cadmium, copper(II), gold(III), mercury (11), molybdenum(VI), tellurium (IV), thallium(I), tin(IV), zinc, and also iron(III), aluminum and chromium(II1) were examined, but no interference was observed in any instance. The precision of the method was investigated by determining the percentage standard deviation from multiple analyses of a series of solutions each containing 0.5 gram of iron and 1.20 ml. of ~ o - ~lead M nitrate; it was found to be 3.55. The results obtained by application of the proposed procedure to the determination of lead in a variety of British Chemical Standard certificated steels and copper-base alloys and in a number of commercial stainless and tungsten steels are shown in Table I. The method has approximately the same sensitivity, is much more rapid, and requires fewer operations than a method which we have recently de-
scribed ( 3 , 4 ) for the spectrophotometric determination of lead in the same materials, using 4-(%pyridylazo)resorcinol as the reagent. ACKNOWLEDGMENT
We are grateful to B. Bagshawe of the Brown-Firth Research Laboratories, Sheffield, England, for providing the commercial samples listed in Table I. LITERATURE CITED
(1) Dagnall, R. M., West, T. S., Talanta 11,1257 (1964). (2) Ibid., p. 1553. (3) Dagnall, R. M., West, T. S., Young, P.. Ibid.. 12.583 (1965). (4) Ibid.. 6. 589. ’ (5j Elwilt, W. T., Gidley, J. A. F., Anal. Chim. Acta 24, 71 (1961). (6) Elwell, W. T., Gidley, J. A. F., “Atomic Abso tion Spectroscopy,” Pergamon Press,%xford, 1961. (7) Gidley, J. A. F., “Colloyium SpectroscoDicum Internationale., Lvons. ” , Vol. IIItp. 263,1961. ~
(8) Gilbert, P. T., ANAL.CHEM.34, 210 R (1962). (9) Robinson, J. W., Anal. Chim.Acta 24, 451 (1961). (10) Russell, B, J., Shelton, J. P., Walsh, A., Spectrocham. Acta 8,317 (1955). (11) Scribner, B. F., Margoshes, M., ANAL.CHEM.36,329 R (1964). (12) Stumpf, K. E., “Colloquium Spectroscopicum Internationale,” Lyons, Vol. 111,p. 279,1961. (13) Walsh. A.., SDectrochim. Acta 7. 108 . . (i955). ‘ (14) Wells, J. E., Hunter, D. P., Analyst 73, 671 (1948). (15) Willis, J. B., ANAL. CHEM.34, 614 (1962). (16) Willis, J. B., Nature 191, 381 (1961). R. M. DAGNALL T. S. WEST P. YOUNQ Chemistry Dept. Imperial College London, S.W. 7 U. K. FINANCIAL support for P. Y. received from the British Welding Research Association and United Dairies Ltd., London, England.
Solvent Extraction Separation of Palladium(II) and Platinum(1V) with Mesityl Oxide SIR: Mesityl oxide has been used for the extraction (4-6) of uranium(VI), and zirconium(1V). On extending these studies it was found that palladium(I1) and platinum(1V) can be quantitatively extracted from solutions containing either 3M aluminum chloride and 6M hydrochloric acid or 2M aluminum chloride and 5M hydrochloric acid, respectively. Palladium(I1) or platinum(1V) from the organic phase was stripped with water and was subsequently determined spectrophotometrically as the complex (1, I,IO) with stannous chloride. Various methods for the solvent extraction of palladium(I1) and platinum(1V) have been summarized by different workers (3, 7, 8). Parshall and Wilkinson (9) first reported the formation of the complexes of palladium(I1) and platinum(1V) with mesityl oxide. They give the probable compositions of the species as (CeH90PdCl)S and CeHloClzOPt,but no attempt was made to use mesityl oxide as an extractant for these metals. This paper describes the systematic studies on the solvent extraction of palladium(I1) and platinum(1V) with mesityl oxide as an extractant. The proposed method is simple, rapid, and provides for the separation of micro amounts of these metals from a large number of other ions present a t micro levels.
Table 1.
Mesityl oxide concn. 100% (8.70M)
75% (6.52M)
Distribution Ratio as the Function of Acidity
Initial HC1, M 1
2 3 4 4.5 5 5.5 6 2 3 4
5
6 60% (5.22M)
1
2
3
4 5 6 50% (4.35M)
... ...
... ... ... ...
...
...
