ANALYTICAL CHEMISTRY, VOL. 50, NO. 4, APRIL 1978
be a serious problem. The efficacy of the backflush procedure has been shown by the significant deposition of contaminants, similar t o those previously observed, on the glass injection sleeve, which is replaced each time the pyroprobe is removed prior to backflushing. Our experience has shown the advantages of using a precolumn, together with backflushing, as the main column has been kept free of contamination and the replacement frequency of the precolumn has been minimized, thus avoiding t h e regular replumbing involved in a precolumn system that does not incorporate backflushing. T h e relatively low cost
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of the valve, allied to t h e advantages outlined above, makes this system an attractive alternative to an automatic backflush arrangement.
LITERATURE CITED (1) P. A. Quinn, J . Chfomatogr. Sci., 12, 796 (1974). (2) M. Needleman and P. Stuchbery, “AnalyticalPyrolysis”,C. E. R. Jones and C. A. Cramers, Ed., Elsevier, Amsterdam, 1976, p 77. (3) M. V. Stack. H. D. Donoghue, J. E. Tyler, and M. Marshall, ref. 2, p 57.
RECEIVEDfor review September 19, 1977. Accepted December 19, 1977.
Gas Chromatographic Determination of Dissolved Hydrogen and Oxygen in Photolysis of Water Steven J. Valenty General Electric Corporate Research and Development, Schenectady, New York 1230 1
T h e use of visible light energy to decompose water into hydrogen and oxygen is a subject of current interest (1-3). T h e principal analytical tool used to detect the small amounts of gaseous products produced in these studies has been mass spectrometry. I n a n attempt t o observe trace quantities of H2and O2 which might be evolved during the photolysis of glass supported monolayer assemblies of surfactant derivatives of tris(2,2’-bipyridine)ruthenium(II)( 2 ) , a simple chromatographic method has been utilized and is reported here. Determination of traces of H2, N2,and O2in aqueous solutions by vapor phase chromatography has been reviewed by Tolk a n d co-workers ( 4 ) . In t h e present method, the aqueous solution is injected directly onto a chromatographic column filled with molecular sieves and the eluting H2 and O2 monitored by a standard thermal conductivity detector. The validity of the hydrogen analysis was tested by using the acidic ferrocyanide/isopropanol system as a reference actinometer (5, 6).
EXPERIMENTAL Materials. Linde purified He and Ar were used as carrier gases. The argon was passed through a 20-in. X 0.375-in.stainless steel tube filled with activated “Ridox” (Fisher Scientific) to minimize the oxygen concentration. Molecular sieve 5A (60/80 mesh) was obtained from Supelco. Potassium ferrocyanide (Baker Analyzed), isopropanol (MCB Spectro), and perchloric acid (Baker Analyzed) were used for the hydrogen actinometry experiments as received with triply distilled water as solvent. Apparatus. A Hewlett-Packard F & M Model 5750 Chromatograph equipped with a thermal conductivity detector and 0.125-in. sleeves in the injector block was utilized. The column (stainless steel, 0.125-in. o.d., 0.010-in. wall) is composed of two shorter columns coupled in series; both filled with 60/80 mesh molecular sieve 5A. The “water adsorbing” precolumn (0.5-m length) is attached to the injector followed by the longer (2.1 m) “gas separating” column. The column was activated by heating in a He stream at 300 “C for 4 h before use. Conditions for the gas analyses are given in Table I. The aqueous solutions are sampled by a 100 p L “Pressure-Lok” series A-2 syringe which has a valve behind the needle such that samples can be transferred (and stored) in the syringe barrel without gas loss. A 4-W germicidal lamp (General Electric G4T4-1, output >210 nm) in a convection cooled housing was attached to a thermostated brass photolysis cell holder such that the plane of the “U” shaped lamp was parallel to and 5 cm distant from the cell’s front window. The light intensity was attenuated with fine copper mesh screen. Of the light incident on the cell face, 88% had a wavelength of 253.7 nm with the remainder not photochemically active. 0003-2700/78/0350-0669$0 1.OO/O
Table I. Experimental Conditions Condition 0, analysis Carrier gas He Carrier gas flowd mL/min 60 Injector temp., C 100 Column temp., “ C 60 Detector temp., C 100 TC filament current, mA 240 TC attenuator setting 1x
H, analysis Ar 40 100 60 100 150
1x
Table 11. Observed Analytical Data for Dissolved Gas Detection 0bserva tion Instrument calibration factor, mol/mm peak height Minimum amount detectable, mol, S / N = 4 Maximum injection volume,
H2
0
8.4 X 10.”
1.3 X
1.7 X 10.’’
2.5 X
2
100
50
P L
Minimum concentration detectable, mol, S / N = 4 Precision, % Linearity, % gas saturation Retention time, mina a
3.4
X
2.5
*lo
? 10 2- 100 1.1 f 0.1
2-100 0.9 ? 0 . 1
X 10.’
