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Anal. Chem. 1982, 5 4 , 2094-2097
Prepared for the US. Army Corps of Engineers by the Kansas Geological Survey, The Unlversity of Kansas, Lawrence, KS, 1981. (3) Wen, G. S.; Fishman, M. J.; Hedley, A. G. Ana/yst (London) 1980, f05, 857-862. (4) Moxon, R. E. D.; Dlxon, E. J. J . Aufom. Chem. 1980, 2 , 139-142. (5) Whlttemore, Donald O., Kansas Geological Survey, The University of Kansas, Lawrence, KS, 1980, unpublished work. (6) "Standard Methods for the Examination of Water and Wastewater", 15th ed.; American Publlc Health Association: Washington, DC, 1981; Part 405. (7) Archlmbaud, M.; Bertrand, M. R. Chim. Anal. (Paris) 1970, 52, 531-533. (8) Marti, V. C.; Arozarena, C. E. "Automated Colorimetric Determination of Bromide in Water"; Paper No. 734, Plttsburgh Conference on Analyticai Chemistry and Applied Spectroscopy, Atlantic City, NJ, March 1981. (9) Stenger, V. A.; Kolthoff, I.M. J. Am. Chem. SOC. 1935, 57, 831-833. (10) Wrlght, E. R.; Smlth, R. A.; Messick, B. G. I n "Colorlmetric Determlnation of Nonmetals", 2nd ed.;Boltz, David F.,Howell, James A,, Eds.; Wiiey-Intersclence: New York, 1978; Chapter 2. (11) PBron, A.; Courtot-Coupez, J. Analusis 1978, 6,389-394. (12) Houghton, G. U. J. SOC. Chem. Ind., London 1948, 65,277-280. (13) Soilo, Frank W.; Larson, Thurston E.; McGurk, Florence F. Environ. Sci. Technol. 1971, 5,240-248. (14) "Chloride in Water and Wastewater"; Industrial Method No. 99-70W/ B; Technicon Industrial Systems: Tarrytown, NY, 1974, (15) "Ammonia in Water and Wastewater"; Industrial Method No. 98-7OW; Technlcon Industrlai Systems: Tarrytown, NY, 1973. (18) Glaser, John A.; Foerst, Denis L.; McKee, Gerald D.; Quave, Steven A.; Budde, William L. Environ. Sci. Technol. 1981, 75, 1428-1435.
(17) Anal. Chem. 1980, 52,2242-2249. (18) Zitomer,Jred; Lambert, Jack L. Anal. Chem. 1983, 35, 1731-1734. (19) BBnyai, Eva I n "Indicators"; Blshop, Edmund, Ed.; Pergarnon Press: Oxford, 1972; Chapter 3. (20) "Standard Ultraviolet Spectra Collection"; Sadtler Research Laboratories, 1980; UV Spectra Nos. 10519, 11434, and 25806. (21) Vogel, Arthur I."A Text-Book of Quantitative Inorganic Analysis", 3rd ed.; Longmans, Green and Co. Ltd.: London, 1961; p 392. (22) Goldman, Eugene; Bytes, David J. Am. Water Works Assoc. 1959, 57, 1051-1053. (23) Breslow, Ronakl "Organic Reaction Mechanisms", 2nd ed.; W. A. Benjamln: New York, 1969; p 150. (24) March, Jerry "Advanced Organic Chemistry: Reactions, Mechanisms, and Structure", 2nd ed.; McGraw-Hill: New York, 1977; pp 482-485.
RECEIVED for review May 14, 1982. Accepted July 19, 1982. Presented in part at the 17th Midwest Regional American Chemical Society Meeting, Columbia, MO, Nov 1981 and in part a t the 184th National American Chemical Society Meeting, Kansas City, MO, Sept 1982. Taken in part from the thesis of C.L.B., submitted to the Department of Chemistry in partial fulfillment of the requirements for the Masters degree. This research was funded by the Kansas Geological Survey. Financial support from an NSF equipment grant (CHE 78-03307) toward the purchase of the Perkin-Elmer UV-visible spectrophotometer is gratefully acknowledged.
