CONCLUSIONS Destructive removal of olefins offers several advantages over existing techniques for the quantification of the hydrocarbon types in shale-oil distillate fractions. Handling and manipulation of the sample is minimal; a n elution chromatography is the only preparation prior t o analysis. The method avoids the problems associated with chemical and physical procedures normally used to quantify the three functional types; the specificity of compound-type removal. coupled with the accuracy of the GC readout, gives improved results for complex mixtures containing a significant concentration of olefinic material. The technique is amenable to batch analysis of a large number of samples, and automated GC makes the data readout step
a simple operation not requiring extensive operator time. An accurate analysis can be performed on samples as small as 50 milligrams, and the sample may be in the form of a dilute solution. Received for review May 29, 1973. Accepted October 29, 1973. The work upon which this report is based was done under a cooperative agreement between the Bureau of Mines, U.S.Department of the Interior, and the Universit y of Wyoming. Reference to specific equipment or trade names does not imply endorsement by the Bureau of Mines. Larry P. Jackson was a National Research Council-US. Bureau of Mines Post-Doctoral Research Associate, 1971-73.
Improved Ion-Exchange Technique for the Concentration of Manganese from Sea Water Ralph G . Smith, Jr. Skidaway institute of Oceanography, P.O. Box 73687, Savannah, Ga. 31406
Because manganese occurs a t pg/l. and sub pg/l. levels in sea water, its direct determination is difficult. The sensitivity of 0.002 ppm by direct determination with atomic absorption claimed by some workers ( I ) should be questioned, since it is approximately an order of magnitude greater than has been reported by others ( 2 , 3). Photometric techniques involving leuco base ( 4 ) and leuco crystal violet ( 5 ) have been described; however, samples of varying ionic strengths require special calibration. Most workers concentrate manganese from sea water either by co-precipitation (6, 7) and/or extraction techniques (6, 8 ) . Riley and Taylor (9) have shown that a chelating ion-exchange resin can be used for this purpose. T h e resin, Chelex-100, undergoes swelling and contraction as its counter-ion is changed, causing difficulty in maintaining a constant flow rate through exchange columns. T h e difficulty increases with decreasing resin particle size, making it desirable to use the largest particle size available (50-100 mesh). Bio-Rad Laboratories, the only commercial source of Chelex-100, recently discontinued manufacture of t h e 50-100 mesh size, and attempts to substitute the 100-200 mesh resin using the column technique result in the difficulties described above. This paper describes a quantitative batch technique which uses the small particle size resin and is free of the difficulties of t h e column method. B. P. Fabricand, R . R. Sawyer, S. G .Ungar, and S. Adler, Geochim. Cosmochim. Acta, 26,1023 (1962) E. E. Angino and G. K . Billings, "Atomic Absorption Spectrophotometry in Geology," Elsevier Publishers. Amsterdam, 1967, p 1 2 . Perkin-Elmer Corp., "Analytical Methods for Atomic Absorption Spectrophotometry," Norwalk, Conn., (1971) J. D. H . Strickland and T . R . Parsons, "A Practical Handbook of Sea Water Analysis," 3 r d ed.. Fisheries Research Board of Canada, Ottawa, Canada, 1968, p 109. M . A. Kessick. Jasenka Vuceta, and J. J. Morgan, Environ. Sci. Techno/.. 6,642 (1972). B. A . Loveridge, G. W. C. Milner. G . A . Barnett, A. Thomas, and W. M . Henry, A t . Energy Res. Estab. Rept. I?.3323,36 pp. D. C. Bureli, Ana/. Chim. Acta, 38, 447 (1967) Elizabeth Rona, D. W . Hood, Lowell Muse, and Benjamin Buglio, Limnoi. Oceanogr.. 7, 201 (1962). J . P. Riley and D. Taylor, Deep-sea Res.. 15, 629 (1968).
