of quaternary nitrogen compounds in natural materials and perhaps lead to a further understanding of their metabolic role. LITERATURE CITED
(1) Aronoff, S., Plant Physiol. 31, 355 (1956). (2) Beauchesne, G., Xetien, G., Compt. rend. SOC. biol. 146, 1342 (1952). (3) Blake, Clara, Am. J . Botany 41, 231 (1954). (4) Block, R. J., Durrum, E. E., Zweig, G., "A Manual of Paper Chromatog-
raphy and Electrophoresis," Academic Press, New York, 1955. (5) Bregoff, H., Roberts, E., Delwiche, C. C., J . Biol. Chem. 205, 565 (1953). (6) Dunstan, W. R., Goulding, E., J . Chem. SOC.75, 1004 (1899). (7) Ellinger, P., Abdel Kader, M. M., Biochem. J . 44, 77 (1949).
(8) Folkes, B. F., Analyst 78, 496 (1953). (9) Friedman, S., McFarlane, J. E.,
Bhattacharyya, P. K., Fraenkel, G., Arch. Biochem. Biophys. 59, 484 (1955). (10) Frisell, W. R., Meech, L. A., Mackenzie, C. G., J. Biol. Chem. 207, 709
(1964). ~ ~ . _ ~ , (11) Gilboe, D., Williams, J. K., Jr., Proc. SOC.Exptl. Biol. M e d . 91, 735 (1956). (12) Glick,, D.,. Cereal Chem. 21. 119 (1944). (13) Harris, G., Parsons, R., Chem. & Ind. (London)44, 1312 (1956). (14) Heath, H., Toennies, G., Biochem. J . 68,204 (1958). (15) Huff, J. W., Perlzweig, W. A., J . Biol. Chem. 167, 157 (1947). (16) Johnson, M. J., Ibid., 137, 575 (1941). ( l ? ) Lebine, C., Chargaff, E., Ibid., 192, 465 (1951). (18) Moore, S., Stein, W.H., Ibid., 211, 893 (1954). (19) Pilgeram, L. O., Gal, E. AI., Sassen-
drath, E. N.,Greenberg, D. K, Ibid, 204,367 (1953). (20) Stein, \Ti. H., Moore, S., Cold Spring Harbor Symposia Quant. Biol. 14, 179 (1949). (21) Sweeney, J. P., J . Assoc. Ogic. Agr. Chemists 34,380 (1951). (22) Wall, J. S.,AKAL. CHEM.25, 950 (1953). (23) Wall, J. S., Christianson, D. D., Dimler, R. J., Senti, F., Ibid., 32, 870 (1960). (24) Yemm, E. W.,Cocking, E. C., Analyst 80,209 (1955).
RECEIVEDfor review October 14, 1959. -4ccepted February 12, 1960. Division of Agricultural and Food Chemistry, 133rd Meeting, ACS, San Franclsco, Calif., April 1958. ;\lention of firm names or trade products does not imply that they are endorsed or recommended by the Department of Agriculture over other firms or similar products not mentioned.
Separation and Determination of Argon, Oxygen, and Nitrogen by Gas Chromatography E. W. LARD and R. C. HORN Grace Chemical Division, W. R. Grace & Co., Memphis, lenn.
)A sensitive but simple and rapid method for the separation and determination of argon, oxygen, and nitrogen has been developed. The threshold of detection was less than 2 0 p.p.m. Using carefully activated 5A Linde Molecular Sieve, the argon and oxygen are separated from nitrogen a t 25' C., and the argon-oxygen fraction is separated into its component C. Total analysis parts a t -72' time is 16 minutes. Other types of Linde Molecular Sieves were investigated and were unsatisfactory for separating argon and oxygen.
C
for the determination of argon in mixtures of common gases by the Orsat procedure require the removal of nitrogen from the argon by hot titanium metal. The threshold value with a conventional apparatus is 0.1%. The argon value is determined by difference. As a direct method for argon analysis was desired, the chromatographic technique was explored. Barrer and Robins ( 1 ) reported that mixtures of argon-nitrogen and argon-oxygen could be separated with Nordenite (i\Ta20.zA1203. 10SiOs.6.6H20); however, the technique is not completely suitable for analytical purposes because about 7% of the argon remains on the adsorbent HEMICAL METHODS
878
ANALYTICAL CHEMISTRY
with the oxygen. A recent attempt by Greene (2) to separate oxygen from argon using a 10-foot column filled with Linde 54 RIolecular Sieve was unsuccessful a t dry ice-acetone temperature (-72' C.). Because Barrer's Rfordenite and RIolecular Sieves are both degassed synthetic zeolites, the authors investigated all commercialgrades of hlolecular Sieves a t 25' and -72' C. and found that with rigid adherence to the activation procedure, argon is separated completely from oxygen b y using Type 5A. Subsequent to the development of this method, the work of Vizard and JT7ynne mas reported (4) in the literature; however, their method is not suitable for the separation and detection of small (l.Oyo)quantities of argon. EXPERIMENTAL
Apparatus. A Fisher-Gulf Model 300 partitioner mas modified t o permit t h e use of a n external column. Column Preparation. The columns were prepared by filling a 6-foot length of 0.25-inch standard copper tubing with ground (30/70 mesh) Molecular Sieves t h a t had been activated by drying in an oven a t 300' C. for 1 hour. The column was filled as soon as i t was removed from the oven. Immediately after filling, the column was connected t o t h e apparat u s and a small flow of carrier gas,
helium, was passed through the column until it reached the desired temperaturc. This procedure preserved the activity of the adsorbent during the cooling period. Procedure. Kitrogen m-as separated from t h e oxygen-argon mivture a t 25' C. with a helium flow of 100 ml. per minute. After this separation, t h e column was immersed in a dry ice-acetone b a t h (-72' C.) and t h e sample n-as injected again. Under this condition, the nitrogen remained on the column, and t h e argon and oxygen were separated as t w o distinct peaks. The chromatogram (Figure 1) was obtained from a sample of air, while Figure 2 represents a sample of pure nitrogen from an air fractionation plant. The concentration of each component was calculated using the relative response factors that were reported by Messner et al. (3). I n this calculation, the combined argon and oxygen were determined as one component in the first (25" C.) analysis. From the IOK Table I.
