Selective Separation and Concentration of Silver via Precipitation Chromatography William P. Zeronsa,l Gregory Dabkowski, and Sidney Siggia Department of Chemistry, University of Massachusetts, Amherst, Mass. 01002
The particular reaction of certain metal ions with monosubstituted acetylenic compounds is well known ( 1 ) .
RC
C H + M + + ~i RC = CM
+ H+
(1)
The unique character of this reaction has served as a basis for the qualitative and quantitative determination of the acetylenic functionality. Little use has been made of this specific reactivity for the analysis or separation of the silver ion. This work demonstrates the application of terminal acetylenics to the selective analytical separation and concentration of silver. Nieuwland (2) divides the metalloacetylenic derivatives on the basis of whether the triple bond persists and hydrogen atoms are released or whether metal compounds add to the acetylenic compound with no loss of hydrogen, 1. e . ,
RC=CH
+ MXS
RCE CH*MX
(2)
This work is concerned with those metallo-derivatives which form easily and are reversible in aqueous systems. This limits our interest to silver(I), copper(I), and mercury(1 and 11), because none of the others proceed to completion or react a t all. Analytical separation (3-5) of copper and silver from other metals, using acetylenes, encountered stoichiometric difficulties and varying degrees of hazard. The selectivity of acetylides for copper and silver has been employed in flotation processes (6) as well as in precipitation from ammoniacal solution in batch processes (7). Also, many standard techniques have been described (8-10) for quantitative analysis of acetylenes. This led our work to the field of precipitation chromatography, employing a solid support and an organic precipitating agent immobilized on the support. The solution of silver ion to be analyzed is treated with a 2% w/v sodium acetate solution to attain a basic pH. The solution is then passed through a 6-cm X 1-cm i.d. column of 20% 1-pentadecyne coated on 100-110 Anakrom AB a t a flow rate of 3 ml/min. Final elution was accomplished with 50 or 100 ml of 1:1 nitric acid-water eluent after the column is washed with 50 ml of deionized water.
Present address, Charles Pfizer Inc., Groton, Conn. Nieuwland and R. R. Vogt. "The Chemistry of Acetylenes," Reinhold Publishing Corp., New York. N . Y . , 1945, Chap. 2. fbid., p 41. J. Scheiber, fresenius' Z.Anal. Chem., 48, 529 (1909). V. F. Brameld, M . T. Clark, and A. P. Seyfang, Chem. lnd. (London), 66, 346 (1947). F. Pollitzer, Angew. Chem., 36, 262, (1923). J. T. Terry, U. S. Patent 1544197 (1925); Chem. Abstr., 19, 26.31 J. A.
(1925 ) .
G. S. Masaidova. A . S.Yulkunina, L. S. Gal'braikh, and Z.A. Rogovin. Vysokomol. Soedin., 8, 865 (1966)
S. Siggia, "Quantitative Organic Analysis Via Functional Groups," 3rd ed., John Wiley and Sons. New York, N.Y., 1967, Chap. 9. M . Miocque and J. A. Gautier. Bull. SOC.Chim.. 1958.467. S. Prevost, W. Chodkiewicz, P. Cadiot, and A. Willemart, Bull. SOC.
Chirn., 1960, 1742.
EXPERIMENTAL Apparatus. Analysis was accomplished by using t h e PerkinElmer Models 403 a n d 290 atomic absorption spectrophotometers. In the upper ranges, the Volhard titration method was used. Reagents. All water used t o make up t h e reagents was passed through a Culligan deionizer after being distilled. Sodium Acetate Solution: 2% w / u Sodium Acetate in Water. %agent grade sodium acetate, obtained from the J. T. Baker Chemical Company, was purified by recrystallization from hot methanol and water. A 2% weight/volume solution was prepared and passed through the acetylenic column t o further purify it of silver. Evaporation under reduced pressure recovered the sodium acetate free of silver in a reasonable period of time. Eluent: 1:l HNO3:HzO. Concentrated nitric acid was obtained from the Fisher Scientific Company and diluted 1:l by volume with distilled deionized water. Standard Siluer Solutions. A 1000-ppm stock solution of silver was obtained from the Barnes Engineering Company. Standards ranging from 0.05 t o 10.0 p p m were obtained by taking aliquots of the stock and diluting with 1:l HN03:HzO. T h e standards were used to calibrate t h e atomic absorption spectrophotometer and were made fresh prior to t h e analysis step. T h e trial silver sample solutions were also made from the stock silver solution and t h e 2% sodium acetate solution was used t o make t h e proper dilutions. 1-Pentadecyne was obtained from Farchan Research Laboratories and used directly. 100-110 Anakrom AB was obtained from Analabs, Inc. Procedure. Liquid phases were coated by slurrying weighed amounts of t h e acetylenics with weighed solid supports using anhydrous ethyl ether as solvent. T h e ether was then evaporated by employing a rotary evaporator connected to a water aspirator. Final solvent removal was accomplished by spreading the support on aluminum foil and air drying. Percentage loading was verified by thermogravimetric analysis. Columns were prepared by first slurrying the prepared support with deionized distilled water and then pouring t h e mixture into a buret. A glass wool plug was used to retain t h e support in the column, and t o prevent agitation of the upper layers of the support by t h e eluent. The column was conditioned by passing 5 ml of 2-ppm silver solution in the sodium acetate solution through the column and eluting with 1:l H N 0 3 : H 2 0 . This was repeated three times to take u p any nonreversible sites available. T h e column was then rinsed with the 2% sodium acetate solution in preparation for the following sample run. The low-ppm samples were concentrated a t a flow rate of 3 ml/min. The column was washed with 50 or 100 ml of 1:l HN03:HzO after rinsing with 50 ml of deionized water. Column life is extended by immediately rinsing the excess acid from the column with distilled water followed with about 25 ml of the 2% sodium acetate solution. Standard Perkin-Elmer atomic absorption techniques were followed in the final analysis. Where applicable, the Volhard titration method was used (11).