EXPERIMENTAL Chelex-100 resin is converted to the hydrogen form by washing a suitable quantity three times with an excess of 2 N "OB. Approximately 10 ml of wet resin are required per sample, and an acid:resin ratio of 1:l provides the necessary excess. The resin is washed with redistilled water and converted to the ammonium form by washing three times with 2AVN H 4 0 H . A final washing with redistilled water removes excess base. All preparation steps are carried out in Vycor or polypropylene flasks. T e n ml of t h e ammonium form of the resin is added to 500 ml of sea water having an adjusted p H of 9.0 in a 1-1. polypropylene flask. The sample is equilibrated for 16 hr on a mechanical shaker, after which time the solution is decanted through an ion-exchange column allowing t h e resin particles to pour off last. The flask is washed with redistilled water which is then passed through the column. The sample flask is washed with 30 ml of 'A\' "03 to remove manganese adsorbed on the flask. The resin is t h e n eluted with t h e acid wash. Ten ml of redistilled water are added t o the column to completely flush the resin. The eluate is collected in a Vycor flask and evaporated to dryness a t low temperature. Prolonged heat after dryness should be avoided since this tends t o make t h e residue difficult to redissolve. At this point. t h e residue is redissolved with 1 ml of 2-V HC1 a n d diluted to a 5.0-ml volume with redistilled water in preparation for analysis by atomic absorption spectrophotometry. Acetone or other organic solvents have been used in the diluent by other workers (9) to enhance sensitivity. This, in some cases, leads t o the formation of precipitates which clog the aspiration assembly of t h e atomic absorption system. Standards for atomic absorption analysis may be prepared by spiking previously stripped sea water with incremental amounts of manganese and treating the spiked sample as described in t h e procedure above.
RESULTS A N D DISCUSSION The most critical factor in the above described procedure was to establish the time required for equilibration of the resin with the water sample. To investigate the resin uptake efficiency as a function of time, 500-ml aliquots of sea water were spiked with 10 pCi of carrier-free 54Mn. The samples were equilibrated for varying lengths of time and eluted according t o the described procedure. Aliquots of the eluate and sample solution were then counted in a sodium iodide well detector connected to a n A N A L Y T I C A L C H E M I S T R Y , VOL. 46, NO. 4 , A P R I L 1974
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Table I. Recovery of Added64Mn from Sea Water Equilibration time, hr
2 4
6 8
16 16
16 16 16
Recovery,
70
Efauent
Sample solution
Resin
93 94 95 96 99 99 98 99 99
6.8 6.0 5.2 4.8
0.1 0.2 0.2 0.2 0.2 0.2 0.2 0.1 0.1
1.0 1.0 1.0
1.0 1.0
Ortec single channel analyzer. Results shown in Table I indicate quantitative recovery in 16 hours with less than 1%of the manganese remaining in the water and less than 0.2% remaining on the resin. The recovery efficiency for five samples, each with 10 pCi of 54Mn and each equilibrated for 16 hours. had a coefficient of variation of
=t0.6%. The actual analysis of the samples by atomic absorption was not necessary since previous studies have proved its utility (9). Results in Table I indicate that optimum recovery may conveniently be achieved by equilibrating the samples overnight and eluting them the following morning. This batch-wise method extends the analytical use of Chelex100 to the smaller resin sizes and should be suitable for the concentration of other metals ( I O ) . ACKNOWLEDGMENT The author wishes to thank Robert Rahn and Elizabeth Waiters for their assistance in this work. My special thanks to Herbert Windom for making this work possible and for his review of the manuscript. Received for review June 11, 1973. Accepted November 26, 1973. This work was partially supported by EPA Grant (R-800372). (10) J. P. Riley and D Taylor, Ana/ Chim. Acta, 40, 479 (1968).
