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Spectrophotometric determination of iron in high-purity yttrium oxide with 1-(2-pyridylazo)-2-naphthol
146
SHORT
Spectrophotometric determination oxide with l-(2=pyridylazo)-2-naphthol
of
iron
in
COMMUNICA'ITONS
high-purity
yttrium
Tire growing importance of rare-earth metals in electronics, nuclear chemistry and metallurgy has necessitated the development of methods for their rapid and sensitive determination on the microgram scale; it has also necessitated the development of very scnsitivc methods for trace impurities in high-purity rare-earth materials. The object of the study described in this paper was to adapt the previously described spectrophotometric mctllod for iron in pure solution and clays with I-(a-pyridylazo)-znnphthol (/GPhN)i-:J to the determination of iron in high-purity yttrium oxide. Reccntly, the P-PAN method has been applied to the determination of iron in molybdenum and tungsten” metals, and high-purity galliumfi.
Stawlard solution. of iron(IlI). Tllis was prepared by dissolving 1.000 g of pure metal (gg,gg”/O Johnson Matthey) in a little concentrated hydrochloric acid and diluting to x 1 with reclistilled water. Standard solartion of yftriz~w This was prcparccl by dissolving tllc pure oxide (gg.gg”/o Johnson Matthey) in hydrochloric acid and cliluting to give a I mg/ml solution. P-PAN soldon. A 0.2% (w/v) solution was prepared by dissolving 200 mg of &PAN (Dozin Kagaku, Kurnamoto, Japan) in pure methanol. BaLJSersozaLtio?ts. Potassium chloride-hydrochloric acid and sodium acetateacetic acid buffers were used for the 1)~ adjustment. Organic solvents were purifiecl by the usual methods. All other reagents used were prcparccl from analytical-grade chemicals or from purified materials ancl the solutions were prepared with redistilled water. All measurements were made with a Model EPS 3T Hitachi recording spectrophotometer and EPU-2A Hitachi spcctrophotometcr with r-cm cells. A Yanagimoto 42A type 1)~ meter was used.
Weigh. a 0.2-g sample of well-clried yttrium oside (which contains at least I ,ug of iron) and transfer to a IOO-ml tall beaker. Add 5-10 ml of I + I hydrochloric acid, cover with a watch glass, and heat to dissolve. After evaporation of excess of hydrochloric acid, add IO ml of water. Transfer the solution to a Go-ml separatory funnel. Finally wash the original beaker with small portions of redistilled water, and add to the funnel. The total volume of aclueous solution should bc less than 20 ml. Then, add 4.0 ml of 0.2OA, P-PAN methanolic solution, ancl IO ml of I>H 4 acetate buffer, and shake vigorously for a few minutes. After 15 min, add 10.0 ml of chloroform and shake vigorously for I min. Drain the organic layer into a small stoppered conical flask ancl dry with anhydrous soclium sulfate. Measure the absorbance at 770 nm in a r-cm cell against a reagent blank. Restrlts
ami
disc7tssio~t~
czwve. The absorbance curve of the iron(II1) complex with P-PAN in chloroform is shown in Fig. I. The iron complex shows its absorbance maximum at a very much longer wavelength than those of other /3-FAN complexes. A bsorbame
SHORT
COMMUNICATIONS
I47
Effect of $H itt llte presence of large amoamts of yttrizmt. A series of solutions containing I p.p.m. of iron, 0.5 g of yttrium oxide and z ml of o.z% B-PAN solution was prepared at different pH values. An absorbance plateau was found over the pn range 3.3-5 and the optimum pn range was 3.5-4.5. It is preferable to choose a low 1)~ value in order to ensure avoidance of the reaction between yttrium and P-PAN which occurs in basic medium (above PH 7).