RESULTS AND DISCUSSION A series of acetylenic compounds and supports were evaluated for column use. From Table I, it can be seen that the field was narrowed to four acetylenes coated on 100-110 Anakrom AB. Of these four, the most efficient was 1-pentadecyne. The capacity of the pentadecyne column was determined by a batch experiment to be 0.83 mg Ag+/gram dry resin. Kolthoff and E. 8. Sandell. "Textbook of Quantitative Inorganic Analysis," 3rd ed., Macmillan. New York, N.Y., 1965, p 545.
(11) I . M .
ANALYTICAL CHEMISTRY, VOL. 46, NO. 2, FEBRUARY 1974
309
Table I. Comparison of Stationary Phases and Supports on A n a k r o m AB Stationary phases
State at 25 "C
Column performance
1. 1-Hexyne 2. 1,7-Octadecyne 3. 1-Dodecyne 4. 3-Phenyl-3-hydroxy-1-butyne 5. 1-Phenyl-2-propyn-1-01 6. 1-Pentadecyne 7. 1-Octadecyne 8. Dipropargyl-1,4-benzenedicarboxylate
Liquid Liquid Liquid Solid Liquid Liquid Liquid, solid Solid
Washed off Washed off Retained Washed off Washed off Retained Retained Retained
Comment
supports
Celite Aluminum oxide CTFE 2300 Anakrom AB (100-110) Anakrom AB (300) Anakrom ABS (100-110)
Code
a. Activity for silver b. Difficult to pack when loaded
a, c a, f b, e
c. d. e. f.
C
c, d b, e
Good packing and high loading Poor flow properties Hydrophobic when coated Low affinity for acetylenic phase
Table 11. Recovery of Silver upon Injections Soln concn, ppm
Soln vol., ml
Total Ag+ injected, pg
Amt Ag recovered, pg
Recovery, yo
0.197 0.197 0,197 0.394 0.394 0.394 0.591 0.591 0.591
50 50 50 50 50 50 50 56 50
9.85 9.85 9.85 19.70 19.70 19.70 29.55 29.55 29.55
9.95 9.95 9.75 19.75 19.75 19.50 29.15 29.75 29.15
101.0 101.0 89.9 100.2 100.2 98.9 98.7 101.7 98.7
Av recovery and re1 std dev
100.3 f 1 . 6 99.8
&
0.9
99.3 It 2 . 3
Table 111. Recoveries of Silver Solutions Original volume, 1.
1 1 1 1 1 1 1 1 1
10 10 10 1 5 5 5
5 5 5 5 5 5 5
5 5
Flow rate, ml/min
3 5
10 22 30 35 45 45 100 45 45 48 45 3
3 3 3 3
3 3 3 3 3 3 3
Original concn, ppm
20.0 20.0 20.0 20.0 20.0 20.0
20.0 20.0 45.0 2.00 2.00 2.00 0.200 0,0005 0.0005 0.0005
0.001 0.001 0.001 0.002 0,002 0.002 0.003 0.003 0.003
Final concn, ppm
100 100 100 100 100 100 100 100 100 100 100 100 100
200 198 199 198 198 198 198 194 445 190 192 194 198 0.043 0.046 0.042 0.084 0,081 0.079 0.156 0.150 0.161 0.237 0.217 0.227
A series of eluents were evaluated for elution efficiency. Both 0.10M EDTA and 0.10M ammonium hydroxide failed to elute any silver. Up to 8M sulfuric acid eluted up to 50% of the silver in 50 ml. Varying concentrations of nitric acid were tested for silver removal. From these data as shown in Figure 1, a 1:l mixture of nitric acid to water was chosen. 310
Final elution vol, ml
50 50
50 50 50 50
50 50 50 50 50 50
Recovery, %
100 99 99.5 99 99 99 99 97 99 95 96 98 99 86 93 85 84 81 79 78 75 81 79 72 76
Av recovery and re1 s t d dev
88
=t6
81 f 3
Concn factor
10 10 10 10 10 10 10 10 10 100 100 100 100 100 100 100 100 100 100 100
78 f 3 . 5
100 100 100
76 f 6
100
100
An elution profile for silver using 1 : l HN03:HzO is shown in Figure 2. Table I1 demonstrates silver recoveries for the 1-pentadecyne column upon injection of 50 ml of standard silver solutions containing -2% w/v sodium acetate. Recoveries of silver ion from solutions containing as low as 0.5 ppb were accomplished. For solutions whose origi-
ANALYTICAL CHEMISTRY, VOL. 46, NO. 2, FEBRUARY 1974
8ot L l
! A
t [L
0
w
w
[L
‘h
io
I
I
:0
M O L A R I T Y ACID
I
I
20
l
0 30
6 40
‘MLS. ELUENT
Figure 1. Efficiency of silver elution YS. nitric acid concentration