... ... ... 36.53 36.53 53.86 62.50 44.23 46.15
4
5 6
30% (2.61M)
25% (2.17M)
15% (1.30M)
Distribution ratio Pd(I1) Pt(IV) 0.238 2.30 0.326 3.40 0,592 15.06 1.320 23.48 1.560 ... 6.520 m 20.50 m m
m
0.238 0.238 0.326 0.592 1.109
... ... ...
...
... ... ... ...
...
1.43 1.43 2.91 4.20 1.90 2.09
0.133 0.238 0.326 0.326 0.592
... ... ... ...
... ...
...
4 5 6
... ... ... ... ...
28.96 33.65 33.65 38.42 33.65
... ... ... ...
1.01 1.29 1.29 1.56 1.29
3 4 5 6
7.70 8.60 11.53 15.4
... ...
0.238 0.315 0.326 0.427
...
... ... ... ... ...
0.42 0.52 0.98 1.38 1.56
2
3
2 3
Apparatus and Reagents. A Type C 6 4 quartz spectrophotometer and a Cambridge pH meter were used. Mes-
5 6
ANALYTICAL CHEMISTRY
7.70 7.70 11.53 19.53 30.76
2 3
EXPERIMENTAL
360
Extraction, yo Pd(I1) Pt(1V) 7.70 48.19 11.53 57.68 19.23 85.77 34.60 90.38 38.46 72.30 100 80.76 100 100 100
4
... 9 . .
...
... ... ...
ityl oxide (b.p. 128.7' C.) was an analvtical reagent from the British Drug House. The stock solutions of palladium(I1) and tdatinumWJ) were DreDared bv dissoiving 1 gram 'of palladium chloridk in 500 ml. of water containing 0.5y0 hydrochloric acid and by dissolving 1 gram of chloroplatinic acid in 500 ml. of water containing 5% hydrochloric acid. The solutions were standardized gravimetrically and were found to contain 12 pg. palladium per ml. and 84 pg. of platinum per ml. General Procedure. An aliquot of the solution containing either 48 pg. of palladium(I1) or 84 pg. of platinum(1V) was taken. For the extraction of palladium(II), 25 ml. of the solution containing 3J1 aluminum chloride and 6-11 hydrochloric acid were taken, whereas for the extraction of platinum(IV), the same volume of the solution containing 2J1 aluminum chloride and 5M hydrochloric acid was taken. The solution was transferred to the separating funnel and was extracted with 10 ml. of mesityl oxide for about 20 to 30 seconds. For acidity studies, suitable hydrochloric acid concentration was used, but for the study of effect of salting-out agents or diverse ions, the appropriate concentrations were added before the extraction step. At the end of extraction two layers were allowed to settle. The aqueous phase was then separated from the organic phase. Palladium(I1) or platinum(1V) from the organic phase was stripped by shaking i t for 20 seconds twice, each time with 20 ml. of water. Palladium-(11) or platinum(1V) from the aqueous phase was determined spectrophotometrically a t 635 mp ( I ) or 403 mp (10) as the stannous chloride complex.
Table II.
Saltingout agent AlCls, 1M
2M
Effect of Salting-Out Agent (1 00% Mesityl Oxide)
Initial HC1, M 1
2 3 4 5
1
2
3
3M
MgC12, 4M
4 5 6 2 3 4 5 6 3 4 5 6
Extraction, % ' Pd(I1) Pt(1V)
...
7.70 9.60 9.60 26.90
...
15.4 19.23 23.07 72.30 92.30 11.53 19.23 38.46 72.30 100 11.53 15.14 30.76 57.70
46.15 51.92 76.92 80.76 80.76 48.19 57.68 85.77 90.38
100
100
**.
... ... ...
...
52.69 59.61 67.30
...
0.326 0.427 1.109 3.45
3
4 5 6
ii.53 19.23 26.90
6M
3
... ...
44.23 57.68
... ...
0.238 0.427
...
73.07 76.92 80.75
...
LiCl, 4M
5M 6M
3
4 5 6 2 3 4 4 6
7.70 15.40
ii.53
15.40 57.70
...
... ...
...
m
5M
4 5 6 2
52.89 61.52 78.96
Distribution ratio Pd(I1) Pt(1V) 2.09 0.238 2.70 0.315 8.00 0.315 10.40 0.885 10.40 2.30 d.bri7 3.40 0.592 15.06 0.758 23.48 m 6.52 m 29.70 0.326 ... 0.592 ... 1.56 ... 6.52 ... 2.80 3.90 5.14
...
