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3-Hydroxy-1,3-diphenyltriazene and its substituted derivatives as spectrophotometric reagents for vanadium(V)
196
Anrrlyticc~ Chimica
:a’: Ekcvicr
SHORT
Scientific
Publishing
Cornpuny,
Amsterdam
Ada.
- Printed
7
1 ( 1974) 196-20 I
in The Nethcrlnnds
COMMUNICATION
3-Hydroxy-l,3-diphenyltriazene reagents for vanadium(V)
and its substituted
derivatives
as spectrophotometric
D. CHAKRABORTI D~~pcrr~rnr~r~~1 Clwrnistry.
(Rcccivcd
2nd January
Jtrtltrcpttr
Liuircrsiry.
C’crlcr~rrtr-700032 ( Irrtlitr)
1074)
If a sulfonic acid group (Na-salt) is introduced, in addition to the chelating groups, a water-insoluble organic reagent can often be made water-soluble without substantial alteration in its other properties; yet sometimes the sulfonic acid group may cause anomalous behavior ‘* 2. Work of this type has been reported from this laboratory for colorometric analyses3q5. This communication describes the effects of the introduction of a sulfonic acid group (Na-salt), and a sulfonic acid group along with a methyl group, on the parent organic reagent 3-hydroxy1,3-diphenyltriazene5. A comparative study of all these reagents for the spectrophotometric determination of vanadium(V) is also described. The reagents examined are: I. 3-Hydroxy-l,3_diphenyltriazene (ref. 5) II. 3-Hydroxy-( I-p-sulfonatophenyl, sodium salt)-3-phenyltriazene (ref. 6) III. 3-Hydroxy-( I-o-sulfonatophenyl, sodium salt)-3-phenyltriazene (ref. 7) IV. 3-Hydroxy-( 1-,n-sulfonatophenyl. sodium salt)-3-phenyltriazene V. 1-(4-Sulfonato, sodium salt-6-methylphenyl)-3-hydroxy-3-phenyltriazene VI. 1-(4-Sulfonato, sodium salt-5-methylphenyl)-3-hydroxy-3-phenyltriazene
QJN=N-IHa
N.45/0-N=N-z;0
.,“6;D”=YHY 3
I
II
m
Several workers have already investigated reagents I and II and a comprehensive review is available “. Reagents IV, V and VI are new reagents. Introduction of a sulfonic acid group into the parent reagent (I) makns it water soluble. When the reagent contains a methyl group and a sulfonic acid group (sodium salt), it becomes highly water-soluble. The order of water solubility of the reagents can be represented as: V= VI > IV = II > III. Studies of the color reaction of these reagents with vanadium(V) showed that reagents I. II, IV and VI are sensitive to vanadium and their reactions are very similar. but reagents III and V are not very sensitive and are therefore unsuitable for spectrophotometry; reagent V is the least sensitive. Clearly the positioning of substituents next to the triazene group seriously affects sensitivity.
-
Water
Water
Water
Waler
III
IV
V
VI
(b) 4~0 (c) 410
(c) 410
[“b’,Eow
green
(a) 0.1-S (b) OS-8
-
(b) OS-10
(a) Yellowgreen (b) 410 (c) 410
(a) 0.25-12
-
(a) 0.25-10 (b) OS-10
(a) 0.25-10 (b) OS-10
(a) Yellowfpen
lb) w (c)410
(a) Yel!owgreen
(bf 400 (c) 410
(a) Yellowgreen
(a) Yellow (b) 410 (c) 410
* A 0.1%(w/v) solutionwas used.
Water
(I+11
Water+ ethanot
II
I
0.0075
0.05
0.0095
0,026
0.0085
0.0085
6625
-
5250
-
5875
3-O-4.4
-
3.6-4.6
-
3.3-4.3
5875 3.1-4.2
(a) I:1 (b) 7.5. lo-’
-
(a) 19 (b) 5.0.10-s
-
(b) 6.5*10-’
(il) I:1
(a) I:1 (b) 6.0.10-”
4.0
-
6.0
-
5.0
SPE~ROPHOTOMETRIC DETERMINATIONOF VANADIUM(V)WITH 3-HYDROXY-l,3-~IPHENYLTRIAZENE AND ITS DERIVATIVES
TABLEI
198
SHORT
COMMUNICATION
Of these six rcagcnts. reagent VI is most suitable for the spectrophotometric determination of vanadium(V); it provides the highest sensitivity with the widest permissible pH range. and has the lowest absorbance itself. Reagent VI is therefore described in detail here. whereas data for the other reagents are simply tabulated (Table I). An interesting observation is that reagent I, in acetone at about pH 2-3. gives, in the presence of vanadium(V), a green precipitate which this color complex can be extracted into chloroform. i,,,:,. at 640 nm; unfortunately decomposes rapidly and a turbidity appears. Other reagents did not exhibit this behavior.