Comparison of Highly Lipophilic Crown Ether Carboxylic Acids for Transport of Alkali Metal Cations from Aqueous Solutions into Chloroform Witold A. Charewlcz,' Owl Suk Heo, and Richard A. Bartsch" Department of Chemistry, Texas Tech University, Lubbock, Texas 79409
A new type of llpophlllc crown ether carboxylic acld, symbls[4(5)-tert-butylbenro]-l6-crown-5-oxyacetlc acid (6) Is prepared and compared with P-(sym-dibenzo-16-crown-5oxy)decanolc acid (5) In the competitive extraction and transport of elkall metal catlons from aqueous solutlons Into chloroform. Although the overall complexatlon behavlor of 5 and 6 for alkall metal cations In solvent extractlon and In llquld membrane transport Is qulte slmllar, 6 exhlblts complete excluslon of LI' and enhanced Na+/K+ selectlvity.
In earlier studies (10-12), we have examined the solvent extraction of alkali and alkaline earth metal cations from water into chloroform by crown ether carboxylic acids 1. These
XIC
OZH
n = 1;Y = CH,CH,, CH,CH,CH,, CH,CH,OCH,CH,, CH,CH,OCH,CH,OCH,CH, n = 2; Y = CH,CH,OCH,CH,
The synthesis of novel and specific organic complexing agents often leads to the development of new separation systems for aqueous ions. For example, the preparation and introduction of highly lipophilic hydroxy oximes led to the current utilization of these compounds as commercial extractants for the hydrometallurgy of nonferrous metals ( I ) . The potential of crown ethers (macrocyclic polyethers) as the next generation of specific extracting agents for metal ions (2-4) has been markedly enhanced by the introduction of crown ethers which bear pendant ionizable groups (5-9). In such molecules, the combination of ion binding cavities possessing fiied dimensions with ionizable groups creates novel bifunctional complexing agents. 'Visiting Research Professor from the Institute of Inorganic Research Chemistry and Metallurgy of Rare Elements, Technical University of Wroclaw, 50-370 Wroclaw, Poland.
complexing agents exhibit extraction efficiencies and selectivities which surpass both those of a closely related, nonionizable crown ether and of phenoxyacetic acid. It was also demonstrated that metal ion extraction does not involve concomitant transfer of the aqueous phase anion into the organic medium. This latter factor is of immense importance to potential practical applications of these ionizable crown ethers for metal ion extraction from aqueous solutions (10). In assessing the influence of the bridging group Y in 1 and the number of methylene groups which join the crown ether and the carboxylic acid portions of the molecules, it was noted that the carboxylate forms of these complexing agents were of insufficient lipophilicity to remain completely in the organic phase. Therefore, a second generation of more lipophilic crown ether carboxylic acids 2-5 was synthesized (9) and used for alkali metal extraction (13). Loss of the carboxylate forms
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ANALYTICAL CHEMISTRY, VOL. 54, NO. 12, OCTOBER 1982
of 3-5 to the water layer in extractions was insignificant. These lipophilic crown ether carboxylic acids were subsequently studied as agents for the active transport of alkali metal cations across ti bulk chloroform liquid membrane (14). T o probe the effect of varying the attachment site for the lipophilic group upon cation complexation, we have prepared crown ether carboxylic 6 which is a structural isomer of 5. A comparison of these two crown ether carboxylic acids in the solvent extraction of aqueous alkali m.etal cations into chloroform as well as their transport across a bulk chloroform liquid membrane is now reported. Oiti
L
O
J
6
EXPEIRIMENTALS ~ C T I O N Apparatus. Melting points were taken with either a Mel-Temp or Fisher Johns meltin,gpoint apparatus and are uncorrected. IR spectra were obtained with a Beckman Acculab-8 spectrophotometer and are reported in reciprocal centimeters. 