2.80 4.57 9.30
0.326 0.592 0.885
...
...
0.326 0.427 3.45
... ...
...
67.34 75 82.69
... ...
15.40 19.23
... ...
0.427 0.592
...
1.90 3.40
. .. ...
6.80 8.00 10.40
... ...
5 7.50 11.90 ...
...
RESULTS AND DISCUSSION
Effect of Acidity and Mesityl Oxide Concentration. The concentration of the hydrochloric acid was varied from 1-6M, and that of mesityl oxide from 15-10070 (1.30-8.70M) by dilution with niethylisobutylketone. The distribution ratio was calculated by using relationship :
'E
=
100 D D(Vw/Vo)
(1)
where, V , and Ti, are the volumes of aqueous and organic phases, respectively. The results in Table I show that for the quantitative extraction of either palladium(I1) or platinum(1V) undiluted mesityl oxide should be used. The optimum concentrations are 6 X hydrochloric acid and 351 aluminum chloride for extraction of palladium(II), and 5;M hydrochloric acid and 2M aluminum chloride for the extraction of platinum (IV), since at these concentrations distribution ratios have maximum values. Dilution of mesityl oxide lowers the extraction.
Effect of Salting-out Agent. Varying concentrations of chlorides of aluminum, magnesium, and lithium were used as the salting-out agents. Table I1 shows that a t low acidity addition of these salts increases the distribution ratio, while a t higher acidity the distribution ratio is further increased owing t o the salting-out effect, which thus decreases the dielectric constant of the aqueous phase. The optimum concentration of the salting-out agent is 3;M and 2 M aluminum chloride, respectively, for extraction of palladium(I1) and platinum(1V). Thus, multivalent cations favor extensive ion association. I n all of these studies 100% mesityl oxide was the extractant. Period of Extraction. The extraction was carried out for varying times of shaking. For best results, the solution should not be shaken together for more than 30 seconds. Prolonged shaking has an adverse e3ect on extractability of the ions.
Diverse Ions. The results in Table I11 show the effect of the presence of diverse ions. The tolerance limit was set a t the amount required to cause k2Y0 error in palladium or platinum recovery. Both palladium(I1) and platinum(1V) were extracted as described earlier. Both the metal ions can be extracted in the presence of large amounts (1: 10) of thalliuni(III), bismuth, cadmium, cerium(IV), zinc, barium, phosphate, EDTA (dissodium salt), citrate, tartrate, ascorbate, and malonate. Ions like lead, copper(II), tin(IV), iron(III), chromium, thorium(IV), uranium(VI), cobalt(III), nickel, oxalate, and acetate could be tolerated in the ratio of 1:5. The ions showing strong interference were molybdate, selenite, arsenite, cyanide, sulfocyanide, and thiosulfate in the case of extraction of palladium; and irridium, rhodium, etc., in the case of extraction of platinum (IV). The interference due to anions can be eliminated by passing the solution through an anion exchanger before the extraction step. VOL. 38, NO. 2, FEBRUARY 1966
e
361
Table 111.
Source
Foreign ion
Cd +2 Sn +2 Sn +4 Pt+4 Fe +a Cr +3 Be +2 Zr + 4 Th +4
c5;4 v +5 U
Ti+4 Zn+2 Mn+:a
co
c o +a h-i +2 Ca + 2 Sr + 2 Ba +a w04-'
ASOs-3
m7oz4-6
Cr04-2 Se03-2 po4-3 CN SCN SZO~-~ EDTA-4 Tartrate-3 Oxalate-2 Citrate-3 Acetate+ hlalonate-2 Ascorbate-2
Effect of Diverse Ions
3CdSOa -8Hz0 SnC4 2H20 SnCl4 HzPt Cls .2H20 Fe(NO3)a CrC13 6Hz0 BeSO4 4Hz0 Zr(NOd4 Th(NO& 12H20 Ce(SO& 4H20 U02(N0a)z * 2H20 +
vosoc
Ti(S04)~ ZnSO4 *7Hz0 MnCll .6H20 Cos04 *7H20 C0(NOa)s*6H20 NiClz .6Hz0 CaS04.5H20 SrCl2'2H20 BaC12 '2H20 Na2W04 e2Ha0 NalAsOa (NH&M070r4 * 12H20 K2Cr04 NazSeOs (NHa)3P04 KCN KSCN NazSrOa * 5Hz0 EDTA (disodium salt) Tartaric acid Oxalic acid Citric acid Acetic acid Malonic acid Ascorbic acid
Tolerance limit, pg. Pd(I1) Pt(1V) 457 457 720 720 40 '78 80 39 120 950 760 ... 450 640 800 350 ... 0 ... 0 ... 500 464 ... 575 505 350 540 216 480 490 505 1000 450 450 ... 750 250 510 740 ... 640 ..* 640 640 ... 525 525 505 ... 385 384 580 870 530 605 0 540 0 200 0 0
550 0
... 0
500 500
440
500 480 500 500
...
