsujii and K. Kuga, Anal. Chim. Acta, 72 (1974) 55. 30 K. Tsujii, K. Kuga and I. Sugaya, Chem. Lett., (1975) 695. 31 R. M. Dagnall, K. C. Thompson and T. S. West, Taknta, 15 (1968) 677. 32 D. Kolihova and V. Sychra, Anal. Chim. Acta, 59 (1972) 477.