average value of component of velocity in given direction of ides1 gas molecule of substance i = volume change = mole fraction of solute in region i = ratio of radius of solute molecule ‘;o that of stationary phase molecule = ratio of radius of solute molecule io that of mobile phase molecule = number of nearest neighbors of molerule in bulk liquid phase = niimber of nearest neighbors of molecule in topmost layer of liquid = polarizabi1it.v = fraction of molecules reflected from surface = dielectric eo ?stant = interparticle porosity of column = dipole moment = vibration frc quency of zeropoint motion = vibration frequency of molecule perpendicular to surface = density = time of adsclrrition = convenient pirameter 2, 3 = subscripts clenoting solute, stationary, and mobile phases, respectively b, 8, 1, p , = super- or subscripts denoting following regions or
phasei: hulk liquid, g ~ s , liquid, packing m:iterial, liquid surface, respectively = convenient suhocripts
=
ir
i,j
LITERATURE CITED
(1) Berge, P. C. van, Haarhoff, P. C., Pretorius, l’., Trans. Faraday SOC.58,
2272 (1962). (2) Boer, J. €1. de, “The Dynamical Character of Adsorption,” p. 30, Clarendon Press, Oxford, 1953. (3) Ibid., p. 117. (4) Carman, P. C., “Flow of Gases through Porous Medin,” p. 10, Butterworths, London, 1056. ( 5 ) Clever, H. L., Battino, R., Snylor, J. H., Gross, P. If., J. Phys. Chrm. 61, 1 0 i 8 (1957). (6) Cremer, E., Angew. Chem. 71, 512 (1959). (7) Deemter, J. J. van, Informal Symposium, Gas Chromatography Discussion Group, Cambridge, England, 1957. (8) Duin, H. van, Nature 180, 1473 (1957). (9) Frederick, D. H., Miranda, B. T., Cooke, W. D., A N A L .CHEM.34, 1521 (1962). (10) Giddings, J. C., Ibid., 35, 439 (1963). (11) Giddings, J. C., J. Chromntog. 3, 443 (1960). (12) Giles, C. H., “Chromatographg,” E. Heftmann, ed., Chap. 4, Reinhold, Sew York, 1961. (13) Glasstone, S., Laidler, K. J., Eyringl H., “The Theory of Rate Processes, Chap. 9, hlcGraw-Hill, Xew York, 1941. (14) Hazeldean, G. S. F., Scott, R. P. W., J . I n s t . Petrol. 48, 380 (1962).
(15) Hodgman, C. D., Weast, R. C., Selby, S. AI., eds., “Handbook of Chemistry and Physics,” p. 2513, Chemical
Rubber Publishing Co., Cleveland, 1960. (16) Ketelaar, J. A. A., “Chemical Constitution,” p. 201, Elsevier, Amsterdam, 1958. (17) Ibid., pp. 356-60. (18) Khan, M. A,, “Gas Chromatography 1962,” hf. van Swaay, ed., p. 3, Butterworth, London, 1963 (19) Khan, 11. A., iyature 186, 800 (1960). (20) Kretschmer, C. B., Kowakowska, J., Wiebe, R., Ind. Eng. C‘hem. 38, 506 (1946). , \ -
~
(21) Martin, R. L., ANAL. CEIEM.33, 347 (1961). (22) Moelwyn-Hughes, E. A., “Physical Chemistry,” p. 42, l’ergamon Press, London. 1961. (23) Ibid.; Chap. 7. (24) Ibid., pp. 383-5. (25) Ibid., p. 701. (26) Ibid., p. 751. (27) Ibid., p. 770. (28) Ibid., p. 933. (29) Scott, E. J., Tung, I,. H., Drickamer, H. G.,J. Chpm. P h y s . 19,1075 (1951). (30) Sinfelt, J. H Drickamer, H. G., Ibid., 23, 1095 ( l i 5 5 ) .
(31) Smyth, C. :, “Dielectric Behavionr and Structure, Chap. 1, bIcGmw-Hill, Sew York, 1955. (32) Uhlig, H. H., J . PhUs. Chenk. 41, 121!5 (1937). RECEIVED for review July 5, 1963. Accepted September 16, 1963. G. J. K. is indebted to the South African Counvil for Scientific and Industrial Research for the award of a bursary.