300
1020 950 930 323
From 10 experiments the average recovery of palladium or platinum was 98.5 f 1.5%. Each determination took a total of 40 minutes. The standard deviation was *2%. The special feature of this method is its applicability to the selective extraction of palladium(I1) or platinum(1V) in the presence of a large number of other ions at microlevels.
LITERATURE CITED
(1) Ayres, G. H., Alsop, J. H., 111, ANAL. CHEM.31, 1135 (1959). (2) Ayres, G. H., Meyers, A. S., Zbid., 23, 299 (1951). (3) De, A. K., Rahaman, M. S., Analyst 89. 705 (1964).
(4) Dhara,'S. C:, Khopkar, S. M., Mikrochim. Acta 1965 5 . ( 5 ) Dhara, S. ( Khopkar, S. M., ANAL. CHEM. 37, 1158 (1965). ((5) KhoDkar. S. M., J . Sci. Znd. Res. (India), 24, :142 (1965). (7) Morrison, 3. H., Freiser, H., ANAL. CHEM.?'L, 73R (1962). (8) Morris()n, G. H., Freiser, H., Zbid., 36, l l l R (19-164). (9) Parshall, G . W., Wilkinson, G., Chem. Znd. (London) 1962, 261. (10) Sandell, E. B., "Colorimetriq, Determination of Tracclq nf Metals, 3rd ed., p. 726, Interscience, hlew York, ncn I
__
3
LYJY.
SHRIPAD M. KHOPKAR
1000
1000 660 660 680 800 680
Department of Chemistry Indian Institute of Technology Powai, Bombay-76 N.B., India Project sponsored by the Council of Scientific and Industrial Research (India).
Gas Chromatographic Sugar Analysis in Hydrolyzates of Wood Constituents Quantitative Determination of Mixtures of Arabinose, Xylose, Mannose, Galactose, and Glucose as Their Trimethylsilyl Ether Derivatives
SIR: A rapid and accurate quantitative method for the five sugars commonly found in wood product hydrolysates is needed. Paper chromatography requires about 16 hours to separate arabinose, xylose, mannose, and glucose and an additional 14 hours are needed to separate galactose from t,he high glucose concentrations normally encountered. If the concentration of a single sugar exceeds about 4 mg./ml., the original solution must be diluted and rerun before meaningful reflectance measurements (6) can be taken. I n this laboratory an average of 2.5 days is required, after hydrolyzing the sample, to report four or five sugars. Sweeley, et al. (8) gave a very detailed report of the gas-liquid chro362
ANALYTICAL CHEMISTRY
matography of trimethylsilyl ether (TMSE) derivatives of sugars and related compounds. They showed that arabinose] xylose, mannose, , galactose, and glucose could be identified on a column packed with EGS or SE-52 on Chromosorb-W. Quantitative determinations were not attempted. Richey et al. (6) reported a method using methyl-a-D-galactopyranoside as an internal standard for the analysis of sugars (fucose, mannose, galactose, and glucose). Results were somewhat erratic with an average error of 10%. They operated the gas chromatograph isothermally and used an argon ionization detector which requires a different calibration factor for many isomers and stereoisomers (3). Their standard is not available commercially. Other
methods ( I , 9) have been reported for the determination of glucose as its TMSE derivative. After this work was completed, the separation and determination of arabinose, mannose, galactose, and glucose using methyl-a-Dmannopyranoside as an internal standard was reported ( 7 ) . However, xylose could not be determined in the presence of glucose and an arabinose anomer overlaps a--mannose. Isothermal operation required 70 minutes to elute 8-glucose. I n the present method the problem of numerous calibration factors has been avoided by using a hydrogen flame ionization detector. This detector has been shown (3,4) to give uniform results on a weight basis for stereoisomers and alicyclic and aliphatic compounds of