Pseparcrtiorl ~~f’wcrgmts. Reagents I and II were prepared as suggested by Sogani and Bhattacharyya y. Reagents 111. IV, V and VI were also prepared by this method; the starting materials were orthanilic acid, metanilic acid, 2-amino-5-sulfotoluene and 3-amino-toluene-6-sulfonic acid, respectively. Reagent III is a yellowish white compound (m.p. 168°C decomp.). Reagents IV, V and VI are light yellow, pale yellow and yellowish white (m.p. 164°C. 157°C and 159°C decomp.). respectively. Appcrrwtuscrr~cl solutiorw. Apparatus and solutions of ammonium vanadate and previously other ions were the same as rcportcd water was used 4. Doubly distilled in all preparations. All the chemicals used were of A.R. quality. The reagent was used as a 0.1% (w/v) solution in water. Ahso&~~ CUW~ Jbr Vcutctt/ium( V). To an aliquot of the standard solution containing 100 116 of vanadium in a 50-ml beaker. add 4 ml of the reagent (VI) solution. Add dilute hydrochloricacid to adjust the pH to 3-4. Then dilute with water 0.7 -
0.6 -
0.5 -
ti
0.4 ”
z : 5:
0.3 -
: 0.2 -
0.1 -
380
A00
490
450
410
WAVELE
NQTH,
“m
Fig. I. Absorption spectra of vonxiium(V) complcxcs on the curves corrcsponci to the rcngcnt numbers.
(4
p.p.m.
vunndium).
The
Roman
numerals
SHORT
199
COMMUNICATION
to 25 ml in a volumetric flask and measure the absorbance against the reagent solution as blank. The yellowish green color of the system, corresponding to 4.0 p.p.m. of vanadium, shows maximum absorbance at 400 nm (curve VI, Fig. 1). All measurements for vanadium(V) are made at 410 nm because, at this wavelength, the absorption of the reagent itself is much less. Ejyect
of pN. rengent ami the The absorbance of the system remains unchanged in the pH range 3.0-4.4, but decreases outside these limits. For complete color development. 4 p.p.m. of vanadium requires 3 ml of 0.1% (w/v) reagent solution. The absorbances of the system so produced remain constant for more than 24 h. Beer’s kaw, optittd twtzgge, phototttetric errors. settsitivity anti molar absorptivity The system follows Beer’s law over the range 0.125-8.0 p.p.m. optimal concentration range evaluated by Ringbom’s methodlo is 0.5-8.0. percentage relative error per l”/, absolute photometric error’ ’ for the system is The sensitivity when log IO/I is 0.001, calculated as described by Sandell’ 0.0075 jig cm- 2, and the molar absorptivity is 6625. Cotnpositiott
cwl
stddity
*
The The 2.74. 2, is
oJ’ the cotnplex
The composition of the vanadium complex was determined by the modified Job’s method of continuous variationsI and the mole ratio method14. Figure 2 indicates that vanadium combines with the reagent in the ratio 1 :l.
Fig. 2. Job curves;
vunadium(V)=rcagent
VI=
5.0. 10m4 M.
200
SHORT
COMMUNICATION
The degree of dissociation, cc, was calculated from Harvey and Manning’s equation’ 5. The instability constant evaluated from the equation K = (~~~o(c)“‘(~Rxc)“/ c( l-a) where m=n= 1 for vanadium(V) was found to be 7.5. 10m5 (E,,,=O.56; E, =0.38; c=5. 10-4. ~=0.32). The dissociatibn constant of the complex was also evaluated from a study of the absorbance of complementary mixtures of non-equimolar solutions of metal ions and reagent (Fig. 3). The color of the solution was developed as described previously. The value calculated from the conventional equationI was found to be 7.5.10-5 (l)l=I?= 1; p=3; x=0.33).
