Gas Chromat ogra phic Separation of Hydrogen Chloride, Hydrogen Sulfide, and Water SIR: Hydrogen sulfide, hydrogen chloride, and water have been determined individually in a variety of materials by a number of investigators. Excellent background material can be found in the book by Jeffrey and Kipping (1) and the references contained therein. More recently Hodges and Matson ( 2 ) have separated COe, COS, H2S, CS2, and SOs using several different columns. Bennett (3) determined water in various organic materials using 5 Carbowax 20M on Teflon powder. Prokop’eva and Bukina ( 4 ) coated all the brass in their system with PVC lacquer in the determination of C12, NOCI, and HCl. Philips and Owens (5) used a Teflon capillary column coated with Kel-F oil for the separation of HF, ClZ,and ClF3. Lantheaume (6) used an all nickel and Teflon system in analyzing mixtures of HF and ClF,. The separation and identification of HCl, H2S, and H 2 0 was made possible by a combination and refinement of some of these techniques.
1
EXPERIMENTAL
The apparatus was built around a Teflon detector block fabricated of conventional design from a single block of Teflon and fitted with two Gow Mac type W tungsten filaments. The sensitivity of the cell was similar to a like cell built from 316 Stainless. The sample gas contacts only Teflon or glass, with the exception of the tungsten filament and the liquid substrate. The Teflon cell block is fitted to ‘/*-inch Teflon connecting lines with modified Teflon Swagelok fittings designed to reduce dead volume to a minimum, A six-way glass stopcock is used as the sampling valve. The cell block and fittings are enclosed in an aluminum heat sink and are placed with the column and inlet system within a constant temperature oven. A conventional bridge power supply and output voltage divider are used to operate the cell. Dry helium at a pressure of 15 psig is split at a tee. The reference stream passes through a 10-turn micrometer valve (Nupro SS-2M) directly into the reference side of the cell and out to the atmosphere. The sample stream passes through a like valve into a 2.5 meter X l/c-inch 0.d. X 0.030inch wall Teflon tubing packed with 5 % Carbowax 20M on Fluoropak 80. The column connects to the sample inlet of the cell with the outlet vented to the atmosphere. The helium flow is 33 ml per minute at both the reference and sample stream exits. The column is held at 90” C, the detector at 100” C, and the flash heater and sample valve at 150” C. The air peak is partially resolved from the HzS at just under 1 minute, followed by HCI and HzO at 3.2 and 6.2 minutes, respectively, as shown in Figure 1. The chro-
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ANALYTICAL CHEMISTRY
9
1
Figure 1. Separation of air, H2S, HCl, and H20 on 5 % Carbowax 20M on Fluoropak 80 Col. temp., 90” C Carrier gas, helium at 33 cc/min Sample size, 1.0 cc
matograph was recorded on a 5-mv, 1-second recorder. Areas are measured with an Instron integrator. Results of two typical samples are shown in Table I. DISCUSSION
The samples analyzed for by this technique were samples that were the result of some ZnC12-H2S-H20 equilibrium studies. Other liquid substrates were investigated, the most noteworthy being a mixture of propylene carbonate and Apiezon L. It is felt that one or more of the new porous polymer packings might do the job equally well, but this approach was not studied. Chromosorb W was tried and gave good
t
(1) P. G. Jeffrey and P. J. Kipping, “G s Analysis by Gas Chrornatography,” Chaps. 12-14, Macrnill n New York, 1964. (2) C. T. Hodges and R. F. Matson, ANAL.CHEM., 37, 1065 (1965). (3) 0. F. Bennett, fbid.,36, 684 (1964). (4) M. F. Prokop’eva and V. K. Bukina, Uzbeksk. Ch’m. Zh., 7 (6), 30 (1963). (5) T. R. Philips, and D. R. Owens, “Gas Chromatography 1960,” R . P. W. Scott, ed., pp. 308-15, Butterworths, London, 1961. (6) R. A. Lantheaume, ANAL.CmM., 36,486 (1964).
1 2 3 4 5 6 1 8 RETENTION TIME IN MINUTES
Table I.
