COMMUNICATIONS
Emission Spectrographic Determination of Barium in Sea Water Using a Cation Exchange Concentration Procedure Barney J. Szabo' and Oiva Joensuu Institute of Marine Sciences, University of Miami, Miami, Fla.
A concentration technique employing Dowex 50W cation exchange resin is described for the determination of barium in sea water. The separated barium is precipitated as fluoride together with calcium and strontium and measured by emission spectrographic analysis. The vertical distribution of barium in sea water has been measured in the Caribbean Sea and the Atlantic Ocean. The barium content varied between 7 and 23 pg. per liter; in two profiles, the lowest concentrations were at a depth of about 1000 meters.
ard error was 18%. Turekian and Johnson (1966) using the same method of concentration determined barium in sea water by neutron activation analysis. The coefficient of variation and standard error were reported to be the same. I n the work reported, the barium in sea water is concentrated using Dowex 50W-X8 cation exchange resin and hydrochloric acid as the eluting agent. The ion exchange procedure is monitored by utilizing a sensitive color test. The barium is precipitated as a fluoride together with calcium and strontium and is measured by using emission spectrographic analysis.
Experimental
T
he early measurements of barium content in sea water, using emission spectrographic analysis of ocean salt, revealed only the upper limits (Englehart, 1936; Black and Mitchell, 1952). Bowen (1956) employed a simplified ion exchange concentration technique using strongly acidic resin. The reported recovery was 88 %; the ignited resin was analyzed by neutron activation. Chow and Goldberg (1960) and ChDw and Patterson (1 966) utilized a n isotope dilution technique, with a mass spectrometer, for the measurement of sea water samples. Bolter et 01. (1964) employed neutron activation analysis of the freeze-dried ocean salt. The strontium content in the sea water was assumed to be constant and was used as a n internal standard. Turekian and Schutz (1965) reported the emission spectrographic analysis of sea water samples. The barium was coprecipitated with calcium and strontium oxalate. The recovery of barium determined using carrier-free Ba1-lotracer varied from 50 to 70%; the coefficient of variation was about 25 For duplicate determination, the stand-
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Present address, U. S. Geological Survey, Denver. Colo. 80225
Apparatus and Reagents. The ion exchange apparatus was designed for oceanographic use aboard ship. The upflow-type ion exchanger is described in Figure 1 with all the significant dimensions indicated. All reagents were prepared with double-distilled water and were stored in polyethylene bottles. Hydrochloric acid solutions were prepared by bubbling HC1 gas through distilled water. The cation exchange resin used was Dowex 5OW-X8, 100 to 200 mesh. The reagents employed for the color test solution were: N a O H solution, 51% (J. T. Baker Chemical Co.), 320 grams diluted to 1 liter; Cal-Red indicator (Scientific Service Laboratory, Inc., Dallas) triturated with NaCl in 1 t o 100 ratio; magnesium solution, 0.1M prepared from spectrochemically pure magnesium rods (Johnson, Matthey and Co., Ltd.) by dissolving the appropriate weight in a minimum amount of hydrochloric acid and diluting to volume; EDTA solution, 0.01M, prepared from the disodium salt of (ethylenedinitri1o)tetraacetic acid. Procedure. The column was filled with the resin slurry allowing about 1 cc. for swelling which occurred when sea water passed through the column. The resin in the column was conditioned by passing 200 ml. of 5M HCl through it; Volume 1, Number 6 , June 1967 499
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o ) POROUS FOLYETHYLEK PLUG b ) RUBBER CAP (USED FOR SERUM BOTTLE STOPPER)
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TEFLON STOPCOCK WITH METERING VALVE (KIMBLE LABORATORY GLASSWARE) TYGON TUBING U SHAPED CAPILLARY ADAPTER
0 CAPILLARY TUBING; o 7mm INSIDE, 8 rnm OUTSIDE D I M E T E R @
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ION EXCHANGE COLUMN RECEIVING RECEPTACLE
Figure 1. Ion exchange apparatus used for barium analysis
500 Environmental Science and Technology
this was followed by a wash with 25 ml. of distilled water. One hundred milliliters of distilled water, then 100 ml. of sea water samples were added to the glass bulk reservoir, and the diluted sea water was allowed to pass through with a flow rate of 0.6 ml. per minute. The bulb was rinsed with 25 ml. of distilled water, which was passed through the column. The column was then eluted with 1 M HCI solution. The first 100 ml. of the effluent, which eluted the alkali metals and major part of the magnesium (ascertained by EDTA titration), was discarded. The next portion of effluent of this preliminary elution was received in a beaker containing the color test solution (described below) until the change of color indicated the completion of the preliminary elution. Preparation and Use of the Color Test Solution. T o a tallform 200-ml. beaker, 10 ml. of NaOH solution were added, followed by 10 ml. of 0.1M magnesium solution, and the mixture was stirred. One hundred milligrams of 1 to 100 mixture of Cal-Red indicator and NaCl were added next, and the mixture was stirred again; the solution was blue. To the above test solution, 5 ml. of 0.01M EDTA were also added -that is, a quantity sufficient to complex about 5 % of the calcium content in sea water samples. The calcium content was calculated from the known chlorinity value using the Ca (mg.!g.),;CI (mg.,'g.) ratio of 0.0211. The indicator (Patton and Reeder, 1956) changes color from pure blue to wine red a t p H 12 to 14 when calcium is present. As little as 1 x 10-6 mmole of calciuni produced a positively identifiable color change. The blue color of the pure indicator did not change when several millimoles of magnesium salt were added because of the immediate formation of the very insoluble Mg(OH)n precipitate. Since the acidic effluent was neutralizing the blue-colored indicator solution continually, the pH was maintained between l l and 14 by the addition of 5-ml. portions of NaOH solution. When the blue color of the indicator began to fade because of the dilution, another portion (about 100 mg.) of indicator mixture was added to the beaker and stirred. The change of the indicator color from blue to wine red signaled the first appearance of free calcium ions in the s o h tion, and the preliminary elution was considered complete. Final Elution and Chemical Processing. After the completion of the preliminary elution, the flow was stopped, and the column was eluted with 200 ml. of 5M HCI. The eluate was received in a 250-ml. Teflon beaker, evaporated to 2 to 3 ml., and transferred to an 8-ml. platinum crucible. The solution was evaporated to 1 to 2 ml. then 0.5 ml. of concentrated H F was added and evaporated to dryness. The precipitate was ignited for a half hour at 500" C. in a muffle furnace, The crucible was cooled in a desiccator and weighed. The precipitate was scraped off with a platinum spatula and transferred to a small plastic vial for the spectrographic analysis. Standards for the spectrographic analysis were prepared by mixing known amounts of BaC03 with barium free CaF2. Yttrium was used as an internal standard (0.1 2 Y, 9.9% NaCI, 90% graphite). The standards and samples were mixed with internal standard and graphite in the ratio of 1 : 1 : 2 and filled in a 1/8-jnch electrode (Ultra Carbon Corp. Type NO. 5790). Electrodes were burned with a 10-amp. arc in a 10% oxygen and 90% argon atmosphere using a Stallwood blower (Stallwood, 1954) in conjunction with a Bausch and Lomb dual grating spectrograph and Eastman I-F plates. Spectrum
Table I. Barium-133 Isotope Recovery from Sea Water Using Dowex 50W-X8, 100- to 2OO-Mesh, Ion Exchange Resin Fraction Passing Through Column
Volume Collected. MI.
Volume before Final Measurement. MI.
0-230
8
