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Extraction—spectrophotometric determination of palladium(ii) with 2-nitroso-5-diethylaminophenol
Anclytica Chimica Acta, 101(1978) 169-175 OELsevier Scientific Publishing Company, Amsterdam
- Printed in The Netherlands
EXTRACTION-SPECTROPMOTOMETRIC DETERMINATION OF PALLADI~~II) WITH 2-NITROSO-5-DIETI-IYLAMINOI’IIENOL
RYOJI
TGEI*,
SI-IOJI MOTOMIZU
and SHOICHI
HAIIADA
Department of Chemistry, Fatuity of Science. Okayama University, Tsushima. Okayama-shi (Jaw4 (Received
28th February
1978)
An estraction-spectrophotometric determination of pailadium(I1) with 2-nitroso-Sdiethy~~inopheno1 is described. Complex formation and estraction of the complex with chloroform are possible with aqueous phases of about 2.5 M sulfuric acid. The molar absorptivity of the complex is 4.38 x 10’ 1 mol-’ cm-* at 486 nm. Few of the common ions interfere at concentrations of 10-4-10-3 M; more than 10m5 M &(IV), lo-’ M W(VI), 5 x 10m6 hl _4u(III) and 10Y6 M iodide cause negative errors. The method can be applied to the determination of palladium in catalysts for automobile exhaust purifiers.
Palladium(II) -the first of the Irving-Williams series - forms very stable complexes with many chelating reagents, so that many ligands have been proposed for determinations of palladium. Of these reagents, various nitroso compounds (nitrosophenols Cl 1, nitrosonaphthols [Z---4] and pnitrosodimethylaniline [5] ) react with palladium in acidic solutions and provide sensitive spectrophotometric determinations of palladium. 2-Nitroso-5-diethylainophenol (nitroso-DEAP) and 2-nitroso-&dimethylaminophenol (nitroso-DMAP), which were first used for the sensitive extraction-spectrophotometric determination of cobalt [6 ] and iron [7 1, react with palladium in a strongly acidic solution. The complexes formed are easily extracted into chloroform and show the largest mofar absorptivities in the visible region of all the nitroso compounds proposed so far, except for ~-ni~osodimethyl~i~e [5f which gives a molar absorptivity of 8.6 X 10c 1 mol-’ cm-’ at 525 nm, but does not react at such high acidities. This paper describes the extraction-spectrophotometric determination of palladium with nitroso-DEAP. The method has many advantages in simplicity and sensitivity, in accuracy and precision, and in an abbreviated list of interferences.
173 EXPERIMENTAL
Appara fus and reagents
A Hitachi Perk&Elmer Model 139 spectrophotometer and a Hitachi Model EPS3T recording spectrophotometer were used to measure absorbances in a quartz cell of lo-mm path length. An Iwaki Model KM shaker was used. Standard palladium(II) solution. Weigh approximately 1.26 g of palladium nitrate into a porcelain evaporating dish, add about 20 ml of 12 M HCl, and evaporate nearly to dryness. Dissolve the residue in 100 ml of 0.5 M HCl. Standardize this solution by the gravimetric dimethylglyoxime method [S]. Pipette accurate amounts of the standardized solution into a beaker, add 2 ml each of concentrated sulfuric and nitric acids, and evaporate to white fumes. Add 0.5 ml of nitric acid and evaporate to white fumes, and repeat this process. Finally add 2-5 ml of water and evaporate to white fumes. Dilute this with 0.5 M H2SOG, transfer the solution to a l-l volumetric flask and dilute to the mark with 0.5 M H,SO, to give a 2 X 10e5 M palladium solution. 2-Nitroso-5-diethylaminophenol. Nitroso-DEAP was obtained by nitrosation of the parent compound (m-diethylaminophenol) in acidic aqueous solution with sodium nitrite [ 91; the crude nitroso compound was recrystallized twice from hydrochloric acid solution. An aqueous solution (6 X 10m3RI) in 0.05 M HSO, was used. Other reagents were of analytical-reagent grade. Standard procedure
Pipette up to 5 ml of the solution containing palladium(I1) into a stoppered test tube, and dilute to 5 ml with distilled water. Add 4.5 ml of about 5.5 M sulfuric acid and 0.5 ml of nitroso-DEAP solution and mix well. Shake the mixture with 5 ml of chloroform for 1 min. Discard the aqueous phase and wash the organic phase with 5 ml of 2.5 M sulfuric acid by shaking for about 1 min by hand, to remove the excess of reagent. Measure the absorbance of the organic phase at 486 nm. RESULTS
Effects of experimental variables The time necessary for complete formation of the palladium(I1) complex
with nitroso-DEAP is ca. 30 s at room temperature. The absorbance of the complex extracted into ctioroform does not change for at least a day. The time necessary for complete extraction of the complex is 30 s by hand or mechanical shaking. When the palladium concentration is about 10m5M, the addition of 0.1 ml of nitroso-DEAP solution (6 X 10e3 M) suffices for complete extraction of palladium; accordingly 0.5 ml of reagent solution should be used for safety.