See Table I for carrier gas and flow rate used.
The photolysis cell, constructed of either Teflon or A1 alloy, is demountable and is assembled from four side pieces and two quartz windows using Teflon tape as gasket material around the perimeters of the windows. For these experiments, the light path through the cell is either 0.5 cm (ferrioxalate actinometry) or 0.1 cm (hydrogen actinometry) and the cell’s contents accessed through a septum seal in the top. The cell front window was masked to provide a 2.3 cm X 2.6 cm opening. A Perkin-Elmer Model 575 was used to record all ultraviolet and visible absorption spectra. Procedure. Ferrioxalate actinometry was used for the light intensity determination at 254 nm (7). The light intensities used in this study are 5.0 f 0.1 X einstein/s/cm2 (bare lamp output) and 4.5 f 0.1 X einstein/s/cm2 (Cu mesh attenuated output). Routine calibration was done by injecting known volumes of a H2 or O2 saturated aqueous solution (25 f 1 “C, under 1 atm of pure gas) into the chromatograph. In another method, standard solutions containing less than saturation concentrations of Hz were prepared by 254 nm photolysis ( I = 0.1 cm, 25 “C) of a Nz purged M K,[Fe(CN),], aqueous solution (1.0 mL) containing: 1.0 X G 1978 American Chemical Society
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ANALYTICAL CHEMISTRY, VOL. 50, NO. 4, APRIL 1978
Table 111. Comparison of H, Actinometer and VPC Results % Reactiona (No. of samples)
VPC % H, satd H,O ( + % Err)b
Calcd % H, satd H , O ( + % Err)c
0 0 0 7 (3) 6 (8) 5 (10) 10 (10) 1 0 (4) 14 ( 3 ) 19 (10) 28 ( 5 ) 15 (6) a Calculated from the absorbance at 420 nm for [Fe"'(CN), 13-,emax =. 1.00 X l o 3 M-' cm-'. VPC % H, satd H,O = (Peak Height H, a t [)/(Peak Height H, satd H , O ) X 100, where f is the photolysis time. Calcd % H, satd H,O = (No. Moles H, at t)/(No. Moles H,in satd H , O ) x 1 0 0 = [ ( f a ) ( I o z )(@v (t)/mL]/(7.6 x 1 0 ' 7 / m L ) x 100, where f a = 0.55, Io12 3.0 X l(r8einstein s - ' , @ H , , * = 0.43, f is the photolysis time. ,j)
1.0 X M HC104 and 0.10 M isopropanol. The solutions were analyzed for H2 assuming @ . H ~= 0.43 ( 5 ) . Peak heights were measured with a millimeter ruler.
injected. T h e reported procedure, while utilizing standard and readily available equipment, approaches the sensitivity for dissolved H2detection (- 1 x 10+ M) of the best published chromatography method ( 4 ) which requires specialized apparatus. T h e photolysis of acidic aqueous ferrocyanide solutions containing the hydrogen atom donor isopropanol, was found to provide a useful calibrated source of Hz in subsaturation concentrations under conditions nearly identical t o those employed for the monolayer experiments. As noted in Table 111, the results of the two methods are the same a t low conversions to ferricyanide. At conversions >15%, deviations occur and become increasingly larger a t higher conversions.
ACKNOWLEDGMENT I am indebted to P. Behnken, D. A. Bolon, G. L. Gaines, Jr., and J. E. Girard for loan of equipment and helpful discussions in the course of this work.
LITERATURE CITED (1) K . R.