'H NMR spectra were recorded with a Varian EM-360 spectrometer and chemical shifts are reported in park per million (6) downfield from Me4Si. Elemental anttilysis was performed by Galbraith Laboratories (Knoxville, TN). Concentrations of alkali metal cations in aqueous phases were determined with a Dioiiex Model 10 ion chromatograph. Organic complexing agent concentrations in the chloroform phases were measured with a Gary Model 17 ultraviolet-visible spectrophotometer. pH measurements were made wi€h a Fisher Scientific Accumet Model 620 pH meter and Corning 76050 glass body combination electrodes. During the transport experiments conStant pH levels were maintained in the aqueous source phase using a Fisher Scientific Model 650 pH controller and a Corning 76050 glass body combination electrode to control a Sage Instruments Model 341A syringe pump. For the transport experiments, the phases were mixed with Model CA constant speed motors from Hurst Industries (Princeton, IN). Synthesis of Bis[2-(4- or 5-tert-butyl-2-hydroxyphenoxy)ethyl] Ether (7). Under nitrogen, 100 g (0.60 mol) of 4tert-butylcatechol (Aldrich) was dissolved in 500 mL of 1-butanol and 18.0 g (0.45mol) of NaOH in 19 mL of water was added. The stirred solution was heated to reflux and 15.5 g (0.11 mol) of bis(2-chloroethyl) ether (Aldrich) was added dropwise during 2 h. After the reaction solution was allowed to reflux for 2 days, it was cooled to room temperature and evaporated in vacuo. The oily residue was dissolvlgd in CHzClzand washed with 1M NaOH (2 X 150 mL) to remove most of the excess 4-tert-butylcatechol, and the CHzClzwas evaporated in vacuo. The resulting oil was dissolved in 1 L of pentane and the pentane solution was washed with 100 mL of 1 N NaOH (to completely remove the 4-tertbutylcatechol) followed by 100 mL of 1 1vI HC1 and then NaCl solution. The pentane riolution was dried with MgS04,concentrated to half volume by evaporation in vacuo, and allowed t o stand until precipitation of the product was complete. Filtration and drying of the white solid gave 18.6 g (42% yield) of 7 of suitable purity to be used in the next synthetic step. Recrystallization from MeOH gave crystals: mp 52-55 "C; IR (deposited film) 3580-3100 cm-' (OH); lH NMR (CDClJ 6 1.25 (9, 18), 3.46-3.95 (m, 4), 3.95-4.20 (m, 4), 6.66-7.04 (m, 6), 7.54 (br s, 2).
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Synthesis of sym -Hydroxybis[4( 5)-tert-butylbenzol-16crown-5 (8). Under nitrogen, 20.0 g (0.050 mol) of 7 was dissolved in 1.5 L of MeOH and concentrated aqueous NaOH was added until the pH was 9-10, After the stirred solution was heated to reflux, 4.0 mL (0.051 mol) of epichlorohydrin (Aldrich) in 15 mL of MeOH was added over a 12-h period. The pH of the reaction solution was adjusted from 8 to 10 by the addition of concentrated aqueous NaOH and 4.0 mL of epichlorohydrin in 15 mL of MeOH was added over a 5-h period. The pH of the reaction solution was again adjusted to 9-10 by the addition of concentrated aqueous NaOH and 4.0 mL of epichlorohydrin in 10 mL of MeOH was added over a 2-h period. After the reaction solution was cooled to room temperature, it was neutralized with concentrated HC1 and the solvent was evaporated in vacuo. To the resultant residue, EtzO and water were added. The solid which formed at the ether-water interface was filtered and dried. Additional solid was obtained by concentrating the ether layer. The combined solids (13.5 g, 59% yield) were of sufficient purity to be used in the next synthetic step. Recrystallization from MeOH gave white crystals: mp 175-177 "C; IR (deposited film) 3600-3100 cm-l; (OH); 'H NMR (CDC1,) 6 2.27 (s, 18);3.57 (br s, I),3.74-4.40 (m, 13),6.78-7.13 (m, 6). Anal. Calcd for C27H3806: C, 70.71; H, 8.35. Found: C, 70.58; H, 8.40. Syntheses of sym -Bis[4(5)tert -butylbenzol16-crown-5oxyacetic Acid (6). Under nitrogen, 2.0 g (39 mmol) of NaH dispersion in mineral oil (Aldrich) was washed with pentane to remove the mineral oil. Dry THF (150 mL) and then 3.0 g (6.55 mmol) of 8 were added and stirred at room temperature for 0.5 h. Bromoacetic acid (1.82 g, 13.0 mmol, Aldrich) in 50 mL of dry THF was added dropwise during 0.5 h, and stirring at room temperature was continued for 2 h. The reaction solution was heated to reflux for 10 min and cooled, and water was carefully added to decompose the excess NaH. Evaporation of the THF in vacuo gave an oil to which aqueous NaOH and CHzClzwere added. The CHzClzlayer was washed with 6 M HC1, dried with MgS04, and evaporated in vacuo to give an oil. The oil was dissolved in a large amount of refluxing pentane. After the solution was cooled to room temperature, partial evaporation of the pentane in vacuo at 0 "C gave a solid which was