The effect of acidity on the extraction of the palladium complex was examined. As shown in Fig. 1, the absorbance of the complex measured against a reagent blank was constant for concentrations of sulfuric acid from 2-3 M though the absorbance of the reagent blank varied from 0.15 to 0.04; in these experiments, the excess of reagent was not removed. To reduce the absorbance of the reagent blank, the organic phase was washed with dilute sulfuric acid after extraction of the complex; washing with 2.5-3 M sulfuric acid reduced the absorbances of the reagent blanks to about 0.004. The effect of volume of the aqueous phase was examined for the standard procedure. When the aqueous phase was varied from 5 to 50 ml, the absorbance of the complex in the organic phase was not affected, provided that the concentration of suifutic acid in the aqueous phase was maintained at about 2.5 M. Chloroform was the best of the nine organic solvents tested (chloroform, carbon tetrachloride, 1,2-dichloroethane, benzene, toluene, isobutyl methyl ketone, isoamyl alcohol, ethyl acetate and ligroin). When 5 ml of chloroform was used, all the palladium was removed from the aqueous phase in the first extraction. When a second extraction was done, palladium was not detected in the organic phase.
Composition of the extracted species The composition of the palladium complex
was examined by the molar ratio methods, in which the concentration of the reagent was varied. The p~ladium~~~):nitroso-Dam ratio was found to be 1: 2 (Fig. 2). Calibrarion *graphand molar absorptiuity The calibration graph with the reagent blank as reference was a straight line through the origin over the range O-2 X 10e5 M Pd. The molar
0.5
0.1
Fig. 1. Effect of acid concentration at 486 nm. (1) Reagent blank with CHCl, reference; (2) fPd] = 8.52 x lo-’ PUI with CHCl, reference; (3) [Pd] = 8.52 X 10m6 M with a reagent blank.reference. The organic phases were not washed with 2.5 M H=SO,.
172
0.4
s
0.3
2 2
0.2
11
I
-z 0.1
2
0
I
2
[F-W]
3 ’
4
380
[:w
460 Wcveknqth
540
620
(ml
Fig. 2. Composition of palladium complex with nitroso-DEAF’ [Pd] = 1.60 X lo-’ CHCI, reference at 486 nm.
M with
Fig. 3. Absorption spectra. (1) [Pd] = 8.52 x 10m6 M with Cl-ICI, reference; (2) reagent blank with CHC15 reference_ The organic phases were washed with 2.5 M H$O,.