Separation of the Trivalent Actinides from the Lanthanides by Extraction Chromatography Terry D. Filer Health Services Laboratory. U.S. Atomic Energy Commission, Idaho Falls. ldaho 83401
One of the more difficult problems in actinide chemistry is the separation of the trivalent actinides from the trivalent lanthanides. The solution of this problem is necessary in the analysis of greater than gram quantities of soil because of the presence of milligram quantities of the rare earths. Since even microgram quantities of the rare earths have been shown to produce serious losses in the electrodeposition of the trivalent actinides ( I ) , a separation procedure with high decontamination factors is needed. Single-step liquid-liquid extraction procedures did not provide sufficiently large decontamination factors. Anion exchange involving ammonium thiocyanate ( 2 ) and cation exchange involving hydrochloric acid-ethanol ( 3 ) provide excellent decontamination factors but are cumbersome and time-consuming. Extraction chromatography provides an attractive means of separating metal ions of close chemical similarity because it combines the multiplate process of ion exchange without sacrificing to a great extent the simplicity, selectivity, and speed of liquid-liquid extraction. Bis(2-ethylhexyl)orthophosphoric acid (HDEHP) is an excellent reagent for intragroup separations of the trivalent lanthanide or actinide ions ( 4 , 5 ) because separation factors are higher than those observed in ion exchange methods. Also, the high reaction rate of HDEHP with these ions permits relatively high flow rates. Extraction (1) K. W. Puphal and D. R. Olsen. Ana/. Chem.. 4 4 , 284 (1972). (2) J. S. Coleman, L. B. Asprey. and R. C. Chisholm, J , Inorg. NucI. Chem.. 31, 1167 (1969). (3) K. Street, Jr., and G. T. Seaborg, J. Amer. Chem. SOC.,72, 2790 (1950). (4) D. F. Peppard. G. W. Mason, J. L. Maier, and W. J, Driscoll, J. Inorg. Nuci. Chem.. 4, 334 (1957) (5) D. F. Peppard, G. W. Mason, W. J. Driscoll, and R. Sironen, J. Inorg. Nuci. Chem.. 7, 276 (1958).
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chromatographic methods based on HDEHP for the separation of lanthanides in mineral acid systems have been reviewed (6). Kooi and coworkers used the HDEHP-hydrochloric acid system for the chromatographic separation of several transplutonium elements (7, 8). Moore and Jurriaanse (9) extended the use of HDEHP in extraction chromatography to nitric acid systems, utilizing Teflon (Du Pont) powder as an inert support. All of these procedures, however, are based on the extraction of lanthanides and trivalent actinides by HDEHP from mineral acid solutions. The distribution coefficients of the two groups of elements overlap, with americium behaving most like cerium or praseodymium. Therefore, the separation of lanthanides from trivalent actinides is not clean even with the use of a multiplate process such as extraction chromatography. Weaver and Kappelmann (10) showed that the substitution of carboxylic acids for mineral acids shifts the americium distribution coefficients downward slightly relative to the lanthanides. In addition, the presence of strongly complexing aminopolyacetic acids causes a much larger shift. Percival and Martin (11) showed that the light trivalent lanthanides and actinium could be separated from americium by extraction in HDEHP from an aqueous solution containing diethylenetriaminepentaace(6) E. Cerrai. Chromatogr. Rev.. 6.129 (1964). (7) J. Kooi, R. Boden, and J. Wijkstra. J . Inorg. Nucl. Chern.. 26, 2300 (1964). (8) J. Kooi and R . Boden, Radiochirn. Acta. 3. 226 (1964). (9) F. L. Moore and A. Jurriaanse, Anal. Chern.. 39. 733 (1967). (10) B. Weaver and F. A. Kappelmann. J Inorg. Nucl. Chem . 30. 263 (1967). (11) D. R. Percival and D. B. Martin, "Sequential Determination of Radium-226, Radium-228, Actinium-227, and Thorium Isotopes in Environmental and Process Waste Sampies," U.S. Atomic Energy Commission, Idaho Falls. Idaho. in preparation.