RESULTS AND DISCUSSION T h e analytical data observed for the detection of dissolved
Hz a n d O2 are presented in Table 11. While the maximum volume that can be injected directly on column is limited, this method has proved more sensitive and reproducible than two systems tested in this laboratory based on stripping the gases from a larger volume of solution (1-3 mL) by passing a finely dispersed carrier gas stream through t h e liquid before the drying and analyzing columns (8). T h e long term, transient (5-10 min) decrease in carrier gas flow following liquid injection results in an irreproducible baseline which effectively limits the size of injection. T h e use of larger diameter precolumns resulted in peak broadening and consequent decrease in sensitivity. Currently, t h e "water-absorbing'' precolumn is changed after a total of ca. 1 mL liquid has been
Mann, N. S.Lewis, V. M. Miskowski, D. K. Erwin, G. S. Hammond,
and H. 6.Gray, J . Am. Chem. Soc., 99, 5525 (1977). (2) G. Sprintschnik, H. W. Sprintschnik, P. P. Kirsch, and D. G. Whitten, J . Am. Chem. Soc., 99, 4947 (1977);ibid., 98, 2337 (1976). (3) P. A. Jacobs, J. 6.Vytterhceven. and H. K. Beyer, J. Chem. Soc., Chem. Commum., 1977. 128. (4) A. Tolk. W. A. Linaerak. A. Kout. and D. Boraer. Anal. Chim. Acta. 45. 137 (1969) (5) P L Airey and F S Dainton, Proc R SOC London. Ser A , 291, 340, 478 (1966). (6) R. E. Hintze and P. C. Ford, J . A m . Chem. SOC., 97, 2664 (1975). (7) C. A. Parker, "Photoluminescenceof Solvtions", Elsevier, New York, N.Y., 1968. (8) J. W. Swinnerton, V. J. Linnenborn, and C. H . Cheek, Anal. Chern.. 34, 483 (1962).
RECEIVED for review October 21, 1977. Accepted December 7, 1977. This research was partially supported by the Division of Basic Energy Sciences, Department of Energy (EG-77C-02-4395).
Separation of Rhodium-103m from Ruthenium-103 by Solvent Extraction Jih-Hung Chiu, Robert R. Landolt," and Wayne V. Kessler Bionucleonics Department, Purdue University, West Lafayette, Indiana 47907
A previous paper (1) reported a procedure for the separation from Io3Ru. T h e yield of loBrnRh was 94 f 0.6 % , and of loBmRh t h e amount of lo3Ru contamination was 3.8 0.7%. Continued work to improve the separation procedure has resulted in one t h a t is considerably better. T h e procedure of Meadows and Matlack ( 2 ) ,developed for t h e separation of radioruthenium from fission product waste, was modified and used in the initial steps. T h e yield of 10BrnRhwas quantitative and there was no measurable lo3Ru contamination.
*
EXPERIMENTAL Reagents. A ruthenium carrier solution containing 3 g of ruthenium chloride (Alpha Products) in 500 mL of distilled water was prepared. The solution was filtered through Whatman 41 paper. SpectrAR grade carbon tetrachloride (Mallinckrodt) was used without further purification. Ruthenium-103 in equilibrium with loSmRhwas obtained from Amersham/Searle as ruthenium chloride in 4 N HCl. A stock solution containing 1 gCi of lo3Ru/mL in 6 N HC1 was prepared. Separation Procedure. The procedure of Meadows and Matlack (2) was followed with modifications. A 0.5-mL aliquot
of the 103R~/103mRh stock solution was placed in a 60-mL separatory funnel containing 2 mL of concentrated HC1 and 2 mL of ruthenium carrier solution. With frequent swirling, 12 N NaOH was added dropwise until black ruthenium hydroxide precipitated. Ten more drops of NaOH was added, followed by 1 mL of 5% sodium hypochlorite with thorough mixing. The ruthenium hydroxide dissolved and the solution turned green. After 1 h, 10 mL of carbon tetrachloride was added, followed by dropwise addition of 6 N HC1, with swirling, until the color suddenly turned light yellowish green. Four more drops of HC1 was added. The contents of the funnel were mixed for 1 min, and the carbon tetrachloride layer containing ' 0 3 R ~ 0was 4 drained, leaving the 103mRhin the aqueous layer. The aqueous layer was extracted with an additional 10 mL of carbon tetrachloride and was then drained into a graduated 50-mL centrifuge tube. Purification of 103mRh. The aqueous solution in the tube was gently boiled over a flame for 3 to 5 min until the volume was reduced to less than 10 mL. Suspended carbon tetrachloride, residual Io3RuO4,and residual chlorine evaporated. The solution was cooled and diluted to 10 mL. A 5.0-mL aliquot was placed in a polypropylene counting tube. The lmmRhand lo3Ruactivities were measured immediately by y-ray spectrometry in the manner previously reported ( I ) .
0003-2700/78/0350-0670$01,00/0 1978 American Chemical Society