absorptivity calculated from the slope of the graph was 4.38 X 10’ 1 mol-’ at 486 nm. The absorption spectra in chloroform are shown in Fig. 3. Effects
cm-’
of diverse ions
The interferences of diverse ions (Table 1) were examined by using 5 ml of sample solution containing palladium(H) (8.52 X 10m6 M) and each diverse ion. Iridium(IV j and tungsten(V1) at concentrations above 10s5 M and gold(II1) above 5 X lo-‘ M cause negative errors even when 1 ml of reagent solution is used. Iodide reacts with palladium to give negative errors. De termination
of palladium in catalysts for automobile
exhaust purifiers
The palladium of the samples analysed was supported on a carrier made of silica or alumina (bead diameter, 3-5 mm). Sample A was brown, sample C was black, and sample B contained a mixture of grey and white beads. The procedure for preparation of sample solution was as follows. Crush and grind the samples to a powder and weigh about 0.2 g into a beaker. Add 5 ml of aqueous (I + 4) formic acid solution and heat on the water bath nearly to dryness. Add 5 ml of aqua regia and heat on the water bath until nitrogen o-tides are removed. sulfuric acid and 2 ml of concentrated
Then,
add 3 ml of concentrated
nitric acid and heat on a sand bath to white fumes. Thereafter, follow the method given for the preparation of standard palladium solutions, and finally dilute to 100 ml with distilled water. Sample B proved to be more insoluble than other samples, and the sample solution had to be filtered before use. When the samples were not crushed and ground as described above, the palladium contents obtained were a little higher than those obtained for ground samples, but the variation of the
173 TABLE Effect
I of diverse
ions
Maximum tolerable concn. (M)
1022
K+, Na+, NO,-, Cl-. Mg’+, Ca’+, Sr’+, Ba’+, Pb’+, Mnz+, Zn*+, Cd2+, Co”, Ni”, Cu”, Wg’+, Ag’, AI’* Fe’+, Mo(VI), U(VI)b Ck(VIII), Pt(IV), ZriIV), Rh(III)b, Brwb Rii(IE) Ir( IV)b, W( VI)b Au{ III)b ISMaximum tested. bl ml of nitroso-DEAP
solution (6 x lo-’
10-z a 10-3H 10” 5 x lo-s lo-$ 5 x 10-s 10-6 M) was used.
resnlts obtained was almost the same (Table 2). The recovery of the palladium was examined, as shown in Table 3, by adding known amounts of palladium to a sample {without crushing) which was then treated as in the above dissolution procedure. From Tables 3 and 4, sample C did not contain palladium. DISCUSSION
The molar absorptivities of the palladium(I1) complexes of other nitroso compounds are compared with nitroso-DEAP in Table 4. The palladium complexes of the nitroso compounds were all extracted very easily with 5 ml of chloroform, and the organic phases were washed with 5 ml of TABLE
2
Determination of palladium in catalysts (In each case, the result given is the mean of 3 determinations; solution were taken.)
Sample
A
Sample soin.
Pd found
(mp/lOO
(W)
3.55.5a 148.9” 186.3a 170.3b 174.2b 180.4b 171.4b
ml)
0.163 0.164 0.176 0.175 0.183 0.184 0.199
f. 0.001 c 0,001 2 0.002 i: 0.001 2 0.001 + 0.001 + 0.002
Sample
B (grey) (white) C
2-ml aliquots
of sample
Sample sobs. (rag/100 ml)
Pd found
156Xb 146.3b 168.3b
0.176 f 0.00 0.123 * 0.00’ ozo
(%)
aAbout 0.5-6.7 g of sample was crushed and ground, and the ground sampte was analysed. bWithout crushing and grinding the sample.
174 TABLE
3
Recovery
of palladium
Sample
Sample soln.” (mg/lOO ml)
g key) (white) C
149.6 164.7 149.8 170.2
Pd added (rg)
Pd recoveryb (%)
283.2 283.2 283.2
100.7 99.1 f* 0.2 0.5 98.0 + 0.6 97.6 + 0.3
-
%‘ithout crushing and grinding the sample; 2-ml aliquots of sample solution each case. bMean values of the three determinations_ TABLE
were used in
4
Molar absorptivities chloroform
E (X 10’ 1 mol-’
cm-‘)
of palladium complexes
extracted
Reagents
nm
E
Reagents
2-Nitroso-I-naphthol
309 376 385 564
5.0 2.5 2.5 1.0
6-Chloro-l-nitroso-2-naphthol
4-Chloro-2-nitroso-1-naphthol .