0:e
0
Fig. 3. Job’s method
Ejyect
of diverse
0:4
0.6
cw/[Ml+ CR1 for the dissociation constant;
0. 6
vanadium(V)=O.S*
1.0
10q3 M, rcagen: VI= 1.5. low3 M.
ions
In the vanadium(V)-reagent VI system, EDTA, oxalate, fluoride, Fe3+, Pd2 +, Mo6+, Cr3+ and Ti4+ interfered. The system, however, tolerates the presence of the following ions, the tolerance limits of which in p.p.m. are given in parentheses: Ni2+(50), Co2’(10), Mn2+( lo), WOi-(20), UO$+( lo), La3+(30), Ce3+(20), Zn’+( loo), Cd2+(200), Hg2+(100), As3+( 100) and Th4+(40). Cu2’ interfered but in the presence of sodium thiosulfate (5 ml of lo/, solution), it could be, tolerated up to 50 p.p.m. Li +, Na+, K +? Br-, I-, Cl-, PO;-, boric acid, citrate and tartrate did not interfere.
REFERENCES 1 H. C. Wingfield and J. H. Yoe, .4rtul. Claim. ktu, 14 (1956) 446. 2 E. L. Stelle and J. H. Yoe, Anal. Chew., 29 (1957) 1622; AmL Chim. Actu, 20 (1959)
205.
SHORT 3 4 5 6 7 8 9. 10 11 12 13 14 15 16
201
COMMUNICATION
D. Chakraborti. Aflu/. C/I~W. Acrcr, 00 (1974) 000. A. K. Majumdar and D. Chakraborti, Amd. Chitn. Acfa. 53 (1971) 127, 393. N. C. Sogani and S. C. Bhattacharyya, Anal. Chem.. 28 (1956) 81. N. C. Sogani and S. C. Bhattacharyya, Anal. Chem., 35 (1958) 542. B. C. Roy, Ph.D. Thesis, Jadavpur University, India. D. N. Purohit, Tulunru. 14 (1967) 353. N. C. Sogani and B. C. Bhattacharyya, .I. Imfiia~t Chem. Sot.. 36 (1959) 563. A. Ringborn, 2. Ad. Chem., 115 (1938) 332. G. H. Ayres, Ard. Chem., 2 1 ( 1949) 652. E. 8. Sandell, Colorometric Determimrtiou o_f’Truce Met&, Interscience, New p. 84. P. Job, Co,npi Re&., 180 (1925) 928; AWL Chhr. (Pork), 9 (1928) 113. J. H. Yoe and A. K. Jones. f~~rl. Eng. Chem., And. Ed., 16 (1944) 111. A. E. Harvey Jr. and D. L. Manning, J. Amer. Chem. SW., 72 ( 1950) 4488. A. K. Majumdar and B. Sen, Amtl. Chim. Acru, 8 (1953) 369.
York,
3rd Edn.,
1959,
Anrrlyticc~ Chimica
:a’: Ekcvicr
SHORT
Scientific
Publishing
Cornpuny,
Amsterdam
Ada.
- Printed
7
1 ( 1974) 196-20 I
in The Nethcrlnnds
COMMUNICATION
3-Hydroxy-l,3-diphenyltriazene reagents for vanadium(V)
and its substituted
derivatives
as spectrophotometric
D. CHAKRABORTI D~~pcrr~rnr~r~~1 Clwrnistry.
(Rcccivcd
2nd January
Jtrtltrcpttr
Liuircrsiry.
C’crlcr~rrtr-700032 ( Irrtlitr)
1074)
If a sulfonic acid group (Na-salt) is introduced, in addition to the chelating groups, a water-insoluble organic reagent can often be made water-soluble without substantial alteration in its other properties; yet sometimes the sulfonic acid group may cause anomalous behavior ‘* 2. Work of this type has been reported from this laboratory for colorometric analyses3q5. This communication describes the effects of the introduction of a sulfonic acid group (Na-salt), and a sulfonic acid group along with a methyl group, on the parent organic reagent 3-hydroxy1,3-diphenyltriazene5. A comparative study of all these reagents for the spectrophotometric determination of vanadium(V) is also described. The reagents examined are: I. 3-Hydroxy-l,3_diphenyltriazene (ref. 5) II. 3-Hydroxy-( I-p-sulfonatophenyl, sodium salt)-3-phenyltriazene (ref. 6) III. 3-Hydroxy-( I-o-sulfonatophenyl, sodium salt)-3-phenyltriazene (ref. 7) IV. 3-Hydroxy-( 1-,n-sulfonatophenyl. sodium salt)-3-phenyltriazene V. 1-(4-Sulfonato, sodium salt-6-methylphenyl)-3-hydroxy-3-phenyltriazene VI. 1-(4-Sulfonato, sodium salt-5-methylphenyl)-3-hydroxy-3-phenyltriazene
QJN=N-IHa
N.45/0-N=N-z;0
.,“6;D”=YHY 3
I
II
m
Several workers have already investigated reagents I and II and a comprehensive review is available “. Reagents IV, V and VI are new reagents. Introduction of a sulfonic acid group into the parent reagent (I) makns it water soluble. When the reagent contains a methyl group and a sulfonic acid group (sodium salt), it becomes highly water-soluble. The order of water solubility of the reagents can be represented as: V= VI > IV = II > III. Studies of the color reaction of these reagents with vanadium(V) showed that reagents I. II, IV and VI are sensitive to vanadium and their reactions are very similar. but reagents III and V are not very sensitive and are therefore unsuitable for spectrophotometry; reagent V is the least sensitive. Clearly the positioning of substituents next to the triazene group seriously affects sensitivity.