filtered. The white crystals (2.9 g, 86% yield) had mp 55-56 "C; IR (deposited film) 3600-2400 cm-l (COOH),1750-1720 cm-l (C=O); 'H NMR (CDC13)6 1.27 ( 8 , 18), 3.50-4.90 (m, 15), 6.60-7.30 (m, 6), 10.26 (br s, 1);UV (CHCl,) ,A, = 272 nm (e = 3650). Reagents. Sources of reagent grade inorganic chemicals and solvent purification methods were as previously described (10). Procedure. The procedure for solvent extraction experiments was the same as was previously reported (10). The liquid membrane transport experiments were conducted with the cell illustrated in Figure 1. The organic phase (50 mL) M solution of the crown ether carboxylic acid was a 1.0 X in chloroform. The aqueous source phase (100 mL) was 0.20 M in each of the five alkali metal chlorides, while the aqueous receiving phase (5.0 mL) was 0.20 M HC1. During a transport experiment, the pH of the aqueous source phase was kept at 10.0 by adding 1.0 M NaOH solution. The aqueous source phase was stirred at 200 rpm and the organic and receiving aqueous phases were stirred at 120 rpm, respectively. Contact areas of the aqueous source-chloroform and aqueous receiving-chloroformphases were 26.0 and 1.1cm2,respectively. The cation transport experiments were conducted for 47-52 h at room temperature (20-23 "C) with 0.025-mL samples of the aqueous receiving phase being periodically removed for measurement of the alkali metal ion concentration. RESULTS AND DISCUSSION Synthesis of the New Lipophilic of Crown Ether Carboxylic Acid 6. Preparation of the crown ether carboxylic acid 6 was accomplished by using the series of reactions outlined in Scheme I. Although bis[2-(4- or 5-tert-butyl-2hydroxyphenoxy)ethyl] ether has been reported by Pederson (15),the synthetic procedure involved the use of a protecting group and neither experimental details nor product yields were provided. Therefore, we developed an alternative procedure which utilized an excess of 4-tert-butylcatechol (recoverable) instead of a protecting group. For the one-step conversion
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ANALYTICAL CHEMISTRY, VOL. 54, NO. 12, OCTOBER 198'2
I
3
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4 T
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4
5
6
7
8
9
10
11
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6
7
8
9
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PH
Flgure 2. Concentrations of metals (X103) and complexing agent (X102) in the chloroform phase vs. the equilibrium pH of the aqueous phase for competitive extractlons of 0.25 M alkali metal cations by (a) 0.050 M 5 ( 1 3 )and (b) 0.050 M 6: W = complexing agent, V = Li, 0 = Na, 0 = K, A = Rb, 0 = Cs.
t l L + -56
I
Flgure 1. Liquid membrane transport cell with dimensions given in mm: 1 = combination electrode, 2 = 120 rpm glass stirrer, 3 = internal tube which separates receiving phase and source phase, 4 = glass capillary tube for adding NaOH solution, 5 = receiving phase, 6 = source phase, 7 = glass supports for internal glass tube, 8 = 200 rpm magnetic stirring bar, 9 = chloroform phase.
Scheme I. Synthetic Route to Lipophilic Crown Ether Carboxylic Acid 6
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of 4-tert-butylcatechol into 7,higher yields were obtained with 1-butanol as the solvent compared with water or aqueous ethanol. TLC of the product 7 indicated the predominant presence of one of the three possible isomers (tert-butyl groups in the 4,4', 5,5', and 4,5' positions). On the basis of the greater acidity of rn-cresol than p-cresol(16), we suggest that the 4,4' isomer predominates. Transformation of 7 to 8 utilized our recently published ring closure method (17), with the modification that the insolubility of 7 in water required the use of ethanol as the solvent. Best yields of 8 were obtained from three sequential additions of NaOH and epichlorohydrin to the ethanolic solution of 7. TLC indicated the presence of primarily one isomer in the product. The structure of 7 was confirmed by IR and lH NMR spectra and elemental analysis. Conversion of 8 into the 6 was accomplished as before (9) with slight modification of the workup procedure. The lipophilic crown ether carboxylic acid 6 was obtained as an oil which could be converted into a low melting solid. The R and lH NMR spectra. The structure of 6 was supported by I IR spectrum of 6 shows a single carbonyl absorption at 1750-1720 cm-' and thereby differs from that reported (9) for 5 in which two carbonyl absorptions at 1710 and 1685 cm-l