316 370 568
5.1 2.4 1.2
P-Bromo-2-nitroso-1-naphthol
316 372 570
1-Nitroso-2-naphthol
267 282 441 505
into nm
E
301
4.2
6-Bromo-1-nitroso-2-naphthol
303 434 514
4.6 2.7 1.1
5.4 2.4 1.2
2-Nitroso-5-methosyphenol
400 420
3.3 3.3
2.7 2.8 2.7 1.1
2-Nitroso-5-dimethylaminophenol (Nitroso-DMAP)
486
4.3
2-Nitroso-5-diethylamino-
486
4.4
434 516
2.5 1.1
phenol (Nitroso-DEAP)
distilled water and then with 5 ml of 1 M sodium hydroxide solution to remove the excess of reagent, before the absorption spectra of the organic phases were measured. For all these reagents, the percentage extractions of palladium were over 99% With nitroso-DMAP and nitroso-DEAP, palladium reacts completely even in very acidic solution and the excess of reagent is soluble in acidic solution; with the other reagents, the complexes are insolubie in strongly acidic solution_ Fortunately, the excess of nitroso-D-MN? and nitroso-DEAP in chloroform is more easily removed with 2.5 M sulfuric acid than with sodium hydroxide solution and the absorbance of the reagent blanks was small (0.004) and constant. Though the molar absorptivity of the complex with 4bromo-2-nitroso-l-naphthol at 316 nm is the largest of
175
al1 the reagents and wavelengths examined, the reagent blank is larger and more variable than that of nitroso-DEAI?; moreover, removal of the excess of reagent is troublesome because the palladium reaction must take place in acidic solution whereas the excess of reagent must be removed with basic solution. The absorption maxima of nitroso-DMAP and nitroso-DEAP complexes lie in the visible region and their molar absorptivities tie the highest in that region. The absorbance of nitroso--D&UP complex extracted into chloroform decreases gradually, so that DEAP is certainly the most useful of these nitroso compounds. REFERENCES 1 K. Kodama, Research Reports of the Nagoya Municipal Industrial Research Institute, No. 19 (1958) 1. 2 K. D. Cheng, Anal. Chem., 26 (1954) 1894. 3 K. Kodama, Research Reports of the Nagoya Municipal Industrial Research Institute, No.19 (1958)4. 4 S. Komatsu and S. Kamiyama, Nippon Kagaku Zasshi, 81 (1960) 1094. 5 J. II. Yoe and J. J. Kirkland, Anal. Chem., 26 (1954) 1335. 6 K. Tsei and S. Motomizu, Analyst, 101 (1976) 497_ 7 K. Tijei, S. Motomitu and T. Korenaga. Analyst, 100 (1975) 629. 8 C. L. Wilson and D. 1%‘.Wilson, Comprehensive Analytical Chemistry, Vol. 10, Elsevier, Amsterdam, 1962, p. 6%. 9 R. MGhlam, Ber., 25 (1892) 1059.
- Printed in The Netherlands
EXTRACTION-SPECTROPMOTOMETRIC DETERMINATION OF PALLADI~~II) WITH 2-NITROSO-5-DIETI-IYLAMINOI’IIENOL
RYOJI
TGEI*,
SI-IOJI MOTOMIZU
and SHOICHI
HAIIADA
Department of Chemistry, Fatuity of Science. Okayama University, Tsushima. Okayama-shi (Jaw4 (Received
28th February
1978)
An estraction-spectrophotometric determination of pailadium(I1) with 2-nitroso-Sdiethy~~inopheno1 is described. Complex formation and estraction of the complex with chloroform are possible with aqueous phases of about 2.5 M sulfuric acid. The molar absorptivity of the complex is 4.38 x 10’ 1 mol-’ cm-* at 486 nm. Few of the common ions interfere at concentrations of 10-4-10-3 M; more than 10m5 M &(IV), lo-’ M W(VI), 5 x 10m6 hl _4u(III) and 10Y6 M iodide cause negative errors. The method can be applied to the determination of palladium in catalysts for automobile exhaust purifiers.
Palladium(II) -the first of the Irving-Williams series - forms very stable complexes with many chelating reagents, so that many ligands have been proposed for determinations of palladium. Of these reagents, various nitroso compounds (nitrosophenols Cl 1, nitrosonaphthols [Z---4] and pnitrosodimethylaniline [5] ) react with palladium in acidic solutions and provide sensitive spectrophotometric determinations of palladium. 2-Nitroso-5-diethylainophenol (nitroso-DEAP) and 2-nitroso-&dimethylaminophenol (nitroso-DMAP), which were first used for the sensitive extraction-spectrophotometric determination of cobalt [6 ] and iron [7 1, react with palladium in a strongly acidic solution. The complexes formed are easily extracted into chloroform and show the largest mofar absorptivities in the visible region of all the nitroso compounds proposed so far, except for ~-ni~osodimethyl~i~e [5f which gives a molar absorptivity of 8.6 X 10c 1 mol-’ cm-’ at 525 nm, but does not react at such high acidities. This paper describes the extraction-spectrophotometric determination of palladium with nitroso-DEAP. The method has many advantages in simplicity and sensitivity, in accuracy and precision, and in an abbreviated list of interferences.