A Combustion-Gas Chromatographic Method for the Simultanecus Determination of Carbon and Sulfur in Ferrous Metals W. K. STUCKEYI and 1. M. WALKER Department of Chemistry, Kansas State College o f Pittsburg, Pitfsburg, Kan.
b A method is described in which the sample is combusted in a pressurized stream of oxygen with a high frequency induction furnace. The combustion products are swept onto a &foot silica gel columrl, which is then purged oxygen-free with helium, the combustion products eluted by temperature programming, detected by a thermal conductivity detector, and recorded on a strip chart recorder equipped with a Disc Chart Integrator. The analysis time, from sample firing through complete elution of the combustion products i s 17 minutes. Carbon compositions analyzecl were from 0.01 1 to 3.28%. S,ulfur compositions ranged from 0.01 1 to 0.32970;. The method could easily b e adapted to a routine analysis with no change in accuracy or precision.
T
of ferrous metals in an oxygen atmosphere and the qubsequent analysis of the combustion products by various techniques has been reported for both carbon and sulfur (1, 4, 8, 10). Recently, infrared spectrometry has been used for carbon determinations with results reproducible to 0.001% ( 5 ) . I n addition, the sulfur content of steels has been detected after combustion by neutron activation analysis ( 2 ) and by spectrophotometric means ( 3 ) . Hon ever, a simultaneous method for carbon and sulfur is the most desirable. Several methods have been reported for simultaneous carbon-sulfur analysis in steels involving titrations (6),but the instrumental approach appears to be preferred. The far ultraviolet region of the spectrum ha. heen used t o deHE COMBUSTION
termine sulfur, phosphorus, carbon, and silicon. The mass spectrometw has also been used as a detector (7) and there is now an instrument commercially available using infrared means for detection. Gas chromatography is an excellent means of detection and is ideal for this type of analysis. However, only recently have the techniques involved in elemental analysis of organic compounds been extended to the determination of carbon in ferrous metals (11). The proposed simultaneous method utilizes gas chromatographic separation of the combustion products and detection by a thermal conductivity detector. 1 Present address, Department of Chemistry, Kansas State I‘niversitv, \fmhattnn, Knn.
VOL. 35, NO. 13, DECEMBER 1963
2015
Table 1.
N.B.S. steel sample
82a 122d 16d 129b 8i
1Oe 10g
55e
170a 133a
Results
N.B.S., % 2.24 3.28 1.01 0.094 0.077 0,406
0.240 0.011 0.052 0.120
Found, % 2.18 3.17 1.01 0.095 0.074 0.412 0.245 0.012 0.049
0.127
S
Std. dev. f0.02 fO.01 f O. O l =to.002 rto.001 *0.005
rt0.002 10.001 f0.002 10.002
a
ANALYTICAL CHEMISTRY
Mean
error, yo -0.06
-0.11
0.00
+0.001
-0.003 +0.000 +0.005
+0.001 -0.003
$0.007
N.B.S., 70 Found, % 0.106 0.102 0.084 0.092 0.039 0.033 0.211 0.224 0.060 0.064 0.049 0.047 0.014 0.109 0.011 0.011 0.021 0.022 0.329 0.346
n
EXPERIMENTAL
Apparatus and Materials. The system of Walker and Kuo ( 2 1 ) wa9 employed with certain modifications (Figure 1). The quartz combustion tube and double O-ring seal described by Kuo, Bender, and Walker (9) allowed the samples to be combusted in a pressurized stream of osygen. For this study, the brass components were rhodium plated. A stainless steel system was used from the quartz combustion tube through the silica gel column using l/r-inch tubing and Aminco stainless steel valves, Models 44-1585 and 45-4003. A few grams of W. A. Hammond Drierite Co. calcium sulfate was placed in the tubing immediately following the combustion chamber to prevent the possible adsorption of sulfur dioxide by moist ure. A 4-fOOt column was prepared using Matheson, Coleman and Bell chromatographic grade silica gel (60- to 80mesh) and stainless steel tubing. A column oven was constructed of transcite with glass wool insulation, so that one side of the oven was mounted on hinges to allow easy access to the oven and t o increase the cooling rate. The connections, including the bIower and thermistor, were retained from an original F &I M Scientific oven. Procedure. A carefully timed procedure was followed for each determination. The helium two-stag? regulator was first set for 16 p.s.i. and the flow rates of 60 ml. per minute on the sample side and 15 ml. per minute on the reference side checked. The recorder and integrator were turned on, the detector current set a t 130 ma., and the system allowed 24 hours to eliiilibrixe. Block temperature was 200" C. The oxygen regulator was then set for 16 p.9.i. This resulted in an owgen flow rate of 67 ml. per minute. All crucibles were prefired for 15 minutes immediately before firing to ensure a carbon, sulfur-free blank. The prefiripg was accomplished using 0.4 gram of 170a steel and 1.0 gram of tin accplerator. The prefired crucible was then charged with 0.500 h 0.0005 gram of the steel samnle and 1.0 gram of tirl accelerator. After the charged crucible was reloaded into the furnace, VI was opened completely for 1 minute and the combuition tube purged. With thp attenuator on the x 512 poiition,
2016
of Carbon-Sulfur Determinations
C
Std. dev.