are observed. Thus it appears that the strong intramolecular hydrogen bonding of the carboxylic acid group with the polyether oxygens which is suggested for 5 is not present in 6. This indicates a greater conformational flexibility of the carboxylic acid group in 6. Solvent Extraction of Alkali Metal Cations from Water i n t o Chloroform by Lipophilic Crown E t h e r Carboxylic Acids 5 a n d 6. The lipophilic crown ether carboxylic acids 5 and 6 are structural isomers. By movement of the lipophilic group attachment site from the vicinity of the carboxylic acid group to the aromatic rings, the oxyacetic acid group in 6 should possess greater conformational flexibility than that in 5. In addition, for 6 the basicity of the crown ether oxygens might be expected to increase slightly since the attachment of alkyl groups to aromatic rings of benzo crown ethers induces enhanced cation binding (18). In our previous studies of alkali metal cation extraction by crown ether carboxylic acids (10,11), it was demonstrated that the efficiencies and selectivity orders for competitive extractions are often quite different from expectations based upon the results of single ion extractions. Therefore, competitive extractions were used in this investigation. In Figure 2, the results for extractions of aqueous solutions in which the concentrations of each alkali metal chloride were 0.25 M with 0.050 M chloroform solutions of 6 are compared with those previously reported (13) for 5 under identical conditions. In agreement with the earlier results for 5 , loss of the complexing agent 6 from the organic phase is insignificant (filled squares in Figure 2) even when the aqueous phase becomes highly alkaline. Curve shapes for the alkali metal cation concentrations in the organic phase as a function of the aqueous phase pH are quite similar for 5 and 6 with the exceptions that Li+ is completely excluded from the chloroform phase using 6 and the Na+/K+ selectivity is slightly improved. At a given aqueous phase pH, total loading of alkali metal cations in the organic phases is very similar for 5 and 6. T r a n s p o r t of Alkali Metal Cations across a Bulk Chloroform Membrane by Crown E t h e r Carboxylic Acids 5 a n d 6. The competitive transport of alkali metal cations across a chloroform liquid membrane using a different transport cell and crown ether carboxylic acid 5 has been reported earlier (14). In such experiments, the active transport of metal ions from an alkaline aqueous source phase through a chloroform phase and into an acidic aqueous receiving phase is driven by the countertransport of protons (19). Results for the competitive transport of alkali metal cations from an aqueous source phase which was 0.20 M in each alkali
Anal. Chem. 1982, 5 4 , 2097-2102
I
1
l
I
b
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2097
mated to be 2.0-2.4 A (10). Thus, Na+ with an ionic diameter of 1.90 A (20) provides the best fit of the cation with the cavity. Although the overall complexation behavior of 5 and 6 is quite similar, 6 exhibits complete exclusion of Li+ and enhances the Na+/K+ selectivity somewhat. Such increases in selectivity with a variation in the lipophilic group attachment site encourage the preparation and testing of additional lipophilic crown ether carboxylic acids.
LITERATURE CITED
20
10
60 0
20
LO
60
Time (hrsl
Figure 3. Competitive transport of aikall metal cations across a chloroform membrane by crown ether carboxylic acids (a) 5 and (b) 6: V = Li, 0 = Na, 0 =I K, A = Rb, 0 =: Cs.
metal chloride across a chloroform liquid membrane using M solutions) crown ether carboxylic acids 5 and 6 (1.0 X and the transport cell illustrated in Figure 1 are presented in Figure 3. Comparison of these results reveal that under identical conditions 6 is a somewhat more efficient transport agent. The selectivity for transport by 5 is Na+ > K+ > Rb+ = Cs+ = Li+, whereas that for 6 is Na' > K+ > Rb+ = Cs+ > Li+. In agreement with the results from solvent extraction, transport by 6 completely excludes Li+ from the organic phase and enhances the NaC/K+selectivity over that of 5. C:ONCLU SION Si