-
Water
Water
Water
Waler
III
IV
V
VI
(b) 4~0 (c) 410
(c) 410
[“b’,Eow
green
(a) 0.1-S (b) OS-8
-
(b) OS-10
(a) Yellowgreen (b) 410 (c) 410
(a) 0.25-12
-
(a) 0.25-10 (b) OS-10
(a) 0.25-10 (b) OS-10
(a) Yellowfpen
lb) w (c)410
(a) Yel!owgreen
(bf 400 (c) 410
(a) Yellowgreen
(a) Yellow (b) 410 (c) 410
* A 0.1%(w/v) solutionwas used.
Water
(I+11
Water+ ethanot
II
I
0.0075
0.05
0.0095
0,026
0.0085
0.0085
6625
-
5250
-
5875
3-O-4.4
-
3.6-4.6
-
3.3-4.3
5875 3.1-4.2
(a) I:1 (b) 7.5. lo-’
-
(a) 19 (b) 5.0.10-s
-
(b) 6.5*10-’
(il) I:1
(a) I:1 (b) 6.0.10-”
4.0
-
6.0
-
5.0
SPE~ROPHOTOMETRIC DETERMINATIONOF VANADIUM(V)WITH 3-HYDROXY-l,3-~IPHENYLTRIAZENE AND ITS DERIVATIVES
TABLEI
198
SHORT
COMMUNICATION
Of these six rcagcnts. reagent VI is most suitable for the spectrophotometric determination of vanadium(V); it provides the highest sensitivity with the widest permissible pH range. and has the lowest absorbance itself. Reagent VI is therefore described in detail here. whereas data for the other reagents are simply tabulated (Table I). An interesting observation is that reagent I, in acetone at about pH 2-3. gives, in the presence of vanadium(V), a green precipitate which this color complex can be extracted into chloroform. i,,,:,. at 640 nm; unfortunately decomposes rapidly and a turbidity appears. Other reagents did not exhibit this behavior.
Pseparcrtiorl ~~f’wcrgmts. Reagents I and II were prepared as suggested by Sogani and Bhattacharyya y. Reagents 111. IV, V and VI were also prepared by this method; the starting materials were orthanilic acid, metanilic acid, 2-amino-5-sulfotoluene and 3-amino-toluene-6-sulfonic acid, respectively. Reagent III is a yellowish white compound (m.p. 168°C decomp.). Reagents IV, V and VI are light yellow, pale yellow and yellowish white (m.p. 164°C. 157°C and 159°C decomp.). respectively. Appcrrwtuscrr~cl solutiorw. Apparatus and solutions of ammonium vanadate and previously other ions were the same as rcportcd water was used 4. Doubly distilled in all preparations. All the chemicals used were of A.R. quality. The reagent was used as a 0.1% (w/v) solution in water. Ahso&~~ CUW~ Jbr Vcutctt/ium( V). To an aliquot of the standard solution containing 100 116 of vanadium in a 50-ml beaker. add 4 ml of the reagent (VI) solution. Add dilute hydrochloricacid to adjust the pH to 3-4. Then dilute with water 0.7 -
0.6 -
0.5 -
ti
0.4 ”
z : 5:
0.3 -
: 0.2 -
0.1 -
380
A00
490
450
410
WAVELE
NQTH,
“m
Fig. I. Absorption spectra of vonxiium(V) complcxcs on the curves corrcsponci to the rcngcnt numbers.
(4
p.p.m.
vunndium).