Type
Approx. Retention Time, Rlin. Separa02 Ar Kz tion
+
1.4 1.0 0.5
2.5 1.3 0.5
1.1 0.3 0 6-ft. column, He 100 ml./min., 25' C.,
5A 13X 4A a
Effect of Type of Molecular Sieve"
0.5 ml. air.
1
-
3
ma
n
"YlS$
Figure 1 . Determination of argon, oxygen, and nitrogen in dry air sample 5 A Molecular Sieve used in obtaining chromatograms A and
A Sample vol., ml. Column, ft. Temp. of analysis, C. Carrier gas flow, ml./min.
0.5 6 25 100
B
3
2
0
I
4
3
2
1
0
T i m a , minutes
Figurer2. Determination of argon, oxygen, and nitrogen in pure nitrogen sample
B 0.5
4 - 72
5A Molecular Sieve used in obtaining chromatograms A and B A B Sample vol., ml. 10 10 Column, ft. 2.5 6 Temp. of analysis, C. 72 25 Carrier gas now, ml./min. 100 100
70
-
temperature (-i2" C.) run, the ratio of argon t o oxygen peak area was determined and u a s used to calculate thz argon and olygen peak areas of the 25 C. run. Thus. all peak areas of the room temperature run are available for calculation of the concentration of each component. It has been suggested that nitrogen rmerged after about 90 minutes as a well defined peak ( 5 ) . Honever, the authors found that the nitrogen component of a sample of air was not eluted from a 6foot 5 6 Molecular Sieve column maintained at -72" C. for 2 hours. A t the cnd of this period the column was warmed by means of a hot water bath, and 4 minutes after immersion a well dcfined peak appeared. Dpon repetition of this experiment, but with only 1.1 hours of refrigeration, the nitrogen appeared again after 4 minutes. This seems t o indicate that the nitrogen does not migrate along the length of the column a t -72" C. and is thus irreversibly adsorbed. I n addition to being suitable for the separation of argon and oxygen, Type 5.2 Molecular Sieve showed superior ability to separate oxygen from nitrogen a t room temperature (Table I). DISCUSSION AND CONCLUSIONS
The method described was specifically developed for the analysis of various streams frequently required in synthetic ammonia plants. Table I1 shows the results of typical analyses :IS well as standard deviation calcula-
Table II.
Determination of Nitrogen Oxygen, and Argon %ru' %O % .4r Dry -4ir 77.88 21.23 0.89 78.25 20.88 0.87 21.27 0.91 77.82 77.91 21.23 0.86 78.21 20.91 0.88 Av. 78.01 21.10 0.58 Av. dev. from mean =I= 0.07 f 0.07 10.02 Dry air composition by vol., at sea level 78 03 20.99 0.94 others 0.04f Pure Nitrogen 99.859 0.082 0.059 99.867 0.076 0.057 99.860 0.082 0.058 99.862 0.078 0.060 99.870 0.076 0.054 Av. 99.864 0.079 0.058 Av. dev. from mean AO. 005 f O ,003 f O .003
tions. Calibration curves are eliminated by the use Of response factors for each component. The use of these factors eliminates secondarv standards, need for reproducible coiumn temperatures, or carrier gas flow rates as long as they remain constant throughout a single analysis. The method is sensitive t o 20 p.p.m. when the total bridge current of the thermistor-tvne -. thermal conductivitv cell is 25 ma. and a 10-ml. sample is used.
LITERATURE CITED
(1) Barrer, R. >I., Robins, *4.,Tram. Faraday SOC.49, 807 (1953). 121 Greene. S. A.. ANAL. CHEhf. 31. 480 11959). (31 Messner, A. E., Rosie, D. M., Argabright, Ibid., 31, 230 (1959). (4) Vizard, G. S., Wynne, A,, Chem. & Ind. 1959,196. ( 5 ) Vizard, G. S.,Wynne, 8., Kational Coal Board. Parkeate. Rotherham England, private coGm;nication. I
,
RECEIVED for revieff December 9, 1959, Accepted March 24, 1960.
VOL. 32, NO. 7, JUNE 1960
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