173 EXPERIMENTAL
Appara fus and reagents
A Hitachi Perk&Elmer Model 139 spectrophotometer and a Hitachi Model EPS3T recording spectrophotometer were used to measure absorbances in a quartz cell of lo-mm path length. An Iwaki Model KM shaker was used. Standard palladium(II) solution. Weigh approximately 1.26 g of palladium nitrate into a porcelain evaporating dish, add about 20 ml of 12 M HCl, and evaporate nearly to dryness. Dissolve the residue in 100 ml of 0.5 M HCl. Standardize this solution by the gravimetric dimethylglyoxime method [S]. Pipette accurate amounts of the standardized solution into a beaker, add 2 ml each of concentrated sulfuric and nitric acids, and evaporate to white fumes. Add 0.5 ml of nitric acid and evaporate to white fumes, and repeat this process. Finally add 2-5 ml of water and evaporate to white fumes. Dilute this with 0.5 M H2SOG, transfer the solution to a l-l volumetric flask and dilute to the mark with 0.5 M H,SO, to give a 2 X 10e5 M palladium solution. 2-Nitroso-5-diethylaminophenol. Nitroso-DEAP was obtained by nitrosation of the parent compound (m-diethylaminophenol) in acidic aqueous solution with sodium nitrite [ 91; the crude nitroso compound was recrystallized twice from hydrochloric acid solution. An aqueous solution (6 X 10m3RI) in 0.05 M HSO, was used. Other reagents were of analytical-reagent grade. Standard procedure
Pipette up to 5 ml of the solution containing palladium(I1) into a stoppered test tube, and dilute to 5 ml with distilled water. Add 4.5 ml of about 5.5 M sulfuric acid and 0.5 ml of nitroso-DEAP solution and mix well. Shake the mixture with 5 ml of chloroform for 1 min. Discard the aqueous phase and wash the organic phase with 5 ml of 2.5 M sulfuric acid by shaking for about 1 min by hand, to remove the excess of reagent. Measure the absorbance of the organic phase at 486 nm. RESULTS
Effects of experimental variables The time necessary for complete formation of the palladium(I1) complex
with nitroso-DEAP is ca. 30 s at room temperature. The absorbance of the complex extracted into ctioroform does not change for at least a day. The time necessary for complete extraction of the complex is 30 s by hand or mechanical shaking. When the palladium concentration is about 10m5M, the addition of 0.1 ml of nitroso-DEAP solution (6 X 10e3 M) suffices for complete extraction of palladium; accordingly 0.5 ml of reagent solution should be used for safety.
The effect of acidity on the extraction of the palladium complex was examined. As shown in Fig. 1, the absorbance of the complex measured against a reagent blank was constant for concentrations of sulfuric acid from 2-3 M though the absorbance of the reagent blank varied from 0.15 to 0.04; in these experiments, the excess of reagent was not removed. To reduce the absorbance of the reagent blank, the organic phase was washed with dilute sulfuric acid after extraction of the complex; washing with 2.5-3 M sulfuric acid reduced the absorbances of the reagent blanks to about 0.004. The effect of volume of the aqueous phase was examined for the standard procedure. When the aqueous phase was varied from 5 to 50 ml, the absorbance of the complex in the organic phase was not affected, provided that the concentration of suifutic acid in the aqueous phase was maintained at about 2.5 M. Chloroform was the best of the nine organic solvents tested (chloroform, carbon tetrachloride, 1,2-dichloroethane, benzene, toluene, isobutyl methyl ketone, isoamyl alcohol, ethyl acetate and ligroin). When 5 ml of chloroform was used, all the palladium was removed from the aqueous phase in the first extraction. When a second extraction was done, palladium was not detected in the organic phase.