In both solvent extraction and transport across liquid membranes, lipophilic crown ether carboxylic acids 5 and 6 exhibit similar complexation behavior for alkali metal cations. For both types of experiments and both ionizable crown ethers, preferential complexatiop with Na+ is observed. From an examination of Corey-Pauling-Kortuni (CPK) space-Glling models, the polyether cavity diameterfi for 5 and 6 are esti-
Fiett, D. S. J . Chem. Technol. Biofechnol. 1979, 2 9 , 258-272. Marcus, Y.; Asher, L. E. J . Phys. Chem. 1978, 82, 1246-1254. Gerow, I.H.; Davis, M. W. Sep. Sci. Technol. 1979, 74, 395-414. Gerow, I . H.; Smith, J. E.; Davis, M. W. Sep. Sci. Technol. 1981, 76, 519-548. Helgeson, R. C.; Timko, J. M.; Cram, D. J . J . Am. Chem. SOC.1973, 95,3023-3025. Newcomb, M.; Cram, D. J. J . Am. Chem. SOC. 1977, 97, 1257-1259. Nakamura, H.; Takagi, M.; Ueno, T. Talanta 1979, 26, 921-927. Frederick, L. A,; Fyles, T. M.; Gorprasad, N. P.; Whitfield, D. M. Can. J. Chem. 1981, 59, 1724-1733. Bartsch, R. A.; Heo, G. S.; Kang, S, I,; Liu, Y.; Strzelbicki, J.J. Org. Chem. 1982, 47, 457-460. Strzelbickl, J., Bartsch, R. A. Anal. Chem. 1981, 53, 1894-1899. Strzelbicki, J., Bartsch, R. A. Anal. Chem. 1981, 53, 2247-2250. Strzelbickl, J., Heo, G. S.; Bartsch, R. A. Sep. Sci. Technol. 1982, 17,635-643. Strzelbicki, J.; Bartsch, R. A. Anal. Chem. 1961, 5 3 , 2251-2253. Strzeiblcki, J.; Bartsch, R. A. J . Membr. Sci. 1982, 70, 35-47. Pederson, C. J. J . Am. Chem. SOC. 1967, 89, 7017-7036. Weast, R. C., Ed. "CRC Handbook of Chemistry and Physics", 6lst ed.; CRC Press: Boca Raton, FL, 1980; p 0-165. Heo, G. S.; Bartsch, R. A.; Schlobohm, L. L.; Lee, J. G. J . Org. Chem. 1981, 4 1 , 3574-3575. Ungaro, R.; El Hal, B.; Smid, J. J . Am. Chem. SOC. 1976, 98, 5198-5202. Schwind, R. A.; Giliigan, T. J.; Cussler, E. L. I n "Synthetic Multidentate Macrocyclic Compounds"; Izatt, R. M., Christensen, J. J., Eds.; Academic Press: New York, 1978, pp 298-299. Moore, W. E.; Amman, D.; Bissig, R.; Pretsch, E.; Simon, W. I n "Progress in Macrocyclic Chemistry"; Izatt, R. M., Christensen, J. J. Eds.; Wiiey-Intersclence: New York, 1979; Vol. 1, p 9.
RECEIVED for review April 30, 1982. Accepted July 19, 1982. This research was supported by the Department of Energy (Contract DE-ASOS-80ER-10604) and the Texas Tech University Center for Energy Research.
Interference of Volatile Hydride Forming Elements in Selenium Determination by Atomic Absorption Spectrometry with Hydride Generation Ji'Ji Dgdina Institute of Nuclear Biology and Radiochemistry, Czechoslovak Academy of Sciences, V i d e k k i 1083, 142 20 Prague 4, Czechoslovakia
Interferences of Sn, Pb, As, Sb, Bi, Te, and Hg In concentrations up to 125 ,ug mL-'in Se determinatlon with a flamein-tube atomlzer were! studled. Hg and Pb dld not cause Interferences. 75Setraicer studles revealed that only As and BI caused llquld phase Interferences. Sm, As, Sb, BI, and Te exhlblted strong gaseous phase lnterfercsnces the magnltude of whlch depended on the condltlons of atomlzatlon. The gaseous phase effects were due to an acceleratlon of decay of the free analyte atalms or due to a decrease In the level of the hydrogen radlcal populatlon. By use of a specially deslgned atomizer the Interferences were reduced to a level 2-3 orders of magnltuide lower than that In the flameless, electrlcally heated quartz tube atomizers.
The hydride formation followed by atomization in a flame
or a flameless device has become a well-established method for determination of elements forming volatile hydrides. The method is highly sensitive and less vulnerable to interferences than the one employing electrothermal atomizers (1). Nevertheless, the interferences may still represent a serious problem. Although their mechanism is still little known, even the interferences caused by volatile hydride forming elements are usually ascribed solely to processes taking place during hydride formation in, and its release from, the liquid sample (2-4); however, the possiblity of interferences taking place in the gaseous phase should also be taken into consideration (5, 6). The aim of this work was to determine the magnitude and nature of interferences of Hg(II), Sn(IV), Pb(II), As(III), Sb(III), Bi(III), and Te(1V) in medium concentrations in the determination of selenium. In the method used the hydride
0003-2700/82/0354-2097$01.25/00 1982 American Chemical Society