The
Roman
numerals
SHORT
199
COMMUNICATION
to 25 ml in a volumetric flask and measure the absorbance against the reagent solution as blank. The yellowish green color of the system, corresponding to 4.0 p.p.m. of vanadium, shows maximum absorbance at 400 nm (curve VI, Fig. 1). All measurements for vanadium(V) are made at 410 nm because, at this wavelength, the absorption of the reagent itself is much less. Ejyect
of pN. rengent ami the The absorbance of the system remains unchanged in the pH range 3.0-4.4, but decreases outside these limits. For complete color development. 4 p.p.m. of vanadium requires 3 ml of 0.1% (w/v) reagent solution. The absorbances of the system so produced remain constant for more than 24 h. Beer’s kaw, optittd twtzgge, phototttetric errors. settsitivity anti molar absorptivity The system follows Beer’s law over the range 0.125-8.0 p.p.m. optimal concentration range evaluated by Ringbom’s methodlo is 0.5-8.0. percentage relative error per l”/, absolute photometric error’ ’ for the system is The sensitivity when log IO/I is 0.001, calculated as described by Sandell’ 0.0075 jig cm- 2, and the molar absorptivity is 6625. Cotnpositiott
cwl
stddity
*
The The 2.74. 2, is
oJ’ the cotnplex
The composition of the vanadium complex was determined by the modified Job’s method of continuous variationsI and the mole ratio method14. Figure 2 indicates that vanadium combines with the reagent in the ratio 1 :l.
Fig. 2. Job curves;
vunadium(V)=rcagent
VI=
5.0. 10m4 M.
200
SHORT
COMMUNICATION
The degree of dissociation, cc, was calculated from Harvey and Manning’s equation’ 5. The instability constant evaluated from the equation K = (~~~o(c)“‘(~Rxc)“/ c( l-a) where m=n= 1 for vanadium(V) was found to be 7.5. 10m5 (E,,,=O.56; E, =0.38; c=5. 10-4. ~=0.32). The dissociatibn constant of the complex was also evaluated from a study of the absorbance of complementary mixtures of non-equimolar solutions of metal ions and reagent (Fig. 3). The color of the solution was developed as described previously. The value calculated from the conventional equationI was found to be 7.5.10-5 (l)l=I?= 1; p=3; x=0.33).
0:e
0
Fig. 3. Job’s method
Ejyect
of diverse
0:4
0.6
cw/[Ml+ CR1 for the dissociation constant;
0. 6
vanadium(V)=O.S*
1.0
10q3 M, rcagen: VI= 1.5. low3 M.
ions
In the vanadium(V)-reagent VI system, EDTA, oxalate, fluoride, Fe3+, Pd2 +, Mo6+, Cr3+ and Ti4+ interfered. The system, however, tolerates the presence of the following ions, the tolerance limits of which in p.p.m. are given in parentheses: Ni2+(50), Co2’(10), Mn2+( lo), WOi-(20), UO$+( lo), La3+(30), Ce3+(20), Zn’+( loo), Cd2+(200), Hg2+(100), As3+( 100) and Th4+(40). Cu2’ interfered but in the presence of sodium thiosulfate (5 ml of lo/, solution), it could be, tolerated up to 50 p.p.m. Li +, Na+, K +? Br-, I-, Cl-, PO;-, boric acid, citrate and tartrate did not interfere.
REFERENCES 1 H. C. Wingfield and J. H. Yoe, .4rtul. Claim. ktu, 14 (1956) 446. 2 E. L. Stelle and J. H. Yoe, Anal. Chew., 29 (1957) 1622; AmL Chim. Actu, 20 (1959)
205.
SHORT 3 4 5 6 7 8 9. 10 11 12 13 14 15 16
201
COMMUNICATION
D. Chakraborti. Aflu/. C/I~W. Acrcr, 00 (1974) 000. A. K. Majumdar and D. Chakraborti, Amd. Chitn. Acfa. 53 (1971) 127, 393. N. C. Sogani and S. C. Bhattacharyya, Anal. Chem.. 28 (1956) 81. N. C. Sogani and S. C. Bhattacharyya, Anal. Chem., 35 (1958) 542. B. C. Roy, Ph.D. Thesis, Jadavpur University, India. D. N. Purohit, Tulunru. 14 (1967) 353. N. C. Sogani and B. C. Bhattacharyya, .I. Imfiia~t Chem. Sot.. 36 (1959) 563. A. Ringborn, 2. Ad. Chem., 115 (1938) 332. G. H. Ayres, Ard. Chem., 2 1 ( 1949) 652. E. 8. Sandell, Colorometric Determimrtiou o_f’Truce Met&, Interscience, New p. 84. P. Job, Co,npi Re&., 180 (1925) 928; AWL Chhr. (Pork), 9 (1928) 113. J. H. Yoe and A. K. Jones. f~~rl. Eng. Chem., And. Ed., 16 (1944) 111. A. E. Harvey Jr. and D. L. Manning, J. Amer. Chem. SW., 72 ( 1950) 4488. A. K. Majumdar and B. Sen, Amtl. Chim. Acru, 8 (1953) 369.
York,
3rd Edn.,
1959,