Composition of the extracted species The composition of the palladium complex
was examined by the molar ratio methods, in which the concentration of the reagent was varied. The p~ladium~~~):nitroso-Dam ratio was found to be 1: 2 (Fig. 2). Calibrarion *graphand molar absorptiuity The calibration graph with the reagent blank as reference was a straight line through the origin over the range O-2 X 10e5 M Pd. The molar
0.5
0.1
Fig. 1. Effect of acid concentration at 486 nm. (1) Reagent blank with CHCl, reference; (2) fPd] = 8.52 x lo-’ PUI with CHCl, reference; (3) [Pd] = 8.52 X 10m6 M with a reagent blank.reference. The organic phases were not washed with 2.5 M H=SO,.
172
0.4
s
0.3
2 2
0.2
11
I
-z 0.1
2
0
I
2
[F-W]
3 ’
4
380
[:w
460 Wcveknqth
540
620
(ml
Fig. 2. Composition of palladium complex with nitroso-DEAF’ [Pd] = 1.60 X lo-’ CHCI, reference at 486 nm.
M with
Fig. 3. Absorption spectra. (1) [Pd] = 8.52 x 10m6 M with Cl-ICI, reference; (2) reagent blank with CHC15 reference_ The organic phases were washed with 2.5 M H$O,.
absorptivity calculated from the slope of the graph was 4.38 X 10’ 1 mol-’ at 486 nm. The absorption spectra in chloroform are shown in Fig. 3. Effects
cm-’
of diverse ions
The interferences of diverse ions (Table 1) were examined by using 5 ml of sample solution containing palladium(H) (8.52 X 10m6 M) and each diverse ion. Iridium(IV j and tungsten(V1) at concentrations above 10s5 M and gold(II1) above 5 X lo-‘ M cause negative errors even when 1 ml of reagent solution is used. Iodide reacts with palladium to give negative errors. De termination
of palladium in catalysts for automobile
exhaust purifiers
The palladium of the samples analysed was supported on a carrier made of silica or alumina (bead diameter, 3-5 mm). Sample A was brown, sample C was black, and sample B contained a mixture of grey and white beads. The procedure for preparation of sample solution was as follows. Crush and grind the samples to a powder and weigh about 0.2 g into a beaker. Add 5 ml of aqueous (I + 4) formic acid solution and heat on the water bath nearly to dryness. Add 5 ml of aqua regia and heat on the water bath until nitrogen o-tides are removed. sulfuric acid and 2 ml of concentrated
Then,
add 3 ml of concentrated
nitric acid and heat on a sand bath to white fumes. Thereafter, follow the method given for the preparation of standard palladium solutions, and finally dilute to 100 ml with distilled water. Sample B proved to be more insoluble than other samples, and the sample solution had to be filtered before use. When the samples were not crushed and ground as described above, the palladium contents obtained were a little higher than those obtained for ground samples, but the variation of the
173 TABLE Effect
I of diverse
ions
Maximum tolerable concn. (M)
1022
K+, Na+, NO,-, Cl-. Mg’+, Ca’+, Sr’+, Ba’+, Pb’+, Mnz+, Zn*+, Cd2+, Co”, Ni”, Cu”, Wg’+, Ag’, AI’* Fe’+, Mo(VI), U(VI)b Ck(VIII), Pt(IV), ZriIV), Rh(III)b, Brwb Rii(IE) Ir( IV)b, W( VI)b Au{ III)b ISMaximum tested. bl ml of nitroso-DEAP
solution (6 x lo-’
10-z a 10-3H 10” 5 x lo-s lo-$ 5 x 10-s 10-6 M) was used.
resnlts obtained was almost the same (Table 2). The recovery of the palladium was examined, as shown in Table 3, by adding known amounts of palladium to a sample {without crushing) which was then treated as in the above dissolution procedure. From Tables 3 and 4, sample C did not contain palladium. DISCUSSION
The molar absorptivities of the palladium(I1) complexes of other nitroso compounds are compared with nitroso-DEAP in Table 4. The palladium complexes of the nitroso compounds were all extracted very easily with 5 ml of chloroform, and the organic phases were washed with 5 ml of TABLE
2
Determination of palladium in catalysts (In each case, the result given is the mean of 3 determinations; solution were taken.)
Sample
A
Sample soin.