Analysis of Typical Samples
Sample No. I
HzS,
Z
90.8 89.5 90.3 91 .O
HC1, Z 0.0 0.1 0.2 0.0
H20,
Z
9.2 10.4 9.5 9.0
HzS,
Sample No. 2
Z
52.5 54.9 55.5 52.6
HCI,
Z
12.0 12.3 13.7 13.7
HzO,
Z
35.5 32.8 30.8 33.7
separation, but with tailing. Nickel filaments were tried and gave approximately 50% of the sensitivity of the tungsten along with some stability problems. Teflon-clad filaments were also tried and found to give only about 10% of the sensitivity of the tungster.. Examination of the tungsten filaments after a number of determinations showed no evidence of corrosion. It was necessary to saturate the system with HCI prior to injecting the sample. This was done routinely by injecting 5 ml of HCI gas prior to each determination. Low HC1 results were obtained if this step was omitted. The lower limit of detectabi iity of all three components is believed to be about 0.1 %, however no samples were run containing less than 10 H2Sor H"O and conditioning might be necessary for them also at the lower levels. Air in the samples was there only as an impurity and, indeed, most samples showed much less than is shown in Figure 1. The glass stopcock
sampling valve was found to be less than ideal, and the Teflon modification as shown by Graven and Harmon (7) would surely be an improvement. EDWARDL. OBERMILLER GEORGE 0.CHARLIER Research Division Consolidation Coal Co. Library, Pa. 15129 RECEIVED for review October 10, 1966. Accepted January 3, 1967. (7) W. M. Graven and H. R. Harmon, ANAL.CHEM., 37, 1626 (1965).
Degradation of Glutamine at Elevated Temperatures in Ion Exchange Chromatography Mixtures of 1.0 pc of I4C-labeled glutamine (Schwarz Bioresearch, Inc., Orangeburg, N. Y.; specific activity 6.58 mcjmm) and 0.25 pmole of unlabeled glutamine (L-glutamine, CP, Mann Research Lab., New York, N. Y . ) were chromatographed at two temperatures. In the first experiment, the column temperature was maintained at 30" C for 41i2 hours and then raised to 60" C. In the second experiment, a uniform column temperature of 60" C was maintained. Amino acid solutions were freshly prepared in distilled water just prior to use. Eluting buffer was pumped through the column at the rate of 0.50 mljminute. It was determined that 0.1075 ml/minute of column effluent was normally discarded via the h overflow tube just before the proportioning pump manifold. In these experiments, this overflow was collected in 10-minute fractions (1.075 ml). Portions were subsequently assayed for I4Cradioactivity with a liquid scintillation counter. Recovery of total added radioactivity was 100 in both experiments.
SIR: In a previous >itudy( I ) of amino acid separation by ion exchange chromatclgraphy, it was found that glutamine could not be quantitatively recovered at elevated column temperatures. At temperahres of 25" C, glutamine recovery was 100%; in contrast, at 60" C, only 24% of added glutamine could be accounted for. Loss of glutamine was not paralleled by formation or increase of glutamic acid. This finding indicated that hydrolytic dzamidation of glutamine to glutamic acid was not the cause of glutamine loss during chromatography at elevated temperatures. To clarify this question, chromatographic experiments employing carbon-14-labeled glutamine were performed. Chromatography was carried out with the Technicon Co. AutoAnalyzer system of arnirio acid analysis as previously described
(0. (1) I. Oreskes, F. Cantor, and S. Kupfer, ANAL.CHEM., 37, 1720 (1965).
:::r
25,000
GLUTAMINE l90.7Yl
20,000 W
5 '5,000
PRE-GLUTAMINE Ia . 3 ~I ,
fa L
10,000
f 8
5,000
.-------_-. ._.--_-* ~
0100
110
IM
,
130
----5
GLUTAMIC ACID I O X 1
I--.cI.-~
IqO
0
I50
00 MINUTES
Figure 1. Chroniatography of glutamine at column temperature of 30" C from 0 to 270 minutes, then 60" C thereafter VOL. 39, NO. 3, MARCH 1967
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