Mean error, Yo
f O .005 f O ,003
+0.004
f0.002 rto. 012 f0.003 f0.001 f0.003 f 0 .001
f O ,002 f0.009
-0.008 +0.006 -0.013 -0.004
+o.ooz
-0.005 0.000 $0 001
+o
,017
the maximum temperature of 350" C. and stabilize a t 30" C. The periods during prefiring, column oven cooling, and sample combustion are more than adequate to carefully weigh all materials and record the results for each determination. RESULTS
C Figure tern
I.
Schematic diagram of sys-
A.
Oxygen plus oxidation products Silica gel column Detector block Sample side E. Reference side F. Helium supply VI, Vz, VS. Valves
8. C. D.
V 3 was closed simultaneously while V Z was being opened. This allowed oxygen to pass through the column. The combustion was then initiated. After 7 minutes, the furnace was turned off and V2 closed and Va opened simultaneoiiily. After an additional 1 minute, 45 seconds, the oven door was calosed and recorder chart drive started at 1 inch per minute. For the most rapid and accurate determination, a special temperature program technique was employed which resulted in a nonlinear program. The oven temperature was initially 30" C. The indicator of the temperature programmer was set a t 100" C. with a temperature setting of 42" per minute. The oven heater and the temperature programmer were activated simultaneously. The programming indicator begins increasing a t 42' per minute. The oven temperature then increases a t the madmum rate until the oven temperature and the programmer temperature coincidp. From this temperature upward, the programming rate is 42" per minute. This technique gave a maximum increase in temperature up t o 150" C. and resulted in the best carbon dioxide peak. After both carbon dioxide and sulfur dioyide had been eluted from the column, the chart drive on the recorder and the temperature programmer were turned off. The indicator on the ternl)wztiire controller was then set a t 30" ('. Appro\imately 15 minutes were allowed for the oven t o cool from
The results are shown in Table I. To correlate between samples of varying composition, a series of attenuation factors were evaluated, using the X1 position as reference. The attenuator was first set on the X1 position and the bridge set out of balance. An average value of counts per inch was found over a 5- to 10-minute period. The attenuator was then changed to the X 2 position and the average counts per inch again evaluated. The ratio of the counts per inch values on the two positions was the attenuation factor. A program was written for a Royal Precision Electronic Computer LGP-30 to calculate results. A mean sensitivity of all samples was taken as a standard to calibrate the instrument and to calculate the carbon-sulfur percentage for each run. An average of five runs was taken as the per cent found. Standard deviations were computed for the five runs on each sample. The program allowed all results to be calculated in 15 minutes. A combustion time of 7 minutes was found adequate for all samples except 122d, which contained the highest percentage of carbon. This sample was combusted 8 minutes. More erratic results were obtained with samples 122d and 82a compared to the other samples. Less uniform combustions are felt to be responsible. CONCLUSION
The overall sensitivity showed 46,550 counts per mg. of carbon. One microgram of carbon would accordingly give a maximum deflection approximately 2% of full scale with the attenuator on the x1 position. The apparatus showed a sulfur sensitivity of 20,710 counts per nig.
Since various compositions can be compensated by simply changing attenuations, the method is applicable to a wide range of concentrations. Also, no reagents or special techniques are necessary. The apparatus could easily be adapted, by means of solenoid valves and timers, so that cnly one master switch would be needed for the entire determination. The procedure would then consist only of loading the sample, activating the master switch, and reading the result. Use of calibration curves would result in an analysis requiring only about 5 minutes if a technician’s time per run. The time per analysis could be reduced by shortening the time required t o elute the sulfur dioxide from the
column. An oven capable of being programmed at a faster rate could conceivably reduce the total analysis time to 15 miniitcs or less.
(4) Cain, J. R., Max Eng. Chem. 1- --(5) Charpenet, No. 153, 39 (1961). (6) Hale, C. I T . , Jr., Muehlberg, W. F., IND. ENG. CHEM.,ANAL. ED. 8, 317 (19.?fi\
ACKNOWLEDGMENT
The authors gratefully acknowledge assistance from Thomas Dunphy, presently of Colorado State University, in preparing the computer program. LITERATURE CITED
(1) Bennet, E. L., Harley, J. H., Fowler, R. M., ANAL.CHEM.22, 445 (1950). (2) Bouton, P., Hoste, J., Anal. Chim. Acta 27,315 (1962). (3) Burke, K. E., David, C. &I., ANAL. CHEM.34, 1747 (1962).