Pd found
(mp/lOO
(W)
3.55.5a 148.9” 186.3a 170.3b 174.2b 180.4b 171.4b
ml)
0.163 0.164 0.176 0.175 0.183 0.184 0.199
f. 0.001 c 0,001 2 0.002 i: 0.001 2 0.001 + 0.001 + 0.002
Sample
B (grey) (white) C
2-ml aliquots
of sample
Sample sobs. (rag/100 ml)
Pd found
156Xb 146.3b 168.3b
0.176 f 0.00 0.123 * 0.00’ ozo
(%)
aAbout 0.5-6.7 g of sample was crushed and ground, and the ground sampte was analysed. bWithout crushing and grinding the sample.
174 TABLE
3
Recovery
of palladium
Sample
Sample soln.” (mg/lOO ml)
g key) (white) C
149.6 164.7 149.8 170.2
Pd added (rg)
Pd recoveryb (%)
283.2 283.2 283.2
100.7 99.1 f* 0.2 0.5 98.0 + 0.6 97.6 + 0.3
-
%‘ithout crushing and grinding the sample; 2-ml aliquots of sample solution each case. bMean values of the three determinations_ TABLE
were used in
4
Molar absorptivities chloroform
E (X 10’ 1 mol-’
cm-‘)
of palladium complexes
extracted
Reagents
nm
E
Reagents
2-Nitroso-I-naphthol
309 376 385 564
5.0 2.5 2.5 1.0
6-Chloro-l-nitroso-2-naphthol
4-Chloro-2-nitroso-1-naphthol .
316 370 568
5.1 2.4 1.2
P-Bromo-2-nitroso-1-naphthol
316 372 570
1-Nitroso-2-naphthol
267 282 441 505
into nm
E
301
4.2
6-Bromo-1-nitroso-2-naphthol
303 434 514
4.6 2.7 1.1
5.4 2.4 1.2
2-Nitroso-5-methosyphenol
400 420
3.3 3.3
2.7 2.8 2.7 1.1
2-Nitroso-5-dimethylaminophenol (Nitroso-DMAP)
486
4.3
2-Nitroso-5-diethylamino-
486
4.4
434 516
2.5 1.1
phenol (Nitroso-DEAP)
distilled water and then with 5 ml of 1 M sodium hydroxide solution to remove the excess of reagent, before the absorption spectra of the organic phases were measured. For all these reagents, the percentage extractions of palladium were over 99% With nitroso-DMAP and nitroso-DEAP, palladium reacts completely even in very acidic solution and the excess of reagent is soluble in acidic solution; with the other reagents, the complexes are insolubie in strongly acidic solution_ Fortunately, the excess of nitroso-D-MN? and nitroso-DEAP in chloroform is more easily removed with 2.5 M sulfuric acid than with sodium hydroxide solution and the absorbance of the reagent blanks was small (0.004) and constant. Though the molar absorptivity of the complex with 4bromo-2-nitroso-l-naphthol at 316 nm is the largest of
175
al1 the reagents and wavelengths examined, the reagent blank is larger and more variable than that of nitroso-DEAI?; moreover, removal of the excess of reagent is troublesome because the palladium reaction must take place in acidic solution whereas the excess of reagent must be removed with basic solution. The absorption maxima of nitroso-DMAP and nitroso-DEAP complexes lie in the visible region and their molar absorptivities tie the highest in that region. The absorbance of nitroso--D&UP complex extracted into chloroform decreases gradually, so that DEAP is certainly the most useful of these nitroso compounds. REFERENCES 1 K. Kodama, Research Reports of the Nagoya Municipal Industrial Research Institute, No. 19 (1958) 1. 2 K. D. Cheng, Anal. Chem., 26 (1954) 1894. 3 K. Kodama, Research Reports of the Nagoya Municipal Industrial Research Institute, No.19 (1958)4. 4 S. Komatsu and S. Kamiyama, Nippon Kagaku Zasshi, 81 (1960) 1094. 5 J. II. Yoe and J. J. Kirkland, Anal. Chem., 26 (1954) 1335. 6 K. Tsei and S. Motomizu, Analyst, 101 (1976) 497_ 7 K. Tijei, S. Motomitu and T. Korenaga. Analyst, 100 (1975) 629. 8 C. L. Wilson and D. 1%‘.Wilson, Comprehensive Analytical Chemistry, Vol. 10, Elsevier, Amsterdam, 1962, p. 6%. 9 R. MGhlam, Ber., 25 (1892) 1059.