650 700 600 Wavelength (nm)
550
500
750
800
Fig. 1. Al~sorb;uw2 curve of iroti(l I I)-/3-LaAN curnl~lcx 2 p.p.m. iron, cxtrnctccl frown pit 4.0 aqueous solution.
iI1
Effect of reapnt concedratio?r. Generally z ml of o.z’j/, reagent solution was satisfactory for up to 3 p.p.m. of iron. In the presence of large amounts of yttrium oxide, the addition of a large excess of reagent accelerates the reaction. Coloarr deveZo@etlt and stability. The minimum time of standing before cxtraction with chloroform for complete colour development of the iron complex was IO min at room temperature (15-30”). The colour of the chloroform extract was very stable and suitable for quantitative work. Effect of yttrizcnt oxide. The absorbance at PH 4 of a series of solution, each containing IO ~6 of iron with varying amounts of yttrium oxide, was measured in order to study any effect of the major component. The results indicated that at least 0.5 g of yttrium oxide did not interfere with the absorbance of iron complex (see Table I). Beer’s Law. The absorbance of the chloroform extract of the iron--p-PAN complex conformed to Beer’s law up to ca. 3 p.p.m. of iron. Diverse io?ts. The effects of diverse ions on the reaction have already been reported in detail 1. The amounts of calcium, magnesium, silica, lead, copper, titanium, TABLE EFIZCT
Y&3
I OF
YTTHIIJhf
OXIDE
(d
Absorbance at 770 nl,8
added
Nil
0.300
0.1
0.305
0.2
0.300
Y203 added (6) o-3 0.4 0.5
A bsor.?mnce al 770 wwt 0.310 0.312 0.290
SHORT
148
COMMUNICATIONS
tantalum, nickel and rare-earth metals normally contained in high-purity yttrium oxide do not interfere. Even in the presence of other impurities which form chloroform-extractable P-PAN co~nplexcs, iron can be determined without interference because of its characteristic absorbance maximum at long waveleng-th.
__.__.-.-____ \~20:1 (hd
-_.
_.
.- ._.. _.
.._
._.
iakcr1
__
._......-_.
- ---
I vo.91 (jig) ___-_.---_-. ..-
‘I’dC!,L ..- _....-_--.-.-.._,. --._
---..
_--.._
1:o I, ,ld -.----
-. .
. -.
._._
wr
_ .--.
. ..-__
0.200
2.5
2.7
-k
0.2
0.200
5.0
5.2
+
0.2
-I-
0.
-
0.1 0.2 0.3
0.200
10.0
0.500 0.500 0.500
_--_.Tf\.BI,B
IO.1
2.5 5.0
2 .4 ,).8 9.7
10.0
..--...-_.-_. - -----__..._. -..
._..
I
..- .__. .-
IL 1
DIZTEI~MINATION
017
Cotnnrcrcid yllrium oxide _--__._---_
-.
COhlhl~I~CIAL
IRON
IN
Iron
(p.fi.wr
YTTRIUM
O.XII~I~
.)
. ._ ...-__ -.-.---_-5.1 5.0 1
11 09.9% B gg.g%
4.3 4 *5 4.2
5.0
4.3
Detemcination of iron in yttriwt oxide. Samples of yttrium oxide which contained known amounts of iron were obtained, to assess the validity of the recommended procedure. Typical results are shown in Table II. The results are in excellent agreement over a wide range of iron contents. Several commercial samples of high-purity yttrium oxide were also analyzed. Typical results are shown in Table III. Government Industrial Resenrch Institute, Hirate-nzachi, Kita-hr., Nagoya (Ja$an) I S. SHIBATA, 2
S. S~UATA,
A?gal.
Chim.
AC.%. 23 (IgGo) 25 (xgGr)
rl?lal. Chinr. Acts,
Saozo
KAZUO RYOZO
March Bth, 1969)
A,laZ. Chi?u. Ada,
46 (1969)
146-148
GOTO
NAKASHIMA
434, 348.
3 li. l’exIIIsL, z. A~kzZ. Clll??~~., 221 (1gGG) 132. 4 R. PUSCIII~L, E. LASSNXK AND li. KATZBNGRUUET, Chcnhl-Amdysl, 5G (rgG7) 5 V. P. SHVEDOV AND 0. KLUG, CIwm. Awal. (IVursaw), II (rg66) 237.