(7)
3132
(
(8)€10
23, 1696 (9) Kuo, C J. M., Ibid., (10) Pepkowitz Ibid., 26, 102 (11) Walker, J. 2017 (1963). RECEIVEDfor review July 11, 1963. Accepted October 9, 1963. Abstracted from a thesis by W. K. Stuckey, submitted
.
in partial fulfi1.lment for the degree of Master of Science at Kansas State College of Pittsburg, Pittsbiirg, Xan.
Carbon Determination in Ferrous Metals by Gas Chromatography J. M. WALKER and C:.
W. KUO’
Department of Chemisfry, Kansas State College of Pitfsburg, Pittsburg, Kan.
b An extremely sensitive and highly precise method for the determination of carbon content in ferrous metals b y gas chromatogrlgphy was developed. Samples were combusted in a high frequency induction furnace, their gaseous products passed through a &foot 5-A. molecular sieve column, and detected b y a thermoconductivity detector. The c a r b m dioxide was trapped in the coluinn a t 100’ C. while oxygen was swept out b y the helium carrier gas after complete combustion. The carbon dioxide peak came off the column a t about 275” C. b y means of temperature programming while its area was measured b y a disk chart integrator. Eight different NBS steel and iron saniples with carbon contents varying from 0.01 1 to 3.28% were run. This metk80d permits detection of 0.0005% carbon a t the maximum detector sensitivity. The time required for a single run i s approximately 20 minutes. Some advantages of this technique are its simplicity of operation, broad detection range (0.0005 to 20% carbon), and high sensitivity.
T
HE PROCEDURE clf carbon determination in ferrous metals has been well established. Many methods and their modifications have appeared in the literature (1-8, 6, 11, 18). They can be classified mainly as the following categories: the wet chemical method, the direct combustion method, the vacuum
fusion (low-pressure combustion) method, the electroconductometric method, and the spectrographic and mass spectroscopic methods. The trend of development in this field is to seek a rapid and highly sensitive method which would enable one to detect not only very low carbon content, but also very high carbon content as well. The gas chromatographic technique appears to be a step in the right direction. Although there has not been any published paper concerning the carbon determination in ferrous metals by gas chromatographic technique, papers were given a t the 1962 and 1963 meetings of the Pittsburgh Conference of Analytical Chemistry and Applied Spectroscopy (6, 8). I n addition, several workers did utilize this technique in the determination of carbon and hydrogen in organic compounds. Duswalt and Brandt (4) combusted their sample in an oxygen stream. Sundberg and Maresh ( l a )using copper oxide as internal oxidizing agent, burned their sample in a helium atmosphere. In both cases, the combusted gases were led through a liquid nitrogen trap and the carbon dioxide was trapped. Since silica gel columns were used in both cases, the liquid nitrogen trap is a necessity so as to get rid of the excess oxygen and to concentrate the gases for quick injection into the sample column. Recently, Nightingale and Walker (9) developed a simultaneous C-H-N determination using a gas chromatographic technique. They introduced the coupling of the high fre-
quency induction furnace and the gas chromatograph. These workers made use of a 5 A. molecular sieve column and eliminated the troublesome liquid nitrogen trap. Still, an internal oxidizing agent, silver permanganate, was used instead of burning the sample in an oxygen atmosphere. Parsons, Pennington, and Walker (10) also utilized the highfrequency furnace-gas chromatograph combination in the determination of nitrogen. The work described here is based on the retention of carbon dioxide by the 5 A. molecular sieve. The carbon dioxide in the combusted mixture was trapped and “stored” in the molecular sieve column under isothermal conditions while the excess oxygen passed on through. Helium, the carrier gas, was used to purge the oxygen from the column hence the need for an internal oxidizing agent and the liquid nitrogen trap was eliminated. The carbon dioxide peak was obtained through temperature programming. EXPERIMENTAL
Apparatus and Materials. A schematic diagram of the entire system is shown in Figure 1. The apparatus consisted of a Leco high frequency induction furnace Model 523, a F & 11 Scientific Model 500 linear-programmed temperature gas chromatograph, with a 4-foot 5-A. molecular sieve column, and two Hevy Duty Present address, The Dow Chemical Co. ,Williamsburg, Va. VOL. 35, NO. 13, DECEMBER 1963
2017