nal concentrations were 0.2 ppm and below, final analysis was performed by atomic absorption. Above that level, final analysis was performed using the Volhard titration (Table 111). To demonstrate the selectivity of the column for silver, 1 liter of a solution containing 60 ppm copper, 10 ppm nickel, 20 ppm zinc, 0.25 ppm lead, 20 ppm calcium, 0.22 ppm manganese, 0.06 ppm iron, 20 ppm cadmium, and 20 ppm Ag was passed through it a t a flow rate of 3 ml/min. Recoveries for silver averaged 97.0 f 1.1%.Copperfl) and mercury(1) and (11) were the only interferences. No other ions were retained by the column. The ease of oxidation of Cu(1) left only mercury(1) and (11) as interferences. Mercury works its interference in two ways. Mercury(1) will react with the acetylene to the extent that if 250 ml of solution a t a concentration of 500 ppm of mercury(1) is passed through the column, 14% is retained. At the same concentration, mercury(I1) is retained to the extent of 4%. Mercury(I1) under acidic conditions can hydrate the acetylene to the corresponding ketone (12). However, selective reduction or analysis by atomic absorption provides a means of selectively nullifying the interference.
CONCLUSIONS
A commercially available, long chain terminal acetylene coated on a solid support has the ability to selectively concentrate and/or separate silver from a variety of cations over a wide range of concentrations. Its advantages (12) M.Kutscherov, Chem. Ber., 14, 1532 (1881).
Figure 2. Elution curve for silver with 8M nitric acid
lie in its ease of preparation and minimum amount of sample handling and treatment. Cationic interferences are minimal and can be excluded with relative ease. Furthermore, a study of the acetylides formed using differential scanning calorimetry demonstrated no safety hazard requiring unusual precautions for the laboratory use of acetylenics as column materials. Considering the recovery of silver, adsorption effects account for silver losses (13, 14). Radiometric methods using lloAg have been used to follow concentration steps and account for silver losses (15). To obtain reproducible results, one must be mindful of adsorption effects which are buffer, container, concentration, time, temperature, and technique dependent. The overall performance of the acetylenic column is comparable with other existing silver concentration techniques (16). With regard to its selectivity, its performance is unchallenged. Received for review April 30, 1973. Accepted October 5 , 1973. This work was supported under Grant PRF 5399AC by the Donors of the Petroleum Research Fund administered by the American Chemical Society. (13) F. K. West, P. W. West, and F. A. Iddings, Anal. Chem., 38, 1566 (1966). (14) R. Woodriff, B. R. Culver, D. Schrader, and A. B. Super, Anal. Chem., 45, 231 (1973). (15) T. Chao,M. Fishrnan, and J. Ball. Anal. Chim. Acta, 47, 189 (1969). (16) /bid., p 190.
Determination of Total Cyanide in the Presence of Palladium George W. Latimer, Jr., L. Ruth Payne, and Marguerite Smith PPG Industries, P. 0.Box 4026, Corpus Christi, Texas 78408
The problem of determining cyanide in the presence of metal ions which form acid-stable, cyano complexes has been dealt with in a number of ways. If the sample is a solid and free from other nitrogen-containing materials, carbon and nitrogen values have been used (1-3), although not always successfully ( 3 ) . Fusion with potassium (1) F. Feigl and G. B. Heisig, J . Amer. Chem. Soc., 73, 5630-5 (1951). (2) W. L. Magnuson, E. Griswald, and J. Kleinberg, lnorg. Chem.. 3, 88-93 (1964). (3) C. J. L. Lock and G. Wilkinson, J. Chem. SOC., 1962, 2281-5.
in a nickel bomb has proved satisfactory for cyano-rhenium complexes ( 3 ) ,but is tedious and cannot be applied directly to aqueous systems. Many acid-stable complexes are analyzed by distilling the cyanide from acidified mercuric magnesium chloride solution or after refluxing the compound with cuprous chloride ( 4 ) ; however, even with such vigorous conditions, recoveries of cyanide from systems containing palladium, mercury, and cobalt range between 4-90% ( 4 ) . (4) C. T. Elly. J. Water Pollut. Contr. Fed.. 40, 848-56 (1968).
A N A L Y T I C A L CHEMISTRY, VOL. 46, NO. 2, FEBRUARY 1974
311