(Received
SHIBATA
63.
SHORT
Spectrophotometric determination oxide with l-(2=pyridylazo)-2-naphthol
of
iron
in
COMMUNICA'ITONS
high-purity
yttrium
Tire growing importance of rare-earth metals in electronics, nuclear chemistry and metallurgy has necessitated the development of methods for their rapid and sensitive determination on the microgram scale; it has also necessitated the development of very scnsitivc methods for trace impurities in high-purity rare-earth materials. The object of the study described in this paper was to adapt the previously described spectrophotometric mctllod for iron in pure solution and clays with I-(a-pyridylazo)-znnphthol (/GPhN)i-:J to the determination of iron in high-purity yttrium oxide. Reccntly, the P-PAN method has been applied to the determination of iron in molybdenum and tungsten” metals, and high-purity galliumfi.
Stawlard solution. of iron(IlI). Tllis was prepared by dissolving 1.000 g of pure metal (gg,gg”/O Johnson Matthey) in a little concentrated hydrochloric acid and diluting to x 1 with reclistilled water. Standard solartion of yftriz~w This was prcparccl by dissolving tllc pure oxide (gg.gg”/o Johnson Matthey) in hydrochloric acid and cliluting to give a I mg/ml solution. P-PAN soldon. A 0.2% (w/v) solution was prepared by dissolving 200 mg of &PAN (Dozin Kagaku, Kurnamoto, Japan) in pure methanol. BaLJSersozaLtio?ts. Potassium chloride-hydrochloric acid and sodium acetateacetic acid buffers were used for the 1)~ adjustment. Organic solvents were purifiecl by the usual methods. All other reagents used were prcparccl from analytical-grade chemicals or from purified materials ancl the solutions were prepared with redistilled water. All measurements were made with a Model EPS 3T Hitachi recording spectrophotometer and EPU-2A Hitachi spcctrophotometcr with r-cm cells. A Yanagimoto 42A type 1)~ meter was used.
Weigh. a 0.2-g sample of well-clried yttrium oside (which contains at least I ,ug of iron) and transfer to a IOO-ml tall beaker. Add 5-10 ml of I + I hydrochloric acid, cover with a watch glass, and heat to dissolve. After evaporation of excess of hydrochloric acid, add IO ml of water. Transfer the solution to a Go-ml separatory funnel. Finally wash the original beaker with small portions of redistilled water, and add to the funnel. The total volume of aclueous solution should bc less than 20 ml. Then, add 4.0 ml of 0.2OA, P-PAN methanolic solution, ancl IO ml of I>H 4 acetate buffer, and shake vigorously for a few minutes. After 15 min, add 10.0 ml of chloroform and shake vigorously for I min. Drain the organic layer into a small stoppered conical flask ancl dry with anhydrous soclium sulfate. Measure the absorbance at 770 nm in a r-cm cell against a reagent blank. Restrlts
ami
disc7tssio~t~
czwve. The absorbance curve of the iron(II1) complex with P-PAN in chloroform is shown in Fig. I. The iron complex shows its absorbance maximum at a very much longer wavelength than those of other /3-FAN complexes. A bsorbame
SHORT
COMMUNICATIONS
I47
Effect of $H itt llte presence of large amoamts of yttrizmt. A series of solutions containing I p.p.m. of iron, 0.5 g of yttrium oxide and z ml of o.z% B-PAN solution was prepared at different pH values. An absorbance plateau was found over the pn range 3.3-5 and the optimum pn range was 3.5-4.5. It is preferable to choose a low 1)~ value in order to ensure avoidance of the reaction between yttrium and P-PAN which occurs in basic medium (above PH 7).
650 700 600 Wavelength (nm)
550
500
750
800
Fig. 1. Al~sorb;uw2 curve of iroti(l I I)-/3-LaAN curnl~lcx 2 p.p.m. iron, cxtrnctccl frown pit 4.0 aqueous solution.
iI1
Effect of reapnt concedratio?r. Generally z ml of o.z’j/, reagent solution was satisfactory for up to 3 p.p.m. of iron. In the presence of large amounts of yttrium oxide, the addition of a large excess of reagent accelerates the reaction. Coloarr deveZo@etlt and stability. The minimum time of standing before cxtraction with chloroform for complete colour development of the iron complex was IO min at room temperature (15-30”). The colour of the chloroform extract was very stable and suitable for quantitative work. Effect of yttrizcnt oxide. The absorbance at PH 4 of a series of solution, each containing IO ~6 of iron with varying amounts of yttrium oxide, was measured in order to study any effect of the major component. The results indicated that at least 0.5 g of yttrium oxide did not interfere with the absorbance of iron complex (see Table I). Beer’s Law. The absorbance of the chloroform extract of the iron--p-PAN complex conformed to Beer’s law up to ca. 3 p.p.m. of iron. Diverse io?ts. The effects of diverse ions on the reaction have already been reported in detail 1. The amounts of calcium, magnesium, silica, lead, copper, titanium, TABLE EFIZCT
Y&3
I OF
YTTHIIJhf
OXIDE
(d
Absorbance at 770 nl,8
added
Nil
0.300
0.1
0.305
0.2
0.300
Y203 added (6) o-3 0.4 0.5
A bsor.?mnce al 770 wwt 0.310 0.312 0.290
SHORT
148
COMMUNICATIONS
tantalum, nickel and rare-earth metals normally contained in high-purity yttrium oxide do not interfere. Even in the presence of other impurities which form chloroform-extractable P-PAN co~nplexcs, iron can be determined without interference because of its characteristic absorbance maximum at long waveleng-th.
__.__.-.-____ \~20:1 (hd
-_.
_.
.- ._.. _.
.._
._.
iakcr1
__
._......-_.
- ---
I vo.91 (jig) ___-_.---_-. ..-
‘I’dC!,L ..- _....-_--.-.-.._,. --._
---..
_--.._
1:o I, ,ld -.----
-. .
. -.
._._
wr
_ .--.
. ..-__
0.200
2.5
2.7
-k
0.2
0.200
5.0
5.2
+
0.2
-I-
0.
-
0.1 0.2 0.3
0.200
10.0
0.500 0.500 0.500
_--_.Tf\.BI,B
IO.1
2.5 5.0
2 .4 ,).8 9.7
10.0
..--...-_.-_. - -----__..._. -..
._..
I
..- .__. .-
IL 1
DIZTEI~MINATION
017
Cotnnrcrcid yllrium oxide _--__._---_
-.
COhlhl~I~CIAL
IRON
IN
Iron
(p.fi.wr
YTTRIUM
O.XII~I~
.)
. ._ ...-__ -.-.---_-5.1 5.0 1
11 09.9% B gg.g%
4.3 4 *5 4.2
5.0
4.3
Detemcination of iron in yttriwt oxide. Samples of yttrium oxide which contained known amounts of iron were obtained, to assess the validity of the recommended procedure. Typical results are shown in Table II. The results are in excellent agreement over a wide range of iron contents. Several commercial samples of high-purity yttrium oxide were also analyzed. Typical results are shown in Table III. Government Industrial Resenrch Institute, Hirate-nzachi, Kita-hr., Nagoya (Ja$an) I S. SHIBATA, 2
S. S~UATA,
A?gal.
Chim.
AC.%. 23 (IgGo) 25 (xgGr)
rl?lal. Chinr. Acts,
Saozo
KAZUO RYOZO
March Bth, 1969)
A,laZ. Chi?u. Ada,
46 (1969)
146-148
GOTO
NAKASHIMA
434, 348.
3 li. l’exIIIsL, z. A~kzZ. Clll??~~., 221 (1gGG) 132. 4 R. PUSCIII~L, E. LASSNXK AND li. KATZBNGRUUET, Chcnhl-Amdysl, 5G (rgG7) 5 V. P. SHVEDOV AND 0. KLUG, CIwm. Awal. (IVursaw), II (rg66) 237.
(Received
SHIBATA
63.